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Montgomery TM, Lehmann KDS, Gregg S, Keyser K, McTigue LE, Beehner JC, Holekamp KE. Determinants of hyena participation in risky collective action. Proc Biol Sci 2023; 290:20231390. [PMID: 38018101 PMCID: PMC10685128 DOI: 10.1098/rspb.2023.1390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 11/03/2023] [Indexed: 11/30/2023] Open
Abstract
Collective action problems arise when cooperating individuals suffer costs of cooperation, while the benefits of cooperation are received by both cooperators and defectors. We address this problem using data from spotted hyenas fighting with lions. Lions are much larger and kill many hyenas, so these fights require cooperative mobbing by hyenas for them to succeed. We identify factors that predict when hyena groups engage in cooperative fights with lions, which individuals choose to participate and how the benefits of victory are distributed among cooperators and non-cooperators. We find that cooperative mobbing is better predicted by lower costs (no male lions, more hyenas) than higher benefits (need for food). Individual participation is facilitated by social factors, both over the long term (close kin, social bond strength) and the short term (greeting interactions prior to cooperation). Finally, we find some direct benefits of participation: after cooperation, participants were more likely to feed at contested carcasses than non-participants. Overall, these results are consistent with the hypothesis that, when animals face dangerous cooperative dilemmas, selection favours flexible strategies that are sensitive to dynamic factors emerging over multiple time scales.
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Affiliation(s)
- Tracy M. Montgomery
- Department of Integrative Biology and Program in Ecology, Evolution, and behavior, Michigan State University, 288 Farm Lane, East Lansing, MI 48824, USA
- Mara Hyena Project, PO Box 164-00502, Karen, Nairobi, Kenya
- Department for the Ecology of Animal Societies, Max Planck Institute for Animal Behavior, Bücklestraße 5a, 78467 Konstanz, Germany
- Center for the Advanced Study of Collective Behavior, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
| | - Kenna D. S. Lehmann
- Department of Integrative Biology and Program in Ecology, Evolution, and behavior, Michigan State University, 288 Farm Lane, East Lansing, MI 48824, USA
- Human Biology Program, Michigan State University, 288 Farm Lane, East Lansing, MI 48824, USA
- Mara Hyena Project, PO Box 164-00502, Karen, Nairobi, Kenya
| | - Samantha Gregg
- Department of Integrative Biology and Program in Ecology, Evolution, and behavior, Michigan State University, 288 Farm Lane, East Lansing, MI 48824, USA
| | - Kathleen Keyser
- Department of Integrative Biology and Program in Ecology, Evolution, and behavior, Michigan State University, 288 Farm Lane, East Lansing, MI 48824, USA
| | - Leah E. McTigue
- Department of Integrative Biology and Program in Ecology, Evolution, and behavior, Michigan State University, 288 Farm Lane, East Lansing, MI 48824, USA
- Rocky Mountain Research Station, Colorado State University, 240 W Prospect St, Fort Collins, CO 80525, USA
| | - Jacinta C. Beehner
- Department of Psychology, University of Michigan, 530 Church Street, Ann Arbor, MI 48109, USA
- Department of Anthropology, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109, USA
| | - Kay E. Holekamp
- Department of Integrative Biology and Program in Ecology, Evolution, and behavior, Michigan State University, 288 Farm Lane, East Lansing, MI 48824, USA
- Mara Hyena Project, PO Box 164-00502, Karen, Nairobi, Kenya
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Anderson AP, Renn SCP. The Ancestral Modulation Hypothesis: Predicting Mechanistic Control of Sexually Heteromorphic Traits Using Evolutionary History. Am Nat 2023; 202:241-259. [PMID: 37606950 DOI: 10.1086/725438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
AbstractAcross the animal kingdom there are myriad forms within a sex across, and even within, species, rendering concepts of universal sex traits moot. The mechanisms that regulate the development of these trait differences are varied, although in vertebrates, common pathways involve gonadal steroid hormones. Gonadal steroids are often associated with heteromorphic trait development, where the steroid found at higher circulating levels is the one involved in trait development for that sex. Occasionally, there are situations in which a gonadal steroid associated with heteromorphic trait development in one sex is involved in heteromorphic or monomorphic trait development in another sex. We propose a verbal hypothesis, the ancestral modulation hypothesis (AMH), that uses the evolutionary history of the trait-particularly which sex ancestrally possessed higher trait values-to predict the regulatory pathway that governs trait expression. The AMH predicts that the genomic architecture appears first to resolve sexual conflict in an initially monomorphic trait. This architecture takes advantage of existing sex-biased signals, the gonadal steroid pathway, to generate trait heteromorphism. In cases where the other sex experiences evolutionary pressure for the new phenotype, that sex will co-opt the existing architecture by altering its signal to match that of the original high-trait-value sex. We describe the integrated levels needed to produce this pattern and what the expected outcomes will be given the evolutionary history of the trait. We present this framework as a testable hypothesis for the scientific community to investigate and to create further engagement and analysis of both ultimate and proximate approaches to sexual heteromorphism.
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Jiménez R, Burgos M, Barrionuevo FJ. The Biology and Evolution of Fierce Females (Moles and Hyenas). Annu Rev Anim Biosci 2023; 11:141-162. [PMID: 36130099 DOI: 10.1146/annurev-animal-050622-043424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Talpid moles and spotted hyenas have become the paradigms of anatomical and behavioral female masculinization. Females of many mole species develop ovotestes that produce testosterone, show external genitalia that resemble that of males, and close their vaginal orifice after every estrus, and female spotted hyenas lack an external vaginal orifice and develop a pseudoscrotum and a large pseudopenis through which they urinate, mate, and give birth. We review current knowledge about several significant aspects of the biology and evolution of these females, including (a) their specific study methods; (b) their unique anatomical features, and how these peculiarities influence certain physiological functions; and (c) the role that steroid hormones as well as genetic and environmental factors may have in urogenital system development, aggressive behavior, and social dominance. Nevertheless, both mole and hyena females are exceptionally efficient mothers, so their peculiar genitalia should not call into question their femininity.
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Affiliation(s)
- Rafael Jiménez
- Department of Genetics, Institute of Biotechnology, and Center of Biomedical Research (CIBM), University of Granada, Armilla, Granada, Spain; , ,
| | - Miguel Burgos
- Department of Genetics, Institute of Biotechnology, and Center of Biomedical Research (CIBM), University of Granada, Armilla, Granada, Spain; , ,
| | - Francisco J Barrionuevo
- Department of Genetics, Institute of Biotechnology, and Center of Biomedical Research (CIBM), University of Granada, Armilla, Granada, Spain; , ,
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McCormick SK, Laubach ZM, Strauss ED, Montgomery TM, Holekamp KE. Evaluating drivers of female dominance in the spotted hyena. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.934659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
IntroductionDominance relationships in which females dominate males are rare among mammals. Mechanistic hypotheses explaining the occurrence of female dominance suggest that females dominate males because (1) they are intrinsically more aggressive or less submissive than males, and/or (2) they have access to more social support than males.MethodsHere, we examine the determinants of female dominance across ontogenetic development in spotted hyenas (Crocuta crocuta) using 30 years of detailed behavioral observations from the Mara Hyena Project to evaluate these two hypotheses.ResultsAmong adult hyenas, we find that females spontaneously aggress at higher rates than males, whereas males spontaneously submit at higher rates than females. Once an aggressive interaction has been initiated, adult females are more likely than immigrant males to elicit submission from members of the opposite sex, and both adult natal and immigrant males are more likely than adult females to offer submission in response to an aggressive act. We also find that adult male aggressors are more likely to receive social support than are adult female aggressors, and that both adult natal and immigrant males are 2–3 times more likely to receive support when attacking a female than when attacking another male. Across all age classes, females are more likely than males to be targets of aggressive acts that occur with support. Further, receiving social support does slightly help immigrant males elicit submission from adult females compared to immigrant males acting alone, and it also helps females elicit submission from other females. However, adult females can dominate immigrant males with or without support far more often than immigrant males can dominate females, even when the immigrants are supported against females.DiscussionOverall, we find evidence for both mechanisms hypothesized to mediate female dominance in this species: (1) male and female hyenas clearly differ in their aggressive and submissive tendencies, and (2) realized social support plays an important role in shaping dominance relationships within a clan. Nevertheless, our results suggest that social support alone cannot explain sex-biased dominance in spotted hyenas. Although realized social support can certainly influence fight outcomes among females, adult females can easily dominate immigrant males without any support at all.
