Seasonal resource categorisation and behavioural adaptation among non-human primates: Implications for hominin carnivory in the Early Pleistocene

Seasonality plays a critical role in determining the yearly dietary variability of many nonhuman primates living in tropical and subtropical environments. Much previous research has emphasised the seasonal importance of both preferred resources—eaten whenever available—and fallback foods—eaten during periods of scarcity to compensate for an insufficient availability of preferred resources. However, previous discussions of this dichotomy have often overlooked why different populations of the same taxon may exhibit a different level of engagement with identical resources, especially those that require some degree of technological investment by virtue of being embedded. Similarly, not enough attention has been given to diachronic trends in the incorporation of novel resources to seasonal consumption patterns among non-human primates.In this paper, we present a framework for understanding the spatio-temporal relationships between preferred and fallback resources in a more systematic way, explicitly through the lens of landscape knowledge and seasonal fluctuations in quality and availability. We argue it is the interplay between resource quality and the available knowledge pertaining to its exploitation that will determine the categorisation of a resource. In this regard, the accumulation of further information through encounter, experimentation, and behavioural (including technological) innovation enables resources with high nutritional potential to attain preferred status. We end with an exploration of the gradual consolidation of the hominin carnivory niche in the Early Pleistocene of East Africa, to demonstrate the utility of our framework—specifically the interplay between seasonality and the concept of landscape knowledge—for understanding behavioural change in the archaeological record.

Food preference of captive mona monkey (Cercopithecus mona) in University of Lagos, Nigeria

In the wild, nonhuman primates' preferences for some food may not be quite clear due to the seasonality and utilization of fallback foods during periods of scarcity. Understanding the most preferred foods could aid schedules of serving them to captive primates. Against this background, the study was carried out to determine the food preference of captive mona monkeys offered foods consumed by their counterparts in the degraded and fragmented urban forest, biodiversity rich rainforest, and in a zoo. The feeding trials were conducted in the service area of the University of Lagos. Four adult monkeys (two males and two females) were offered weighed amounts of 13 different foods served in batches of five, using the cafeteria method. Each food type was offered separately in a food trough at 10:00 hrs each day. Left over was withdrawn and measured after 24 hours. Position of the food trough was changed every day. Water was provided ad libitum in a water trough. The difference between offered and left-over weights was regarded as intake. Food preference was determined from the coefficient of preference (COP), and a unitary value was considered preferred. In decreasing order of preference, the preferred foods that had COP ≥ 1 were Musa sapientum, Zea mays, and Solanum melongena. The mona monkey and other sympatric species held in captivity could be provided with these foods in addition to other foods that could meet their nutritional needs. Nutritional assays of these foods could provide clues to their being preferred above others. Dans la nature, les préférences des primates non humains pour certains aliments peuvent ne pas être tout à fait claires en raison de la saisonnalité et de l'utilisation des aliments de remplacement pendant les périodes de pénurie. Comprendre les aliments les plus préférés pourrait faciliter les horaires de les servir aux primates captifs. Dans ce contexte, l'étude a été menée pour estimer la préférence alimentaire des singes mona en captivité qui offraient des aliments consommés par leurs homologues dans la forêt urbaine dégradée et fragmentée, la forêt tropicale riche en biodiversité et dans un zoo. Les essais d'alimentation ont été menés dans l’aire de service de l'Université de Lagos. Quatre singes adultes (deux mâles et deux femelles) se sont vus offrir des quantités pesées de 13 aliments différents servis par lots de cinq, en utilisant la méthode de la cafétéria. Chaque type de nourriture était offert 184 séparément dans une auge à 10 h chaque jour. Le surplus a été prélevé et mesuré après 24 heures. La position de l'auge a été changée chaque jour. L'eau était fournie à volonté dans un bac à eau. La différence entre le poids offert et le poids restant a été considérée comme un apport. La préférence alimentaire a été déterminée à partir du coefficient de préférence (COP), et une valeur unitaire a été considérée comme préférée. Par ordre décroissant de préférence, les aliments préférés qui avaient un COP ≥ 1 étaient Musa sapientum, Zeamays et Solanummelongena. Le singe mona et d'autres espèces sympatriques gardées en captivité pourraient recevoir ces aliments en plus d'autres aliments qui pourraient répondre à leurs besoins nutritionnels. Les dosages nutritionnels de ces aliments pourraient fournir des indices sur leur préférence aux autres.

Oral Processing Behavior of Diana Monkeys (Cercopithecus diana) in Taï National Park, Côte d’Ivoire

Primates are hypothesized to “fall back” on challenging-to-process foods when preferred foods are less available. Such dietary shifts may be accompanied by changes in oral processing behavior argued to be selectively important. Here, we examine the oral processing behavior of Diana monkeys (<i>Cercopithecus diana</i>) in the Taï Forest across their dietary breadth, testing relationships among food intake, fruit availability, preference, and oral processing behaviors including those involved in food ingestion and breakdown. We conducted 1,066 focal follows from April 2016 to September 2017 documenting frequencies of incisor, canine, and cheek tooth mastications (i.e., chews) per ingestive action (<i>n</i> = 11,906 feeding events). We used phenological survey and scan sample data collected between 2004 and 2009 to examine dietary preference and food availability. Our analyses show that Diana monkeys processed foods in significantly different ways (<i>H</i>₂ = 360.8, <i>p</i> &#x3c; 0.001), with invertebrates requiring the least oral processing, fruit requiring intermediate amounts, and leaves requiring the most oral processing. There was no relationship between fruit availability and consumption of preferred or nonpreferred fruits (<i>p</i> &#x3e; 0.05); however, preferred fruits were processed with significantly fewer mastications (i.e., less chewing) than nonpreferred fruits (<i>U</i> = 6,557, <i>p</i> &#x3c; 0.001). We thus demonstrate that, when preferred foods are scarce, Diana monkeys do not fall back on difficult-to-process foods. Changes in processing profiles occurred throughout the year and not solely when preferred foods were in short supply. Though preferred fruits required less processing than nonpreferred fruits, we found no relationship between fruit preference and fruit availability. Diana monkeys’ lack of readily identifiable fallback foods may be attributable to the relatively high tree diversity and productivity of the Taï Forest. We conclude that Diana monkeys engage in resource switching, consuming a relatively easy-to-process diet year-round.

