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Wright E.,Max Planck Institute for Evolutionary Anthropology | Grueter C.C.,University of Western Australia | Seiler N.,Max Planck Institute for Evolutionary Anthropology | Abavandimwe D.,Karisoke Research Center | And 3 more authors.
American Journal of Physical Anthropology | Year: 2015

Objective Here, we compare food availability and relate this to differences in energy intake rates, time spent feeding, and daily travel distance of gorillas in the two populations. Comparative intraspecific studies investigating spatiotemporal variation in food availability can help us understand the complex relationships between ecology, behavior, and life history in primates and are relevant to understanding hominin evolution. Differences in several variables have been documented between the two mountain gorilla populations in the Virunga Massif and Bwindi Impenetrable National Park, but few direct comparisons that link ecological conditions to feeding behavior have been made. Materials and Methods Using similar data collection protocols we conducted vegetation sampling and nutritional analysis on important foods to estimate food availability. Detailed observations of feeding behavior were used to compute energy intake rates and daily travel distance was estimated through GPS readings. Results Food availability was overall lower and had greater temporal variability in Bwindi than in the Virungas. Energy intake rates and time spent feeding were similar in both populations, but energy intake rates were significantly higher in Bwindi during the period of high fruit consumption. Daily travel distances were significantly shorter in the Virungas. Conclusions Overall, despite the differences in food availability, we did not find large differences in the energetics of gorillas in the two populations, although further work is needed to more precisely quantify energy expenditure and energy balance. These results emphasize that even species with high food availability can exhibit behavioral and energetic responses to variable ecological conditions, which are likely to affect growth, reproduction, and survival. Am J Phys Anthropol 158:487-500, 2015. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc. Source


Grueter C.C.,University of Western Australia | Stoinski T.S.,Dian Fossey Gorilla Fund International
PLoS ONE | Year: 2016

Humans are unique among primates for not only engaging in same-sex sexual acts, but also forming homosexual pair bonds. To shed light on the evolutionary origins of homosexuality, data on the occurrence and contexts of same-sex behavior from nonhuman primates may be of particular significance. Homosexual behavior involving females is poorly researched in most primate taxa, exceptions being Japanese macaques, rhesus macaques, Hanuman langurs and bonobos. We present data on homosexual behavior in female mountain gorillas in the Virunga Volcanoes (Rwanda) and test four functional hypotheses, namely reconciliation, affiliation, dominance expression and sexual arousal. Homosexual interactions between females involved both ventro-dorsal and ventro-ventral copulations accompanied by vocalizations and courtship displays. The only sociosexual hypothesis that received partial empirical support is the social status hypothesis, i.e., that mounting reaffirms the dominance hierarchy. There is also some limited evidence that same-sex behavior reflects an overall state of arousal or is triggered via a 'pornographic' effect. An adaptive function of female homosexual behavior is not readily apparent, and we tentatively conclude (until a more rigorous test becomes available) that it may simply be related to sexual gratification or that it is an evolutionary by-product of an adaptation. © 2016 Grueter, Stoinski. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source


Rushmore J.,University of Georgia | Caillaud D.,Dian Fossey Gorilla Fund International | Caillaud D.,University of Texas at Austin | Hall R.J.,University of Georgia | And 3 more authors.
Journal of the Royal Society Interface | Year: 2014

Many endangered wildlife populations are vulnerable to infectious diseases for which vaccines exist; yet, pragmatic considerations often preclude largescale vaccination efforts. These barriers could be reduced by focusing on individuals with the highest contact rates. However, the question then becomes whether targeted vaccination is sufficient to prevent large outbreaks. To evaluate the efficacy of targeted wildlife vaccinations, we simulate pathogen transmission and control on monthly association networks informed by behavioural data from a wild chimpanzee community (Kanyawara N = 37, Kibale National Park, Uganda). Despite considerable variation across monthly networks, our simulations indicate that targeting the most connected individuals can prevent large outbreaks with up to 35% fewer vaccines than random vaccination. Transmission heterogeneities might be attributed to biological differences among individuals (e.g. sex, age, dominance and family size). Thus, we also evaluate the effectiveness of a trait-based vaccination strategy, as trait data are often easier to collect than interaction data. Our simulations indicate that a trait-based strategy can prevent large outbreaks with up to 18% fewer vaccines than random vaccination, demonstrating that individual traits can serve as effective estimates of connectivity. Overall, these results suggest that fine-scale behavioural data can help optimize pathogen control efforts for endangered wildlife. © 2014 The Author(s) Published by the Royal Society. Source


