Diet, feeding behavior, and jaw architecture of Taï monkeys: Congruence and chaos in the realm of functional morphology

Abstract

We review feeding and mandibular anatomy in a community of West African monkeys. We use field observations, food material property data, and skeletal specimens from the Ivory Coast's Taï Forest to explore the factors that shape mandibular architecture in colobines and cercopithecines. Despite excellent geographic control across our sample, the fit between bone form (as conventionally described) and functional activity (as we perceive it) is not spectacular. We present a thought experiment to assess how well we could reconstruct diet in the Taï monkeys if we only had skeletons and teeth to study. This exercise indicated that we would be correct about half the time. Our analyses reinforce the notion that diet is anything but a monolithic variable and that better success at relating mandibular form to food must incorporate information on ingestive and processing behavior, geometric and material properties of foods, and both material and structural data on jaws themselves.

Lesser spot-nosed monkeys coordinate alarm call production with associated Campbell’s monkeys

“…In this study, we investigated the alarm call system of lesser spot-nosed monkeys and the influence of Campbell's monkey vocal behaviour. Lesser spot-nosed and Campbell's monkeys form robust mix-species associations, forage mainly in the lower canopy and have the same social organisation (McGraw and Rowe 1996;Buzzard 2006Buzzard , 2010McGraw et al 2007;Daegling 2020). We first established the male Campbell's monkey alarm call N 'kroo' per trials c lesser spot-nosed monkey call repertoire when encountering three types of danger (eagle, leopard and falling tree) and corresponding Campbell's monkey alarm call, and identified three call types, 'kroo', 'tcha' and 'kow', the latter mainly produced as combinations ('tcha-kow'; see Oates (1985) for alternative terminology).…”

“…In the Taï Forest (Ivory Coast), up to eight monkey species regularly form mixed-species associations (McGraw et al 2007). Amongst them, Diana monkeys typically forage in the highest canopy parts with a fruit-rich diet, whereas Campbell's monkeys have a more generalist diet and exploit levels below the main canopy while lesser spot-nosed monkeys (Cercopithecus petaurista) prefer foliage in the lower levels with a large proportion of leaves in their diet (McGraw 2000;Wolters and Zuberbühler 2003;Kane and McGraw 2017;McGraw and Daegling 2020). These three guenon species spend the majority of their time in association (75-88%, Buzzard 2010).…”

Anthroengineering: an independent interdisciplinary field

“…Does a skull's ability to resist masticatory loads dictate or limit an animal's or species’ diet? Does natural selection select for skull form based on its ability to resist masticatory loads [10–13,100–102]?Primate tooth shape is undoubtedly correlated with diet [56,103], likely because teeth have evolved to break down foods consumed more efficiently [56,104,105]. However, the interactions between multicusped teeth and food items are so complex that we lack an efficient model for describing these relationships and, thereby, predicting food item breakdown from tooth shape [64,106,107].…”

Oral processing, sexual selection, and size variation in the circumorbital region of Colobus and Piliocolobus

“…At Taï, the preferred food of C. polykomos is the seeds of Pentaclethra macrophylla, which account for approximately 13% of the annual diet and up to 55% in some months (Korstjens, 2001). Although P. macrophylla seeds are soft, the dry fruit that houses the seeds is tough and has a large work of fracture (Daegling & McGraw, 2001;McGraw et al, 2016;McGraw & Daegling, 2020). C. polykomos engages in lengthy bouts of aggressive incisor tooth use to open P. macrophylla, spending upward of 15 min processing a single one before masticating the seeds (and sometimes the pod) with its postcanine dentition (McGraw et al, 2016).…”

“…The sample used in this study consisted of 98 crania, 21 C. polykomos (females: n = 12; males: n = 9) and 77 P. badius (females: n = 28; males: n = 49), collected by WSM from the study grid of the Taï Monkey Project (McGraw & Daegling, 2020). Nearly all skulls were complete, although taphonomic damage and a lack of corresponding mandibles for some crania reduced sample sizes for several measurements.…”