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Tamura M, Akomo-Okoue EF, Mangama-Koumba LB, Wilfried EEG, Mindonga-Nguelet FL. Does kinship with the silverback matter? Intragroup social relationships of immature wild western lowland gorillas after social upheaval. Primates 2024; 65:397-410. [PMID: 39126443 PMCID: PMC11335836 DOI: 10.1007/s10329-024-01149-1] [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: 11/13/2023] [Accepted: 07/29/2024] [Indexed: 08/12/2024]
Abstract
In primates living in one-male groups, the sole resident male is often an important social partner for group immatures. For such groups, however, replacement of the male and subsequent disruptions of their relationships are almost inevitable. Here, we described social relationships of immature wild western lowland gorillas within a habituated group, where two natal and eight immigrant immatures lived with the resident silverback. We recorded 5 m proximities among group members as an indicator of social closeness. We found that natal immatures spent more time within 5 m of the silverback than immigrant ones. The social closeness between the silverback and the younger immigrant immatures sharply increased after 1 year, but these values were still below those of the natal immatures. Regarding the development of independence from the mother, we found no significant difference between natal and immigrant immatures. The socially preferred nonmother mature for natal immatures was the silverback, whereas many immigrant immatures preferred a paternal adult sister who had previously co-resided with them in a previous group. Our results suggest that familiarity may be an important determinant of the social closeness between the silverback and immatures, but 1 year of co-residence might be too short to construct sufficient familiarity. The paternal sister may have played a pivotal role in the assimilation of immigrant immatures into the non-natal group. Nonetheless, it is not negligible that the silverback and immigrant immatures formed day-to-day close proximities. His tolerance toward co-residence with immigrant immatures can be considered a reproductive tactic.
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Affiliation(s)
- Masaya Tamura
- Laboratory of Human Evolution Studies, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan.
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Grebe NM, Schmidt J, Eckardt W, Umuhoza R, Mayo D, Stoinski TS, Santymire RM, Rosenbaum S. Examining the dual hormone hypothesis in wild male mountain gorillas (Gorilla beringei beringei). Horm Behav 2024; 164:105588. [PMID: 38880022 DOI: 10.1016/j.yhbeh.2024.105588] [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: 11/07/2023] [Revised: 05/16/2024] [Accepted: 06/10/2024] [Indexed: 06/18/2024]
Abstract
The Challenge Hypothesis is an influential framework for understanding how androgens are involved in the promotion of competitive behavior during mating-related challenges and has been tested extensively in studies across scientific disciplines. Mixed support in psychological research led scholars to develop the Dual Hormone Hypothesis as a potential path forward, which argues that glucocorticoids moderate the relationship between androgens and status-striving. In the current study, we examine the Challenge Hypothesis and the Dual Hormone Hypothesis in wild male mountain gorillas, representing the first time the latter hypothesis has been tested in a non-human primate. In a sample of 30 adult males comprising over 600 days of observation, we find some limited support for the Challenge Hypothesis. Greater daily rates of targeted aggression toward other adult males corresponded to higher fecal androgen metabolites 1-2 days following observations, though this pattern did not fully generalize to dominance rank or other competitive behaviors examined. However, we find no support for the Dual Hormone Hypothesis: neither dominance rank nor any category of competitive behavior was predicted by the interaction between androgens and glucocorticoids. We close by discussing how this initial investigation might be leveraged toward the development of an expanded Dual Hormone Hypothesis that draws on the large evidence base in primate behavioral ecology.
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Affiliation(s)
- Nicholas M Grebe
- Department of Anthropology, University of Michigan, Ann Arbor, MI, United States of America.
