RESEARCH ARTICLE Highly Nested Diets in Intrapopulation Monkey–Resource Food Webs WESLEY DÁTTILO 1 , JUAN CARLOS SERIO‐SILVA 2 *, COLIN A. CHAPMAN 3,4 , AND VÍCTOR RICO‐GRAY 1 1 Instituto de Neuroetología, Universidad Veracruzana, Xalapa, Veracruz, Mexico 2 Red de Biología y Conservación de Vertebrados, Instituto de Ecología A.C., Xalapa, Veracruz, Mexico 3 Department of Anthropology & McGill School of Environment, McGill University, Montreal, Quebec, Canada 4 Wildlife Conservation Society, Bronx, New York Recently several studies have focused on the structure of ecological networks to provide insights into ecological and coevolutionary dynamics of interacting species. However, rarely have the tools of ecological networks been used to understand how feeding relationships vary among individuals of the same population. Here we use 7 years of data and network analyzed to examine the intrapopulation diet variation in a group of howler monkeys (Alouatta palliata). We show that individual monkey–resource food webs are nested, but not modular and the stability of these patterns is independent of time of day or season. Our findings indicated that individuals do not forage randomly when compared to null models and that the diets of more selective monkeys represent subsets of the diets of other individuals. Moreover, there are no subgroups that eat a particular set of available plant species more frequently than other sets, suggesting that the spatial strategy of group foraging plays an important role in the feeding ecology of each group given that individuals of the same group tend to share similar resources while the group remains at a feeding site. Since the diets of more selective individuals are a subset of other monkeys, we suggest that more selective monkeys are able to outcompete others for preferred foods. Additionally, we did not observe differences in nutritional content or spatial abundance of more frequently eaten plant species when compared with less frequently eaten species, but in most cases, the more frequently eaten plant species were Ficus (Moraceae). This reinforces the important role that Ficus trees play in howler monkey feeding ecology, likely due to its year‐round availability. Am. J. Primatol. 76:670–678, 2014. © 2014 Wiley Periodicals, Inc. Key words: complex networks; intrapopulation variation; modularity; nestedness; social animals INTRODUCTION Trophic interactions affect all attributes of eco- systems and play an important role in the stability and diversity of communities and populations in space and time [O’Gorman & Emmerson, 2009]. Despite this, few studies have evaluated how feeding relation- ships vary within populations [Bolnick et al., 2003; Inger et al., 2006], but see studies on Oreochromis aureus [Gu et al., 1997], Epipedobates flavopictus [Biavati et al., 2004], Gracilinanus microtarsus [Martins et al., 2006], and Procolobus rufomitratus [Chapman et al., 2002]. These studies have shown that there can be wide variation in rates of resource consumption by individuals in a population [Bolnick et al., 2003; Shine et al., 2002]. For example, a species of intertidal snail (Nucella melones) consumes 21 prey taxa, but any one individual consumes only one to five of these taxa, ignoring prey species eaten by others. In the case of gray‐cheeked mangabeys (Lophocebus albigena) and redtail monkeys (Cercopithecus asca- nius), high ranking females use agonism to monopo- lize sodium rich bark [Chancellor & Isbell, 2009; Rode et al., 2006; Rothman et al., 2012]. Thus, group members may exhibit alternative feeding strategies. The little evidence available to date suggests that some individuals are more selective (concentrate their feeding efforts on a small number of foods), while others are more opportunistic [Araújo et al., 2010; Bolnick et al., 2002; Pires et al., 2011]. Several studies have recently used tools derived from network analysis to describe the dietary variation found in a population [Araújo et al., 2010; Contract grant sponsor: Conselho Nacional de Desenvolvimento Científico (CNPq) Ã Correspondence to: Juan Carlos Serio‐Silva, Red de Biología y Conservación de Vertebrados, Instituto de Ecología, A.C.— INECOL, Antigua Carretera a Coatepec No. 351, El Haya, Xalapa 91070, Veracruz, Mexico. E‐mail: juan.serio@inecol.mx; serioju@yahoo.com Received 9 September 2013; revised 16 December 2013; revision accepted 11 January 2014 DOI: 10.1002/ajp.22261 Published online 5 February 2014 in Wiley Online Library (wileyonlinelibrary.com). American Journal of Primatology 76:670–678 (2014) © 2014 Wiley Periodicals, Inc.