1
|
Pace C, Goertz CEC, Woodie K, Belovarac J, Rouse N, Abraham T, Tuomi P, Garner MM. HISTOLOGIC ANALYSIS OF TESTICULAR DEVELOPMENT AND SEXUAL MATURATION IN REHABILITATED NORTHERN SEA OTTERS ( ENHYDRA LUTRIS KENYONI). J Zoo Wildl Med 2023; 54:367-373. [PMID: 37428701 DOI: 10.1638/2022-0129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/23/2023] [Indexed: 07/12/2023] Open
Abstract
As part of routine captive management of the species, sea otter (Enhydra lutris) males are often castrated to prevent reproduction, to preserve limited spaces for future nonreleasable stranded individuals, and to minimize potential aggression among cohorts. To determine the relative stage of testicular development, testicles from 14 castrated, rehabilitated northern sea otters (Enhydra lutris kenyoni) were submitted for histologic examination. Eight of the otters (aged 201, 304, 344, 352, 360, 373, 401, and 1,423 d old) had evidence of varying degrees of sexual maturity. Histologic grading of maturity of individual testicles showed inactive testes, spermatocytes with some maturation of spermatogenic precursors, and fully active spermatogenesis. Spermatozoa were seen in the otters that were 401 and 1,423 d old (1.1 and 3.9 yr old). Sexual maturity for wild male sea otters in Alaska has been previously reported to occur from 3 to 5-6 yr. Social maturity, or the ability to breed and reproduce, may occur a few years later than the onset of physiologic maturity; age, weight, territory quality, and the length of time holding a territory may influence a male otter's mating success. Early testicular development in rehabilitated sea otters may be related to abundant resources, lack of competition, and decreased environmental pressures. Additionally, these findings have implications for husbandry and management practices in short- and long-term care facilities.
Collapse
Affiliation(s)
| | | | | | | | - Natalie Rouse
- Alaska SeaLife Center, Seward, AK 99664, USA
- Alaska Veterinary Pathology Service, AK 99577, USA
| | - Taylor Abraham
- University of California-Davis, School of Veterinary Medicine, Davis, CA 95616, USA
| | | | | |
Collapse
|
2
|
Rogers FD, Peña CJ, Mallarino R. African striped mice (Rhabdomys pumilio) as a neurobehavioral model for male parental care. Horm Behav 2023; 152:105364. [PMID: 37087766 DOI: 10.1016/j.yhbeh.2023.105364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 03/27/2023] [Accepted: 04/12/2023] [Indexed: 04/25/2023]
Abstract
Parental care is diversely demonstrated across the animal kingdom, such that active practitioners and repertoires of parental behavior vary dramatically between and within taxa. For mammals, maternal care is ubiquitous while paternal and alloparental care are rare. The African striped mouse, a rodent species in the family Muridae, demonstrates maternal, paternal, and alloparental care. Because socio-environmental factors can considerably influence the development of their social behavior, including that of paternal and alloparental care, African striped mice are considered socially flexible. Here, we highlight African striped mice as a new model for the neurobiological study of male parental care. We first provide essential background information on the species' natural ecological setting and reproductive behavior, as well as the species-relevant interaction between ecology and reproduction. We then introduce the nature of maternal, paternal, and alloparental care in the species. Lastly, we provide a review of existing developmental and neurobiological perspectives and highlight potential avenues for future research.
Collapse
Affiliation(s)
- Forrest Dylan Rogers
- Princeton Neuroscience Institute, Princeton University, Washington Rd., Princeton, NJ 08544, United States of America; Department of Molecular Biology, Princeton University, 119 Lewis Thomas Laboratory, Washington Rd., Princeton, NJ 08544, United States of America.
| | - Catherine Jensen Peña
- Princeton Neuroscience Institute, Princeton University, Washington Rd., Princeton, NJ 08544, United States of America
| | - Ricardo Mallarino
- Department of Molecular Biology, Princeton University, 119 Lewis Thomas Laboratory, Washington Rd., Princeton, NJ 08544, United States of America
| |
Collapse
|
3
|
Rochais C, Schradin C, Pillay N. Cognitive performance is linked to survival in free-living African striped mice. Proc Biol Sci 2023; 290:20230205. [PMID: 36883277 PMCID: PMC9993040 DOI: 10.1098/rspb.2023.0205] [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] [Indexed: 03/09/2023] Open
Abstract
Cognition is shaped by evolution and is predicted to increase fitness. However, the link between cognition and fitness in free-living animals is unresolved. We studied the correlates of cognition and survival in a free-living rodent inhabiting an arid environment. We tested 143 striped mice (Rhabdomys pumilio) using a battery of cognitive tests, including: (i) an attention task, (ii) two problem-solving tasks, (iii) a learning and reversal learning task, and (iv) an inhibitory control task. We related cognitive performance with days of survival. Better problem-solving and inhibitory control performance were significant correlates of survival. Surviving males showed greater reversal learning which may be related to sex-specific behavioural and life-history characteristics. Specific cognitive traits and not a composite measure of general intelligence underpins fitness in this free-living rodent population, enhancing our understanding of the evolution of cognition in non-human animals.
Collapse
Affiliation(s)
- Celine Rochais
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Braamfontein 2000, Johannesburg, South Africa
| | - Carsten Schradin
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Braamfontein 2000, Johannesburg, South Africa
- IPHC, UNISTRA, CNRS, 23 Rue du Loess, 67200 Strasbourg, France
| | - Neville Pillay
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Braamfontein 2000, Johannesburg, South Africa
| |
Collapse
|
4
|
Weil R, Pillay N, Rochais C. Characteristics influencing local enhancement in free-living striped mice. Behav Processes 2022; 197:104621. [PMID: 35301065 DOI: 10.1016/j.beproc.2022.104621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 02/22/2022] [Accepted: 03/10/2022] [Indexed: 11/02/2022]
Abstract
Social learning is widespread across species; however, we still know little about the impact of individual differences in behaviour on social transmission. We aimed to investigate factors influencing social learning in free-living Rhabdomys pumilio, a group-living, arid-adapted mouse. We studied 52 mice in a lid opening task in a field laboratory. We created observer-demonstrator dyads with demonstrators either opening lids or not. We measured success of observers to open lids, their attention and latency to open and time spent interacting with the device. We also considered influences of observer age, sex, group size and personality traits. Demonstrator success did not influence observer success, although attention towards the demonstrator did impact the observers' time spent with the device. Males were more successful than females and more active/explorative observers interacted with the device faster and for a longer time compared to less active/explorative counterparts. We found no influence of age and group size on mouse success. Striped mice appeared to use cues from other individuals to learn how to solve the task and it was influenced by sex and personality. Striped mice in this studied population may use local enhancement to acquire information socially.