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Curren LJ, Sawdy MA, Scribner KT, Lehmann KDS, Holekamp KE. Endurance rivalry among male spotted hyenas: what does it mean to “endure”? Behav Ecol Sociobiol 2022. [DOI: 10.1007/s00265-022-03212-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Lehmann KDS, Jensen FH, Gersick AS, Strandburg-Peshkin A, Holekamp KE. Long-distance vocalizations of spotted hyenas contain individual, but not group, signatures. Proc Biol Sci 2022; 289:20220548. [PMID: 35855604 PMCID: PMC9297016 DOI: 10.1098/rspb.2022.0548] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
In animal societies, identity signals are common, mediate interactions within groups, and allow individuals to discriminate group-mates from out-group competitors. However, individual recognition becomes increasingly challenging as group size increases and as signals must be transmitted over greater distances. Group vocal signatures may evolve when successful in-group/out-group distinctions are at the crux of fitness-relevant decisions, but group signatures alone are insufficient when differentiated within-group relationships are important for decision-making. Spotted hyenas are social carnivores that live in stable clans of less than 125 individuals composed of multiple unrelated matrilines. Clan members cooperate to defend resources and communal territories from neighbouring clans and other mega carnivores; this collective defence is mediated by long-range (up to 5 km range) recruitment vocalizations, called whoops. Here, we use machine learning to determine that spotted hyena whoops contain individual but not group signatures, and that fundamental frequency features which propagate well are critical for individual discrimination. For effective clan-level cooperation, hyenas face the cognitive challenge of remembering and recognizing individual voices at long range. We show that serial redundancy in whoop bouts increases individual classification accuracy and thus extended call bouts used by hyenas probably evolved to overcome the challenges of communicating individual identity at long distance.
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Affiliation(s)
- Kenna D. S. Lehmann
- School of Biological Sciences, University of Nebraska—Lincoln, 1101T Street, Lincoln, NE 68588, USA
| | - Frants H. Jensen
- Department of Biology, Syracuse University, 107 College Place, Syracuse, NY 13244, USA,Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Andrew S. Gersick
- Dept of Ecology and Evolutionary Biology, Princeton University, 106A Guyot Hall, Princeton, NJ 08544, USA
| | - Ariana Strandburg-Peshkin
- Biology Department, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany,Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany,Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behaviour, Bücklestrasse 5a, 78467 Konstanz, Germany
| | - Kay E. Holekamp
- Department of Integrative Biology, Michigan State University, 288 Farm Lane, East Lansing, MI 48824 USA,Ecology, Evolution, and Behavior Program, Michigan State University, 293 Farm Lane, East Lansing, MI 48824, USA
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Laubach ZM, Gering E, Yang E, Montgomery TM, Getty T, Holekamp KE. Associations between Toxoplasma gondii infection and steroid hormone levels in spotted hyenas. Int J Parasitol Parasites Wildl 2022; 17:53-59. [PMID: 34984167 PMCID: PMC8693151 DOI: 10.1016/j.ijppaw.2021.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 11/24/2021] [Accepted: 11/24/2021] [Indexed: 11/30/2022]
Abstract
Toxoplasma gondii is a common parasite that infects warm-blooded animals and influences host physiology. T. gondii is known to target the host's central nervous system, affecting circulating levels of steroid hormones, fear-related behaviors, and health, although these effects appear to vary among host taxa. Here, we investigated the relationship between T. gondii infection and levels of plasma testosterone and cortisol within a wild population of spotted hyenas (Crocutacrocuta, n = 109). In our analyses, we accounted for age and sex via stratified regression analyses. We detected a negative association between circulating plasma testosterone and T. gondii infection among female cubs and subadults as well as adult male hyenas. We found no associations between T. gondii infection and cortisol in any age class or sex group of hyenas. Our work adds to a growing body of literature by characterizing the relationship between T. gondii infection and physiology in a novel host in its natural habitat. In a broader context, our findings indicate that responses to infection vary with characteristics of the host and point to a clear need for additional studies and priorities for future work that include diverse taxa and ecological settings. Toxoplasma gondii infects diverse hosts and leads to differences in hormone levels. The relationship between T. gondii infection and host hormone response is mixed. We assessed if wild spotted hyena hormones differed by T. gondii infection. Testosterone was lower in infected female cub/subadult and adult males hyenas. Our results parallel laboratory findings but provide added realism of a wild animal.
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Affiliation(s)
- Zachary M. Laubach
- Michigan State University, Department of Integrative Biology and Program in Ecology, Evolution and Behavior, MI, USA
- University of Colorado, Boulder, Department of Ecology and Evolutionary Biology, CO, USA
- Mara Hyena Project, Kenya
- Corresponding author. University of Colorado, Boulder, Department of Ecology and Evolutionary Biology, CO, USA.
| | - Eben Gering
- Nova Southeastern University, Department of Biological Sciences, Halmos College of Natural Sciences and Oceanography, FL, USA
| | - Erik Yang
- Nova Southeastern University, Department of Biological Sciences, Halmos College of Natural Sciences and Oceanography, FL, USA
| | - Tracy M. Montgomery
- Mara Hyena Project, Kenya
- Max Planck Institute of Animal Behavior, Department for the Ecology of Animal Societies, Konstanz, Germany
| | - Thomas Getty
- Michigan State University, Department of Integrative Biology and Program in Ecology, Evolution and Behavior, MI, USA
| | - Kay E. Holekamp
- Michigan State University, Department of Integrative Biology and Program in Ecology, Evolution and Behavior, MI, USA
- Mara Hyena Project, Kenya
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8
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McCormick SK, Holekamp KE. Aggressiveness and submissiveness in spotted hyaenas: one trait or two? Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.01.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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9
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Fromme L, Yogui DR, Alves MH, Desbiez AL, Langeheine M, Quagliatto A, Siebert U, Brehm R. Morphology of the genital organs of male and female giant anteaters ( Myrmecophaga tridactyla). PeerJ 2021; 9:e11945. [PMID: 34447632 PMCID: PMC8364315 DOI: 10.7717/peerj.11945] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 07/20/2021] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND The giant anteater belongs to the supraorder Xenarthra which occupies a systematically isolated position among placental mammals. The species is categorized as Vulnerable by the International Union for Conservation of Nature, and understanding its reproductive characteristics is critical for future conservation efforts. METHODS Gross and microscopic anatomy of the genital organs of 23 male and 21 female adult and young roadkill giant anteaters in Brazil were studied. RESULTS Male giant anteaters presented a short conical penis, intraabdominal testes, and prostate, vesicular and bulbourethral glands. A tubular remnant of the partially fused Müllerian ducts extended from the seminal colliculus through the prostate gland, continued cranially in the genital fold, bifurcated, and attached with one elongation each to the left and right epididymal corpus. The structure presented a total length of up to 10 cm and contained a yellowish liquid in its lumen. Histologically, the caudal section of this structure resembled the female vagina, the middle portion corresponded to the uterus, and the extensions showed characteristics of uterine tubes. In adult female giant anteaters, ovoid ovaries with occasional seminiferous cord-like structures were observed. The animals possessed a simple uterus, which was directly continuous with the vaginal canal. The caudal portion of the vagina had two lumina, separated by a longitudinal septum and opening into two apertures into the vaginal vestibule, cranial to the urethral opening. In the urethral and the lateral vestibular wall, glandular structures with characteristics of male prostate and bulbourethral glands, respectively, were found. The vestibule opened through a vertical vulvar cleft to the exterior. A pair of well-differentiated Wolffian ducts with a central lumen originated ventrally at the vaginal opening into the vestibule and passed in a cranial direction through the ventral vaginal and uterine wall. Each duct extended highly coiled along the ipsilateral uterine tube until the lateral pole of the ovaries where it merged with the rete ovarii. DISCUSSION The reproductive morphology of giant anteaters reveals characteristics shared with other Xenarthrans: intraabdominal testes, a simple uterus, and a double caudal vagina. The persistence of well-differentiated genital ducts of the opposite sex in both males and females, however, singles them out among other species. These structures are the results of an aberration during fetal sexual differentiation and possess secretory functions. The possibility of a pathological degeneration of these organs should be considered in reproductive medicine of the species. CONCLUSION Knowledge of the unique reproductive characteristics of the giant anteater is essential for future reproductive management of the species. Additionally, further research on the peculiarities of the persisting genital duct structures might help to understand sexual differentiation in placental mammals in general.