Rosenbaum S.,University of California at Los Angeles | Hirwa J.P.,Dian Fossey Gorilla Fund International | Silk J.B.,Arizona State University | Vigilant L.,Max Planck Institute for Evolutionary Anthropology | Stoinski T.S.,Dian Fossey Gorilla Fund International
PLoS ONE | Year: 2016

Sexually selected infanticide is an important source of infant mortality in many mammalian species. In species with long-term male-female associations, females may benefit from male protection against infanticidal outsiders. We tested whether mountain gorilla (Gorilla beringei beringei) mothers in single and multi-male groups monitored by the Dian Fossey Gorilla Fund's Karisoke Research Center actively facilitated interactions between their infants and a potentially protective male. We also evaluated the criteria mothers in multimale groups used to choose a preferred male social partner. In single male groups, where infanticide risk and paternity certainty are high, females with infants <1 year old spent more time near and affiliated more with males than females without young infants. In multi-male groups, where infanticide rates and paternity certainty are lower, mothers with new infants exhibited few behavioral changes toward males. The sole notable change was that females with young infants proportionally increased their time near males they previously spent little time near when compared to males they had previously preferred, perhaps to encourage paternity uncertainty and deter aggression. Rank was a much better predictor of females' social partner choice than paternity. Older infants (2-3 years) in multi-male groups mirrored their mothers' preferences for individual male social partners; 89% spent the most time in close proximity to the male their mother had spent the most time near when they were <1 year old. Observed discrepancies between female behavior in single and multi-male groups likely reflect different levels of postpartum intersexual conflict; in groups where paternity certainty and infanticide risk are both high, male-female interests align and females behave accordingly. This highlights the importance of considering individual and group-level variation when evaluating intersexual conflict across the reproductive cycle. © 2016 Rosenbaum et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source


Rosenbaum S.,University of California at Los Angeles | Hirwa J.P.,Dian Fossey Gorilla Fund International | Silk J.B.,Arizona State University | Vigilant L.,Max Planck Institute for Evolutionary Anthropology | Stoinski T.S.,Dian Fossey Gorilla Fund International
Animal Behaviour | Year: 2015

Kin discrimination mechanisms are expected to evolve when they provide fitness benefits. To date, evidence for kin discrimination is mixed across taxa and mating systems even when it would apparently be beneficial. In animals with promiscuous mating systems, males were long believed to abstain from parenting behaviours partly because the costs of offspring misidentification outweighed the benefits of dual parenting. Conversely, males in monogamous systems could parent because of high paternity certainty. However, recent work has shown that in some species males parent despite high false paternity rates, and males in some promiscuous systems discriminate between their own and other males' offspring. Here we evaluate the impact of male dominance rank, paternity and age on male-immature relationships in wild mountain gorillas. Mountain gorillas provide an interesting context for assessing paternal kin discrimination because (1) male-immature relationships are strong, and (2) while their morphological characteristics suggest an evolutionary history of single-male groups, a substantial fraction contain multiple adult males. In our sample of 21 males and 49 genotyped immatures living in multimale groups monitored by the Dian Fossey Gorilla Fund's Karisoke Research Center, we found that male rank was the primary predictor of male-immature relationship strength. There was little evidence that paternity or age were related to relationship patterns. Male-immature dyads were closer social partners in 2011-12 when groups were smaller and reproductive skew lower, than comparable dyads in 2003-04 when groups were larger and skew higher. Gorillas' lack of paternal kin discrimination provides further behavioural evidence that the species' multimale social structure is evolutionarily novel. However, patterning of male-immature relationships and genetic paternity suggest a persistent minority of two-male groups throughout G.beringei's evolutionary history. This may help explain their ability to live in multimale, multifemale social units despite possessing morphological characteristics typical of harem systems. © 2015 The Association for the Study of Animal Behaviour. Source

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