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Wang LQ, Liu ZT, Wang JJ, Fang YH, Zhu H, Shi K, Zhang FS, Shuai LY. Complex effects of testosterone level on ectoparasite load in a ground squirrel: an experimental test for the immunocompetence handicap hypothesis. Parasit Vectors 2024; 17:164. [PMID: 38555448 PMCID: PMC10981293 DOI: 10.1186/s13071-024-06261-1] [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: 02/09/2024] [Accepted: 03/23/2024] [Indexed: 04/02/2024] Open
Abstract
BACKGROUND The immunocompetence handicap hypothesis suggests that males with a higher testosterone level should be better at developing male secondary traits, but at a cost of suppressed immune performance. As a result, we should expect that males with an increased testosterone level also possess a higher parasite load. However, previous empirical studies aimed to test this prediction have generated mixed results. Meanwhile, the effect of testosterone level on parasite load in female hosts remains poorly known. METHODS In this study, we tested this prediction by manipulating testosterone level in Daurian ground squirrels (Spermophilus dauricus), a medium-sized rodent widely distributed in northeast Asia. S. dauricus is an important host of ticks and fleas and often viewed as a considerable reservoir of plague. Live-trapped S. dauricus were injected with either tea oil (control group) or testosterone (treatment group) and then released. A total of 10 days later, the rodents were recaptured and checked for ectoparasites. Fecal samples were also collected to measure testosterone level of each individual. RESULTS We found that testosterone manipulation and sex of hosts interacted to affect tick load. At the end of the experiment, male squirrels subjected to testosterone implantation had an averagely higher tick load than males from the control group. However, this pattern was not found in females. Moreover, testosterone manipulation did not significantly affect flea load in S. dauricus. CONCLUSIONS Our results only lent limited support for the immunocompetence handicap hypothesis, suggesting that the role of testosterone on regulating parasite load is relatively complex, and may largely depend on parasite type and gender of hosts.
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Affiliation(s)
- Li-Qing Wang
- Grassland Research Institute, Chinese Academy of Agricultural Sciences, Hohhot, China
| | - Zhi-Tao Liu
- College of Life Sciences, Harbin Normal University, Harbin, China
| | - Jian-Jun Wang
- Inner Mongolia Autonomous Region Comprehensive Center for Disease Control and Prevention, Hohhot, China
| | - Yu-Han Fang
- College of Life Sciences, Huaibei Normal University, Huaibei, China
| | - Hao Zhu
- College of Life Sciences, Huaibei Normal University, Huaibei, China
| | - Ke Shi
- College of Life Sciences, Huaibei Normal University, Huaibei, China
| | - Fu-Shun Zhang
- Grassland Research Institute, Chinese Academy of Agricultural Sciences, Hohhot, China
| | - Ling-Ying Shuai
- College of Life Sciences, Huaibei Normal University, Huaibei, China.
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2
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Drea CM, Davies CS. Meerkat manners: Endocrine mediation of female dominance and reproductive control in a cooperative breeder. Horm Behav 2022; 145:105245. [PMID: 35988450 DOI: 10.1016/j.yhbeh.2022.105245] [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: 03/15/2022] [Revised: 07/18/2022] [Accepted: 08/08/2022] [Indexed: 11/16/2022]
Abstract
This article is part of a Special Issue (Hormones and Hierarchies). To gain more balanced understanding of sexual selection and mammalian sexual differentiation processes, this review addresses behavioral sex differences and hormonal mediators of intrasexual competition in the meerkat (Suricata suricatta) - a cooperative breeder unusual among vertebrates in its female aggression, degree of reproductive skew, and phenotypic divergence. Focused on the evolution, function, mechanism, and development of female dominance, the male remains a key reference point throughout. Integrated review of endocrine function does not support routine physiological suppression in subordinates of either sex, but instead a ramp up of weight, reproduction, aggression, and sex steroids, particularly androgens, in dominant females. Important and timely questions about female competition are thus addressed by shifting emphasis from mediators of reproductive suppression to mediators of reproductive control, and from organizational and activational roles of androgens in males to their roles in females. Unusually, we ask not only how inequity is maintained, but how dominance is acquired within a lifetime and across generations. Antiandrogens administered in the field to males and pregnant dominant females confirm the importance of androgen-mediated food competition. Moreover, effects of maternal endocrine milieu on offspring development reveal a heritable, androgenic route to female aggression, likely promoting reproductive priority along dominant matrilines. Integrating endocrine measures with long-term behavioral, ecological, morphological, and life-history data on normative and experimental individuals, across life stages and generations, provides better appreciation of the role of naturally circulating androgens in regulating the female phenotype, and sheds new light on the evolution of female dominance, reproductive inequity, and cooperative breeding.