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Affiliation(s)
- Lilja Fromme
- Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Hannover, Germany
- Institute for Anatomy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Débora R. Yogui
- Project Anteaters and Highways, Instituto de Conservação de Animais Silvestres (ICAS), Campo Grande, Brazil
- Nashville Zoo, Nashville, TN, United States of America
| | - Mario Henrique Alves
- Project Anteaters and Highways, Instituto de Conservação de Animais Silvestres (ICAS), Campo Grande, Brazil
- Fundación Zoológica de Cali, Valle del Cauca, Colombia
| | - Arnaud L.J. Desbiez
- Project Anteaters and Highways, Instituto de Conservação de Animais Silvestres (ICAS), Campo Grande, Brazil
- Royal Zoological Society of Scotland (RZSS), Edinburgh, United Kingdom
- Instituto de Pesquisas Ecológicas (IPÊ), São Paulo, Brazil
| | - Marion Langeheine
- Institute for Anatomy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - André Quagliatto
- Laboratório de Ensino e Pesquisa em Animais Silvestres (LAPAS), Universidade Federal de Uberlândia, Uberlândia, Brazil
| | - Ursula Siebert
- Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Ralph Brehm
- Institute for Anatomy, University of Veterinary Medicine Hannover, Hannover, Germany
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10
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OUP accepted manuscript. J Mammal 2021. [DOI: 10.1093/jmammal/gyab168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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11
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Cunha GR, Liu G, Sinclair A, Cao M, Glickman S, Cooke PS, Baskin L. Androgen-independent events in penile development in humans and animals. Differentiation 2020; 111:98-114. [DOI: 10.1016/j.diff.2019.07.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Revised: 07/11/2019] [Accepted: 07/12/2019] [Indexed: 01/28/2023]
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12
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Baskin L, Shen J, Sinclair A, Cao M, Liu X, Liu G, Isaacson D, Overland M, Li Y, Cunha GR. Development of the human penis and clitoris. Differentiation 2018; 103:74-85. [PMID: 30249413 DOI: 10.1016/j.diff.2018.08.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 08/21/2018] [Accepted: 08/21/2018] [Indexed: 12/17/2022]
Abstract
The human penis and clitoris develop from the ambisexual genital tubercle. To compare and contrast the development of human penis and clitoris, we used macroscopic photography, optical projection tomography, light sheet microscopy, scanning electron microscopy, histology and immunohistochemistry. The human genital tubercle differentiates into a penis under the influence of androgens forming a tubular urethra that develops by canalization of the urethral plate to form a wide diamond-shaped urethral groove (opening zipper) whose edges (urethral folds) fuse in the midline (closing zipper). In contrast, in females, without the influence of androgens, the vestibular plate (homologue of the urethral plate) undergoes canalization to form a wide vestibular groove whose edges (vestibular folds) remain unfused, ultimately forming the labia minora defining the vaginal vestibule. The neurovascular anatomy is similar in both the developing human penis and clitoris and is the key to successful surgical reconstructions.
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Cattet M, Stenhouse GB, Boulanger J, Janz DM, Kapronczai L, Swenson JE, Zedrosser A. Can concentrations of steroid hormones in brown bear hair reveal age class? CONSERVATION PHYSIOLOGY 2018; 6:coy001. [PMID: 29399362 PMCID: PMC5788069 DOI: 10.1093/conphys/coy001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 12/17/2017] [Accepted: 01/05/2018] [Indexed: 06/01/2023]
Abstract
Although combining genetic and endocrine data from non-invasively collected hair samples has potential to improve the conservation of threatened mammals, few studies have evaluated this opportunity. In this study, we determined if steroid hormone (testosterone, progesterone, estradiol and cortisol) concentration profiles in 169 hair samples collected from free-ranging brown bears (Ursus arctos) could be used to accurately discriminate between immature and adult bears within each sex. Because hair samples were acquired opportunistically, we also needed to establish if interactions between hormones and several non-hormone factors (ordinal day, year, contact method, study area) were associated with age class. For each sex, we first compared a suite of candidate models by Akaike Information Criteria model selection, using different adult-age thresholds (3, 4 and 5 years), to determine the most supported adult age. Because hair hormone levels better reflect the endocrine state at an earlier time, possibly during the previous year, then at the time of sampling, we re-analysed the data, excluding the records for bears at the adult-age threshold, to establish if classification accuracy improved. For both sexes, candidate models were most supported based on a 3-year-old adult-age threshold. Classification accuracy did not improve with the 3-year-old bear data excluded. Male age class was predicted with a high degree of accuracy (88.4%) based on the concomitant concentrations of all four hormones. Female age class was predicted with less accuracy (77.1%) based only on testosterone and cortisol. Accuracy was reduced for females, primarily because we had poor success in correctly classifying immature bears (60%) whereas classification success for adult females was similar to that for males (84.5%). Given the small and unbalanced sample used in this study, our findings should be viewed as preliminary, but they should also provide a basis for more comprehensive future studies.
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Affiliation(s)
- Marc Cattet
- RGL Recovery Wildlife Health & Veterinary Services, 415 Mount Allison Crescent, Saskatoon, Saskatchewan S7H 4A6, Canada
- Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4, Canada
| | - Gordon B Stenhouse
- fRI Research and Alberta Environment and Parks, 1176 Switzer Drive, Hinton, Alberta T7V 1X6, Canada
| | - John Boulanger
- Integrated Ecological Research, 924 Innes Street, Nelson, British Columbia V1L 5T2, Canada
| | - David M Janz
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4, Canada
| | - Luciene Kapronczai
- Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada
| | - Jon E Swenson
- Faculty of Environmental Sciences and Nature Resource Management, Norwegian University of Life Sciences, PO Box 5003, NO-1432 Ås, Norway and Norwegian Institute for Nature Research, Høgskoleringen 9, 7034 Trondheim, Norway
| | - Andreas Zedrosser
- Department of Natural Sciences and Environmental Health, Telemark University College of Southeast Norway, NO-3800 Bø i Telemark, Norway
- Department for Integrative Biology, Institute for Wildlife Biology and Game Management, University for Natural Resources and Life Sciences, Vienna A-1180, Austria
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Davies CS, Smyth KN, Greene LK, Walsh DA, Mitchell J, Clutton-Brock T, Drea CM. Exceptional endocrine profiles characterise the meerkat: sex, status, and reproductive patterns. Sci Rep 2016; 6:35492. [PMID: 27752129 PMCID: PMC5067592 DOI: 10.1038/srep35492] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 09/30/2016] [Indexed: 11/17/2022] Open
Abstract
In vertebrates, reproductive endocrine concentrations are strongly differentiated by sex, with androgen biases typifying males and estrogen biases typifying females. These sex differences can be reduced in female-dominant species; however, even the most masculinised of females have less testosterone (T) than do conspecific males. To test if aggressively dominant, female meerkats (Suricata suricatta) may be hormonally masculinised, we measured serum androstenedione (A4), T and estradiol (E2) in both sexes and social classes, during both ‘baseline’ and reproductive events. Relative to resident males, dominant females had greater A4, equivalent T and greater E2 concentrations. Males, whose endocrine values did not vary by social status, experienced increased T during reproductive forays, linking T to sexual behaviour, but not social status. Moreover, substantial E2 concentrations in male meerkats may facilitate their role as helpers. In females, dominance status and pregnancy magnified the unusual concentrations of measured sex steroids. Lastly, faecal androgen metabolites replicated the findings derived from serum, highlighting the female bias in total androgens. Female meerkats are thus strongly hormonally masculinised, possibly via A4’s bioavailability for conversion to T. These raised androgen concentrations may explain female aggressiveness in this species and give dominant breeders a heritable mechanism for their daughters’ competitive edge.
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Affiliation(s)
- Charli S Davies
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Kendra N Smyth
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.,University Program in Ecology, Duke University, Durham, NC 27708, USA
| | - Lydia K Greene
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.,University Program in Ecology, Duke University, Durham, NC 27708, USA
| | - Debbie A Walsh
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Jessica Mitchell
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Tim Clutton-Brock
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Mammal Research Institute, University of Pretoria, Pretoria, South Africa.,Department of Zoology, University of Cambridge, Cambridge, UK
| | - Christine M Drea
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.,University Program in Ecology, Duke University, Durham, NC 27708, USA.,Department of Biology, Duke University, Durham, USA
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Greene LK, Wallen TW, Moresco A, Goodwin TE, Drea CM. Reproductive endocrine patterns and volatile urinary compounds of Arctictis binturong: discovering why bearcats smell like popcorn. Naturwissenschaften 2016; 103:37. [PMID: 27056047 DOI: 10.1007/s00114-016-1361-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 03/22/2016] [Accepted: 03/27/2016] [Indexed: 12/21/2022]
Abstract
Members of the order Carnivora rely on urinary scent signaling, particularly for communicating about reproductive parameters. Here, we describe reproductive endocrine patterns in relation to urinary olfactory cues in a vulnerable and relatively unknown viverrid--the binturong (Arctictis binturong). Female binturongs are larger than and dominate males, and both sexes engage in glandular and urinary scent marking. Using a large (n = 33), captive population, we collected serum samples to measure circulating sex steroids via enzyme immunoassay and urine samples to assay volatile chemicals via gas chromatography-mass spectrometry. Male binturongs had expectedly greater androgen concentrations than did females but, more unusually, had equal estrogen concentrations, which may be linked to male deference. Males also expressed a significantly richer array of volatile chemical compounds than did females. A subset of these volatile chemicals resisted decay at ambient temperatures, potentially indicating their importance as long-lasting semiochemicals. Among these compounds was 2-acetyl-1-pyrroline (2-AP), which is typically produced at high temperatures by the Maillard reaction and is likely to be responsible for the binturong's characteristic popcorn aroma. 2-AP, the only compound expressed by all of the subjects, was found in greater abundance in males than females and was significantly and positively related to circulating androstenedione concentrations in both sexes. This unusual compound may have a more significant role in mammalian semiochemistry than previously appreciated. Based on these novel data, we suggest that hormonal action and potentially complex chemical reactions mediate communication of the binturong's signature scent and convey information about sex and reproductive state.
