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Michael W. Miller - One of the best experts on this subject based on the ideXlab platform.
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Mountain lions prey selectively on prion-infected Mule deer
Biology Letters, 2010Co-Authors: Caroline E. Krumm, N. Thompson Hobbs, Mary M Conner, Don O. Hunter, Michael W. MillerAbstract:The possibility that predators choose prey selectively based on age or condition has been suggested but rarely tested. We examined whether mountain lions (Puma concolor) selectively prey upon Mule deer (Odocoileus hemionus) infected with chronic wasting disease, a prion disease. We located kill sites of mountain lions in the northern Front Range of Colorado, USA, and compared disease prevalence among lion-killed adult (> or =2 years old) deer with prevalence among sympatric deer taken by hunters in the vicinity of kill sites. Hunter-killed female deer were less likely to be infected than males (odds ratios (OR) = 0.2, 95% confidence intervals (CI) = 0.1-0.6; p = 0.015). However, both female (OR = 8.5, 95% CI = 2.3-30.9) and male deer (OR = 3.2, 95% CI = 1-10) killed by a mountain lion were more likely to be infected than same-sex deer killed in the vicinity by a hunter (p < 0.001), suggesting that mountain lions in this area actively selected prion-infected individuals when targeting adult Mule deer as prey items.
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human land use influences chronic wasting disease prevalence in Mule deer
Ecological Applications, 2005Co-Authors: Matthew L Farnsworth, Mary M Conner, Lisa L Wolfe, Thompson N Hobbs, Kenneth P Burnham, Elizabeth S Williams, David M Theobald, Michael W. MillerAbstract:Human alteration of landscapes can affect the distribution, abundance, and behavior of wildlife. We explored the effects of human land use on the prevalence of chronic wasting disease (CWD) in Mule deer (Odocoileus hemionus) populations residing in north-central Colorado. We chose best approximating models estimating CWD prevalence in relation to differences in human land use, sex, and geographic location. Prevalence was higher in developed areas and among male deer, suggesting anthropogenic influences on the occurrence of disease. We also found a relatively high degree of variation in prevalence across the three study sites, suggesting that spatial patterns in disease may be influenced by other factors operating at a broader, landscape scale. Our results suggest that multiple factors, including changes in land use, differences in exposure risk between sexes, and landscape-scaled heterogeneity, are associated with CWD prevalence in north-central Colorado.
T H Cluttonbrock - One of the best experts on this subject based on the ideXlab platform.
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a unified models analysis of the development of sexual size dimorphism in damaraland mole rats fukomys damarensis
Journal of Mammalogy, 2019Co-Authors: T H Cluttonbrock, Jack ThorleyAbstract:Individual variation in growth rates often generates variation in fitness. However, the ability to draw meaningful inferences from growth data depends on the use of growth models that allow for direct comparisons of growth between the sexes, between populations, and between species. Unlike traditional sigmoid functions, a recently parameterized family of unified growth models provides a reliable basis for comparisons since each parameter affects a single curve characteristic and parameters are directly comparable across the unified family. Here, we use the unified-models approach to examine the development of sexual size dimorphism in Damaraland mole-rats (Fukomys damarensis), where breeding males are larger than breeding females. Using skeletal measurements, we show here that the larger size of male Damaraland mole-rats arises from an increased growth rate across the entire period of development, rather than through sex differences in the duration or timing of growth. Male-biased skeletal size dimorphism is not unusual among rodents, and our measures of sex differences in size in captive mole-rats are close to sexual size differences in the wild, where size dimorphism = 1.04 (male:female). We hope our study will encourage the wide use of unified growth models by mammalogists.