Collapse
Affiliation(s)
- Richard Weil
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.
| | - Neville Pillay
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Céline Rochais
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| |
Collapse
|
5
|
Making sense of strengths and weaknesses observed in adolescent lab rodents. Curr Opin Psychol 2022; 45:101297. [DOI: 10.1016/j.copsyc.2021.12.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 12/16/2021] [Accepted: 12/28/2021] [Indexed: 11/19/2022]
|
6
|
Kanyile SN, Pillay N, Schradin C. Bachelor groups form due to individual choices or environmental disrupters in African striped mice. Anim Behav 2021. [DOI: 10.1016/j.anbehav.2021.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
7
|
Seasonal changes in problem-solving in wild African striped mice. Anim Cogn 2021; 25:401-413. [PMID: 34591197 DOI: 10.1007/s10071-021-01559-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 08/20/2021] [Accepted: 09/04/2021] [Indexed: 10/20/2022]
Abstract
Innovative problem-solving ability is a predictor of whether animals can successfully cope with environmental changes. These environmental changes can test the limits of animals, for example when energy availability decreases seasonally and, hence, problem-solving performance decreases because less energy is available for cognitive processes. Here, we investigated: (1) how problem-solving performance changed between seasons that differed significantly in food availability; (2) whether these changes were related to environmentally induced physiological changes in blood glucose and ketone levels, indicators of energy availability; and (3) whether individual variation in problem-solving was related to sex differences. We studied 99 free-ranging African striped mice, Rhabdomys pumilio, in the Succulent Karoo, South Africa, 55 during the hot dry summer with low food availability and 44 during the cold wet winter with higher food availability. We measured their problem-solving abilities using a food extraction task and found no seasonal differences in problem-solving success. However, mice solved the problem faster in summer versus winter. In summer, food availability was reduced and blood ketones increased but there was no seasonal difference in blood glucose levels. There were no correlation between problem-solving performance and blood glucose or ketone levels. Overall, more males solved the task than females. It appears that in striped mice cognitive functions can be maintained under harsh environmental conditions.
Collapse
|
8
|
Rimbach R, Pillay N, Schradin C. Prolonged growth during the food-restricted dry season in a small African mammal. J Mammal 2021. [DOI: 10.1093/jmammal/gyaa169] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
Studying how different environmental parameters, such as resource availability and ambient temperature, affect growth rates aids to understand the evolution of different growth strategies. Low levels of food availability restrict growth, and high ambient temperature can constrain growth via trade-offs between body temperature maintenance and heat produced during digestion. We studied growth of African striped mice (Rhabdomys pumilio), a small mammal living in a seasonally arid habitat. Striped mice are born during spring with high food availability and low ambient temperature, and typically enter the food-restricted dry season before reaching adulthood. We predicted low food availability and high ambient temperature would negatively affect growth. We therefore expected an extended period of slow growth during the long dry season. We repeatedly measured body length of 369 free-living individuals, examined how ambient temperature and food availability influenced growth rate, and seasonal changes in growth rate. In addition, we investigated whether mice (N = 27) born in summer (atypical breeding season) have slower growth rates than those born in spring. Growth rate increased with increasing food availability and decreased with increasing ambient temperature. Individuals born in summer grew slower than those born in spring. Sexes reached asymptotic body length at 258 days (females) and 285 days (males), which is an unusually long growth period compared with other small rodents. As most striped mice live for less than 1 year, this period encompasses the entire life for most individuals, but stops at old age, which could indicate senescence. Our results demonstrate a positive influence of food availability on growth, a relationship mediated by ambient temperature. We conclude that striped mice enter the food-restricted dry season before postnatal growth is terminated, and early exposure to harsh environmental conditions during the long dry season likely explains the prolonged growth period in striped mice.
Collapse
Affiliation(s)
- Rebecca Rimbach
- School of Animal, Plant, and Environmental Sciences, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein 2001, Johannesburg, South Africa
| | - Neville Pillay
- School of Animal, Plant, and Environmental Sciences, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein 2001, Johannesburg, South Africa
| | - Carsten Schradin
- School of Animal, Plant, and Environmental Sciences, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein 2001, Johannesburg, South Africa
- Université de Strasbourg, CNRS, UMR 7178, Institut Pluridisciplinaire Hubert Curien, Département Écologie, Physiologie et Éthologie, 23, rue Becquerel, F-67000 Strasbourg, France
| |
Collapse
|
9
|
Rochais C, Pillay N, Schradin C. Do alternative reproductive tactics predict problem-solving performance in African striped mice? Anim Cogn 2021; 24:703-716. [PMID: 33420858 DOI: 10.1007/s10071-020-01459-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 12/08/2020] [Accepted: 12/11/2020] [Indexed: 11/24/2022]
Abstract
In changing environments, animals face unexpected problems to solve. Not all individuals in a population are equally able to solve new problems. It still remains unclear what factors (e.g. age and body condition) influence the propensity of problem solving. We investigated variation in problem-solving performance among males following alternative reproductive tactics (ARTs). We studied a free-ranging population of the African striped mouse (Rhabdomys pumilio). Adult male striped mice can employ 3 ARTs: (1) dominant group-living breeders, (2) philopatric living in their natal group, and (3) solitary-living roamers. ARTs in male striped mice reflect differences in competitiveness, sociality and physiology which could influence their problem-solving performance. We tested a total of 48 males in 2 years with two tasks: a string-pulling task to reach food and a door-opening task to reach the nest. Since male striped mice differ in personality traits independent of ARTs, we also measured activity, boldness and exploration. In addition, we assessed the association of body condition and age with problem solving. Problem solving was related the interaction of age and ARTs. The younger philopatrics had better performance in a food-extraction task whereas the older breeders were faster at solving the door-opening task. Individual differences in traits related to personality were significant correlates of problem-solving performance: pro-active mice (i.e. more active and explorative and bolder) performed better in both tasks. Finally, problem-solving performance was not consistent between the two tasks. Our study provides evidence of correlates of ARTs, age and personality on problem-solving abilities.