| | - Josephine Schmidt
- Department of Anthropology, University of Michigan, Ann Arbor, MI, United States of America
| | | | | | - Dominic Mayo
- Department of Anthropology, University of Michigan, Ann Arbor, MI, United States of America
| | - Tara S Stoinski
- Dian Fossey Gorilla Fund, Atlanta, GA, United States of America
| | - Rachel M Santymire
- Department of Biology, Georgia State University, Atlanta, GA, United States of America
| | - Stacy Rosenbaum
- Department of Anthropology, University of Michigan, Ann Arbor, MI, United States of America
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3
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van Noordwijk MA, LaBarge LR, Kunz JA, Marzec AM, Spillmann B, Ackermann C, Rianti P, Vogel ER, Atmoko SSU, Kruetzen M, van Schaik CP. Reproductive success of Bornean orangutan males: scattered in time but clustered in space. Behav Ecol Sociobiol 2023; 77:134. [PMID: 38076722 PMCID: PMC10700224 DOI: 10.1007/s00265-023-03407-6] [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: 06/22/2023] [Revised: 11/13/2023] [Accepted: 11/15/2023] [Indexed: 12/22/2023]
Abstract
Abstract The social and mating systems of orangutans, one of our closest relatives, remain poorly understood. Orangutans (Pongo spp.) are highly sexually dimorphic and females are philopatric and maintain individual, but overlapping home ranges, whereas males disperse, are non-territorial and wide-ranging, and show bimaturism, with many years between reaching sexual maturity and attaining full secondary sexual characteristics (including cheek pads (flanges) and emitting long calls). We report on 21 assigned paternities, among 35 flanged and 15 unflanged, genotyped male Bornean orangutans (Pongo pygmaeus wurmbii), studied from 2003 to 2018 in Tuanan (Central Kalimantan, Indonesia). All 10 infants born since mid-2003 with an already identified sire were sired by flanged males. All adult males ranged well beyond the study area (c. 1000 ha), and their dominance relations fluctuated even within short periods. However, 5 of the 10 identified sires had multiple offspring within the monitored area. Several sired over a period of c. 10 years, which overlapped with siring periods of other males. The long-calling behavior of sires indicated they were not consistently dominant over other males in the area around the time of known conceptions. Instead, when they were seen in the area, the known sires spent most of their time within the home ranges of the females whose offspring they sired. Overall, successful sires were older and more often resident than others. Significance statement It is difficult to assess reproductive success for individuals of long-lived species, especially for dispersing males, who cannot be monitored throughout their lives. Due to extremely long interbirth intervals, orangutans have highly male-skewed operational sex ratios and thus intensive male-male competition for every conception. Paternity analyses matched 21 immature Bornean orangutans with their most likely sire (only 10 of 50 genotyped males) in a natural population. Half of these identified sires had multiple offspring in the study area spread over periods of at least 10 years, despite frequently ranging outside this area. Dominance was a poor predictor of success, but, consistent with female mating tactics to reduce the risk of infanticide, known "sires" tended to have relatively high local presence, which seems to contribute to the males' siring success. The results highlight the importance of large protected areas to enable a natural pattern of dispersal and ranging. Supplementary Information The online version contains supplementary material available at 10.1007/s00265-023-03407-6.
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Affiliation(s)
- Maria A. van Noordwijk
- Department of Evolutionary Anthropology, University of Zurich, Zürich, Switzerland
- Comparative Socio-Ecology Group, May Planck Institute of Animal Behavior, Konstanz, Germany
| | - Laura R. LaBarge
- Comparative Socio-Ecology Group, May Planck Institute of Animal Behavior, Konstanz, Germany
| | - Julia A. Kunz
- Department of Evolutionary Anthropology, University of Zurich, Zürich, Switzerland
- Institute des Sciences de l’Evolution Montpellier, University of Montpellier, Montpellier, France
| | - Anna M. Marzec
- Department of Evolutionary Anthropology, University of Zurich, Zürich, Switzerland
| | - Brigitte Spillmann
- Department of Evolutionary Anthropology, University of Zurich, Zürich, Switzerland
| | - Corinne Ackermann
- Department of Evolutionary Anthropology, University of Zurich, Zürich, Switzerland
| | - Puji Rianti
- Division of Animal Biosystematics and Ecology, Department of Biology, IPB University, Bogor, Indonesia
- Primate Research Center, IPB University, Bogor, Indonesia
| | - Erin R. Vogel
- Department of Anthropology, Center for Human Evolution Studies, Rutgers, The State University of New Jersey, New Brunswick, USA
| | | | - Michael Kruetzen
- Department of Evolutionary Anthropology, University of Zurich, Zürich, Switzerland
| | - Carel P. van Schaik
- Department of Evolutionary Anthropology, University of Zurich, Zürich, Switzerland
- Comparative Socio-Ecology Group, May Planck Institute of Animal Behavior, Konstanz, Germany
- Center for the Interdisciplinary Study of Language Evolution (ISLE), University of Zurich, Zürich, Switzerland
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Morrison RE, Ndayishimiye E, Stoinski TS, Eckardt W. Multiple mechanisms for inbreeding avoidance used simultaneously in a wild ape. Proc Biol Sci 2023; 290:20231808. [PMID: 37848059 PMCID: PMC10581766 DOI: 10.1098/rspb.2023.1808] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 09/21/2023] [Indexed: 10/19/2023] Open
Abstract
Mating with close kin can have considerable negative fitness consequences, which are expected to result in selective pressure for inbreeding avoidance mechanisms, such as dispersal, mate choice and post-copulatory biases. Captive studies have suggested that inbreeding avoidance through mate choice is far less widespread than expected and may be absent where other mechanisms already limit inbreeding. However, few studies have examined multiple mechanisms of inbreeding avoidance simultaneously, particularly in the wild. We use 13 years of detailed dispersal, copulation and paternity data from mountain gorillas to examine inbreeding avoidance. We find that partial dispersal of both sexes results in high kinship in multimale groups, but that copulations between close kin occur 40% less than expected. We find strong kin discrimination in mate choice, with significant avoidance of maternal kin but more limited avoidance of paternal kin. We find no evidence for post-copulatory inbreeding avoidance. Our analyses support familiarity-based mechanisms of kin identification and age-based avoidance that limits mating between fathers and daughters in their natal group. Our findings demonstrate that multiple complementary mechanisms for inbreeding avoidance can evolve in a single species and suggest that inbreeding avoidance through mate choice may enable more flexible dispersal systems to evolve.