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Affiliation(s)
- Lydia K Greene
- University Program in Ecology, Duke University, Durham, NC, USA
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
| | - Timothy W Wallen
- Department of Chemistry, Hendrix College, Conway, AR, USA
- National Center for Environmental Health, Division of Laboratory Sciences, Clinical Chemistry Branch, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Anneke Moresco
- Carnivore Preservation Trust (now Carolina Tiger Rescue), 1940 Hanks Chapel Road, Pittsboro, North Carolina, 27312, USA
- Denver Zoo, 2300 Steele Street, Denver, Colorado, 80205, USA
| | | | - Christine M Drea
- University Program in Ecology, Duke University, Durham, NC, USA.
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA.
- Department of Biology, Duke University, Durham, NC, USA.
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16
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Yoshida KCS, Van Meter PE, Holekamp KE. Variation among free-living spotted hyenas in three personality traits. BEHAVIOUR 2016. [DOI: 10.1163/1568539x-00003367] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Inter-individual differences in behaviour, termed ‘animal personality’, are often consistent over time and across contexts and can be significantly related to fitness. However, most studies of animal personality are conducted in the laboratory or involve experimental protocols. Here, we used longitudinal scan and all-occurrence data collected under naturalistic conditions over 21 years to study boldness, aggressiveness, and sociability in a wild population of spotted hyenas (Crocuta crocuta). We found significant variation among individual hyenas in all three traits; however, whereas both sexes exhibited consistent inter-individual differences in aggressiveness and sociability, males were less consistent than females in their boldness. Heritability and maternal effects were small but significant for both boldness and sociability. A large proportion of the variation in aggressiveness could be attributed to genetic and maternal effects, supporting previous research linking hormone exposure in utero to aggressive behaviour later in life. All three traits were correlated with at least one measure of fitness. Particularly aggressive females were more successful in raising their offspring to reproductive maturity than less aggressive females. Interestingly, the reproductive benefits of sociability depended on social rank; for low-ranking hyenas, gaining feeding tolerance via sociability may significantly enhance reproductive success. Both boldness and sociability were linked to survival, but these traits affected longevity in different ways; highly social hyenas lived longer than those that were less social, but selection on boldness was stabilizing, favoring hyenas with intermediate boldness values that balance the benefits of risky behaviour against risks of injury and death.
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Affiliation(s)
- Kathryn C. Shaw Yoshida
- Las Vegas Natural History Museum, 900 Las Vegas Boulevard N, Las Vegas, NV 89101, USA
- Ecology, Evolutionary Biology & Behavior Program, Michigan State University, 293 Farm Lane, Room 103, East Lansing, MI 48824, USA
- Department of Integrative Biology, Michigan State University, 288 Farm Lane, Room 203, East Lansing, MI 48824, USA
| | - Page E. Van Meter
- Department of Integrative Biology, Michigan State University, 288 Farm Lane, Room 203, East Lansing, MI 48824, USA
- Division of Clinical Therapeutics, New York State Psychiatric Institute, 1051 Riverside Drive, New York, NY 10032, USA
| | - Kay E. Holekamp
- Ecology, Evolutionary Biology & Behavior Program, Michigan State University, 293 Farm Lane, Room 103, East Lansing, MI 48824, USA
- Department of Integrative Biology, Michigan State University, 288 Farm Lane, Room 203, East Lansing, MI 48824, USA
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17
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Smyth KN, Drea CM. Patterns of parasitism in the cooperatively breeding meerkat: a cost of dominance for females. Behav Ecol 2015. [DOI: 10.1093/beheco/arv132] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
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18
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Gesquiere LR, Ziegler TE, Chen PA, Epstein KA, Alberts SC, Altmann J. Measuring fecal testosterone in females and fecal estrogens in males: comparison of RIA and LC/MS/MS methods for wild baboons (Papio cynocephalus). Gen Comp Endocrinol 2014; 204:141-9. [PMID: 24798581 PMCID: PMC4155009 DOI: 10.1016/j.ygcen.2014.04.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 04/14/2014] [Accepted: 04/18/2014] [Indexed: 10/25/2022]
Abstract
The development of non-invasive methods, particularly fecal determination, has made possible the assessment of hormone concentrations in wild animal populations. However, measuring fecal metabolites needs careful validation for each species and for each sex. We investigated whether radioimmunoassays (RIAs) previously used to measure fecal testosterone (fT) in male baboons and fecal estrogens (fE) in female baboons were well suited to measure these hormones in the opposite sex. We compared fE and fT concentrations determined by RIA to those measured by liquid chromatography combined with triple quadropole mass spectrometry (LC/MS/MS), a highly specific method. Additionally, we conducted a biological validation to assure that the measurements of fecal concentrations reflected physiological levels of the hormone of interest. Several tests produced expected results that led us to conclude that our RIAs can reliably measure fT and fE in both sexes, and that within-sex comparisons of these measures are valid: (i) fTRIA were significantly correlated to fTLC/MS/MS for both sexes; (ii) fTRIA were higher in adult than in immature males; (iii) fTRIA were higher in pregnant than non-pregnant females; (iv) fERIA were correlated with 17β-estradiol (fE2) and with estrone (fE1) determined by LC/MS/MS in pregnant females; (v) fERIA were significantly correlated with fE2 in non-pregnant females and nearly significantly correlated in males; (vi) fERIA were higher in adult males than in immature males. fERIA were higher in females than in males, as predicted, but unexpectedly, fTRIA were higher in females than in males, suggesting a difference in steroid metabolism in the two sexes; consequently, we conclude that while within-sex comparisons are valid, fTRIA should not be used for intersexual comparisons. Our results should open the field to important additional studies, as to date the roles of testosterone in females and estrogens in males have been little investigated.
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Affiliation(s)
- Laurence R Gesquiere
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA; Department of Biology, Duke University, Durham, NC, USA.
| | - Toni E Ziegler
- National Primate Research Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Patricia A Chen
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Katherine A Epstein
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Susan C Alberts
- Department of Biology, Duke University, Durham, NC, USA; Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya
| | - Jeanne Altmann
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA; Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya; Department of Veterinary Anatomy and Physiology, University of Nairobi, Chiromo Campus, P.O. Box 30197 00100, Nairobi, Kenya
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19
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Development of the external genitalia: perspectives from the spotted hyena (Crocuta crocuta). Differentiation 2014; 87:4-22. [PMID: 24582573 DOI: 10.1016/j.diff.2013.12.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2013] [Revised: 11/14/2013] [Accepted: 12/06/2013] [Indexed: 11/23/2022]
Abstract
This review/research paper summarizes data on development of the external genitalia of the spotted hyena, a fascinating mammal noted for extreme masculinization of the female external genitalia. The female spotted hyena is the only extant mammal that mates and gives birth through a pendulous penis-like clitoris. Our studies indicate that early formation of the phallus in both males and females is independent of androgens; indeed the phallus forms before the fetal testes or ovaries are capable of synthesizing androgens. Likewise, pre- and postnatal growth in length of the penis and clitoris is minimally affected by "androgen status". Nonetheless, several internal morphologies, as well as external surface features of the phallus, are androgen-dependent and thus account for dimorphism between the penis and clitoris. Finally, estrogens play a critical role in penile and clitoral development, specifying the position of the urethral orifice, determining elasticity of the urethral meatus, and facilitating epithelial-epithelial fusion events required for proper formation of the distal urethra/urogenital sinus and prepuce. Accordingly, prenatal inhibition of estrogen synthesis via administration of letrozole (an aromatase inhibitor) leads to malformations of the glans as well as the prepuce (hypospadias). The effects of prenatal androgens, anti-androgens and impaired estrogen synthesis correlated with the tissue expression of androgen and estrogen receptors.
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20
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Swanson EM, McElhinny TL, Dworkin I, Weldele ML, Glickman SE, Holekamp KE. Ontogeny of sexual size dimorphism in the spotted hyena (Crocuta crocuta). J Mammal 2013. [DOI: 10.1644/12-mamm-a-277.1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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21
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French JA, Mustoe AC, Cavanaugh J, Birnie AK. The influence of androgenic steroid hormones on female aggression in 'atypical' mammals. Philos Trans R Soc Lond B Biol Sci 2013; 368:20130084. [PMID: 24167314 PMCID: PMC3826213 DOI: 10.1098/rstb.2013.0084] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dimorphism on dominance and agonistic behaviour in mammals tends to be strongly biased toward males. In this review, we focus on a select few species of mammals in which females are as or more aggressive than males, and/or are dominant to males, and explore the role of androgenic hormones in mediating this important difference. While the data are not as clear-cut as those published on traditional laboratory mammals, our review highlights important endocrine substrates for both organizational and activational influences of steroids on female aggressive behaviour. We highlight areas in which further observations and experiments are crucial, especially the potential facilitative effects of androgens on female aggression. Finally, new and innovative techniques, including molecular genetics and receptor pharmacology, portend important insights into the ways in which androgenic hormones regulate aggressive behaviour in 'atypical' female mammals.