Collapse
Affiliation(s)
- Celine Rochais
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.
| | - Neville Pillay
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Carsten Schradin
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.,IPHC, UNISTRA, CNRS, 23 Rue du Loess, 67200, Strasbourg, France
| |
Collapse
|
10
|
Vobrubová B, Fraňková M, Štolhoferová I, Kaftanová B, Rudolfová V, Chomik A, Chumová P, Stejskal V, Palme R, Frynta D. Relationship between exploratory activity and adrenocortical activity in the black rat (Rattus rattus). JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 335:286-295. [PMID: 33411407 DOI: 10.1002/jez.2440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 12/18/2020] [Accepted: 12/22/2020] [Indexed: 11/05/2022]
Abstract
The relationship between physiological and behavioral stress markers is documented in several rodent species. However, there is no information regarding the role of adrenocortical activity in behavior of the black rat (Rattus rattus). Therefore, we hypothesize that the adrenocortical activity of black rats varies between individuals and is related to some of the behaviors in a novel environment. To test this hypothesis, we (i) validated a method for quantifying glucocorticoid metabolites from feces (fGCMs) with an enzyme immunoassay (EIA); (ii) examined variation and diurnal rhythms of feces and GCM production; and (iii) examined the relationship between GCM levels and exploratory behavioral traits. We fulfilled the first aim (i) by successfully performing an ACTH challenge test to validate the use of a 5α-pregnane-3β,11β,21-triol-20-one EIA for measuring fGCMs. Second (ii) we detected considerable consistent interindividual variability in production of both feces and glucocorticoids. The peak production of feces occurred in the first hour of the dark cycle, the peak of fGCMs occurred approximately 3 h later. Lastly, (iii) there was no clear relationship between behavior in the hole board test and GCMs. Grooming, a typical behavioral stress marker, was negatively associated with stress reactivity, while head-dipping in the hole-board test (traditionally considered an exploratory behavior independent of stress) was not correlated with the GCMs. This study offers a first look at GCMs in the black rat, successfully validates a method for their measurement and opens possibilities for future research of the relationship between glucocorticoids and exploratory behavior in this species.
Collapse
Affiliation(s)
- Barbora Vobrubová
- Department of Zoology, Faculty of Science, Charles University, Prague, Czechia.,RP3 Applied Neuroscience and Neuroimaging, National Institute of Mental Health, Klecany, Czechia
| | - Marcela Fraňková
- Division of Crop Protection and Plant Health, Crop Research Institute, Prague, Czechia
| | - Iveta Štolhoferová
- Department of Zoology, Faculty of Science, Charles University, Prague, Czechia.,RP3 Applied Neuroscience and Neuroimaging, National Institute of Mental Health, Klecany, Czechia
| | - Barbora Kaftanová
- Department of Zoology, Faculty of Science, Charles University, Prague, Czechia.,Department of Physiology, Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Veronika Rudolfová
- Department of Zoology, Faculty of Science, Charles University, Prague, Czechia.,RP3 Applied Neuroscience and Neuroimaging, National Institute of Mental Health, Klecany, Czechia
| | - Aleksandra Chomik
- Department of Zoology, Faculty of Science, Charles University, Prague, Czechia
| | - Petra Chumová
- Department of Zoology, Faculty of Science, Charles University, Prague, Czechia
| | - Václav Stejskal
- Division of Crop Protection and Plant Health, Crop Research Institute, Prague, Czechia
| | - Rupert Palme
- Department of Biomedical Sciences, University of Veterinary Medicine, Vienna, Austria
| | - Daniel Frynta
- Department of Zoology, Faculty of Science, Charles University, Prague, Czechia.,RP3 Applied Neuroscience and Neuroimaging, National Institute of Mental Health, Klecany, Czechia
| |
Collapse
|
11
|
Hill DL, Pillay N, Schradin C. Glucocorticoid levels predict subsequent social tactic in females of a facultatively social mammal. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Davina L. Hill
- School of Animal, Plant and Environmental Sciences University of the Witwatersrand Johannesburg South Africa
- Institute of Biodiversity, Animal Health and Comparative Medicine College of Medical, Veterinary and Life Sciences University of Glasgow Glasgow UK
| | - Neville Pillay
- School of Animal, Plant and Environmental Sciences University of the Witwatersrand Johannesburg South Africa
| | - Carsten Schradin
- School of Animal, Plant and Environmental Sciences University of the Witwatersrand Johannesburg South Africa
- Université de StrasbourgCNRSIPHC UMR 7178 Strasbourg France
| |
Collapse
|
12
|
How does cognitive performance change in relation to seasonal and experimental changes in blood glucose levels? Anim Behav 2019. [DOI: 10.1016/j.anbehav.2019.10.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
13
|
Rimbach R, Blanc S, Zahariev A, Pillay N, Schradin C. Daily energy expenditure of males following alternative reproductive tactics: Solitary roamers spend more energy than group-living males. Physiol Behav 2018; 199:359-365. [PMID: 30521878 DOI: 10.1016/j.physbeh.2018.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Revised: 10/25/2018] [Accepted: 12/03/2018] [Indexed: 12/21/2022]
Abstract
In many species, males follow alternative reproductive tactics (ARTs), where one tactic (called bourgeois) has much higher reproductive success than alternative tactics followed by males with lower competitive ability. The extent to which ARTs differ in energetic costs is unknown, but it is important to understand the fitness payoffs of ARTs. We studied male African striped mice (Rhabdomys pumilio) which follow one of three ARTs: heavy bourgeois males defend harems of females and have 10 times higher reproductive success than smaller roamers, which have ten times higher reproductive success than philopatric males, which remain in their natal group and are the smallest males. Bourgeois and philopatric males live in social groups that defend one territory, while roamers are solitary and roam over larger areas. We predicted that roamers will face higher energetic costs compared to group-living males because they do not gain thermoregulatory benefits of huddling in groups and might travel larger distances as they have larger home ranges. We measured daily energy expenditure (DEE) of 30 males, resting metabolic rate (RMR) of 79 males, travel distances and daily ranges of 31 males and changes in body mass of 51 males. Roamers had higher DEE and higher RMR than both types of group-living males. Philopatric males had shorter travel distances and smaller daily ranges than both roamers and bourgeois males, which did not differ from each other. This indicates that the higher DEE of roamers compared to bourgeois males cannot be explained by larger travel distances. Philopatrics gained body mass faster than bourgeois males and roamers, thereby increasing their competitive ability and thus the probability of later switching to a tactic of higher reproductive success. Our results suggest that roamers suffer energetic costs that might reduce their ability of gaining body mass and thus the likelihood of switching to the bourgeois tactic, indicating evolutionary trade-offs between investing energy into roaming versus gaining body mass.