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Affiliation(s)
- Christine M Drea
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708-0383, USA; Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.
| | - Charli S Davies
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708-0383, USA; Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
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3
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Drea CM, Davies CS, Greene LK, Mitchell J, Blondel DV, Shearer CL, Feldblum JT, Dimac-Stohl KA, Smyth-Kabay KN, Clutton-Brock TH. An intergenerational androgenic mechanism of female intrasexual competition in the cooperatively breeding meerkat. Nat Commun 2021; 12:7332. [PMID: 34921140 PMCID: PMC8683399 DOI: 10.1038/s41467-021-27496-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 11/22/2021] [Indexed: 12/27/2022] Open
Abstract
Female intrasexual competition can be intense in cooperatively breeding species, with some dominant breeders (matriarchs) limiting reproduction in subordinates via aggression, eviction or infanticide. In males, such tendencies bidirectionally link to testosterone, but in females, there has been little systematic investigation of androgen-mediated behaviour within and across generations. In 22 clans of wild meerkats (Suricata suricatta), we show that matriarchs 1) express peak androgen concentrations during late gestation, 2) when displaying peak feeding competition, dominance behaviour, and evictions, and 3) relative to subordinates, produce offspring that are more aggressive in early development. Late-gestation antiandrogen treatment of matriarchs 4) specifically reduces dominance behaviour, is associated with infrequent evictions, decreases social centrality within the clan, 5) increases aggression in cohabiting subordinate dams, and 6) reduces offspring aggression. These effects implicate androgen-mediated aggression in the operation of female sexual selection, and intergenerational transmission of masculinised phenotypes in the evolution of meerkat cooperative breeding.
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Affiliation(s)
- Christine M Drea
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA.
- Department of Biology, Duke University, Durham, NC, 27708, USA.
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.
| | - Charli S Davies
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Lydia K Greene
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
- Duke Lemur Center, Duke University, Durham, NC, 27705, USA
| | - Jessica Mitchell
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
- Nuffield Centre for International Health and Development, University of Leeds, Leeds, West Yorkshire, LS2 9JT, UK
| | - Dimitri V Blondel
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
- Department of Biology, North Carolina Wesleyan College, Rocky Mount, NC, 27804, USA
| | - Caroline L Shearer
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
| | - Joseph T Feldblum
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
- Department of Anthropology and Society of Fellows, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Kristin A Dimac-Stohl
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
- Department of Biology, Duke University, Durham, NC, 27708, USA
| | - Kendra N Smyth-Kabay
- Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
- Boston Consulting Group, Bethesda, MD, 20814, USA
| | - Tim H Clutton-Brock
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
- Department of Zoology, University of Cambridge, Cambridge, CB2 3EJ, UK
- Mammal Research Institute, University of Pretoria, 0002, Pretoria, South Africa
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4
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Spence‐Jones HC, Brehm AM, Cram D, Gaynor D, Thorley J, Manser MB, Clutton‐Brock TH. Deferred benefits of dominance for natal males in a cooperative breeder, the Kalahari meerkat. J Zool (1987) 2021. [DOI: 10.1111/jzo.12918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- H. C. Spence‐Jones
- Kalahari Research Centre Kuruman River Reserve Northern Cape South Africa
| | - A. M. Brehm
- Kalahari Research Centre Kuruman River Reserve Northern Cape South Africa
| | - D. Cram
- Kalahari Research Centre Kuruman River Reserve Northern Cape South Africa
- Department of Zoology University of Cambridge Cambridge UK
| | - D. Gaynor
- Kalahari Research Centre Kuruman River Reserve Northern Cape South Africa
- Mammal Research Institute University of Pretoria Pretoria South Africa
| | - J. Thorley
- Kalahari Research Centre Kuruman River Reserve Northern Cape South Africa
- Department of Zoology University of Cambridge Cambridge UK
| | - M. B. Manser
- Kalahari Research Centre Kuruman River Reserve Northern Cape South Africa
- Mammal Research Institute University of Pretoria Pretoria South Africa
- Animal Behaviour Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich Switzerland
