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Malungo IB, Gravett N, Ganswindt A, Manger PR. Male blue wildebeest increase activity during the rut, but not at the expense of rest. J Comp Physiol B 2024; 194:265-278. [PMID: 37115234 PMCID: PMC11233297 DOI: 10.1007/s00360-023-01493-6] [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: 10/14/2022] [Revised: 04/05/2023] [Accepted: 04/20/2023] [Indexed: 04/29/2023]
Abstract
Rest is a state of adaptive inactivity that increases the efficiency of activity by regulating its timing and reducing energy use when activity is not beneficial. Thus, animals can go without rest when specific demands, such as mating, favour being awake. Sexually active male blue wildebeest (bulls) are typically territorial, and it has been reported that when a bull is protecting a harem during the mating season (rut), he neither eats nor rests. We examined the daily activity and inactivity patterns of dominant bulls by means of actigraphy for 3 months, which included the rut. We also measured faecal androgen metabolite (fAM) levels and subcutaneous temperature, both of which have variances known to delineate the rut. During the rut, wildebeest bulls experienced higher levels of activity, fAM, and a greater daily range of subcutaneous temperature. Despite previous reports, the male blue wildebeest rested daily during the rut, and while the amount of rest was low, it was not substantially lower than prior to the rut. The amount of time spent inactive increased substantially after the rut. The timing of daily activity and inactivity patterns did not vary substantially across the recording period. Across the recording period, the average daily ambient temperatures decreased (seasonality), and the subcutaneous temperature followed this pattern, although it was not as marked. It appears that in the post-rut period a substantive increase in time spent at rest occurs, potentially allowing the wildebeest bulls time to recover following a period of intense activity.
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Affiliation(s)
- Illke B Malungo
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193, South Africa
| | - Nadine Gravett
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193, South Africa
| | - André Ganswindt
- Endocrine Research Laboratory, Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Soutpan Rd, Onderstepoort, Pretoria, South Africa
- Department of Zoology and Entomology, Faculty of Natural and Agricultural Sciences, Mammal Research Institute, University of Pretoria, Lynnwood Rd, Hatfield, Pretoria, South Africa
| | - Paul R Manger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, 2193, South Africa.
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2
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Majelantle TL, Ganswindt A, Hart DW, Hagenah N, Ganswindt SB, Bennett NC. The dissection of a despotic society: exploration, dominance and hormonal traits. Proc Biol Sci 2024; 291:20240371. [PMID: 38714210 PMCID: PMC11095815 DOI: 10.1098/rspb.2024.0371] [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: 08/15/2023] [Revised: 03/27/2024] [Accepted: 03/27/2024] [Indexed: 05/09/2024] Open
Abstract
Naked mole-rats (Heterocephalus glaber) live in large colonies with one breeding female (queen), one to three breeding males (BMs) and the remainder are non-reproductive subordinates. The animals have a linear dominance rank with the breeders at the top of the hierarchy. We investigated how dominance rank in naked mole-rats differs with exploration (the propensity to explore a novel environment) and related endocrine markers. Exploration behaviour, faecal progestagen metabolite (fPM), faecal glucocorticoid metabolite (fGCM), faecal androgen metabolite (fAM) and plasma prolactin concentrations were quantified in breeding, high-, middle- and low-ranked females and males from five naked mole-rat colonies. There were no significant differences between the dominance rank and exploration behaviour. Interestingly, the queens and high-ranking females had higher fGCM and fAM concentrations compared with middle- and low-ranked females. The queens had significantly higher fPM concentrations than all other ranked females, since they are responsible for procreation. In the males, the BMs had higher fGCM concentrations compared with high- and low-ranked males. In addition, BMs and middle-ranking males had overall higher prolactin levels than all other ranked males, which could be linked to cooperative care. Overall, the results suggest that physiological reproductive suppression is linked to high dominance rank.
