Biology subjects

Almeida-Warren, K.

Publications and source records attributed to Almeida-Warren, K..

3 recordsLinked to original sources

bioRxiv2024

Old age variably impacts chimpanzee engagement and efficiency in stone tool use

We know vanishingly little about how long-lived apes experience senescence in the wild, particularly with respect to their foraging behaviors, which are essential for survival. Some wild apes use tools during foraging and, given the additional cognitive and physical challenges presented by tool use, we predict that such behaviors are at a heightened risk of senescence. However, until the present, longitudinal analysis of the effects of progressive aging on wild ape tool-use behaviors has not been possible due to a lack of available data. In response to this research gap, we sampled data from a longitudinal video archive that contained footage of wild chimpanzees engaging in one of their most complex forms of tool use - the cracking of hard-shelled nuts with hammers and anvil stones, termed nut cracking - at an outdoor laboratory at Bossou, Guinea. By sampling data over a 17-year period, we describe how the extent to which wild chimpanzees engage in - and efficiently perform - nut cracking changes between the ages of approximately 39-44 to 56-61 years of age. Over this extended sampling period, chimpanzees began attending experimental nut cracking sites less frequently than younger individuals. Several elderly chimpanzees exhibited reductions in efficiency across multiple components of nut cracking, including taking more time to select stone tools prior to use, and taking longer to crack open nuts and consume the associated pieces of kernel. Two chimpanzees also began using less streamlined behavioral sequences to crack nuts, including a greater number of actions (such as more numerous strikes of the hammer stone). Most notably, we report interindividual variability in the extent to which elderly chimpanzees tool-use behaviors changed during our sample period - ranging from small to profound reductions in tool engagement and efficiency - as well as differences in the specific aspects of nut cracking behaviors that changed for each individual as they aged. We discuss the possible causes of these changes with reference to research into senescence in captive primates, and provide future directions for research of primate aging in both captive and wild settings.

animal behavior and cognition↗

bioRxiv2022

Interpreting phytolith assemblages at chimpanzee (Pan troglodytes verus) nut-cracking sites in Bossou Forest, Guinea

The nut-cracking behaviour of the chimpanzees of Bossou Forest has been long documented and studied in order to understand ultimate drivers for this form of durophagy by these apes. At sites in which they break open the nuts of the oil palm (Elaeis guineaeensis) on stone anvils with stone hammers, fragments of the tools as well as remnants of the nuts may be deposited into local sediments; however, they may become less visible at the macroscopic level as these sites are no longer used (become dormant). We build upon work that has been done to document this unique cultural heritage in West African chimpanzees by interpreting phytolith assemblages in sediments at active nut-cracking sites (used within the last two months). We compare these assemblages with those found in sediments of sites that have been dormant for ~10 years and sites where chimpanzees have not been observed to access and crack open oil palm nuts with stone tools. We predicted that larger assemblages of spheroid echinates, a phytolith associated with palms, would be found at active nut-cracking sites, however we found no statistical difference between total spheroid echinates (measured as total number found per gram of dry sediment) assemblages produced across active nut-cracking, dormant, or non-nut-cracking sites. This may have been due to small sample size (N[≤]6 sediment samples for each of the three sites) and so further sample collection and analyses are needed for inter-site comparisons. We also measured 2D area (m2), perimeter and maximum diameter of spheroid echinates found in nut endocarps (shells) and leaflets from an oil palm frond. Intra-specific differences from all three measurements were found with these phytoliths being larger in the nut endocarp than the leaflet. This has implications for (re)interpreting the assemblages of spheroid echinate phytoliths at the three sites to determine if there is a greater productivity larger-sized spheroid echinates that fall within the size range of those measured for the nut endocarp (mean maximum diameter of 14.9 m versus 7.8 m for those found in oil palm leaflet). Finally, we argue for the importance of initialising and continuing the interpretation of phytolith assemblages in local sediments that are located near sites where directed plant input by non-human taxa has occurred, in this case, chimpanzees cracking open oil palm nuts using stone tools. This is important to refine our interpretation of phytolith assemblages where human and non-human taxa who use complex foraging strategies share ecological spaces.

animal behavior and cognition↗

bioRxiv2021

Landscaping the behavioural ecology of primate stone tool use

Ecology is fundamental to the development, transmission, and perpetuity of primate technology. Previous studies on tool site selection have addressed the relevance of targeted resources and raw materials for tools, but few have considered the broader foraging landscape. In this first landscape-scale study of the ecological contexts of wild chimpanzee (Pan troglodytes verus) tool-use, we investigate the conditions required for nut-cracking to occur and persist over time at discrete locations in Bossou (Guinea). We examine this at three levels: selection, frequency of use, and inactivity. We find that, further to the presence of a nut tree and availability of raw materials, abundance of food-providing trees as well as proximity to nest sites were significant predictors of nut-cracking occurrence. This suggests that the spatial distribution of nut-cracking sites is mediated by the broader behavioural landscape and is influenced by non-extractive foraging of predictable resources, as well as non-foraging activities. Additionally, the number of functional tools was greater at sites with higher frequency of nut-cracking and was negatively correlated with site inactivity. Our findings indicate that the technological landscape of the Bossou chimpanzees shares affinities with the favoured places model of hominin site formation and provides new insights for reconstructing ancient patterns of landscape use. ResumeLecologie est fondamentale pour le developpement, la transmission et la perennite de la technologie des primates. Des etudes anterieures ont identifie la disponibilite des ressources cibles ainsi que les matieres premieres pour les outils comme des facteurs influents dans la selection des emplacements pour les activites technologiques. Cependant, il y a peu detudes qui abordent cette recherche a lechelle du paysage et du comportement fourrager. Dans cette premiere etude paysagere sur lutilisation doutils par le chimpanze sauvage (Pan troglodytes verus), nous recherchons les conditions ecologiques qui influencent la selection, lutilisation et linactivite des emplacements utilises pour le cassage des noix en Bossou, Guinee. Nos resultats montrent quen plus de la presence dun noyer et de la disponibilite des matieres premieres, labondance darbres nourriciers ainsi que la proximite des sites de nidification etaient des predicteurs significatifs de loccurrence du cassage des noix. Cela suggere que la distribution spatiale des sites de cassage de noix est influencee par le paysage comportemental et est influencee par le fourrage non-extractive de ressources previsibles, ainsi que par des activites non-fourragers. Nos resultats indiquent que le paysage technologique des chimpanzes de Bossou partage des affinites avec le modele des << lieux favoris >> de la formation des sites hominides et fournit de nouvelles perspectives pour reconstruire les modes dutilisation du paysage anciens.

ecology↗