Small folivorous primate groups exhibit behavioral and physiological effects of food scarcity

Abstract

The influence of diet and food distribution on the socioecology of group-living species has long been debated, particularly for primates. It has typically been assumed that folivorous primates experience relatively little feeding competition due to the abundant, widespread nature of their food, freeing them to form large groups in response to predation, to disperse with relative ease, and to have egalitarian female social relationships. Recent studies, however, have come to different conclusions about the extent to which folivorous primates are limited by food and experience food competition and how these factors affect folivore socioecology. To better understand the selective pressures that diet places on folivores, we investigated how 2 small highly folivorous groups of colobus monkeys (Colobus guereza) in Kibale National Park, Uganda, responded behaviorally and physiologically to a steep reduction in availability of their most important foods. The monkeys decreased their reliance on their 2 most frequently eaten food species and increased their daily path length, number of feeding patches visited/day, size of individual feeding areas, percentage of time spent feeding, and dietary diversity. They also showed evidence of physiological costs, in that lactating females' urinary C-peptide levels (i.e., insulin production) declined as top foods became scarce, and parasite loads slightly, but significantly, increased in 2 of 3 adult females examined. These results suggest that highly folivorous primates, even in very small groups, may experience behavioral and physiological effects of food limitation, within-group scramble competition for food, and possibly substantial selective pressures during periods of food scarcity.

Diet and Dietary-Niche Breadth of Diurnal Rain Forest Primates in the Central Western Ghats, India

“…In some previous studies it has been reported that, although folivorous primates have a higher chance of diet selection because of resource abundance, they are selective by nature and use very few resources for overall consumption [Harris et al, 2009]. Although lion-tailed macaques were not observed to consume leaves, bonnet macaques occasionally consumed leaves, mainly young and whole-leaf flush or their petioles.…”

Reproductive Ecology of Female Chimpanzees

“…Briefly, C-peptide is a byproduct of the production of insulin, one of the key hormones regulating intermediary metabolism and a key chemical signal and regulator of energy balance [Rubenstein et al, 1969;Schwartz et al, 1992;Strack et al, 1995;Norman & Litwack, 1997]. C-peptide, therefore, offers a noninvasive way to track changes in energetic condition in wild primates and has been validated against measures of weight loss/gain [Valeggia & Ellison, 2004;Deschner et al, 2008;Girard-Buttoz et al, 2011], dietary quality Harris et al, 2010;Georgiev et al, 2011], food availability [Emery Thompson & Knott, 2008], estimated caloric intake [Emery Thompson & Knott, 2008], and activity levels in a variety of primate species. C-peptide is valuable for monitoring the costs of lactation not only because it provides a general biomarker for energy balance but also because changes in insulin production and sensitivity are essential for the metabolic shifts that divert maternal energy toward milk production [Flint et al, 1979;Jones et al, 1984;Vernon, 1989;Tigas et al, 2002].…”

Linking feeding ecology and population abundance: a review of food resource limitation on primates

“…Deficiency in macronutrients can also be shown by urinalysis that quantify ketone and c-peptide concentrations as indices of energy balance (Harris et al 2009;Harrison et al 2010;MacIntosh et al 2012) and urea and d…”