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Affiliation(s)
- Tshepiso Lesedi Majelantle
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 400364, South Africa
| | - Andre Ganswindt
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 400364, South Africa
| | - Daniel William Hart
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 400364, South Africa
| | - Nicole Hagenah
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 400364, South Africa
| | - Stefanie Birgit Ganswindt
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 400364, South Africa
| | - Nigel Charles Bennett
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 400364, South Africa
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3
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Wallace KME, Hart DW, Hagenah N, Ganswindt A, Bennett NC. A comprehensive profile of reproductive hormones in eusocial Damaraland mole-rats (Fukomys damarensis). Gen Comp Endocrinol 2023; 333:114194. [PMID: 36538992 DOI: 10.1016/j.ygcen.2022.114194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 11/03/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022]
Abstract
In species where sociality and group cohesion are primarily determined by the maintenance of a reproductive division of labour and cooperative behaviours, the eusocial Damaraland mole-rat (Fukomys damarensis) presents a model which provides behavioural and endocrine distinctions between sex (males and females) and reproductive class (breeders and non-breeders). Although previous studies have demonstrated the endocrine aspects of reproductive suppression and behaviour in Damaraland mole-rats, they have focused on one hormone separately and on different conspecifics and samples across time. Unfortunately, this could introduce extrinsic biases when using these studies to compile complete hormonal profiles for comparisons. This study, therefore, set out to obtain a profile of the reproductive hormones from breeding and non-breeding male and female Damaraland mole-rats at a single point in time, from which circulating plasma prolactin and urinary progesterone, testosterone, and cortisol were measured. As expected, plasma prolactin and urinary cortisol did not differ between the breeders and non-breeders. However, breeders (both male and female) possessed increased urinary testosterone and progesterone concentrations compared to their non-breeding counterparts. These results, in conjunction with the variation in the expression of the respective hormonal receptors within the brains of breeders and non-breeders suggest that elevated testosterone and progesterone in breeders establish a neural dominance phenotype, which ultimately aids in controlling breeding activities. This study has emphasised the need for holistic, comprehensive profiling of reproductive endocrine systems.
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Affiliation(s)
- Kyra M E Wallace
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
| | - Daniel W Hart
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
| | - Nicole Hagenah
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa; Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
| | - Andre Ganswindt
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa; Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
| | - Nigel C Bennett
- Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa; Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
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Jacobs PJ, Oosthuizen MK. Laterality in the Damaraland Mole-Rat: Insights from a Eusocial Mammal. Animals (Basel) 2023; 13:627. [PMID: 36830415 PMCID: PMC9951763 DOI: 10.3390/ani13040627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 02/07/2023] [Accepted: 02/08/2023] [Indexed: 02/15/2023] Open
Abstract
Lateralization is the functional control of certain behaviors in the brain being processed by either the left or right hemisphere. Behavioral asymmetries can occur at an individual and population level, although population-level lateralization is less common amongst solitary species, whereas social species can benefit more from aligning and coordinating their activities. We assessed laterality (individual and population) through turning biases in the eusocial Damaraland mole rat, Fukomys damarensis. We considered factors such as breeding status (queen or subordinate), environment (wild-caught or captive), sex (male or female), colony and body mass. All individuals together demonstrated significant left-turning biases, which was also significant at the population level. Wild-caught animals were more strongly lateralized, had a wider spread over a laterality index and lacked the population-level left-turning bias as compared to captive mole rats. Subordinate animals were more lateralized than queens, demonstrating social status differences in turning biases for social mole rats. This emphasizes the importance of animal handling and context when measuring and interpreting behavioral asymmetries.