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Affiliation(s)
- Robin E. Morrison
- Dian Fossey Gorilla Fund, Musanze, Rwanda
- Human Evolutionary Ecology Group, Department of Evolutionary Anthropology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Robbins MM, Akantorana M, Arinaitwe J, Breuer T, Manguette M, McFarlin S, Meder A, Parnell R, Richardson JL, Stephan C, Stokes EJ, Stoinski TS, Vecellio V, Robbins AM. Comparative life history patterns of female gorillas. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2023; 181:564-574. [PMID: 37345324 DOI: 10.1002/ajpa.24792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 03/16/2023] [Accepted: 05/24/2023] [Indexed: 06/23/2023]
Abstract
OBJECTIVES Several theories have been proposed to explain the impact of ecological conditions on differences in life history variables within and between species. Here we compare female life history parameters of one western lowland gorilla population (Gorilla gorilla gorilla) and two mountain gorilla populations (Gorilla beringei beringei). MATERIALS AND METHODS We compared the age of natal dispersal, age of first birth, interbirth interval, and birth rates using long-term demographic datasets from Mbeli Bai (western gorillas), Bwindi Impenetrable National Park and the Virunga Massif (mountain gorillas). RESULTS The Mbeli western gorillas had the latest age at first birth, longest interbirth interval, and slowest surviving birth rate compared to the Virunga mountain gorillas. Bwindi mountain gorillas were intermediate in their life history patterns. DISCUSSION These patterns are consistent with differences in feeding ecology across sites. However, it is not possible to determine the evolutionary mechanisms responsible for these differences, whether a consequence of genetic adaptation to fluctuating food supplies ("ecological risk aversion hypothesis") or phenotypic plasticity in response to the abundance of food ("energy balance hypothesis"). Our results do not seem consistent with the extrinsic mortality risks at each site, but current conditions for mountain gorillas are unlikely to match their evolutionary history. Not all traits fell along the expected fast-slow continuum, which illustrates that they can vary independently from each other ("modularity model"). Thus, the life history traits of each gorilla population may reflect a complex interplay of multiple ecological influences that are operating through both genetic adaptations and phenotypic plasticity.
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Affiliation(s)
- Martha M Robbins
- Department of Primate Behavior and Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Moses Akantorana
- Department of Primate Behavior and Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | | | - Thomas Breuer
- Mbeli Bai Study, Wildlife Conservation Society Congo Program, Brazzaville, Democratic Republic of the Congo
- World Wide Fund for Nature, Berlin, Germany
| | - Marie Manguette
- Mbeli Bai Study, Wildlife Conservation Society Congo Program, Brazzaville, Democratic Republic of the Congo
| | - Shannon McFarlin
- Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, DC, USA
| | - Angela Meder
- Berggorilla Regenwald Direkthilfe, Hoevelhof, Germany
| | - Richard Parnell
- Mbeli Bai Study, Wildlife Conservation Society Congo Program, Brazzaville, Democratic Republic of the Congo
| | - Jack L Richardson
- Department of Anthropology, Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, DC, USA
| | - Claudia Stephan
- Mbeli Bai Study, Wildlife Conservation Society Congo Program, Brazzaville, Democratic Republic of the Congo
- Nouabalé-Ndoki Foundation, Brazzaville, Democratic Republic of the Congo
| | - Emma J Stokes
- Mbeli Bai Study, Wildlife Conservation Society Congo Program, Brazzaville, Democratic Republic of the Congo
| | - Tara S Stoinski
- Dian Fossey Gorilla Fund International, Atlanta, Georgia, USA
| | | | - Andrew M Robbins
- Department of Primate Behavior and Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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6
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Robbins MM. Reflections on connections. Primates 2023; 64:191-197. [PMID: 36867278 PMCID: PMC9982802 DOI: 10.1007/s10329-023-01059-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 02/18/2023] [Indexed: 03/04/2023]
Affiliation(s)
- Martha M Robbins
- Department of Primate Behavior and Evolution, Max Planck Institute for Evolutionary Anthropology, Leizpig, Germany.