Ecometric modelling of tooth shape and precipitation gradients among lemurs on Madagascar

Ecometric modelling relates spatial environmental variables to phenotypic characters to better understand morphological adaptation and help reconstruct past environments. Here, the community means of the dental topography metrics Dirichlet normal energy (DNE) and orientation patch count (OPC) are tested against annual precipitation and precipitation seasonality among lemurs across Madagascar. Dry, seasonal environments are expected to be associated with high DNE and OPC, as lemurs living in these environments are more likely to rely on tougher foods. Ecometric models are also used to calculate ecometric loads for lemur taxa hypothesized to be experiencing evolutionary disequilibria and to reconstruct annual precipitation and precipitation seasonality at the ~500 years BP subfossil cave site of Ankilitelo. DNE was highest in highly seasonal but wet environments. Seasonal exploitation of fallback foods and the availability of new leaves during wet periods may be most important in driving community DNE. OPC was weakly predicted by annual precipitation and seasonality but its distribution appeared to be driven by a stepwise increase in its community values in rainforest environments. The lemur fauna from Ankilitelo appears to resemble communities from moister environments than occur in the spiny desert zone in which the site is situated today.

Ecological variation in cognition: Insights from bonobos and chimpanzees

Bonobos and chimpanzees are closely related, yet they exhibit important differences in their wild socio-ecology. Whereas bonobos live in environments with less seasonal variation and more access to fallback foods, chimpanzees face more competition over spatially distributed, variable resources. This chapter argues that bonobo and chimpanzee cognition show psychological signatures of their divergent wild ecology. Current evidence shows that despite strong commonalities in many cognitive domains, apes express targeted differences in specific cognitive skills critical for wild foraging behaviours. In particular, bonobos exhibit less accurate spatial memory, reduced levels of patience and greater risk aversion than do chimpanzees. These results have implications for understanding the evolution of human cognition, as studies of apes are a critical tool for modelling the last common ancestor of humans with nonhuman apes. Linking comparative cognition to species’ natural foraging behaviour can begin to address the ultimate reason for why differences in cognition emerge across species. Les bonobos et les chimpanzés sont prochement liés, pourtant ils montrent d’importantes différences dans leur sociologie naturelle. Alors que les bonobos vivent dans des environnements avec peu de diversité de climat entre saisons et plus d’accès à des ressources de nourriture alternatives, les chimpanzés ménagent une compétition étalée spatialement et des ressources plus variées. Je soutiens que la cognition des chimpanzés et bonobos montre les signatures psychologiques de leur écologie naturelle divergente. Les témoignages courants montrent que, malgré les forts points communs dans en cognition, les grands singes expriment des différences au niveau de compétences cognitives importantes au butinage. En particulier, les bonobos démontrent une mémoire spatial moin précise, moin de patience, et plus d’aversion de risques que les chimpanzés. Ces résultats fournissent des signes dans l’étude de l’évolution de la cognition humaine. Les études des grands singe sont un outil d’importance majeure dans la modélisation du dernier ancêtre commun des humains et grands singes non-humains. Faire des liens cognitives comparatives entre le butinage des différentes espèces peut commencer à dévoiler les raisons pour les différences de cognition entre espèces.

Dietary proclivities of Paranthropus robustus from Swartkrans, South Africa

Pleistocene Paranthropus robustus fossils from Swartkrans have yielded stable isotope values suggesting some foraging on C4 plants possibly including underground storage organs. Dental microwear texture analysis on P. robustus (SK 6, SK 34 and SK 47) from Swartkrans Member 1 is performed to examine whether tooth surface damage from mastication agrees with prior dietary inferences from carbon isotopes. There is considerable variation in textural characteristics among the P. robustus specimens. Specifically, adult SK 34 stands apart from the two subadult specimens, SK 6 and SK 47, suggesting life history could be reflected in patterns of dental microwear texture characteristics, although seasonality and availability of fallback foods may also explain the variation observed in P. robustus. The fossils all exhibit elevated surface texture complexity, resembling the values for Lophocebus albigena and Cebus apella, and to a lesser extent, Pan troglodytes. Paranthropus robustus is dissimilar to primary folivores, such as Trachypithecus cristatus or folivore- frugivores such as Alouatta palliata suggesting leaves comprised very little of its diet. The textural fill volume of P. robustus differs from that observed in extant primates from tropical forests indicating extreme durophagy, perhaps a function of differences in habitat. Ingestion of extraneous grit on the underground parts of plants and from terrestrial resources, perhaps as fallback foods or as dietary staples, may account for these enamel textural properties and may help explain the mixed C3/C4 isotopic signal in P. robustus.