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Affiliation(s)
- Paul J. Jacobs
- Department of Zoology & Entomology, University of Pretoria, Private Bag X20, Pretoria 0028, South Africa
- Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
| | - Maria K. Oosthuizen
- Department of Zoology & Entomology, University of Pretoria, Private Bag X20, Pretoria 0028, South Africa
- Mammal Research Institute, University of Pretoria, Pretoria 0002, South Africa
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5
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Serrano Nájera G, Kin K. Unusual occurrence of domestication syndrome amongst African mole-rats: Is the naked mole-rat a domestic animal? Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.987177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The Naked mole-rat (NMR) is becoming a prominent model organism due to its peculiar traits, such as eusociality, extreme longevity, cancer resistance, and reduced pain sensitivity. It belongs to the African mole-rats (AMR), a family of subterranean rodents that includes solitary, cooperative breeding and eusocial species. We identified and quantified the domestication syndrome (DS) across AMR, a set of morphological and behavioural traits significantly more common and pronounced amongst domesticated animals than in their wild counterparts. Surprisingly, the NMR shows apparent DS traits when compared to the solitary AMR. Animals can self-domesticate when a reduction of the fear response is naturally selected, such as in islands with no predators, or to improve the group’s harmony in cooperative breeding species. The DS may be caused by alterations in the physiology of the neural crest cells (NCC), a transient population of cells that generate a full range of tissues during development. The NCC contribute to organs responsible for transmitting the fear response and various other tissues, including craniofacial bones. Therefore, mutations affecting the NCC can manifest as behavioural and morphological alterations in many structures across the body, as seen in neurocristopathies. We observed that all social AMRs are chisel-tooth diggers, an adaption to hard soils that requires the flattening of the skull. We hypothesise that chisel-tooth digging could impose a selective pressure on the NCC that triggered the DS’s appearance, possibly facilitating the evolution of sociality. Finally, we discuss how DS traits are neutral or beneficial for the subterranean niche, strategies to test this hypothesis and report well-studied mutations in the NMR that are associated with the NCC physiology or with the control of the fear response. In conclusion, we argue that many of the NMR’s unconventional traits are compatible with the DS and provide a hypothesis about its origins. Our model proposes a novel avenue to enhance the understanding of the extraordinary biology of the NMR.
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Hart DW, Bennett NC, Voigt C. Social stress is unlikely to play a major role in reproductive suppression of female subordinate naked mole-rats and Damaraland mole-rats. Biol Lett 2022; 18:20220292. [PMID: 36285462 PMCID: PMC9597399 DOI: 10.1098/rsbl.2022.0292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Daniel W. Hart
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Nigel C. Bennett
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Cornelia Voigt
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
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7
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Finn KT, Thorley J, Bensch HM, Zöttl M. Subterranean Life-Style Does Not Limit Long Distance Dispersal in African Mole-Rats. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.879014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dispersal from the natal site to breeding sites is a crucial phase in the life history of animals and can have profound effects on the reproductive ecology and the structure of animal societies. However, few studies have assessed dispersal dynamics in subterranean mammals and it is unknown whether dispersal distances are constrained by living underground. Here we show, in social, subterranean Damaraland mole-rats (Fukomys damarensis), that a subterranean lifestyle does not preclude long distance dispersal and that both sexes are capable of successfully dispersing long distances (>4 km). Body condition did not predict dispersal distance, but dispersers from larger groups traveled farther than individuals from smaller groups. Subsequently we show in a phylogenetically controlled comparative analysis of dispersal distances in subterranean and surface-dwelling rodents that living underground does not constrain dispersal distances and that dispersal capacity is mainly a consequence of body size in both lifestyles.
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8
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Hart DW, van Vuuren AKJ, Erasmus A, Süess T, Hagenah N, Ganswindt A, Bennett NC. The endocrine control of reproductive suppression in an aseasonally breeding social subterranean rodent, the Mahali mole-rat (Cryptomys hottentotus mahali). Horm Behav 2022; 142:105155. [PMID: 35334327 DOI: 10.1016/j.yhbeh.2022.105155] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 03/01/2022] [Accepted: 03/10/2022] [Indexed: 12/24/2022]
Abstract
Cooperative behaviour, sociality and reproductive suppression in African mole-rats have been extensively studied. Nevertheless, endocrine correlates of some species of social mole-rats have been neglected, and these species may hold the key to understanding the behavioural and physiological complexity that allows the maintenance of social groups in African mole-rats. In this study, we investigated endocrine correlates implicated in the suppression of reproduction and cooperative behaviours, namely glucocorticoids (a stress-related indicator) through faecal glucocorticoid metabolites (fGCMs), plasma testosterone (an indicator of aggression) and plasma prolactin in the Mahali mole-rat (Cryptomys hottentotus mahali) across reproductive classes (breeding females and males, non-breeding females and males) and season (wet and dry). Breeders possessed higher levels of testosterone than non-breeders. In reproductively suppressed non-breeding females, fGCMs were significantly higher than in breeders. Furthermore, an adrenocorticotropic hormone stimulation test (ACTH challenge test) on both male and female non-breeders revealed that female non-breeders show a more significant response to the ACTH challenge than males. At the same time, plasma prolactin levels were equally elevated to similar levels in breeding and non-breeding females. Chronically high levels of prolactin and fGCM are reported to cause reproductive suppression and promote cooperative behaviours in non-breeding animals. Furthermore, there was a negative relationship between plasma prolactin and progesterone in non-breeding females. However, during the wet season, a relaxation of suppression occurs through reduced prolactin which corresponds with elevated levels of plasma progesterone in non-breeding females. Therefore, prolactin is hypothesised to be the primary hormone controlling reproductive suppression and cooperative behaviours in non-breeding females. This study provides new endocrine findings for the maintenance of social suppression in the genus Cryptomys.