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Affiliation(s)
- Jeffrey A. French
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
- Department of Biology, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Aaryn C. Mustoe
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Jon Cavanaugh
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Andrew K. Birnie
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
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22
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Social dominance and behavioral consequences of intrauterine position in female groups of the social rodent Octodon degus. Physiol Behav 2013; 119:161-7. [DOI: 10.1016/j.physbeh.2013.06.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 05/12/2013] [Accepted: 06/03/2013] [Indexed: 11/17/2022]
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23
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Curren LJ, Weldele ML, Holekamp KE. Ejaculate quality in spotted hyenas: intraspecific variation in relation to life-history traits. J Mammal 2013. [DOI: 10.1644/12-mamm-a-057.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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24
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A comparison of innovative problem-solving abilities between wild and captive spotted hyaenas, Crocuta crocuta. Anim Behav 2013. [DOI: 10.1016/j.anbehav.2012.11.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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25
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Holekamp KE, Smith JE, Strelioff CC, Van Horn RC, Watts HE. Society, demography and genetic structure in the spotted hyena. Mol Ecol 2011; 21:613-32. [PMID: 21880088 DOI: 10.1111/j.1365-294x.2011.05240.x] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spotted hyenas (Crocuta crocuta) are large mammalian carnivores, but their societies, called 'clans', resemble those of such cercopithecine primates as baboons and macaques with respect to their size, hierarchical structure, and frequency of social interaction among both kin and unrelated group-mates. However, in contrast to cercopithecine primates, spotted hyenas regularly hunt antelope and compete with group-mates for access to kills, which are extremely rich food sources, but also rare and ephemeral. This unique occurrence of baboon-like sociality among top-level predators has favoured the evolution of many unusual traits in this species. We briefly review the relevant socio-ecology of spotted hyenas, document great demographic variation but little variation in social structure across the species' range, and describe the long-term fitness consequences of rank-related variation in resource access among clan-mates. We then summarize patterns of genetic relatedness within and between clans, including some from a population that had recently gone through a population bottleneck, and consider the roles of sexually dimorphic dispersal and female mate choice in the generation of these patterns. Finally, we apply social network theory under varying regimes of resource availability to analyse the effects of kinship on the stability of social relationships among members of one large hyena clan in Kenya. Although social bonds among both kin and non-kin are weakest when resource competition is most intense, hyenas sustain strong social relationships with kin year-round, despite constraints imposed by resource limitation. Our analyses suggest that selection might act on both individuals and matrilineal kin groups within clans containing multiple matrilines.
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Affiliation(s)
- Kay E Holekamp
- Department of Zoology, Michigan State University, East Lansing, MI 48824-1115, USA.
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26
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Drea CM. Endocrine correlates of pregnancy in the ring-tailed lemur (Lemur catta): implications for the masculinization of daughters. Horm Behav 2011; 59:417-27. [PMID: 20932838 DOI: 10.1016/j.yhbeh.2010.09.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 09/27/2010] [Accepted: 09/30/2010] [Indexed: 10/19/2022]
Abstract
Female ring-tailed lemurs (Lemur catta) are Malagasy primates that are size monomorphic with males, socially dominate males, and exhibit a long, pendulous clitoris, channeled by the urethra. These masculine traits evoke certain attributes of female spotted hyenas (Crocuta crocuta) and draw attention to the potential role of androgens in lemur sexual differentiation. Here, hormonal correlates of prenatal development were assessed to explore the possibility that maternal androgens may shape the masculine morphological and behavioral features of developing female lemurs. Maternal serum 17α-hydroxyprogesterone, dehydroepiandrosterone sulphate (DHEA-S), ∆⁴ androstenedione (androst-4-ene-3,17,dione), testosterone, and 17β-estradiol were charted throughout the 19 pregnancies of 11 ring-tailed lemurs. As in spotted hyenas, lemur pregnancies were associated with an immediate increase in androgen concentrations (implicating early maternal derivation), followed by continued increases across stages of gestation. Pregnancies that produced singleton males, twin males, or mixed-sex twins were marked by greater androgen and estrogen concentrations than were pregnancies that produced singleton or twin females, especially in the third trimester, implicating the fetal testes in late-term steroid profiles. Concentrations of DHEA-S were mostly below detectable limits, suggesting a minor role for the adrenals in androgen biosynthesis. Androgen concentrations of pregnant lemurs bearing female fetuses, although less than those of pregnant hyenas, exceeded preconception and postpartum values and peaked in the third trimester. Although a maternal (and, on occasion, fraternal) source of androgen may exist for fetal lemurs, further research is required to confirm that these steroids would reach the developing female and contribute to her masculinization.
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Affiliation(s)
- Christine M Drea
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708-0383, USA.
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27
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Place NJ, Coscia EM, Dahl NJ, Drea CM, Holekamp KE, Roser JF, Sisk CL, Weldele ML, Glickman SE. The anti-androgen combination, flutamide plus finasteride, paradoxically suppressed LH and androgen concentrations in pregnant spotted hyenas, but not in males. Gen Comp Endocrinol 2011; 170:455-9. [PMID: 21036174 PMCID: PMC3027151 DOI: 10.1016/j.ygcen.2010.10.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Revised: 10/01/2010] [Accepted: 10/23/2010] [Indexed: 11/28/2022]
Abstract
The androgen receptor blocker flutamide and the 5α-reductase inhibitor finasteride have been used in a variety of species to investigate the ontogeny of sexual dimorphisms by treating pregnant females or neonates at critical periods of sexual differentiation. Likewise, we have used these drugs to study the profound masculinization of the external genitalia in female spotted hyenas. However, a potential pitfall of administering flutamide, either alone or in combination with finasteride, is that it maintains or even raises plasma concentrations of luteinizing hormone (LH) and testosterone (T), because negative feedback of the hypothalamic-pituitary-gonadal axis is disrupted. Contrary to expectations, when pregnant spotted hyenas were treated with flutamide and finasteride (F&F), the concentrations of T during late gestation were suppressed relative to values in untreated dams. Herein, we further investigate the paradoxical effects of F&F treatment on a battery of sex hormones in spotted hyenas. Beyond the effects on T, we found plasma concentrations of LH, estradiol, progesterone and androstenedione (A4) were also significantly lower in F&F-treated pregnant hyenas than in controls. Flutamide and finasteride did not have similar effects on LH, T, and A4 concentrations in male hyenas. The paradoxical effect of F&F treatment on LH and T concentrations in the maternal circulation suggests that negative feedback control of gonadotropin and androgen secretion may be modified in spotted hyenas during pregnancy.
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Affiliation(s)
- Ned J Place
- Department of Population Medicine & Diagnostic Sciences, Cornell University, Ithaca, NY 14853, USA.
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28
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Arsznov BM, Lundrigan BL, Holekamp KE, Sakai ST. Sex and the frontal cortex: A developmental CT study in the spotted hyena. BRAIN, BEHAVIOR AND EVOLUTION 2010; 76:185-97. [PMID: 21088374 DOI: 10.1159/000321317] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 09/13/2010] [Indexed: 11/19/2022]
Abstract
The purpose of this study was to examine developmental and individual variation in total endocranial volume and regional brain volumes, including the anterior cerebrum, posterior cerebrum and cerebellum/brain stem, in the spotted hyena (Crocuta crocuta). The spotted hyena is a highly gregarious animal noted for living in large, hierarchically organized groups. The social lives of male and female spotted hyenas do not differ until after puberty, when males disperse from the natal group, while females remain philopatric. Here we sought to determine whether the divergent life histories of male and female spotted hyenas are linked to differences in brain size or organization. Three-dimensional virtual endocasts were created using computed tomography from 46 spotted hyenas skulls (23 females, 22 males, 1 unknown sex) ranging in age from 1 day to 18 years. Brain volume and skull length were highly correlated (r = 0.91), and both reached asymptotic values by 34 months of age. Analyses of total endocranial volume (relative to skull length) and cerebellum/brain stem volume (relative to total endocranial volume) revealed no sex differences. However, relative anterior cerebrum volume, comprised mainly of frontal cortex, was significantly greater in adult males than adult females, and relative posterior cerebrum volume was greater in adult females than adult males. We hypothesize that the demands of neural processing underlying enhanced social cognition required for successful male transfer between matriarchical social groups at dispersal may be greater than cognitive demands on philopatric females.