Collapse
Affiliation(s)
- Rebecca Rimbach
- School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, Private Bag 3, WITS, 2050 Johannesburg, South Africa.
| | - Stéphane Blanc
- IPHC, UNISTRA, CNRS, 23 rue du Loess, 67200 Strasbourg, France
| | | | - Neville Pillay
- School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, Private Bag 3, WITS, 2050 Johannesburg, South Africa
| | - Carsten Schradin
- School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, Private Bag 3, WITS, 2050 Johannesburg, South Africa; IPHC, UNISTRA, CNRS, 23 rue du Loess, 67200 Strasbourg, France
| |
Collapse
|
14
|
Behavioural correlates of group size and group persistence in the African ice rat Otomys sloggetti robertsi. Behav Ecol Sociobiol 2017. [DOI: 10.1007/s00265-017-2293-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
15
|
Trade-offs between reproduction and health in free-ranging African striped mice. J Comp Physiol B 2017; 187:625-637. [DOI: 10.1007/s00360-016-1054-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 11/07/2016] [Accepted: 11/29/2016] [Indexed: 01/09/2023]
|
16
|
Rimbach R, Pillay N, Schradin C. Both thyroid hormone levels and resting metabolic rate decrease in African striped mice when food availability decreases. ACTA ACUST UNITED AC 2016; 220:837-843. [PMID: 27994044 DOI: 10.1242/jeb.151449] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 12/12/2016] [Indexed: 01/13/2023]
Abstract
In response to variation in food availability and ambient temperature (Ta), many animals show seasonal adaptations in their physiology. Laboratory studies showed that thyroid hormones are involved in the regulation of metabolism, and their regulatory function is especially important when the energy balance of an individual is compromised. However, little is known about the relationship between thyroid hormones and metabolism in free-living animals and animals inhabiting seasonal environments. Here, we studied seasonal changes in triiodothyronine (T3) levels, resting metabolic rate (RMR) and two physiological markers of energy balance (blood glucose and ketone bodies) in 61 free-living African striped mice (Rhabdomys pumilio) that live in an semi-arid environment with food shortage during the dry season. We predicted a positive relationship between T3 levels and RMR. Further, we predicted higher T3 levels, blood glucose levels and RMR, but lower ketone body concentrations, during the moist season when food availability is high compared with summer when food availability is low. RMR and T3 levels were negatively related in the moist season but not in the dry season. Both RMR and T3 levels were higher in the moist than in the dry season, and T3 levels increased with increasing food availability. In the dry season, blood glucose levels were lower but ketone body concentrations were higher, indicating a change in substrate use. Seasonal adjustments in RMR and T3 levels permit a reduction of energy expenditure when food is scarce, and reflect an adaptive response to reduced food availability in the dry season.
Collapse
Affiliation(s)
- Rebecca Rimbach
- University of the Witwatersrand, School of Animal, Plant & Environmental Sciences, Private Bag 3, WITS 2050, Johannesburg, South Africa
| | - Neville Pillay
- University of the Witwatersrand, School of Animal, Plant & Environmental Sciences, Private Bag 3, WITS 2050, Johannesburg, South Africa
| | - Carsten Schradin
- University of the Witwatersrand, School of Animal, Plant & Environmental Sciences, Private Bag 3, WITS 2050, Johannesburg, South Africa.,IPHC, UNISTRA, CNRS, 23 rue du Loess, Strasbourg 67200, France
| |
Collapse
|
17
|
Huffman MC, Santo JB, French JA. Prenatal androgen exposure and parental care interact to influence timing of reproductive maturation in marmosets. Am J Primatol 2016; 79:1-12. [DOI: 10.1002/ajp.22588] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 06/29/2016] [Accepted: 07/18/2016] [Indexed: 12/12/2022]
Affiliation(s)
- Michelle C. Huffman
- Callitrichid Research Center; University of Nebraska; Omaha Nebraska
- Department of Psychology; University of Nebraska; Omaha Nebraska
| | | | - Jeffrey A. French
- Callitrichid Research Center; University of Nebraska; Omaha Nebraska
- Department of Psychology; University of Nebraska; Omaha Nebraska
- Department of Biology; University of Nebraska; Omaha Nebraska
| |
Collapse
|
18
|
Nater CR, Canale CI, van Benthem KJ, Yuen CH, Schoepf I, Pillay N, Ozgul A, Schradin C. Interactive effects of exogenous and endogenous factors on demographic rates of an African rodent. OIKOS 2016. [DOI: 10.1111/oik.03384] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chloé R. Nater
- Dept of Evolutionary Biology and Environmental Studies; Univ. of Zurich; Winterthurerstrasse 190 CH-8057 Zurich Switzerland
- Centre for Ecological and Evolutionary Synthesis (CEES), Dept of Biosciences; Univ. of Oslo; Blindern Oslo Norway
| | - Cindy I. Canale
- Dept of Evolutionary Biology and Environmental Studies; Univ. of Zurich; Winterthurerstrasse 190 CH-8057 Zurich Switzerland
| | - Koen J. van Benthem
- Dept of Evolutionary Biology and Environmental Studies; Univ. of Zurich; Winterthurerstrasse 190 CH-8057 Zurich Switzerland
| | - Chi-Hang Yuen
- School of Animal, Plant and Environmental Sciences; Univ. of the Witwatersrand; Braamfontein Johannesburg South Africa
| | - Ivana Schoepf
- School of Animal, Plant and Environmental Sciences; Univ. of the Witwatersrand; Braamfontein Johannesburg South Africa
| | - Neville Pillay
- School of Animal, Plant and Environmental Sciences; Univ. of the Witwatersrand; Braamfontein Johannesburg South Africa
| | - Arpat Ozgul
- Dept of Evolutionary Biology and Environmental Studies; Univ. of Zurich; Winterthurerstrasse 190 CH-8057 Zurich Switzerland
| | - Carsten Schradin
- School of Animal, Plant and Environmental Sciences; Univ. of the Witwatersrand; Braamfontein Johannesburg South Africa
- Inst. Pluridisciplinaire Hubert Curien; Dépt d'Ecologie Physiologie et Ethologie; Strasbourg France
| |
Collapse
|
19
|
Hutchinson E, Atkinson S, Burek Huntington K. Growth and sexual maturation in male northern sea otters ( Enhydra lutris kenyoni) from Gustavus, Alaska. J Mammal 2015. [DOI: 10.1093/jmammal/gyv114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
20
|
Hill DL, Pillay N, Schradin C. Alternative reproductive tactics in female striped mice: heavier females are more likely to breed solitarily than communally. J Anim Ecol 2015; 84:1497-508. [DOI: 10.1111/1365-2656.12431] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 07/22/2015] [Indexed: 12/01/2022]
Affiliation(s)
- Davina L. Hill
- School of Animal, Plant and Environmental Sciences; University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa
| | - Neville Pillay
- School of Animal, Plant and Environmental Sciences; University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa