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Sen S, Carrera SC, Heistermann M, Potter CB, Baniel A, DeLacey PM, Petrullo L, Lu A, Beehner JC. Social correlates of androgen levels and dispersal age in juvenile male geladas. Horm Behav 2022; 146:105264. [PMID: 36155910 DOI: 10.1016/j.yhbeh.2022.105264] [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: 04/05/2022] [Revised: 09/06/2022] [Accepted: 09/09/2022] [Indexed: 11/23/2022]
Abstract
Androgens offer a window into the timing of important male life history events such as maturation. However, when males are the dispersing sex, piecing together normative androgen profiles across development is challenging because dispersing males are difficult to track. Here, we examined the conditions that may be associated with male androgen status (via fecal androgen metabolites, fAMs) and age at dispersal in wild male geladas (Theropithecus gelada). Gelada male life histories are highly variable - dispersal may occur before sexual maturation, dispersal itself can be immediate or drawn out, and, due to their multi-leveled society, social conditions affecting dispersal can vary for juveniles living in different reproductive units within the same band. Using longitudinal data from known natal males, we examined how androgen levels and age at dispersal were associated with: (1) access to maternal resources (i.e., maternal rank, birth of a younger sibling, experiencing maternal loss), and (2) access to male peers (i.e., number of similar-aged males in their unit). We found that androgens were significantly lower in males with high-ranking mothers (in males >2.5 years of age; infant androgens were unrelated) and that having more male peers in their social group and larger groups overall predicted an earlier age at dispersal. Moreover, dispersal in geladas was not preceded or followed by a surge in androgen levels. Taken together, results suggest that social environments can cause individual variation in androgens and dispersal age. Whether this variation leads to differences in male fitness in later life remains to be determined.
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Affiliation(s)
- Sharmi Sen
- Department of Anthropology, University of Michigan, Ann Arbor, MI 48109-1107, USA.
| | - Sofia C Carrera
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109-1107, USA
| | - Michael Heistermann
- Endocrinology Laboratory, German Primate Center, Leibniz Institute for Primate Research, 37077 Göttingen, Germany
| | - Caitlin Barale Potter
- Cedar Creek Ecosystem Science Reserve, University of Minnesota, St. Paul, MN 55108, USA
| | - Alice Baniel
- Center for Evolution and Medicine, Arizona State University, Tempe, AZ 85281, USA; School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
| | - Patricia M DeLacey
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109-1107, USA
| | - Lauren Petrullo
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109-1107, USA
| | - Amy Lu
- Department of Anthropology, Stony Brook University, Stony Brook, NY 11794-4364, USA
| | - Jacinta C Beehner
- Department of Anthropology, University of Michigan, Ann Arbor, MI 48109-1107, USA; Department of Psychology, University of Michigan, Ann Arbor, MI 48109-1107, USA
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8
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Rosenbaum S, Silk JB. Pathways to paternal care in primates. Evol Anthropol 2022; 31:245-262. [PMID: 35289027 DOI: 10.1002/evan.21942] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 10/01/2021] [Accepted: 01/21/2022] [Indexed: 11/06/2022]
Abstract
Natural selection will favor male care when males have limited alternative mating opportunities, can invest in their own offspring, and when care enhances males' fitness. These conditions are easiest to fulfill in pair-bonded species, but neither male care nor stable "breeding bonds" that facilitate it are limited to pair-bonded species. We review evidence of paternal care and extended breeding bonds in owl monkeys, baboons, Assamese macaques, mountain gorillas, and chimpanzees. The data, which span social/mating systems and ecologies, suggest that there are multiple pathways by which conditions conducive to male care can arise. This diversity highlights the difficulty of making inferences about the emergence of male care in early hominins based on single traits visible in the fossil record. We discuss what types of data are most needed and the questions yet to be answered about the evolution of male care and extended breeding bonds in the primate order.