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Affiliation(s)
- D W Hart
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
| | - A K Janse van Vuuren
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - A Erasmus
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - T Süess
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - N Hagenah
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa; Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - A Ganswindt
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa; Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - N C Bennett
- Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa; Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
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9
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Christensen C, Bracken AM, Justin O'Riain M, Heistermann M, King AJ, Fürtbauer I. Simultaneous investigation of urinary and faecal glucocorticoid metabolite concentrations reveals short- versus long-term drivers of HPA-axis activity in a wild primate (Papio ursinus). Gen Comp Endocrinol 2022; 318:113985. [PMID: 35093315 DOI: 10.1016/j.ygcen.2022.113985] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 01/07/2022] [Accepted: 01/24/2022] [Indexed: 12/24/2022]
Abstract
Glucocorticoids (GCs), a class of steroid hormones released through activation of the hypothalamic-pituitary-adrenal (HPA) axis, perform many vital functions essential for survival, including orchestrating an organism's response to stressors by modulating physiological and behavioural responses. Assessing changes and variation in GC metabolites from faecal or urine samples allows for the non-invasive monitoring of HPA-axis activity across vertebrates. The time lag of hormone excretion differs between these sample matrices, which has implications for their suitability for studying effects of different temporal nature on HPA-axis activity. However, simultaneous comparisons of predictors of faecal and urinary GC metabolites (fGCs and uGCs, respectively) are lacking. To address this gap, we employ frequent non-invasive sampling to investigate correlates of fGCs and uGCs in wild chacma baboons (Papio ursinus) (n = 17), including long-term (dominance rank, season, female reproductive state) and short-term (time of day, daily weather conditions) factors. Correlated with increasing day length, fGCs gradually decreased from winter to summer. No seasonal effect on uGCs was found but 'rain days' were associated with increased uGCs. Pregnant females had significantly higher fGCs compared to cycling and lactating females, whereas uGCs were not statistically different across reproductive states. A circadian effect was observed in uGCs but not in fGCs. Dominance rank did not affect either fGCs or uGCs. Our study highlights the difference in inherent fluctuation between uGCs and fGCs and its potential consequences for HPA-axis activity monitoring. While uGCs offer the opportunity to study short-term effects, they undergo more pronounced fluctuations, reducing their ability to capture long-term effects. Given the increasing use of urine for biological monitoring, knowledge of this potential limitation is crucial. Where possible, uGCs and fGCs should be monitored in tandem to obtain a comprehensive understanding of short- and long-term drivers of HPA-axis activity.
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Affiliation(s)
- Charlotte Christensen
- Biosciences, School of Biosciences, Geography and Physics, Faculty of Science and Engineering, Swansea University, SA2 8PP Swansea, UK.