| | - Carsten Schradin
- School of Animal, Plant and Environmental Sciences; University of the Witwatersrand; Private Bag 3 Wits 2050 Johannesburg South Africa
- IPHC-DEPE; Université de Strasbourg; 23 rue Becquerel 67087 Strasbourg France
- CNRS; UMR7178; 67087 Strasbourg France
| |
Collapse
|
21
|
Arginine vasopressin in brains of free ranging striped mouse males following alternative reproductive tactics. J ETHOL 2015. [DOI: 10.1007/s10164-015-0436-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
22
|
Personality does not constrain social and behavioural flexibility in African striped mice. Behav Ecol Sociobiol 2015. [DOI: 10.1007/s00265-015-1937-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
23
|
Hill DL, Pillay N, Schradin C. Alternative reproductive tactics in female striped mice: Solitary breeders have lower corticosterone levels than communal breeders. Horm Behav 2015; 71:1-9. [PMID: 25828632 DOI: 10.1016/j.yhbeh.2015.03.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 03/16/2015] [Accepted: 03/23/2015] [Indexed: 10/23/2022]
Abstract
Alternative reproductive tactics (ARTs), where members of the same sex and population show distinct reproductive phenotypes governed by decision-rules, have been well-documented in males of many species, but are less well understood in females. The relative plasticity hypothesis (RPH) predicts that switches between plastic ARTs are mediated by changes in steroid hormones. This has received much support in males, but little is known about the endocrine control of female ARTs. Here, using a free-living population of African striped mice (Rhabdomys pumilio) over five breeding seasons, we tested whether females following different tactics differed in corticosterone and testosterone levels, as reported for male striped mice using ARTs, and in progesterone and oestrogen, which are important in female reproduction. Female striped mice employ three ARTs: communal breeders give birth in a shared nest and provide alloparental care, returners leave the group temporarily to give birth, and solitary breeders leave to give birth and do not return. We expected communal breeders and returners to have higher corticosterone, owing to the social stress of group-living, and lower testosterone than solitary breeders, which must defend territories alone. Solitary breeders had lower corticosterone than returners and communal breeders, as predicted, but testosterone and progesterone did not differ between ARTs. Oestrogen levels were higher in returners (measured before leaving the group) than in communal and solitary breeders, consistent with a modulatory role. Our study demonstrates hormonal differences between females following (or about to follow) different tactics, and provides the first support for the RPH in females.
Collapse
Affiliation(s)
- Davina L Hill
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa.
| | - Neville Pillay
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa.
| | - Carsten Schradin
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa; Université de Strasbourg, IPHC-DEPE, 23 rue Becquerel 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France; Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| |
Collapse
|
24
|
Nel K, Rimbach R, Pillay N. Dietary protein influences the life-history characteristics across generations in the African striped mouseRhabdomys. ACTA ACUST UNITED AC 2015; 323:97-108. [DOI: 10.1002/jez.1903] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 09/19/2014] [Accepted: 10/14/2014] [Indexed: 11/09/2022]
Affiliation(s)
- Kerith Nel
- School of Animal; Plant & Environmental Sciences; University of the Witwatersrand; Johannesburg South Africa
| | - Rebecca Rimbach
- School of Animal; Plant & Environmental Sciences; University of the Witwatersrand; Johannesburg South Africa
| | - Neville Pillay
- School of Animal; Plant & Environmental Sciences; University of the Witwatersrand; Johannesburg South Africa
| |
Collapse
|
25
|
Schoepf I, Schmohl G, König B, Pillay N, Schradin C. Manipulation of population density and food availability affects home range sizes of African striped mouse females. Anim Behav 2015. [DOI: 10.1016/j.anbehav.2014.10.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
26
|
Raynaud J, Schradin C. Corticosterone Levels Correlate With Alloparental Care in a Sex-Dependent Manner in African Striped Mice,Rhabdomys pumilio. Ethology 2014. [DOI: 10.1111/eth.12317] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Julien Raynaud
- Institute of Evolutionary Biology and Environmental Studies; University of Zurich; Zurich Switzerland
| | - Carsten Schradin
- IPHC-DEPE; Université de Strasbourg; Strasbourg France
- CNRS; Strasbourg France
- School of Animal, Plant and Environmental Sciences; University of the Witwatersrand; Johannesburg South Africa
| |
Collapse
|
27
|
Mackay M, Rymer TL, Pillay N. Separation at weaning from the family is stressful for naturally group-living, but not solitary-living, male African striped mice Rhabdomys. Stress 2014; 17:266-74. [PMID: 24689755 DOI: 10.3109/10253890.2014.910762] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Early separation from a family is stressful for young mammals, but might be more stressful for group-living than solitary species. Using juvenile males of three African striped mice Rhabdomys taxa that are either group (R. pumilio) or solitary (R. dilectus dilectus and R. d. chakae) living, we predicted greater separation anxiety in R. pumilio than R. dilectus because group-living could reduce anxiety in R. pumilio. Three brothers from each of 10 litters per taxon were randomly assigned soon after natural weaning (25 days) to one of three treatments for 10 days: (1) remained with the family (philopatric); (2) separated from the family by a wire mesh barrier (separated); and (3) isolated from the family (isolated). Males were individually tested in a four-arm maze to assess their anxiety responses and sampled for corticosterone concentrations 20 mins and 10 days later. Compared to R. dilectus males, R. pumilio males showed a greater treatment response to separation: philopatric males used the light arms of the maze less and had higher corticosterone concentrations compared to isolated males, which spent the most time in the light arms and had the lowest corticosterone concentrations overall; separated males showed an intermediate behavioural response, but had similar corticosterone concentrations to philopatric males. Thus, separation from a family group is more stressful in group-living Rhabdomys and this stress response dissipates with time. Philopatry and group-living may be more important for young R. pumilio, whereas dispersal at weaning is an important life history event for solitary R. dilectus.