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Affiliation(s)
- Stacy Rosenbaum
- Department of Anthropology, University of Michigan, Ann Arbor, Michigan, USA
| | - Joan B Silk
- School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, USA.,Institute of Human Origins, Arizona State University, Tempe, Arizona, USA
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Graham KE, Badihi G, Safryghin A, Grund C, Hobaiter C. A socio-ecological perspective on the gestural communication of great ape species, individuals, and social units. ETHOL ECOL EVOL 2022; 34:235-259. [PMID: 35529671 PMCID: PMC9067943 DOI: 10.1080/03949370.2021.1988722] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Over the last 30 years, most research on non-human primate gestural communication has been produced by psychologists, which has shaped the questions asked and the methods used. These researchers have drawn on concepts from philosophy, linguistics, anthropology, and ethology, but despite these broad influences the field has neglected to situate gestures into the socio-ecological context in which the diverse species, individuals, and social-units exist. In this review, we present current knowledge about great ape gestural communication in terms of repertoires, meanings, and development. We fold this into a conversation about variation in other types of ape social behaviour to identify areas for future research on variation in gestural communication. Given the large variation in socio-ecological factors across species and social-units (and the individuals within these groups), we may expect to find different preferences for specific gesture types; different needs for communicating specific meanings; and different rates of encountering specific contexts. New tools, such as machine-learning based automated movement tracking, may allow us to uncover potential variation in the speed and form of gesture actions or parts of gesture actions. New multi-group multi-generational datasets provide the opportunity to apply analyses, such as Bayesian modelling, which allows us to examine these rich behavioural landscapes. Together, by expanding our questions and our methods, researchers may finally be able to study great ape gestures from the perspective of the apes themselves and explore what this gestural communication system reveals about apes’ thinking and experience of their world.
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Affiliation(s)
- Kirsty E. Graham
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
| | - Gal Badihi
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
| | - Alexandra Safryghin
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
| | - Charlotte Grund
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
| | - Catherine Hobaiter
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
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Maag N, Paniw M, Cozzi G, Manser M, Clutton-Brock T, Ozgul A. Dispersal decreases survival but increases reproductive opportunities for subordinates in a cooperative breeder. Am Nat 2022; 199:679-690. [DOI: 10.1086/719029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Robbins MM, Robbins AM. Variability of weaning age in mountain gorillas (Gorilla beringei beringei). AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2021; 174:776-784. [PMID: 33511629 DOI: 10.1002/ajpa.24237] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 12/17/2020] [Accepted: 01/08/2021] [Indexed: 12/31/2022]
Abstract
OBJECTIVES Weaning is a key life history milestone for mammals that represents both the end of nutritional investment from the perspective of mothers and the start of complete nutritional independence for the infants. The age at weaning may vary depending on ecological, social, and demographic factors experienced by the mother and infant. Bwindi mountain gorillas live in different environmental conditions and have longer interbirth intervals than their counterparts in the Virunga Volcanoes, yet other life history characteristics of this population remain less well known. We use long-term data from Bwindi Impenetrable National Park, Uganda to examine factors related to weaning age. MATERIALS AND METHODS We analyzed data on infants born in four mountain gorilla groups in Bwindi to quantify their age of weaning (defined as last nipple contact) and to test if the sex of offspring, parity, and dominance rank of mother influences age of weaning. We also compared the age at weaning and time to conception after resumption of mating in Bwindi and Virunga gorillas. RESULTS Bwindi gorillas were weaned at an average age of 57.5 months. No difference was found between age of weaning for primiparous and multiparous mothers, nor did maternal dominance rank influence age of weaning, but sons were weaned at a later age than daughters. The majority of Bwindi mothers were still suckling when they resumed mating and mothers generally conceived before they weaned their previous offspring. The age of weaning was significantly later in Bwindi than in Virunga gorillas. After mothers resumed mating, the time to conceiving the next offspring was not significantly longer for Bwindi females than Virungas females (6 vs. 4 months). DISCUSSION Later weaning age for sons than daughters is similar to findings of other studies of great apes. Bwindi mountain gorillas are weaned at approximately the same age as western gorillas and chimpanzees, which is more than a year later than Virunga mountain gorillas. The results of this study suggest that variation in ecological conditions of populations living in close geographic proximity can result in variation in life history patterns, which has implications for understanding the evolution of the unique life history patterns of humans.