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allo parental care in damaraland mole rats is female biased and age dependent though independent of testosterone levels
Physiology & Behavior, 2018Co-Authors: Philippe Vullioud, Markus Zöttl, D Gaynor, Katy Goddard, Miquel Torrentstico, Nigel C Bennett, T H CluttonbrockAbstract:Abstract In Damaraland mole-rats (Fukomys damarensis), non-breeding subordinates contribute to the care of offspring born to the breeding pair in their group by carrying and retrieving young to the nest. In social mole-rats and some cooperative breeders, dominant females show unusually high testosterone levels and it has been suggested that high testosterone levels may increase reproductive and aggressive behavior and reduce investment in allo-parental and parental care, generating age and state-dependent variation in behavior. Here we show that, in Damaraland mole-rats, allo-parental care in males and females is unaffected by experimental increases in testosterone levels. Pup carrying decreases with age of the non-breeding helper while the change in social status from non-breeder to breeder has contrasting effects in the two sexes. Female breeders were more likely than female non-breeders to carry pups but male breeders were less likely to carry pups than male non-breeders, increasing the sex bias in parental care compared to allo-parental care. Our results indicate that testosterone is unlikely to be an important regulator of allo-parental care in mole-rats.
Mary M Conner - One of the best experts on this subject based on the ideXlab platform.
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Mountain lions prey selectively on prion-infected Mule deer
Biology Letters, 2010Co-Authors: Caroline E. Krumm, N. Thompson Hobbs, Mary M Conner, Don O. Hunter, Michael W. MillerAbstract:The possibility that predators choose prey selectively based on age or condition has been suggested but rarely tested. We examined whether mountain lions (Puma concolor) selectively prey upon Mule deer (Odocoileus hemionus) infected with chronic wasting disease, a prion disease. We located kill sites of mountain lions in the northern Front Range of Colorado, USA, and compared disease prevalence among lion-killed adult (> or =2 years old) deer with prevalence among sympatric deer taken by hunters in the vicinity of kill sites. Hunter-killed female deer were less likely to be infected than males (odds ratios (OR) = 0.2, 95% confidence intervals (CI) = 0.1-0.6; p = 0.015). However, both female (OR = 8.5, 95% CI = 2.3-30.9) and male deer (OR = 3.2, 95% CI = 1-10) killed by a mountain lion were more likely to be infected than same-sex deer killed in the vicinity by a hunter (p < 0.001), suggesting that mountain lions in this area actively selected prion-infected individuals when targeting adult Mule deer as prey items.
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human land use influences chronic wasting disease prevalence in Mule deer
Ecological Applications, 2005Co-Authors: Matthew L Farnsworth, Mary M Conner, Lisa L Wolfe, Thompson N Hobbs, Kenneth P Burnham, Elizabeth S Williams, David M Theobald, Michael W. MillerAbstract:Human alteration of landscapes can affect the distribution, abundance, and behavior of wildlife. We explored the effects of human land use on the prevalence of chronic wasting disease (CWD) in Mule deer (Odocoileus hemionus) populations residing in north-central Colorado. We chose best approximating models estimating CWD prevalence in relation to differences in human land use, sex, and geographic location. Prevalence was higher in developed areas and among male deer, suggesting anthropogenic influences on the occurrence of disease. We also found a relatively high degree of variation in prevalence across the three study sites, suggesting that spatial patterns in disease may be influenced by other factors operating at a broader, landscape scale. Our results suggest that multiple factors, including changes in land use, differences in exposure risk between sexes, and landscape-scaled heterogeneity, are associated with CWD prevalence in north-central Colorado.
Nigel C Bennett - One of the best experts on this subject based on the ideXlab platform.
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allo parental care in damaraland mole rats is female biased and age dependent though independent of testosterone levels
Physiology & Behavior, 2018Co-Authors: Philippe Vullioud, Markus Zöttl, D Gaynor, Katy Goddard, Miquel Torrentstico, Nigel C Bennett, T H CluttonbrockAbstract:Abstract In Damaraland mole-rats (Fukomys damarensis), non-breeding subordinates contribute to the care of offspring born to the breeding pair in their group by carrying and retrieving young to the nest. In social mole-rats and some cooperative breeders, dominant females show unusually high testosterone levels and it has been suggested that high testosterone levels may increase reproductive and aggressive behavior and reduce investment in allo-parental and parental care, generating age and state-dependent variation in behavior. Here we show that, in Damaraland mole-rats, allo-parental care in males and females is unaffected by experimental increases in testosterone levels. Pup carrying decreases with age of the non-breeding helper while the change in social status from non-breeder to breeder has contrasting effects in the two sexes. Female breeders were more likely than female non-breeders to carry pups but male breeders were less likely to carry pups than male non-breeders, increasing the sex bias in parental care compared to allo-parental care. Our results indicate that testosterone is unlikely to be an important regulator of allo-parental care in mole-rats.