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Affiliation(s)
- Bradley M Arsznov
- Department of Psychology, Michigan State University, East Lansing, 48824, USA
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29
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Pangle WM, Holekamp KE. Functions of vigilance behaviour in a social carnivore, the spotted hyaena, Crocuta crocuta. Anim Behav 2010. [DOI: 10.1016/j.anbehav.2010.04.026] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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30
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Mathevon N, Koralek A, Weldele M, Glickman SE, Theunissen FE. What the hyena's laugh tells: sex, age, dominance and individual signature in the giggling call of Crocuta crocuta. BMC Ecol 2010; 10:9. [PMID: 20353550 PMCID: PMC2859383 DOI: 10.1186/1472-6785-10-9] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 03/30/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Among mammals living in social groups, individuals form communication networks where they signal their identity and social status, facilitating social interaction. In spite of its importance for understanding of mammalian societies, the coding of individual-related information in the vocal signals of non-primate mammals has been relatively neglected. The present study focuses on the spotted hyena Crocuta crocuta, a social carnivore known for its complex female-dominated society. We investigate if and how the well-known hyena's laugh, also known as the giggle call, encodes information about the emitter. RESULTS By analyzing acoustic structure in both temporal and frequency domains, we show that the hyena's laugh can encode information about age, individual identity and dominant/subordinate status, providing cues to receivers that could enable assessment of the social position of an emitting individual. CONCLUSIONS The range of messages encoded in the hyena's laugh is likely to play a role during social interactions. This call, together with other vocalizations and other sensory channels, should ensure an array of communication signals that support the complex social system of the spotted hyena. Experimental studies are now needed to decipher precisely the communication network of this species.
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Affiliation(s)
- Nicolas Mathevon
- Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, CA, USA
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31
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Frankand LG, Glickman SE. Giving birth through a penile clitoris: parturition and dystocia in the spotted hyaena (Crocuta crocuta). J Zool (1987) 2009. [DOI: 10.1111/j.1469-7998.1994.tb04871.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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32
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Watts HE, Tanner JB, Lundrigan BL, Holekamp KE. Post-weaning maternal effects and the evolution of female dominance in the spotted hyena. Proc Biol Sci 2009; 276:2291-8. [PMID: 19324728 DOI: 10.1098/rspb.2009.0268] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mammalian societies in which females dominate males are rare, and the factors favouring the evolution of female dominance have yet to be clearly identified. We propose a new hypothesis for the evolution of female dominance and test its predictions with empirical data from the spotted hyena (Crocuta crocuta), a well-studied species characterized by female dominance. We suggest that constraints imposed by the development of a feeding apparatus specialized for bone cracking, in combination with the intensive feeding competition characteristic of spotted hyenas, led to the evolution of female dominance. Specifically, we propose that protracted development of the feeding apparatus in young hyenas led to selection for increased aggressiveness in females as a compensatory mechanism for mothers to secure food access for their young after weaning. Our analyses yielded results consistent with this hypothesis. Morphological and behavioural measurements indicate that skull development is indeed protracted in this species; spotted hyenas do not achieve adult skull size or feeding performance capabilities until after sexual maturity. The period between weaning and completed skull development is particularly challenging, as indicated by high mortality. Finally, maternal presence between weaning and full skull maturity, as well as the relative ability of females to aggressively displace conspecifics from food, are important determinants of offspring survival.
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Affiliation(s)
- Heather E Watts
- Department of Zoology, Michigan State University, East Lansing, MI 48824, USA.
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33
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Van Meter PE, French JA, Dloniak SM, Watts HE, Kolowski JM, Holekamp KE. Fecal glucocorticoids reflect socio-ecological and anthropogenic stressors in the lives of wild spotted hyenas. Horm Behav 2009; 55:329-37. [PMID: 19056392 PMCID: PMC2987620 DOI: 10.1016/j.yhbeh.2008.11.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 11/03/2008] [Accepted: 11/04/2008] [Indexed: 10/21/2022]
Abstract
Our aim was to identify natural and anthropogenic influences on the stress physiology of large African carnivores, using wild spotted hyenas (Crocuta crocuta) as model animals. With both longitudinal data from a single social group, and cross-sectional data from multiple groups, we used fecal glucocorticoids (fGC) to examine potential stressors among spotted hyenas. Longitudinal data from adult members of a group living on the edge of the Masai Mara National Reserve, Kenya, revealed that fGC concentrations were elevated during two periods of social upheaval among adults, especially among younger females; however, prey availability, rainfall, and presence of lions did not influence fGC concentrations among hyenas. Our results suggested that anthropogenic disturbance in the form of pastoralist activity, but not tourism, influenced fGC concentrations among adult male hyenas; rising concentrations of fGC among males over 12 years were significantly correlated with increasing human population density along the edge of the group's home range. As hyenas from this social group were frequently exposed to anthropogenic disturbance, we compared fGC concentrations among these hyenas with those obtained concurrently from hyenas living in three other groups undisturbed by pastoralist activity. We found that fGC concentrations from the undisturbed groups were significantly lower than those in the disturbed group, and we were able to rule out tourism and ecological stressors as sources of variation in fGC among the populations. Thus it appears that both social instability and anthropogenic disturbance, but not the ecological variables examined, elevate fGC concentrations and represent stressors for wild spotted hyenas. Further work will be necessary to determine whether interpopulation variation in stress physiology predicts population decline in groups exposed to intensive anthropogenic disturbance.
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Affiliation(s)
- Page E Van Meter
- Department of Zoology, Michigan State University, East Lansing, MI 48824, USA.
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McFadden D. Masculinization of the mammalian cochlea. Hear Res 2009; 252:37-48. [PMID: 19272340 DOI: 10.1016/j.heares.2009.01.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Revised: 01/08/2009] [Accepted: 01/12/2009] [Indexed: 11/30/2022]
Abstract
Otoacoustic emissions (OAEs) differ between the sexes in humans, rhesus and marmoset monkeys, and sheep. OAEs also are different in a number of special populations of humans. Those basic findings are reviewed and discussed in the context of possible prenatal-androgen effects on the auditory system. A parsimonious explanation for several outcomes is that prenatal exposure to high levels of androgens can weaken the cochlear amplifiers and thereby weaken otoacoustic emissions (OAEs). Prenatal androgen exposure apparently also can alter auditory evoked potentials (AEPs). Some non-hormonal factors possibly capable of producing sex and group differences are discussed, and some speculations are offered about specific cochlear structures that might differ between the two sexes.
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Affiliation(s)
- Dennis McFadden
- Department of Psychology and Center for Perceptual Systems, University of Texas at Austin, Seay Building, 1 University Station, A8000, Austin, TX 78712-0187, USA.
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35
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McFadden D, Pasanen EG, Valero MD, Roberts EK, Lee TM. Effect of prenatal androgens on click-evoked otoacoustic emissions in male and female sheep (Ovis aries). Horm Behav 2009; 55:98-105. [PMID: 18834887 PMCID: PMC2649662 DOI: 10.1016/j.yhbeh.2008.08.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 07/31/2008] [Accepted: 08/26/2008] [Indexed: 11/24/2022]
Abstract
Otoacoustic emissions (OAEs) were measured in male and female Suffolk sheep (Ovis aries). Some sheep had been administered androgens or estrogens during prenatal development, some were gonadectomized after birth, and some were allowed to develop normally. As previously reported for spotted hyenas, gonadectomy did not alter the OAEs for either sex; accordingly, the untreated/intact and the untreated/gonadectomized animals were pooled to form the control groups. The click-evoked otoacoustic emissions (CEOAEs) exhibited by the female control group (N=12) were slightly stronger (effect size=0.42) than those in the male control group (N=15), which is the same direction of effect reported for humans and rhesus monkeys. Females administered testosterone prenatally (N=16) had substantially weaker (masculinized) CEOAEs than control females (effect size=1.15). Both of these outcomes are in accord with the idea that prenatal exposure to androgens weakens the cochlear mechanisms that underlie the production of OAEs. The CEOAEs of males administered testosterone prenatally (N=5) were not different from those of control males, an outcome also seen in similarly treated rhesus monkeys. Males administered dihydrotestosterone (DHT) prenatally (N=3) had slightly stronger (hypo-masculinized) CEOAEs than control males. No spontaneous otoacoustic emissions (SOAEs) were found in any ears, a common finding in non-human species. To our knowledge, this is the first ruminant species measured for OAEs.
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Affiliation(s)
- Dennis McFadden
- Department of Psychology and Center for Perceptual Systems, University of Texas at Austin, 1 University Station A8000, Austin, TX 78712-0187, USA.
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36
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Smith JE, Kolowski JM, Graham KE, Dawes SE, Holekamp KE. Social and ecological determinants of fission–fusion dynamics in the spotted hyaena. Anim Behav 2008. [DOI: 10.1016/j.anbehav.2008.05.001] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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37
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McFadden D. What Do Sex, Twins, Spotted Hyenas, ADHD, and Sexual Orientation Have in Common? PERSPECTIVES ON PSYCHOLOGICAL SCIENCE 2008; 3:309-23. [DOI: 10.1111/j.1745-6924.2008.00082.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The otoacoustic emissions (OAEs) measured in a collection of special populations of humans and certain nonhuman species suggest that OAEs may provide a window into some processes of human prenatal development and sexual differentiation. For reasons that are unclear, OAEs appear to be highly sensitive to events occurring during prenatal development that seem to be related to the degree of exposure to androgens a fetus receives. The (largely circumstantial) evidence for a relationship between androgen exposure and OAE strength comes from a series of studies of twins, children with attention-deficit/hyperactivity disorder, people of differing sexual orientations, and spotted hyenas, among others. Some conclusions are bolstered by parallel studies using auditory evoked potentials (AEPs). OAEs and AEPs are simple, objective, noninvasive measures that appear to have potential as tools of value to researchers working on a wide variety of basic and applied topics beyond audition.