Collapse
Affiliation(s)
- Megan Mackay
- School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg , Wits , South Africa and
| | | | | |
Collapse
|
28
|
Absence of reproductive suppression in young adult female striped mice living in their natal family. Anim Behav 2014. [DOI: 10.1016/j.anbehav.2014.01.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
29
|
Schradin C, Larke RH, Bales KL. Growing up in the family or growing up alone influences behavior and hormones, but not arginine vasopressin receptor 1a expression in male African striped mice. Physiol Behav 2014; 129:205-13. [PMID: 24631307 DOI: 10.1016/j.physbeh.2014.02.060] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 01/16/2014] [Accepted: 02/21/2014] [Indexed: 11/17/2022]
Abstract
In many species males display alternative reproductive tactics (ARTs). While males of different tactics differ behaviorally in the field, it is often not known whether these behavioral differences would also occur under standardized laboratory conditions, nor how ARTs are regulated by the brain. In the present study we kept male African striped mice (Rhabdomys pumilio) in captivity either in family groups or solitary, to mimic ARTs observed in the field. This allowed us to study these males behaviorally under standardized conditions, to replicate physiological findings from the field, and to study the expression of the arginine vasopressin 1a receptor (AVPR1a) in their brains. Changes in either peptide release or receptor expression (or both) might regulate ARTs with differential timelines, with peptide secretion being faster than receptor expression. As observed in the field, family living males had higher corticosterone but lower testosterone levels than singly housed males. Surprisingly, singly housed males were less aggressive while at the same time having higher testosterone levels. We found no differences in AVPR1a expression. In a previous study it was shown that singly housed males have higher levels of AVP stored in their brain, which potentially could be secreted when the social situation changes, for example to establish social bonds. Our study on AVPR1a suggests the hypothesis that, given that the receptor distribution and expression of singly housed males do not differ from that of family-living males, the brains of singly-housed males have a similar capacity to be responsive to AVP when given the chance to interact socially.
Collapse
Affiliation(s)
- Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa; Université de Strasbourg, IPHC-DEPE, 23 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France.
| | - Rebecca H Larke
- Department of Psychology, University of California, Davis, CA 95616, USA
| | - Karen L Bales
- Department of Psychology, University of California, Davis, CA 95616, USA
| |
Collapse
|
30
|
Raynaud J, Schradin C. Experimental increase of testosterone increases boldness and decreases anxiety in male African striped mouse helpers. Physiol Behav 2014; 129:57-63. [PMID: 24534177 DOI: 10.1016/j.physbeh.2014.02.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 07/25/2013] [Accepted: 02/04/2014] [Indexed: 11/25/2022]
Abstract
Males of many species can adjust their behaviors to environmental conditions by changing reproductive tactics. Testosterone surges in adult breeding males typically inhibit the expression of paternal care while facilitating the expression of aggression during environmental changes. Similarly, in non-breeding philopatric males of cooperatively breeding species, up-regulation of testosterone may inhibit alloparental care while facilitating dispersal, i.e. males might become bolder and more explorative. We tested this hypothesis in philopatric male African striped mice, Rhabdomys pumilio. Striped mouse males can either remain in their natal groups providing alloparental care or they can disperse seeking mating opportunities. Compared to philopatric males, dispersed males typically show higher testosterone levels and lower corticosterone levels, and more aggression toward pups and same sex conspecifics. We experimentally increased the testosterone levels of the philopatric males kept in their family groups when pups were present. Testosterone-treated males did not differ significantly from control males in alloparental care and in aggression toward same-sex conspecifics. Compared to the control males, testosterone treated males were bolder, more active, and less anxious; they also showed lower corticosterone levels. The philopatric males were sensitive to our testosterone treatment for dispersal- and anxiety-like behavior but insensitive for social behaviors. Our results suggest a role of testosterone in dispersal.
Collapse
Affiliation(s)
- Julien Raynaud
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | - Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; Université de Strasbourg, IPHC-DEPE, France; CNRS, UMR7178, 67087 Strasbourg, France; School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg, South Africa
| |
Collapse
|
31
|
Schoepf I, Schradin C. Endocrinology of sociality: comparisons between sociable and solitary individuals within the same population of African striped mice. Horm Behav 2013; 64:89-94. [PMID: 23648775 DOI: 10.1016/j.yhbeh.2013.04.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Revised: 04/20/2013] [Accepted: 04/25/2013] [Indexed: 10/26/2022]
Abstract
The social organization of species ranges from solitary-living to complex social groups. While the evolutionary reasons of group-living are well studied, the physiological mechanisms underlying alternative social systems are poorly understood. By studying group-living and solitary individuals of the same species, we can determine hormonal correlates of sociality without the problem of confounding phylogenetic factors. The African striped mouse (Rhabdomys pumilio) is a socially flexible species, which can be solitary or alternatively form complex family groups, depending on population density and the extent of reproductive competition. We predicted group-living striped mice to show signs of reproductive suppression and social stress, resulting in higher corticosterone but lower testosterone levels when compared to solitary-living individuals. To determine whether differences in social organization correlated with hormonal differences, we collected blood samples from free-living striped mice during four breeding seasons when we experimentally induced solitary-living in philopatric individuals by locally reducing population density. Striped mice that were group-living did not change their corticosterone or estosterone levels during the study, indicating that there was no temporal effect during the breeding season. Striped mice of both sexes had significantly lower corticosterone levels after switching from group- to solitary-living. Solitary males - but not solitary females - had higher testosterone levels than group-living conspecifics. Our results suggest that group-living results in physiological stress and can induce reproductive suppression, at least in philopatric males. The switch to solitary-living may thus be a tactic to avoid reproductive competition within groups, and is associated with decreased stress hormone levels and onset of independent reproduction.