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breeding status affects the expression of androgen and progesterone receptor mrna in the brain of male damaraland mole rats
Journal of Zoology, 2016Co-Authors: Cornelia Voigt, Stefan Leitner, Nigel C BennettAbstract:The eusocial Damaraland mole-rat Fukomys damarensis represents an extreme example of reproductive skew, in that reproduction is completely blocked in female subordinate group members. Similarly, male subordinates within the colony show no sexual behaviour. In contrast to females, however, non-reproductive males have functional gonads and do not differ in circulating levels of pituitary hormones and testosterone from reproductive males. Nevertheless, they have reduced numbers of follicle-stimulating hormone (FSH) receptors in their testes and they produce fewer spermatozoa with a large proportion of immature spermatozoa and precursors. To understand the mechanism of reproductive suppression operational in subordinate males, we studied the expression of androgen receptor (AR) and progesterone receptor (PGR) genes in forebrain regions involved in the control of reproductive behaviour in male breeders and non-breeders from intact colonies. While it is well documented that testosterone activates male-typical behaviour, the role of progesterone in this process is less clear as previous studies have produced contradictory results. We found the expression of AR and PGR genes in several forebrain regions of male Damaraland mole-rats. The distribution of AR in males matches our previous findings in females. This is the first report showing the distribution of PGR in mole-rats. We found PGR in all areas which were also sensitive to androgens and oestrogens. Analysis of the optical densities of the AR and PGR hybridization signal revealed that breeding males had increased expression of AR and PGR compared to non-breeders in most brain regions examined, which include the medial preoptic area, the bed nucleus of the stria terminalis, the ventromedial nucleus of the hypothalamus, the arcuate nucleus and the medial amygdala. These status-related differences were more pronounced for PGR than for AR. This study shows that breeding position affects the neuroendocrine phenotype of male Damaraland mole-rats. Furthermore, it suggests that androgens and progesterone might act synergistically in activating sexual behaviour in males.
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Effects of season and social status on gonadal function in social Natal mole-rats
Journal of Mammalogy, 2010Co-Authors: Maria K. Oosthuizen, H. Viljoen, Nigel C BennettAbstract:The reproductive cycle of mammals can be inhibited by 2 factors, seasonal breeding and dominance control, both potentially important in mole-rats. The gonads and gonadal steroids of dominant (reproductive) and subordinate (nonreproductive) Natal mole-rats (Cryptomys hottentotus natalensis) were investigated to determine the effects of season and social status on reproduction within natal colonies. We found no seasonal differences in concentrations of gonadal steroids of male or female mole-rats. Similarly, the gonadal histology and volume showed no seasonal differences. These results, together with the presence of fetuses, confirm the potential for breeding throughout the year. Reproductive and nonreproductive mole-rats display comparable testosterone and estrogen concentrations in males and females, respectively. Follicular development and the presence and number of sperm in nonreproductive animals suggest that the reproductive quiescence in nonreproductive animals is likely to result from behavioral interference of dominant animals or incest avoidance (or both). Urinary progesterone concentrations of reproductive females were significantly higher than those of nonreproductive females. Although follicular development in nonreproductive females proceeds to the level of Graafian follicles, the number of these follicles present in nonreproductive females was significantly less than that in reproductive females. The reproductive physiology of the Natal mole-rat compares with other loosely social mole-rat species inhabiting mesic areas.
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An immunohistochemical study of the gonadotrophin-releasing hormone 1 system in solitary Cape mole-rats, Georychus capensis, and social Natal mole-rats, Cryptomys hottentotus natalensis.