| | - Anna M Bracken
- Biosciences, School of Biosciences, Geography and Physics, Faculty of Science and Engineering, Swansea University, SA2 8PP Swansea, UK
| | - M Justin O'Riain
- Institute for Communities and Wildlife in Africa, Department of Biological Sciences, University of Cape Town, Rondebosch 7701, South Africa
| | | | - Andrew J King
- Biosciences, School of Biosciences, Geography and Physics, Faculty of Science and Engineering, Swansea University, SA2 8PP Swansea, UK
| | - Ines Fürtbauer
- Biosciences, School of Biosciences, Geography and Physics, Faculty of Science and Engineering, Swansea University, SA2 8PP Swansea, UK
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Voigt C, Bennett NC. Gene expression pattern of Kisspeptin and RFamide-related peptide (Rfrp) in the male Damaraland mole-rat hypothalamus. J Chem Neuroanat 2021; 118:102039. [PMID: 34655735 DOI: 10.1016/j.jchemneu.2021.102039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 10/10/2021] [Accepted: 10/10/2021] [Indexed: 11/28/2022]
Abstract
Damaraland mole-rats (Fukomys damarensis) are cooperatively breeding, subterranean mammals, which exhibit high reproductive skew. Reproduction is monopolized by the dominant female of the group, while subordinates are anovulatory. Similarly, male subordinates within the colony show no sexual behaviour although they have functional gonads and do not differ from reproductive males in circulating levels of pituitary hormones and testosterone. However, reproductive status affects the neuroendocrine phenotype of males with breeders possessing increased mRNA expression of androgen and progesterone receptors compared to non-breeders in several forebrain regions implicated in the regulation of reproductive behaviour. The RFamide peptides kisspeptin and RFRP-3, encoded by the Kiss1 and Rfrp gene, are considered potent regulators of gonadotropin release. In females, reproductive inhibition is associated with reduced Kiss1 expression within the arcuate nucleus (ARC) and increased Rfrp expression in the anterior hypothalamus. To assess whether differential gene expression of Kiss1 and Rfrp underlies the difference in reproductive behaviour of males, we studied the expression of both genes by means of in situ hybridisation in wild-caught male Damaraland mole-rats with different reproductive status. The distribution of Kiss1 and Rfrp within the hypothalamus was found to be similar to females. Quantification of the Kiss1 hybridisation signal revealed no significant differences in relation to reproductive status. However, there was a significant positive correlation between testis mass and the number of Kiss1-expressing cells in the ARC and the mRNA content per cell, respectively. Analysis of the Rfrp hybridisation signal along the rostro-caudal extent of the hypothalamus revealed that non-reproductive males possessed an increased number of Rfrp-expressing cells at the level of the dorsomedial hypothalamic nucleus (DMH) than reproductive males. These data suggest the Kiss1 expression within the ARC is not associated with reproductive quiescence in subordinate males but instead, inhibitory effects may be mediated by Rfrp-expressing cells in the DMH.
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Affiliation(s)
- Cornelia Voigt
- Department of Zoology and Entomology, University of Pretoria, 0028 Pretoria, South Africa.
| | - Nigel C Bennett
- Department of Zoology and Entomology, University of Pretoria, 0028 Pretoria, South Africa
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11
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Medger K, Prins A, Lutermann H, Ganswindt A, Ganswindt SB, Bennett NC. Repeatability of daily profiles of baseline glucocorticoid metabolites measured in the urine and faeces of eastern rock sengis (Elephantulus myurus). Gen Comp Endocrinol 2021; 312:113857. [PMID: 34284023 DOI: 10.1016/j.ygcen.2021.113857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 06/24/2021] [Accepted: 07/14/2021] [Indexed: 10/20/2022]
Abstract
Repeatability of hormone concentrations is of great interest for studies investigating the evolution of hormonal traits. Particularly the repeatability of glucocorticoids (GCs) in response to a stressor is frequently investigated, but often only point (initial and/or response value), or single measures are used. A new method takes into account the entire individual hormone profile and generates an individual profile repeatability (PR) score. The method was developed for response profiles, but it may also be valuable for baseline values in species with diurnal changes in hormone concentrations. GCs are determined in a variety of matrices, and repeatability can vary considerably depending on the matrix. We investigated the repeatability of baseline GC metabolite (GCM) concentrations measured in urine (uGCM) and faeces (fGCM) of captive eastern rock sengis (Elephantulus myurus) using the more traditional linear mixed model approach and the PR method. GCMs were assessed over 24 h and measurements were repeated twice with two weeks between replicates. A diurnal rhythm in GCM concentrations associated with the activity period of the sengis was found in urine, but not in the faeces. Urinary GCM concentrations exhibited a moderate repeatability, whereas the repeatability of fGCM concentrations was low. Urinary GCM concentrations and their repeatability differed between the sexes; with higher concentrations and lower PR scores in females. No such sex differences were apparent for fGCM concentrations and the PR score was not able to characterise repeatability of fGCM concentrations, which were lacking a distinct profile. The PR score enabled a successful quantification of the repeatability of the diurnal uGCM profiles. Hormone profile, sex and sample matrix can affect hormonal traits considerably and the results may be obscured if these factors are not carefully considered.