| | - T. H. Clutton‐Brock
- Kalahari Research Centre Kuruman River Reserve Northern Cape South Africa
- Department of Zoology University of Cambridge Cambridge UK
- Mammal Research Institute University of Pretoria Pretoria South Africa
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5
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O'Brien KA, Waterman JM, Anderson WG, Bennett NC. Trade-offs between immunity and testosterone in male African ground squirrels. ACTA ACUST UNITED AC 2018; 221:jeb.177683. [PMID: 29941613 DOI: 10.1242/jeb.177683] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 06/20/2018] [Indexed: 10/28/2022]
Abstract
The immunocompetence handicap hypothesis (ICHH) proposes that testosterone has both beneficial effects on male reproductive potential and negative effects by suppressing the immune system. However, support for the ICHH has been variable and an alternative hypothesis suggests that testosterone may be acting indirectly via cortisol to suppress immunity (the stress-linked ICHH). A third hypothesis is that increased energetic investment in immunity results in the suppression of testosterone. We tested these hypotheses in male Cape ground squirrels (Xerus inauris) through two separate manipulations: first, by triggering a strong immune response using a lipopolysaccharide (LPS) injection and, secondly, by increasing circulating testosterone using silastic testosterone implants. Responding to an immune challenge significantly reduced testosterone, supporting the immune suppression hypothesis, while increasing circulating testosterone had no effect on immunocompetence, body mass, ectoparasite abundances or cortisol levels, failing to support either the ICHH or stress-linked ICHH. Our results add to the increasing body of literature that challenges the ICHH, and we conclude that the trade-off between testosterone and immunity is mediated through immune activation and not through testosterone in male Cape ground squirrels. Being able to test the ICHH, stress-linked ICHH and immune suppression hypotheses in a free-ranging mammal gives us a unique opportunity to examine the mechanisms mediating this trade-off.
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Affiliation(s)
- Kelsey A O'Brien
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Jane M Waterman
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada .,Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
| | - W Gary Anderson
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Nigel C Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
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6
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Smyth KN, Caruso NM, Davies CS, Clutton-Brock TH, Drea CM. Social and endocrine correlates of immune function in meerkats: implications for the immunocompetence handicap hypothesis. ROYAL SOCIETY OPEN SCIENCE 2018; 5:180435. [PMID: 30225031 PMCID: PMC6124081 DOI: 10.1098/rsos.180435] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 06/25/2018] [Indexed: 06/08/2023]
Abstract
Social status can mediate effects on the immune system, with profound consequences for individual health; nevertheless, most investigators of status-related disparities in free-ranging animals have used faecal parasite burdens to proxy immune function in the males of male-dominant species. We instead use direct measures of innate immune function (complement and natural antibodies) to examine status-related immunocompetence in both sexes of a female-dominant species. The meerkat is a unique model for such a study because it is a cooperatively breeding species in which status-related differences are extreme, evident in reproductive skew, morphology, behaviour, communication and physiology, including that dominant females naturally express the greatest total androgen (androstenedione plus testosterone) concentrations. We found that, relative to subordinates, dominant animals had reduced serum bacteria-killing abilities; also, relative to subordinate females, dominant females had reduced haemolytic complement activities. Irrespective of an individual's sex or social status, androstenedione concentrations (but not body condition, age or reproductive activity) negatively predicted concurrent immunocompetence. Thus, dominant meerkats of both sexes are immunocompromised. Moreover, in female meerkats, androstenedione perhaps acting directly or via local conversion, may exert a double-edged effect of promoting dominance and reproductive success at the cost of increased parasitism and reduced immune function. Given the prominent signalling of dominance in female meerkats, these findings may relate to the immunocompetence handicap hypothesis (ICHH); however, our data would suggest that the endocrine mechanism underlying the ICHH need not be mediated solely by testosterone and might explain trade-offs in females, as well as in males.