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Affiliation(s)
- Martha M Robbins
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Andrew M Robbins
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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12
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Robbins MM. Assessing attitudes towards gorilla conservation via employee interviews. Am J Primatol 2020; 83:e23191. [PMID: 32894603 DOI: 10.1002/ajp.23191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 08/03/2020] [Accepted: 08/08/2020] [Indexed: 02/04/2023]
Abstract
To determine the effectiveness of conservation strategies, not only should we monitor biological variables, such as population size and levels of illegal activity, but also we should examine changes in attitudes and behavior of local community members. Here, I use semistructured interviews of employees at two field sites, in Bwindi Impenetrable National Park, Uganda and Loango National Park, Gabon, to understand if their employment influenced their attitude towards gorillas and conservation and led to behavior change. In contrast to western views of gorillas as "gentle giants," staff viewed gorillas as dangerous animals before working for these projects. Overall, employment leads to viewing conservation and gorillas more positively, and in many cases, viewing the gorillas as kin. The most common value attributed to the gorillas was economic, yet intrinsic and non-use existence values were frequently mentioned. Loango staff, but not Bwindi staff, reported behavior change related to hunting and bushmeat consumption, which likely is related to bushmeat consumption being commonplace in Gabon but not in Uganda. The Bwindi staff seemed to have a more positive and broader outlook toward conservation than the Loango staff, possibly because they had more years of formal education, they worked with gorillas longer, there is more history of conservation activities in Bwindi, and/or they have been less directly affected by negative consequences of conservation (e.g., crop raiding). This study shows the importance of explaining that gorillas are not dangerous if not provoked and using their human-like characteristics as a means to change conservation values and interest of local communities, while concurrently recognizing that providing economic benefits and reducing negative effects of wildlife are a reality for conservation buy-in.
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Affiliation(s)
- Martha M Robbins
- Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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13
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Weber A, Kalema-Zikusoka G, Stevens NJ. Lack of Rule-Adherence During Mountain Gorilla Tourism Encounters in Bwindi Impenetrable National Park, Uganda, Places Gorillas at Risk From Human Disease. Front Public Health 2020; 8:1. [PMID: 32117846 PMCID: PMC7031198 DOI: 10.3389/fpubh.2020.00001] [Citation(s) in RCA: 89] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 01/02/2020] [Indexed: 02/06/2023] Open
Abstract
Mountain gorillas (Gorilla beringei beringei) are an endangered primate species, with ~43% of the 1,063 individuals that remain on the planet today residing in Bwindi Impenetrable National Park (BINP) in southwestern Uganda. These primates are at the heart of a growing tourism industry that has incentivized their continued protection, but close proximity between humans and gorillas during such encounters presents well-documented risks for disease transmission. The Uganda Wildlife Authority (UWA) has developed rules to help protect the health of the gorillas, limiting each habituated gorilla group to a single 60 min visit each day by a group of no more than 8 tourists, and emphasizing that humans maintain a >7 m distance from gorillas at all times. A number of studies have documented that not all tour groups respect these rules. This project assesses rule-adherence during gorilla tourism encounters at BINP using both observational and survey-based data collected during the tourism high season between May and August, 2014. Observational data from 53 treks reveal that groups of 1-11 tourists engaged in gorilla viewing encounters between 46 and 98 min in duration. Although 96% of pre-trek briefings conducted by park rangers emphasized the need to maintain >7 m human-gorilla spacing, the 7 m distance rule was violated in over 98% (52 out of 53) of the tours examined in this study. Observational data were collected at 2 min intervals during gorilla-viewing encounters, documenting the nearest distance between any tourist and a gorilla (n = 1,604), of which 1,094 observations (68.2%) took place at a distance less than or equal to 7 m. Importantly, the 7 m rule was violated in visits to all of the gorilla groups habituated during the time of the study. In 224 observations (~14%, per 1,604 total), human-gorilla spacing was 3 m or less. Survey data (n = 243) revealed promising opportunities to improve tourist understanding of and adherence to park rules, with 73.6% of respondents indicating that they would be willing to utilize a precautionary measure of wearing a face-mask during encounters to protect gorilla health.
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Affiliation(s)
- Annalisa Weber
- Applied Research and Evaluation, Division of Global Health Protection, Center for Disease Control, Atlanta, GA, United States
- Environmental Studies Program, Voinovich School for Leadership and Public Affairs, Ohio University, Athens, OH, United States
| | | | - Nancy J. Stevens
- Environmental Studies Program, Voinovich School for Leadership and Public Affairs, Ohio University, Athens, OH, United States
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States
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