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Affiliation(s)
- Dennis McFadden
- Department of Psychology and Center for Perceptual Systems, University of Texas
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38
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Drea CM, Weil A. External genital morphology of the ring-tailed lemur (Lemur catta): females are naturally "masculinized". J Morphol 2008; 269:451-63. [PMID: 17972270 DOI: 10.1002/jmor.10594] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The extravagance and diversity of external genitalia have been well characterized in male primates; however, much less is known about sex differences or variation in female form. Our study represents a departure from traditional investigations of primate reproductive anatomy because we 1) focus on external rather than internal genitalia, 2) measure both male and female structures, and 3) examine a strepsirrhine rather than an anthropoid primate. The subjects for morphological study were 21 reproductively intact, adult ring-tailed lemurs (Lemur catta), including 10 females and 11 males, two of which (one per sex) subsequently died of natural causes and also served as specimens for gross anatomical dissection. Male external genitalia presented a typical masculine configuration, with a complex distal penile morphology. In contrast, females were unusual among mammals, presenting an enlarged, pendulous external clitoris, tunneled by the urethra. Females had a shorter anogenital distance and a larger urethral meatus than did males, but organ diameter and circumference showed no sex differences. Dissection confirmed these characterizations. Noteworthy in the male were the presence of a "levator penis" muscle and discontinuity in the corpus spongiosum along the penile shaft; noteworthy in the female were an elongated clitoral shaft and glans clitoridis. The female urethra, while incorporated within the clitoral body, was not surrounded by erectile tissue, as we detected no corpus spongiosum. The os clitoridis was 43% the length and 24% the height of the os penis. On the basis of these first detailed descriptions of strepsirrhine external genitalia (for either sex), we characterize those of the female ring-tailed lemur as moderately "masculinized." Our results highlight certain morphological similarities and differences between ring-tailed lemurs and the most male-like of female mammals, the spotted hyena (Crocuta crocuta), and call attention to a potential hormonal mechanism of "masculinization" in female lemur development.
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Affiliation(s)
- Christine M Drea
- Department of Biological Anthropology and Anatomy, Duke University, Durham, North Carolina 27708-0383, USA.
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39
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Van Meter PE, French JA, Bidali K, Weldele ML, Brown JL, Holekamp KE. Non-invasive measurement of fecal estrogens in the spotted hyena (Crocuta crocuta). Gen Comp Endocrinol 2008; 155:464-71. [PMID: 17884046 PMCID: PMC2255063 DOI: 10.1016/j.ygcen.2007.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Revised: 08/01/2007] [Accepted: 08/02/2007] [Indexed: 11/28/2022]
Abstract
Fecal hormone analysis is a useful tool for frequent, non-invasive sampling of free-living animals. Estrogens fluctuate throughout life among reproductive states in female animals, and intensive repetitive sampling can permit accurate assessment of female reproductive condition. This type of repetitive sampling is difficult in large carnivores, including the spotted hyena (Crocuta crocuta). Patterns of estrogen secretion in captive and free-living hyenas are virtually unknown. Here we present validation of an enzyme-immunoassay to measure fecal estrogen (fE) concentrations in wild and captive spotted hyenas. Results from high-performance liquid chromatography indicate that an antibody specific for estradiol exhibits high immunoreactivity with our extracted samples. Fecal extract displacement curves paralleled our estradiol standard curve within the range of 20-80% antibody binding. Additionally, animals treated with luteinizing hormone-releasing hormone showed a measurable rise in fE concentrations. Finally, once we controlled for effects of time of day of sample collection from wild hyenas, patterns in fE concentrations resembled those in plasma estradiol, including higher levels of fE in mature than immature females, and higher levels of fE during late than early pregnancy. Together, these results suggest that fE concentrations reflect circulating estrogens in spotted hyenas.
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Affiliation(s)
- Page E Van Meter
- Department of Zoology, Michigan State University, East Lansing, MI 48824, USA.
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40
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Conley AJ, Corbin CJ, Browne P, Mapes SM, Place NJ, Hughes AL, Glickman SE. Placental Expression and Molecular Characterization of Aromatase Cytochrome P450 in the Spotted Hyena (Crocuta crocuta). Placenta 2007; 28:668-75. [PMID: 17198727 DOI: 10.1016/j.placenta.2006.11.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 11/13/2006] [Accepted: 11/17/2006] [Indexed: 11/29/2022]
Abstract
At birth, the external genitalia of female spotted hyenas (Crocuta crocuta) are the most masculinized of any known mammal, but are still sexually differentiated. Placental aromatase cytochrome P450 (P450arom) is an important route of androgen metabolism protecting human female fetuses from virilization in utero. Therefore, placental P450arom expression was examined in spotted hyenas to determine levels during genital differentiation, and to compare molecular characteristics between the hyena and human placental enzymes. Hyena placental P450arom activity was determined at gestational days (GD) 31, 35, 45, 65 and 95 (term, 110), and the relative sensitivity of hyena and human placental enzyme to inhibition by the specific inhibitor, Letrozole, was also examined. Expression of hyena P450arom in placenta was localized by immuno-histochemistry, and a full-length cDNA was cloned for phylogenetic analysis. Aromatase activity increased from GD31 to a peak at 45 and 65, apparently decreasing later in gestation. This activity was more sensitive to inhibition by Letrozole than was human placental aromatase activity. Expression of P450arom was localized to syncytiotrophoblast and giant cells of mid-gestation placentas. The coding sequence of hyena P450arom was 94% and 86% identical to the canine and human enzymes respectively, as reflected by phylogenetic analyses. These data demonstrate for the first time that hyena placental aromatase activity is comparable to that of human placentas when genital differentiation is in progress. This suggests that even in female spotted hyenas clitoral differentiation is likely protected from virilization by placental androgen metabolism. Decreased placental aromatase activity in late gestation may be equally important in allowing androgen to program behaviors at birth. Although hyena P450arom is closely related to the canine enzyme, both placental anatomy and P450arom expression differ. Other hyaenids and carnivores must be investigated to determine the morphological and functional ancestral state of their placentas, as it relates to evolutionary relationships among species in this important taxonomic group.
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Affiliation(s)
- A J Conley
- Department of Population Health & Reproduction, School of Veterinary Medicine, University of California, 1 Shields Avenue, Davis, CA 95616, USA.
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41
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White PP. Maternal response to neonatal sibling conflict in the spotted hyena, Crocuta crocuta. Behav Ecol Sociobiol 2007. [DOI: 10.1007/s00265-007-0422-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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42
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Drea CM. Sex and seasonal differences in aggression and steroid secretion in Lemur catta: are socially dominant females hormonally 'masculinized'? Horm Behav 2007; 51:555-67. [PMID: 17382329 DOI: 10.1016/j.yhbeh.2007.02.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 02/12/2007] [Accepted: 02/14/2007] [Indexed: 11/20/2022]
Abstract
Female social dominance characterizes many strepsirrhine primates endemic to Madagascar, but currently there is no comprehensive explanation for how or why female lemurs routinely dominate males. Reconstructing the evolutionary pressures that may have shaped female dominance depends on better understanding the mechanism of inheritance, variation in trait expression, and correlating variables. Indeed, relative to males, many female lemurs also display delayed puberty, size monomorphism, and 'masculinized' external genitalia. As in the spotted hyena (Crocuta crocuta), a species characterized by extreme masculinization of the female, this array of traits focuses attention on the role of androgens in female development. Consequently, I examined endocrine profiles and social interaction in the ringtailed lemur (Lemur catta) to search for a potential source of circulating androgen in adult females and an endocrine correlate of female dominance or its proxy, aggression. I measured serum androstenedione (A(4)), testosterone (T), and estradiol (E(2)) in reproductively intact, adult lemurs (10 females; 12 males) over four annual cycles. Whereas T concentrations in males far exceeded those in females, A(4) concentrations were only slightly greater in males than in females. In both sexes, A(4) and T were positively correlated, implicating the Delta(4)-biosynthetic pathway. Moreover, seasonal changes in reproductive function in both sexes coincided with seasonal changes in behavior, with A(4) and T in males versus A(4) and E(2) in females increasing during periods marked by heightened aggression. Therefore, A(4) and/or E(2) may be potentially important steroidal sources in female lemurs that could modulate aggression and underlie a suite of masculinized features.
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Affiliation(s)
- Christine M Drea
- Department of Biological Anthropology and Anatomy, Duke University, 08 Biological Sciences Bldg., Box 90383, Durham, NC 27708-0383, USA.