Neuroscience, 2008Co-Authors: Maria K. Oosthuizen, Nigel C Bennett, Clive W. CoenAbstract:Mole-rat species within the family Bathyergidae exhibit a wide range of reproductive strategies and social systems. Various forms of reproductive suppression are dis- played within this family: in the solitary species, breeding is suspended for part of the year and in the social species, reproduction is suppressed in subordinate animals. This study investigated the gonadotrophin-releasing hormone 1 (GnHR-1) systems of breeding and non-breeding solitary Cape mole-rats and social Natal mole-rats for possible inter- and/or intra-species differences. In both species, GnRH-1 cell bodies are predominantly in the medial septum region of the diagonal band or the preoptic area, with relatively few in the mediobasal hypothalamus; a dense concentration of GnRH- 1-immunoreactive (ir) processes is present in the region of the organum vasculosum of the lamina terminalis. In Cape mole-rats, GnRH-1-ir processes are particularly dense within the lateral margins of the median eminence, which is en- folded by a large pars tuberalis of the pituitary gland. Natal mole-rats display GnRH-1-ir processes across the breadth of the median eminence, which is abutted by a relatively small pars tuberalis. There are more GnRH-1-ir cell bodies in Natal mole-rats than in Cape mole-rats (720 vs. 420). No signif- icant differences were found in the number, distribution or size of GnRH-1-ir cell bodies according to season in Cape mole-rats or according to reproductive status or sex in Natal mole-rats. In female and male Natal mole-rats, GnRH-1-immu- noreactivity in the median eminence is less dense in the reproductive animals; no such difference was found in Cape mole-rats between the breeding and non-breeding seasons. These immunohistochemical results are discussed in the light of earlier studies which identified no functional neuroen- docrine impediments underlying regulated reproduction in either Cape or Natal mole-rats. The cumulative findings sug- gest that the principal factors determining seasonal or so- cially induced suppression of reproduction in these species are behavioral rather than neuroendocrine. © 2008 IBRO. Published by Elsevier Ltd. All rights reserved.
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Burrow architecture and burrowing dynamics of the endangered Namaqua dune mole rat (Bathyergus janetta) (Rodentia: Bathyergidae)
Journal of Zoology, 2006Co-Authors: M. Herbst, Nigel C BennettAbstract:The Namaqua dune mole rat Bathyergus janetta is a solitary subterranean rodent that occurs in the arid and sandy regions of Namaqualand. The predictable winter rainfall and high diversity of geophytes, the predominant food resource, enables the mole rat to survive in this extreme environment. Burrowing and burrow system configuration were measured by observing mound production and the excavation of six mole rat burrow systems. A typical burrow system comprises nest chambers, food stores, defecation sites and bolt holes, which serve as a place of retreat when the animal is alarmed or threatened. Males tend to have linear-shaped burrow systems, whereas the burrow systems of females are more reticulate. The linear nature of the male burrow system probably increases the home range used to search for potential mates. Burrow systems undergo constant excavation and re-excavation within the home range. The average burrow length ranges from 71.2 to 165 m with a mean home range of 805.8±375.5 m2.
John C Patton - One of the best experts on this subject based on the ideXlab platform.
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introgressive hybridization and nonconcordant evolutionary history of maternal and paternal lineages in north american deer
Evolution, 1998Co-Authors: James C Cathey, John W. Bickham, John C PattonAbstract:: Introgressive hybridization between Mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus) was studied using sequence analysis of the paternally inherited, Y-linked, Zfy gene. The distribution of Zfy genotypes indicate that male white-tailed deer disperse into the range of Mule deer and successfully breed with Mule deer does. In western Texas, F1 hybrids are rare, but a relatively high proportion of backcross individuals was observed. Phylogenetic analysis of Zfy among white-tailed, Mule, and black-tailed deer was consistent with traditional systematic placement of the latter two being sister-taxa, whereas previous mtDNA studies suggested Mule and white-tailed deer were sister taxa.