Department of Evolutionary Anthropology
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An updated vocal repertoire of wild adult bonobos
Research over the last 20 years has shed important light on the vocal behaviour of our closest living relatives, bonobos and chimpanzees, but mostly relies on qualitative vocal repertoires, for which quantitative validations are absent. Such data are critical for a holistic understanding of a species` communication system and unpacking how these systems compare more broadly with other primate and non-primate species. Here we make key progress by providing the first quantitative validation of a Pan vocal repertoire, specifically for wild bonobos. Using data comprising over 1500 calls from 53 adult individuals collected over 33 months, we employ machine-learning-based random forest analyses and describe 11 acoustically distinguishable call types. We discuss issues associated with resolving vocal repertoires from wild data in great apes and highlight potential future approaches to further capture the complexity and gradedness of the bonobo vocal system.
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Integrated behavioral and metabolically flexible responses of wild orangutans to ecologically driven dietary variation
Diet and nutrition are critical factors influencing energetics and health. Laboratory studies show that organisms adjust to changes in nutrient intake through flexible metabolic responses such as fuel switching. While the physiological effects of nutrient balance in humans have been studied, data from closely related species living in nature are lacking. We integrate macronutrient regulation and metabolic flexibility to elucidate how wild orangutans (Pongo pygmaeus wurmbii) are buffered against natural fluctuations in nutritional resources. We found that these orangutans regulate protein and regularly switch between exogenous and endogenous nutritional substrates as preferred food resource availability declines. When total caloric, lipid, and carbohydrate intake declined during episodes of fruit scarcity, orangutans drew on fat and endogenous amino acids for energy. This strategy is beneficial only in the context of alternating periods of fruit scarcity and abundance. We discuss our findings in relation to the current global obesity pandemic, which has arisen with transitions in human diets toward low-cost, energydense, protein-dilute foods.
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Dispersed female networks: female gorillas’ inter-group relationships influence dispersal decisions
Dispersal is a fundamental aspect of many animal societies, impacting gene flow, knowledge transmission, culture and individual fitness. However, little is known about the information individuals use when dispersing. Mountain gorillas exhibit a flexible dispersal pattern with 50% of both sexes dispersing, and females often dispersing multiple times. Using two decades of data including 152 dispersals from 56 females, we examined how familiarity with individuals in other groups influenced dispersal. We found that females avoided groups containing males from their natal group, but preferred groups containing females they had previously resided with, particularly those from their natal group. This suggests that females prioritize the maintenance of female relationships in their dispersal decisions, while reducing inbreeding risks. Joining a new group can be costly and these pre-existing relationships may reduce dispersal costs. These findings highlight the capacity for wider-scale societies to both shape and be shaped by dispersal decisions, with long-term inter-group relationships representing potential sources of information and support in the dispersal process. This contributes to a better understanding of not only population dynamics in this endangered ape, but also of the foundation of our own flexible society, characterized by individuals moving between social groups throughout their lifetimes.