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43
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Rank-related partner choice in the fission–fusion society of the spotted hyena (Crocuta crocuta). Behav Ecol Sociobiol 2006. [DOI: 10.1007/s00265-006-0305-y] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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44
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Glickman SE, Cunha GR, Drea CM, Conley AJ, Place NJ. Mammalian sexual differentiation: lessons from the spotted hyena. Trends Endocrinol Metab 2006; 17:349-56. [PMID: 17010637 DOI: 10.1016/j.tem.2006.09.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 09/06/2006] [Accepted: 09/18/2006] [Indexed: 10/24/2022]
Abstract
Female spotted hyenas (Crocuta crocuta) are the only female mammals that lack an external vaginal opening. Mating and birth take place through a urogenital canal that exits at the tip of a hypertrophied clitoris. This 'masculine' phenotype spurred a search for an alternate source of fetal androgens. Although androstenedione from the maternal ovary is readily metabolized to testosterone by the hyena placenta, formation of the penile clitoris and scrotum appear to be largely androgen independent. However, secretions from the fetal testes underlie sex differences in the genitalia and central nervous system that are essential for male reproduction. Naturally circulating androgens, acting prenatally, reduce reproductive success in adult female spotted hyenas. Effects on aggression and dominance might offset these reproductive 'costs' of female androgenization in utero.
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Affiliation(s)
- Stephen E Glickman
- Departments of Psychology and Integrative Biology, University of California, Berkeley, CA 94720, USA.
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45
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McFadden D, Pasanen EG, Weldele ML, Glickman SE, Place NJ. Masculinized otoacoustic emissions in female spotted hyenas (Crocuta crocuta). Horm Behav 2006; 50:285-92. [PMID: 16682033 DOI: 10.1016/j.yhbeh.2006.03.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Revised: 03/22/2006] [Accepted: 03/23/2006] [Indexed: 10/24/2022]
Abstract
In humans and rhesus monkeys, click-evoked otoacoustic emissions (CEOAEs) are stronger in females than in males, and there is considerable circumstantial evidence that this sex difference is attributable to the greater exposure to androgens prenatally in males. Because female spotted hyenas are highly androgenized beginning early in prenatal development, we expected an absence of sexual dimorphism in the CEOAEs of this species. The CEOAEs obtained from 9 male and 7 female spotted hyenas confirmed that expectation. The implication is that the marked androgenization to which female spotted hyenas are exposed masculinizes the cochlear mechanism responsible for CEOAEs. The CEOAEs measured in 3 male and 3 female hyenas that had been treated with anti-androgenic agents during prenatal development were stronger than the CEOAEs of the untreated animals, in accord with the implied inverse relationship between prenatal androgen exposure and the strength of the cochlear mechanisms producing CEOAEs. The CEOAEs of three ovariectomized females and two castrated males were essentially the same as those for the untreated females and males, suggesting that there is little or no activational effect of hormones on CEOAE strength in spotted hyenas. Distortion product OAEs (DPOAEs) also were measured. Those sex differences also were generally small (as they are in humans), and the effects of the anti-androgen agents were inconsistent. Thus, prenatal androgen exposure apparently does affect OAEs, but the effects appear to be greater for the reflection-based cochlear mechanism that underlies CEOAEs than for the nonlinear cochlear mechanism underlying DPOAEs.
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Affiliation(s)
- Dennis McFadden
- Department of Psychology and Center for Perceptual Systems, University of Texas, 1 University Station A8000, Austin, TX 78712-0187, USA.
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46
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Koren L, Mokady O, Geffen E. Elevated testosterone levels and social ranks in female rock hyrax. Horm Behav 2006; 49:470-7. [PMID: 16313907 DOI: 10.1016/j.yhbeh.2005.10.004] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Revised: 10/16/2005] [Accepted: 10/18/2005] [Indexed: 11/17/2022]
Abstract
In mammals, males maintain significantly higher testosterone (T, 'the male hormone') levels than females throughout the year and are typically dominant over females. Our study of the cooperatively breeding rock hyrax (Procavia capensis) demonstrated a distinct exception. In most hyrax social groups that we studied, adult females were at the highest social rank within the group and showed higher than or equal T levels to males. To our knowledge, this is the first reported instance of adult female mammals demonstrating higher T levels than adult males. However, although T levels significantly correlated with rank in males, in females such correlations were not detected, suggesting a more complex interplay between behavior and endocrine factors in this species.
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Affiliation(s)
- Lee Koren
- Department of Zoology, Tel-Aviv University, Tel Aviv 69978, Israel
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47
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Beehner JC, Phillips-Conroy JE, Whitten PL. Female testosterone, dominance rank, and aggression in an Ethiopian population of hybrid baboons. Am J Primatol 2005; 67:101-19. [PMID: 16163721 DOI: 10.1002/ajp.20172] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Studies on the relationship between female testosterone (T) measures and behavior, particularly in free-ranging primate populations, remain scant. In this study we used fecal steroid analysis to examine the effects of seasonal, reproductive, and social factors on female T in a group of free-ranging hybrid baboons (Papio sp.) in the Awash National Park of Ethiopia. We collected behavioral and hormonal data from 25 adult females across an 11-month period. Solid phase extraction and radioimmunoassay (RIA) techniques were used to quantify T in 776 fecal samples collected weekly from each female. The results indicate that 1) the females had elevated T during pregnancy and during the wet season relative to other periods, 2) female dominance rank was positively related to T measures, and 3) female T and aggression were positively related within subjects but not across subjects. Higher T concentrations during pregnancy are consistent with other published profiles of pregnancy in primates. In combination with data on foraging, wet season increases in T may indicate contest competition for females. The rank-T relationship may be mediated by supplants or aggression. Finally, we discuss the different interpretations of the hormone-behavior relationship based on within- and across-subject analyses.
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Affiliation(s)
- Jacinta C Beehner
- Department of Anthropology, Washington University, St. Louis, Missouri, USA.
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48
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Glickman SE, Short RV, Renfree MB. Sexual differentiation in three unconventional mammals: spotted hyenas, elephants and tammar wallabies. Horm Behav 2005; 48:403-17. [PMID: 16197946 DOI: 10.1016/j.yhbeh.2005.07.013] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 07/01/2005] [Accepted: 07/06/2005] [Indexed: 11/17/2022]
Abstract
The present review explores sexual differentiation in three non-conventional species: the spotted hyena, the elephant and the tammar wallaby, selected because of the natural challenges they present for contemporary understanding of sexual differentiation. According to the prevailing view of mammalian sexual differentiation, originally proposed by Alfred Jost, secretion of androgen and anti-Mullerian hormone (AMH) by the fetal testes during critical stages of development accounts for the full range of sexually dimorphic urogenital traits observed at birth. Jost's concept was subsequently expanded to encompass sexual differentiation of the brain and behavior. Although the central focus of this review involves urogenital development, we assume that the novel mechanisms described in this article have potentially significant implications for sexual differentiation of brain and behavior, a transposition with precedent in the history of this field. Contrary to the "specific" requirements of Jost's formulation, female spotted hyenas and elephants initially develop male-type external genitalia prior to gonadal differentiation. In addition, the administration of anti-androgens to pregnant female spotted hyenas does not prevent the formation of a scrotum, pseudoscrotum, penis or penile clitoris in the offspring of treated females, although it is not yet clear whether the creation of masculine genitalia involves other steroids or whether there is a genetic mechanism bypassing a hormonal mediator. Wallabies, where sexual differentiation occurs in the pouch after birth, provide the most conclusive evidence for direct genetic control of sexual dimorphism, with the scrotum developing only in males and the pouch and mammary glands only in females, before differentiation of the gonads. The development of the pouch and mammary gland in females and the scrotum in males is controlled by genes on the X chromosome. In keeping with the "expanded" version of Jost's formulation, secretion of androgens by the fetal testes provides the best current account of a broad array of sex differences in reproductive morphology and endocrinology of the spotted hyena, and androgens are essential for development of the prostate and penis of the wallaby. But the essential circulating androgen in the male wallaby is 5alpha androstanediol, locally converted in target tissues to DHT, while in the pregnant female hyena, androstenedione, secreted by the maternal ovary, is converted by the placenta to testosterone (and estradiol) and transferred to the developing fetus. Testicular testosterone certainly seems to be responsible for the behavioral phenomenon of musth in male elephants. Both spotted hyenas and elephants display matrilineal social organization, and, in both species, female genital morphology requires feminine cooperation for successful copulation. We conclude that not all aspects of sexual differentiation have been delegated to testicular hormones in these mammals. In addition, we suggest that research on urogenital development in these non-traditional species directs attention to processes that may well be operating during the sexual differentiation of morphology and behavior in more common laboratory mammals, albeit in less dramatic fashion.
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Affiliation(s)
- Stephen E Glickman
- Department of Psychology, University of California, Berkeley, California 94720, USA.
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49
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Sexually dimorphic patterns of space use throughout ontogeny in the spotted hyena ( Crocuta crocuta ). J Zool (1987) 2005. [DOI: 10.1017/s0952836905007478] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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50
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Carmichael LE, Krizan P, Polischuk Blum S, Strobeck C. GENOTYPING OF PSEUDOHERMAPHRODITE POLAR BEARS IN NUNAVUT AND ADVANCES IN DNA SEXING TECHNIQUES. J Mammal 2005. [DOI: 10.1644/1545-1542(2005)086<0160:goppbi>2.0.co;2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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