Energetic responses to variation in food availability in the two mountain gorilla populations (<i>Gorilla beringei beringei</i>)

Wright, Edward; Grueter, Cyril C.; Seiler, Nicole; Abavandimwe, Didier; Stoinski, Tara S.; Ortmann, Sylvia; Robbins, Martha M.

doi:10.1002/ajpa.22808

Cited by 43 publications

(71 citation statements)

References 77 publications

(133 reference statements)

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“…Their positive correlation could indicate an influence of group size on intragroup feeding competition, whereas our negative correlation is more consistent with theoretical predictions for intergroup contest competition 7,8 . The feeding time of mountain gorillas seems to be more sensitive to differences in energy intake rates than differences in the energy requirements from travel 36,41,72 . If so, then our negative correlation could be interpreted to suggest that larger groups had greater access to areas that facilitate higher energy intake rates.…”

Section: Discussionmentioning

confidence: 99%

“…The Virunga Volcano region contains a range of habitats that vary along an altitudinal gradient from the bamboo zone below 2800 meters to afro-montane vegetation above 3600 meters 36,39,45,73 . Between those two extremes, the additional habitats are the mixed species montane forest with an understory of Mimulopsis spp.…”

Section: Methodsmentioning

confidence: 99%

“…The Virunga mountain gorillas are expected to have weak feeding competition, primarily because their food is abundant 35,36 . Distances between patches are small, which limits the extra travel requirements if larger groups must visit more patches 37,38 .…”

Section: Introductionmentioning

confidence: 99%

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Quadratic relationships between group size and foraging efficiency in a herbivorous primate

Grueter

Robbins

Abavandimwe

et al. 2018

Sci Rep

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The effect of feeding competition on foraging efficiency is an important link between ecological factors and the social organization of gregarious species. We examined the effects of group size on daily travel distances, activity budgets, and energy intake of mountain gorillas in Rwanda. We measured daily travel distances of five groups, activity budgets of 79 gorillas in nine groups, and energy intake data for 23 adult females in three groups over a 16-month period. Travel distances and the proportion of time spent traveling increased with size for most groups, which would be expected if their foraging efficiency is limited by intragroup feeding competition. However, travel distances and times decreased for the largest group, which also had higher energy intake rates than intermediate sized groups. The improved foraging efficiency of the largest group may be explained by advantages in intergroup contest competition. The largest group had much lower home range overlap than the other study groups which may be due to groups avoiding one another as a result of male mating competition. Collectively, our results indicate that intermediate sized groups had the lowest foraging efficiency and provide a new twist on the growing evidence of non-linear relationships between group size and foraging efficiency in primates.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Quadratic relationships between group size and foraging efficiency in a herbivorous primate

Grueter

Robbins

Abavandimwe

et al. 2018

Sci Rep

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“…Conducting studies on gorillas at ecologically similar sites can be challenging because of the large ecological variation within and among gorilla habitats and the small number of habituated groups. For example, there is large variation in plant species composition and density between and within the habitats of the only two populations of mountain gorillas [97, 98]. Western gorillas are found across a much larger range and ongoing habituation efforts should make more comparisons possible in the future, but ecological variation between sites may remain a limitation in some cases given the differences in habitat and diet (e.g.…”

Section: Discussionmentioning

confidence: 99%

Behavioral Variation in Gorillas: Evidence of Potential Cultural Traits

et al. 2016

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The question of whether any species except humans exhibits culture has generated much debate, partially due to the difficulty of providing conclusive evidence from observational studies in the wild. A starting point for demonstrating the existence of culture that has been used for many species including chimpanzees and orangutans is to show that there is geographic variation in the occurrence of particular behavioral traits inferred to be a result of social learning and not ecological or genetic influences. Gorillas live in a wide variety of habitats across Africa and they exhibit flexibility in diet, behavior, and social structure. Here we apply the ‘method of exclusion’ to look for the presence/absence of behaviors that could be considered potential cultural traits in well-habituated groups from five study sites of the two species of gorillas. Of the 41 behaviors considered, 23 met the criteria of potential cultural traits, of which one was foraging related, nine were environment related, seven involved social interactions, five were gestures, and one was communication related. There was a strong positive correlation between behavioral dissimilarity and geographic distance among gorilla study sites. Roughly half of all variation in potential cultural traits was intraspecific differences (i.e. variability among sites within a species) and the other 50% of potential cultural traits were differences between western and eastern gorillas. Further research is needed to investigate if the occurrence of these traits is influenced by social learning. These findings emphasize the importance of investigating cultural traits in African apes and other species to shed light on the origin of human culture.

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“…The habitats and diets of the two remaining populations of mountain gorillas (Virunga Massif and Bwindi Impenetrable National Park, Uganda) are different, largely due to altitudinal variation (Robbins et al 2006b; Wright et al 2015). The mountain gorillas in the Virunga Massif consume almost no fruit because there is so little available and nearly all of their dietary items are available year-round.…”

Section: Introductionmentioning

confidence: 99%

Dispersal and reproductive careers of male mountain gorillas in Bwindi Impenetrable National Park, Uganda

et al. 2019

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Dispersal is a key event in the life of an animal and it influences individual reproductive success. Male mountain gorillas exhibit both philopatry and dispersal, resulting in a mixed one-male and multimale social organization. However, little is known about the relationship between male dispersal or philopatry and reproductive careers in Bwindi mountain gorillas. Here we analyze data spanning from 1993 to 2017 on social groups in Bwindi Impenetrable National Park, Uganda to examine the proportion of males that disperse, age of dispersal, pathways to attaining alpha status, fate of dispersing males and philopatric males, and male tenure length as well as make comparisons of these variables to the Virunga mountain gorilla population. We report previously undocumented cases of dispersal by immature males and old males and we also observed the only known case of a fully mature male immigrating into a breeding group. We used genetic tracking of known individuals to estimate that a minimum of 25% of males that disperse to become solitary males eventually form new groups. No differences were found between the Bwindi and Virunga population in the age of male dispersal, the proportion of males that disperse, the age of alpha male acquisition, and dominance tenure length. The lack of differences may be due to small sample sizes or because the observed ecological variability does not lead to life history differences between the populations. Males in both populations follow variable strategies to attain alpha status leading to the variable one-male and multimale social organization, including dispersal to become solitary and eventually form a group, via group fissioning, usurping another alpha male, or inheriting the alpha position when a previous group leader dies.

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Energetic responses to variation in food availability in the two mountain gorilla populations (Gorilla beringei beringei)

Cited by 43 publications

References 77 publications

Quadratic relationships between group size and foraging efficiency in a herbivorous primate

Quadratic relationships between group size and foraging efficiency in a herbivorous primate

Behavioral Variation in Gorillas: Evidence of Potential Cultural Traits

Dispersal and reproductive careers of male mountain gorillas in Bwindi Impenetrable National Park, Uganda

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