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Affiliation(s)
- Katarina Medger
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
| | - André Prins
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Heike Lutermann
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - André Ganswindt
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Stefanie B Ganswindt
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Nigel C Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa; SARChI Chair of Mammal Behavioural Ecology and Physiology, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
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12
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Freeman AR. Female-female reproductive suppression: impacts on signals and behavior. Integr Comp Biol 2021; 61:1827-1840. [PMID: 33871603 DOI: 10.1093/icb/icab027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Female-female reproductive suppression is evident in an array of mammals, including rodents, primates, and carnivores. By suppressing others, breeding females can benefit by reducing competition from other females and their offspring. There are neuroendocrinological changes during suppression which result in altered behavior, reproductive cycling, and communication. This review, which focuses on species in Rodentia, explores the current theoretical frameworks of female-female reproductive suppression, how female presence and rank impacts reproductive suppression, and some of the proposed mechanisms of suppression. Finally, the understudied role of olfactory communication in female-female reproductive suppression is discussed to identify current gaps in our understanding of this topic.
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Affiliation(s)
- Angela R Freeman
- Department of Psychology, Cornell University, 211 Uris Hall, Cornell University, Ithaca, NY 14853
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13
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Edwards PD, Mooney SJ, Bosson CO, Toor I, Palme R, Holmes MM, Boonstra R. The stress of being alone: Removal from the colony, but not social subordination, increases fecal cortisol metabolite levels in eusocial naked mole-rats. Horm Behav 2020; 121:104720. [PMID: 32081743 DOI: 10.1016/j.yhbeh.2020.104720] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 02/06/2020] [Accepted: 02/14/2020] [Indexed: 12/15/2022]
Abstract
In many social species, hierarchical status within the group is associated with differences in basal adrenocortical activity. We examined this relationship in naked mole-rats (Heterocephalus glaber), eusocial rodents with arguably the most extreme social hierarchies of all mammals. This species lives in colonies where breeding is restricted to one socially dominant 'queen' and her male consorts, and all other individuals are reproductively suppressed 'subordinates'. The relationship between cortisol and social status in naked mole-rats has not fully been elucidated, as prior results on this topic have been contradictory. We used non-invasive feces sampling to measure baseline cortisol levels in eight laboratory colonies of naked mole-rats, to either replicate or reject rank differences. First, we successfully validated an assay to measure fecal cortisol metabolites (FCMs). Removal from the colony for the validation experiment, either alone or with an opposite sex conspecific, induced prolonged elevation of FCM levels on a scale of days to weeks. This increase in cortisol did not prevent the removed animals from sexually maturing. In colony-housed animals, we found no relationship between rank in the social hierarchy and FCM levels. Further, queens, breeding males, and reproductively suppressed subordinates all had equivalent FCM levels. We conclude that this species shows little evidence of the 'stress of dominance' or 'stress of subordination' and that reproductive suppression in naked mole-rats is not driven by elevated cortisol levels.
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Affiliation(s)
- Phoebe D Edwards
- Dept. of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada; Dept. of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Centre for the Neurobiology of Stress, Dept. of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - Skyler J Mooney
- Dept. of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Curtis O Bosson
- Centre for the Neurobiology of Stress, Dept. of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Ilapreet Toor
- Dept. of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Rupert Palme
- Dept. of Biomedical Sciences, University of Veterinary Medicine, 1210 Vienna, Austria
| | - Melissa M Holmes
- Dept. of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada; Dept. of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Dept. of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Rudy Boonstra
- Dept. of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Centre for the Neurobiology of Stress, Dept. of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
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14
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Stress in groups: Lessons from non-traditional rodent species and housing models. Neurosci Biobehav Rev 2020; 113:354-372. [PMID: 32278793 DOI: 10.1016/j.neubiorev.2020.03.033] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 03/06/2020] [Accepted: 03/31/2020] [Indexed: 02/06/2023]
Abstract
A major feature of life in groups is that individuals experience social stressors of varying intensity and type. Social stress can have profound effects on health, social behavior, and ongoing relationships. Relationships can also buffer the experience of exogenous stressors. Social stress has most commonly been investigated in dyadic contexts in mice and rats that produce intense stress. Here we review findings from studies of diverse rodents and non-traditional group housing paradigms, focusing on laboratory studies of mice and rats housed in visible burrow systems, prairie and meadow voles, and mole-rats. We argue that the use of methods informed by the natural ecology of rodent species provides novel insights into the relationship between social stress, behavior and physiology. In particular, we describe how this ethologically inspired approach reveals how individuals vary in their experience of and response to social stress, and how ecological and social contexts impact the effects of stress. Social stress induces adaptive changes, as well as long-term disruptive effects on behavior and physiology.