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Affiliation(s)
- Kendra N. Smyth
- University Program in Ecology, Duke University, Durham, NC, USA
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
- Kalahari Research Trust, Kuruman River Reserve, Van Zylsrus, Northern Cape, South Africa
| | - Nicholas M. Caruso
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, USA
| | - Charli S. Davies
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
- Kalahari Research Trust, Kuruman River Reserve, Van Zylsrus, Northern Cape, South Africa
| | - Tim H. Clutton-Brock
- Kalahari Research Trust, Kuruman River Reserve, Van Zylsrus, Northern Cape, South Africa
- Department of Zoology, University of Cambridge, Cambridge, UK
- Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Christine M. Drea
- University Program in Ecology, Duke University, Durham, NC, USA
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
- Department of Biology, Duke University, Durham, NC, USA
- Kalahari Research Trust, Kuruman River Reserve, Van Zylsrus, Northern Cape, South Africa
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7
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Incidence and biomarkers of pregnancy, spontaneous abortion, and neonatal loss during an environmental stressor: Implications for female reproductive suppression in the cooperatively breeding meerkat. Physiol Behav 2018; 193:90-100. [PMID: 29730033 DOI: 10.1016/j.physbeh.2017.11.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Revised: 10/11/2017] [Accepted: 11/11/2017] [Indexed: 11/22/2022]
Abstract
Meerkats are group-living, insectivorous herpestids in which subordinate members provide extensive care for the dominant female's young. In contrast to some cooperative breeders, subordinate female meerkats are physiologically able to reproduce and occasionally do so successfully; their attempts are more frequently 'suppressed' via eviction or infanticide by the dominant female. Spontaneous abortion and neonatal loss occur with some regularity, further negatively impacting reproductive success. Here, we compared the reproductive outcomes and endocrine profiles, including of serum progesterone (P4), serum estradiol (E2), and fecal glucocorticoid metabolites (fGCm), of dominant and subordinate dams residing within their clans in the Kalahari Desert of South Africa. Our study spanned years of drought, which reduced insect abundance and represented a substantial environmental stressor. Meerkat pregnancies were identified at mid-term and culminated either in spontaneous abortions or full-term deliveries, after which pups were either lost prior to emergence from the natal den (usually within 2days of birth) or emerged at 2-3weeks. Neonatal loss exceeded fetal loss for all females, and contributed to narrowing the status-related disparity in female reproductive output seen during less arid periods. Although E2 concentrations were significantly lower in subordinate than dominant females, they were sufficient to support gestation. Absolute E2 concentrations may owe to androgenic precursors that also attain highest concentrations in dominant dams and may mediate aggression underlying female reproductive skew. Pregnancies terminating in fetal loss were marked by significantly lower P4 concentrations in mid-gestation and modestly lower E2 concentrations overall. Consistently high fGCm concentrations further increased across trimesters, particularly (but not consistently) in subordinates and in aborted pregnancies. Environmental stressors may modulate reproductive outcomes in meerkats through their influence on sex steroids and their effects on intragroup competition. The social and eco-physiological factors affecting intraspecific variation in reproductive output, even in obligate cooperative breeders, may be most apparent during extreme conditions, reflecting the benefits of long-term studies for assessing the impact of climate change.