Collapse
Affiliation(s)
- Ivana Schoepf
- Department of Animal Behaviour, Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
| | | |
Collapse
|
32
|
Schradin C. Intraspecific variation in social organization by genetic variation, developmental plasticity, social flexibility or entirely extrinsic factors. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120346. [PMID: 23569294 DOI: 10.1098/rstb.2012.0346] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Previously, it was widely believed that each species has a specific social organization, but we know now that many species show intraspecific variation in their social organization. Four different processes can lead to intraspecific variation in social organization: (i) genetic variation between individuals owing to local adaptation (between populations) or evolutionarily stable strategies within populations; (ii) developmental plasticity evolved in long-term (more than one generation) unpredictable and short-term (one generation) predictable environments, which is mediated by organizational physiological effects during early ontogeny; (iii) social flexibility evolved in highly unpredictable environments, which is mediated by activational physiological effects in adults; (iv) entirely extrinsic factors such as the death of a dominant breeder. Variation in social behaviour occurs between individuals in the case of genetic variation and developmental plasticity, but within individuals in the case of social flexibility. It is important to study intraspecific variation in social organization to understand the social systems of species because it reveals the mechanisms by which species can adapt to changing environments, offers a useful tool to study the ultimate and proximate causes of sociality, and is an interesting phenomenon by itself that needs scientific explanation.
Collapse
Affiliation(s)
- Carsten Schradin
- Université de Strasbourg, IPHC-DEPE, 23 rue Becquerel, Strasbourg 67087, France.
| |
Collapse
|
33
|
Extinction or Survival? Behavioral Flexibility in Response to Environmental Change in the African Striped Mouse Rhabdomys. SUSTAINABILITY 2013. [DOI: 10.3390/su5010163] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
34
|
Schradin C, Kenkel W, Krackow S, Carter CS. Staying put or leaving home: endocrine, neuroendocrine and behavioral consequences in male African striped mice. Horm Behav 2013; 63:136-43. [PMID: 23079108 DOI: 10.1016/j.yhbeh.2012.10.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 10/08/2012] [Accepted: 10/09/2012] [Indexed: 11/25/2022]
Abstract
Social flexibility occurs when individuals of both sexes can change their social and reproductive tactics, which in turn can influence the social system of an entire population. However, little is known regarding the extent to which individuals of socially flexible species vary in their social behavior and in the underlying physiological mechanisms that support different social tactics. The present study in African striped mice modeled in captivity three male tactics described from the field: (a) philopatric males remaining in the family; (b) solitary roamers; or (c) group-living breeding males. Sixteen pairs and their offspring were kept in captivity, while one male offspring from the family remained as singly housed after he reached 21 days of age. Differences in behavior, morphology, hormone and neuropeptide levels were tested, and physiological measurements were correlated with behavioral measurements. In standardized arena experiments group-living males (philopatrics and breeders) were significantly more aggressive than singly housed males, in agreement with previous data suggesting that group-living, but not roaming males, are territorial. Philopatric males showed signs of reproductive suppression, small testes, lower testosterone and higher corticosterone levels than their singly housed brothers. Higher levels of arginine vasopressin (AVP) were measured in the PVN and BNST of singly housed males compared to group-living males. Based on these findings we hypothesize that roamers are physiologically primed, and capable, if the opportunity to mate arises, to release AVP, form social bonds and become territorial, thus quickly adopting the tactic as breeding male which would yield a higher reproductive success.
Collapse
Affiliation(s)
- Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | | | | | | |
Collapse
|
35
|
Differences in social behaviour between group-living and solitary African striped mice, Rhabdomys pumilio. Anim Behav 2012. [DOI: 10.1016/j.anbehav.2012.08.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
36
|
Raynaud J, Müller K, Schradin C. Experimental increase of testosterone levels in free-ranging juvenile male African striped mice (Rhabdomys pumilio) induces physiological, morphological, and behavioral changes. Gen Comp Endocrinol 2012; 178:108-15. [PMID: 22565164 DOI: 10.1016/j.ygcen.2012.04.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 04/23/2012] [Accepted: 04/26/2012] [Indexed: 10/28/2022]
Abstract
Testosterone influences sexual differentiation in early development, and activates sexual maturation and sex-related behavior in males during puberty. Testosterone can also influence the expression of male alternative reproductive tactics, by either organizational effects (fixed tactics) or by activational effects (plastic tactics). However, the roles of testosterone in sexual maturation and at the same time the expression of alternative reproductive tactics have been little investigated experimentally, and studies of free-ranging mammals are lacking. We conducted a field experiment in free-ranging juvenile African striped mice (Rhabdomys pumilio), a species with alternative reproductive tactics. Juvenile male striped mice reaching puberty can remain in their family as philopatric group-living males with low testosterone levels, or they can disperse and become solitary living roamers with much higher testosterone levels. We tested whether experimentally increased testosterone levels in non-scrotal juvenile males induces puberty and leads to the expression of the roaming tactic. Testosterone-treated males received the hormone for 15days by silastic implants which were empty in control-treated males. When compared to control-treated males, testosterone-treated males had higher testosterone levels, lower corticosterone levels, and became scrotal with descended testes. Testosterone-treated males also had larger testes, larger epididymides, and showed indication of spermatogenesis. Testosterone-treated males did not become solitary-living roamers, but had larger home ranges than control males. We conclude that testosterone can induce sexual maturation and causes juvenile males to increase their home ranges, maybe to search for dispersal opportunities.