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15
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Medger K, Bennett NC, Prins A, Lutermann H, Ganswindt A. Sex and dose-dependent responses of urinary and faecal glucocorticoid metabolite concentrations following an ACTH challenge in eastern rock sengis (Elephantulus myurus). Comp Biochem Physiol A Mol Integr Physiol 2020; 245:110696. [PMID: 32268194 DOI: 10.1016/j.cbpa.2020.110696] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/23/2020] [Accepted: 03/25/2020] [Indexed: 01/18/2023]
Abstract
Non-invasive methods for measuring glucocorticoids and their metabolites are frequently used in ecological, behavioural and physiological studies of mammals. Using faeces, urine and other matrices for such a measurement has considerable advantages in comparison to more traditional methods, but also requires thorough validation of the methods used. Eastern rock sengis (Elephantulus myurus) are fascinating African mammals and the non-invasive monitoring of the adrenocortical activity opens up new opportunities to study their biology. We were able to validate two assays for measuring urinary (uGCM) and faecal glucocorticoid metabolite (fGCM) concentrations in this species using a dose-dependent challenge with adrenocorticotropic hormone (ACTH). A higher concentration of ACTH elicited higher uGCM and fGCM concentrations in both males and females. Interestingly, uGCM and fGCM concentrations and the responses to ACTH were higher in females than in males and small changes in faecal glucocorticoid metabolites could not be reliably detected in males. In contrast to ACTH, a saline injection did not result in an increase in uGCM or fGCM concentrations. The study also provided insight into when responses to a stressor are likely to be detected in the urine and faeces of sengis and opens up new opportunities to study the stress physiology of this and other sengi species. It further emphasises the importance of thoroughly validating non-invasive methods for measuring hormones in both sexes of a species and for incorporating dose-dependent approaches.
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Affiliation(s)
- Katarina Medger
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
| | - Nigel C Bennett
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa; Department of Zoology and Entomology, SARChI Chair of Mammal Behavioural Ecology and Physiology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - André Prins
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Heike Lutermann
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Andre Ganswindt
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa; Endocrine Research Laboratory, Department of Anatomy and Physiology, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
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16
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Palme R. Non-invasive measurement of glucocorticoids: Advances and problems. Physiol Behav 2018; 199:229-243. [PMID: 30468744 DOI: 10.1016/j.physbeh.2018.11.021] [Citation(s) in RCA: 326] [Impact Index Per Article: 54.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 11/16/2018] [Accepted: 11/16/2018] [Indexed: 01/19/2023]
Abstract
Glucocorticoids (GCs; i.e. cortisol/corticosterone) are a central component of the stress response and thus their measurement is frequently used to evaluate the impact of stressful situations. Their metabolites from faeces of various animal species are more and more taken as a non-invasive aid to assess GC release and thus adrenocortical activity. The current literature review includes an extensive collection (1327 papers) and evaluation (see also Supplementary Tables) of the literature on faecal cortisol/corticosterone metabolite (FCM) analysis published to date. It aims at giving reference for researchers interested in implementing FCM analysis into their study or seeking to improve such methods by providing background knowledge on GC metabolism and excretion, conveying insights into methodological issues and stating caveats of FCM analysis and by highlighting prerequisites for and some examples of a successful application of such methods. Collecting faecal samples and analysing FCMs may appear simple and straightforward, but researchers have to select and apply methods correctly. They also need to be aware of the many pitfalls and potentially confounding factors and, last but not least, have to carefully interpret results. Applied properly, measurement of FCMs is a powerful non-invasive tool in a variety of research areas, such as (stress) biology, ethology, ecology, animal conservation and welfare, but also biomedicine.
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Affiliation(s)
- Rupert Palme
- Unit of Physiology, Pathophysiology and Experimental Endocrinology, Department of Biomedical Sciences, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria.
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