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8
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Smyth KN, Greene LK, Clutton-Brock T, Drea CM. Androgens predict parasitism in female meerkats: a new perspective on a classic trade-off. Biol Lett 2017; 12:rsbl.2016.0660. [PMID: 28120802 DOI: 10.1098/rsbl.2016.0660] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 09/27/2016] [Indexed: 12/15/2022] Open
Abstract
The immunocompetence handicap hypothesis posits that androgens in males can be a 'double-edged sword', actively promoting reproductive success, while also negatively impacting health. Because there can be both substantial androgen concentrations in females and significant androgenic variation among them, particularly in species portraying female social dominance over males or intense female-female competition, androgens might also play a role in mediating female health and fitness. We examined this hypothesis in the meerkat (Suricata suricatta), a cooperatively breeding, social carnivoran characterized by aggressively mediated female social dominance and extreme rank-related reproductive skew. Dominant females also have greater androgen concentrations and harbour greater parasite loads than their subordinate counterparts, but the relationship between concurrent androgen concentrations and parasite burdens is unknown. We found that a female's faecal androgen concentrations reliably predicted her concurrent state of endoparasitism irrespective of her social status: parasite species richness and infection by Spirurida nematodes, Oxynema suricattae, Pseudandrya suricattae and coccidia were greater with greater androgen concentrations. Based on gastrointestinal parasite burdens, females appear to experience the same trade-off in the costs and benefits of raised androgens as do the males of many species. This trade-off presumably represents a health cost of sexual selection operating in females.
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Affiliation(s)
- Kendra N Smyth
- University Program in Ecology, Duke University, Durham NC 27708, USA .,Department of Evolutionary Anthropology, Duke University, Durham NC 27708, USA.,Kalahari Research Trust, Kuruman River Reserve, Northern Cape 8467, South Africa
| | - Lydia K Greene
- University Program in Ecology, Duke University, Durham NC 27708, USA.,Department of Evolutionary Anthropology, Duke University, Durham NC 27708, USA.,Kalahari Research Trust, Kuruman River Reserve, Northern Cape 8467, South Africa
| | - Tim Clutton-Brock
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape 8467, South Africa.,Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK.,Mammal Research Institute, University of Pretoria, Pretoria 0028, South Africa
| | - Christine M Drea
- University Program in Ecology, Duke University, Durham NC 27708, USA.,Department of Evolutionary Anthropology, Duke University, Durham NC 27708, USA.,Department of Biology, Duke University, Durham NC 27708, USA.,Kalahari Research Trust, Kuruman River Reserve, Northern Cape 8467, South Africa
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9
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Patterson S, Drewe JA, Pfeiffer DU, Clutton-Brock TH. Social and environmental factors affect tuberculosis related mortality in wild meerkats. J Anim Ecol 2017; 86:442-450. [PMID: 28186336 PMCID: PMC5413830 DOI: 10.1111/1365-2656.12649] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 01/31/2017] [Indexed: 11/27/2022]
Abstract
Tuberculosis (TB) is an important and widespread disease of wildlife, livestock and humans world‐wide, but long‐term empirical datasets describing this condition are rare. A population of meerkats (Suricata suricatta) in South Africa's Kalahari Desert have been diagnosed with Mycobacterium suricattae, a novel strain of TB, causing fatal disease in this group‐living species. This study aimed to find characteristics associated with clinical TB in meerkats. These characteristics could subsequently be used to identify ‘at‐risk’ animals within a population, and target these individuals for control measures. We conducted a retrospective study based on a unique, long‐term life‐history dataset of over 2000 individually identified animals covering a 14‐year period after the first confirmatory diagnosis of TB in this population in 2001. Individual‐ and group‐level risk factors were analysed using time‐dependent Cox regression to examine their potential influence on the time to development of end‐stage TB. Cases of disease involved 144 individuals in 27 of 73 social groups, across 12 of 14 years (an incidence rate of 3·78 cases/100 study years). At the individual level, increasing age had the greatest effect on risk of disease with a hazard ratio of 4·70 (95% CI: 1·92–11·53, P < 0·01) for meerkats aged 24–48 months, and a hazard ratio of 9·36 (3·34–26·25, P < 0·001) for animals aged over 48 months (both age categories compared with animals aged below 24 months). Previous group history of TB increased the hazard by a factor of 4·29 (2·00–9·17, P < 0·01), and an interaction was found between this variable and age. At a group level, immigrations of new group members in the previous year increased hazard by a factor of 3·00 (1·23–7·34, P = 0·016). There was weaker evidence of an environmental effect with a hazard ratio for a low rainfall (<200 mm) year of 2·28 (0·91–5·72, P = 0·079). Our findings identify potential individual characteristics on which to base targeted control measures such as vaccination. Additional data on the dynamics of the infection status of individuals and how this changes over time would complement these findings by enhancing understanding of disease progression and transmission, and thus the implications of potential management measures.