Collapse
Affiliation(s)
- Julien Raynaud
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland.
| | | | | |
Collapse
|
37
|
Schradin C, Eder S, Müller K. Differential investment into testes and sperm production in alternative male reproductive tactics of the African striped mouse (Rhabdomys pumilio). Horm Behav 2012; 61:686-95. [PMID: 22445749 DOI: 10.1016/j.yhbeh.2012.03.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 03/06/2012] [Accepted: 03/07/2012] [Indexed: 11/25/2022]
Abstract
Males that follow alternative reproductive tactics might differ in their investment into testis development and sperm production. The resource-allocation hypothesis predicts that males following a sneaker tactic should invest more into sperm production than dominant territorial males which should invest more into mate guarding. This hypothesis is supported by studies in species where individual males cannot switch between tactics (fixed tactics). Here we present the first data for a species where males can switch between tactics (plastic tactics). We studied African striped mice (Rhabdomys pumilio) in captivity, mimicking three tactics observed in the field: philopatric group-living males, singly-housed males representing roaming males, and group-living breeding males. We measured quantitative and qualitative reproductive traits, as well as serum and testis hormone concentrations. We found no support for the resource-allocation hypothesis, since breeding and singly-housed males invested similarly in testes and sperm. However, philopatric males had significantly smaller testes and epididymides, lower sperm counts, lower testosterone and higher corticosterone levels than males of the two other tactics. Philopatric males did not reach a larger body mass than singly-housed males with well developed reproductive traits, indicating that they did not trade investment in sperm production against growth. Interestingly, testis testosterone concentrations of philopatric males did not differ from those of other males. Our data suggest that philopatric males are reproductively suppressed by the breeding male, but might be ready to increase their serum testosterone levels when social and environmental conditions allow for this physiological switch accompanying the behavioral switch between tactics.
Collapse
Affiliation(s)
- Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
| | | | | |
Collapse
|
38
|
Schoepf I, Schradin C. Better off alone! Reproductive competition and ecological constraints determine sociality in the African striped mouse (Rhabdomys pumilio). J Anim Ecol 2012; 81:649-56. [PMID: 22220746 DOI: 10.1111/j.1365-2656.2011.01939.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ivana Schoepf
- Department of Animal Behaviour, Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland.
| | | |
Collapse
|
39
|
Schradin C, Yuen CH. Hormone levels of male African striped mice change as they switch between alternative reproductive tactics. Horm Behav 2011; 60:676-80. [PMID: 21968215 DOI: 10.1016/j.yhbeh.2011.09.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 08/22/2011] [Accepted: 09/06/2011] [Indexed: 10/17/2022]
Abstract
Alternative reproductive tactics occur when individuals of the same species follow alternative ways to maximize reproductive success. Often younger and smaller males follow tactics that result in lower fitness than that of dominant larger males. The relative plasticity hypothesis predicts that hormone levels change as males change tactics, but direct tests of this hypothesis are missing. It has been demonstrated in a number of studies that males following different tactics also differ in hormone levels (unpaired data), but not that individual males change their hormone levels as they change tactic (paired data). We compared hormone levels in the same individuals before and after they changed their tactic, using field samples collected over a period of 6 years. We studied male striped mice (Rhabdomys pumilio) following three alternative reproductive tactics: 1. alloparental philopatric males; 2. solitary roaming males, and 3. group-living dominant breeders. Testosterone levels increased and corticosterone levels decreased when philopatric males became roamers or breeders. The increase in testosterone levels tended to be higher in philopatric males that became roamers than in philopatric males that became breeders. Testosterone levels decreased when roamers became breeders. Prolactin levels increased when males of any other tactic became breeders. Thus, males significantly changed their hormone profiles as they changed tactics. These results are in agreement with the hypothesis that changes in hormone levels are associated with the switch from one alternative reproductive tactic to another.
Collapse
Affiliation(s)
- Carsten Schradin
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | | |
Collapse
|
40
|
SCHRADIN CARSTEN, LINDHOLM ANNAK, JOHANNESEN JES, SCHOEPF IVANA, YUEN CHIHANG, KÖNIG BARBARA, PILLAY NEVILLE. Social flexibility and social evolution in mammals: a case study of the African striped mouse (Rhabdomys pumilio). Mol Ecol 2011; 21:541-53. [DOI: 10.1111/j.1365-294x.2011.05256.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
41
|
The fitness of dispersing spotted hyaena sons is influenced by maternal social status. Nat Commun 2010; 1:60. [PMID: 20975715 PMCID: PMC2964455 DOI: 10.1038/ncomms1059] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Accepted: 07/29/2010] [Indexed: 12/02/2022] Open
Abstract
Life history theory predicts that mothers should provide their offspring with a privileged upbringing if this enhances their offspring's and their own fitness. In many mammals, high-ranking mothers provide their offspring with a privileged upbringing. Whether dispersing sons gain fitness benefits during adulthood from such privileges (a 'silver spoon' effect) has rarely been examined. In this paper, we show that in the complex, female-dominated society of spotted hyaenas, high-born sons grew at higher rates, were more likely to disperse to clans offering the best fitness prospects, started reproducing earlier and had a higher reproductive value than did lower-born sons. This illustrates the evolutionary importance of maternal effects even in societies in which male size or fighting ability does not influence fitness. By demonstrating for the first time in a non-human mammal that maternal status influences immigration patterns, the study also advances our understanding of two key ecological and evolutionary processes, dispersal and habitat selection. Spotted hyaenas live in clans with a hierarchy of females with different social ranks. In this paper, the sons of high-ranking female hyaenas are shown to have greater fitness than sons born of mothers of medium and low rank. This study highlights the importance of maternal effects in evolution.
Collapse
|
42
|
Spatial variation in gender-biased parasitism: host-related, parasite-related and environment-related effects. Parasitology 2010; 137:1527-36. [PMID: 20550754 DOI: 10.1017/s0031182010000454] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The gender-biased pattern of parasite infestation has been shown to be a complicated phenomenon that cannot be explained by a single mechanism but rather involves several different mechanisms. We asked what are the factors that affect the manifestation and extent of gender-biased parasitism and studied the relationship between parasite-related (mean abundance, mean species richness and total species richness of all parasites), host-related (rodent density and proportion of reproductive males and females both separately and together) and environment-related (mean daily maximal and minimal temperatures, rainfall and relative humidity) factors and the magnitude of gender-biased infestation of a South African rodent Rhabdomys pumilio by ixodid ticks, gamasid mites, lice and fleas. We found that spatial variation in gender differences in parasite infestation was affected by parasite-, host- and environment-related factors, although the set of factors affecting gender differences in infestation differed among higher taxa of ectoparasites. Gender differences in infestation by fleas and lice were affected mainly by parasite-related factors, whereas gender differences in infestation by ticks and, in part, by mites were affected mainly by host-related and environmental factors. In addition, spatial variation in most measures of gender difference in mite infestation remained unexplained.
Collapse
|