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Affiliation(s)
- Stuart Patterson
- Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, University of London, Hawkshead Lane, Hatfield AL9 7TA, UK
| | - Julian A Drewe
- Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, University of London, Hawkshead Lane, Hatfield AL9 7TA, UK
| | - Dirk U Pfeiffer
- Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, University of London, Hawkshead Lane, Hatfield AL9 7TA, UK.,School of Veterinary Medicine, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR
| | - Tim H Clutton-Brock
- Large Animal Research Group, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.,Mammal Research Institute, University of Pretoria, Hatfield, Pretoria, South Africa
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10
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Davies CS, Smyth KN, Greene LK, Walsh DA, Mitchell J, Clutton-Brock T, Drea CM. Exceptional endocrine profiles characterise the meerkat: sex, status, and reproductive patterns. Sci Rep 2016; 6:35492. [PMID: 27752129 PMCID: PMC5067592 DOI: 10.1038/srep35492] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 09/30/2016] [Indexed: 11/17/2022] Open
Abstract
In vertebrates, reproductive endocrine concentrations are strongly differentiated by sex, with androgen biases typifying males and estrogen biases typifying females. These sex differences can be reduced in female-dominant species; however, even the most masculinised of females have less testosterone (T) than do conspecific males. To test if aggressively dominant, female meerkats (Suricata suricatta) may be hormonally masculinised, we measured serum androstenedione (A4), T and estradiol (E2) in both sexes and social classes, during both ‘baseline’ and reproductive events. Relative to resident males, dominant females had greater A4, equivalent T and greater E2 concentrations. Males, whose endocrine values did not vary by social status, experienced increased T during reproductive forays, linking T to sexual behaviour, but not social status. Moreover, substantial E2 concentrations in male meerkats may facilitate their role as helpers. In females, dominance status and pregnancy magnified the unusual concentrations of measured sex steroids. Lastly, faecal androgen metabolites replicated the findings derived from serum, highlighting the female bias in total androgens. Female meerkats are thus strongly hormonally masculinised, possibly via A4’s bioavailability for conversion to T. These raised androgen concentrations may explain female aggressiveness in this species and give dominant breeders a heritable mechanism for their daughters’ competitive edge.
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Affiliation(s)
- Charli S Davies
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Kendra N Smyth
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.,University Program in Ecology, Duke University, Durham, NC 27708, USA
| | - Lydia K Greene
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.,University Program in Ecology, Duke University, Durham, NC 27708, USA
| | - Debbie A Walsh
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Jessica Mitchell
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Tim Clutton-Brock
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Mammal Research Institute, University of Pretoria, Pretoria, South Africa.,Department of Zoology, University of Cambridge, Cambridge, UK
| | - Christine M Drea
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa.,Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.,University Program in Ecology, Duke University, Durham, NC 27708, USA.,Department of Biology, Duke University, Durham, USA
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