Primates (2006) 47:239–247 DOI 10.1007/s10329-005-0172-6 ORIGINAL ARTICLE Pablo R. Stevenson Activity and ranging patterns of Colombian woolly monkeys in north-western Amazonia Received: 28 April 2005 / Accepted: 7 November 2005 / Published online: 28 February 2006 Ó Japan Monkey Centre and Springer-Verlag 2006 Abstract In this study, I revise three aspects of the so- Keywords Daily path length Æ Dominance Æ Lagothrix cioecology of woolly monkeys (genus Lagothrix) that lagothricha Æ Tinigua park might give us a better understanding of the patterns found in this species: (1) the association between tem- poral variation in fruit abundance and diet, activity, and ranging patterns; (2) the individual trade-offs associated Introduction with living in small or large groups, and (3) the rela- tionship between social dominance and foraging success. Woolly monkeys (genus Lagothrix) are one of the largest Using behavioral and ecological data collected during primates in the New World (Peres 1994a) and are widely 3 years in Tinigua Park, Colombia, I found that woolly distributed in areas of central and western Amazonia monkeys tend to avoid open-degraded forests, where (Fooden 1963). Group size varies (range 10–49) (Peres fruit production is generally lower than it is in mature 1996), and groups usually include several philopatric forests. Diet and activity budgets were highly associated males, several adult females, and their offspring. Males with temporal patterns of fruit production. Daily path are consistently dominant over females (Nishimura length was positively correlated with group size and 1994) and more than half of all aggressive interactions monthly fruit abundance, and negatively correlated with are observed in fruit-feeding contexts (Stevenson et al. habitat quality. I found differences in activity budgets 1994). Woolly monkeys prefer to feed on ripe fruits, but and the diet preferences of different age/sex classes. For they also consume young leaves, seeds, and animal prey example, adult males rest more and juveniles play more (Izawa 1975; Soini 1986; Stevenson 1992, 2004a; than other classes. Juveniles and adult females without Stevenson et al. 1994; Peres 1994b; Defler and Defler infants look for arthropods more often than adult males 1996; Di Fiore and Rodman 2001; Di Fiore 2004). They and females with young infants, who showed the highest are known to consume more than 100 different species of frequencies of fruit feeding. Dominant adult males were fruits in all places where they have been extensively not consistently the most efficient foragers on fruits studied (see references above) and their highly diverse according to two different indexes. Most of these results diet is associated with the efficient role they play as seed are consistent with the expectations from strong intra- dispersers (Yumoto et al. 1999; Stevenson 2000, 2002; group competition for resources. However, females with Dew 2001). The seed shadows generated by woolly infants received benefits during feeding similar to those monkeys depend mainly on their ranging patterns of dominant adult males, which may be mediated by (Stevenson 2002). However, we are still uncertain about differential aggression from males to other group the factors affecting moving patterns. The main aim of members (juveniles and females without infants). this paper is to associate the temporal patterns of habitat use with spatial variation in fruit abundance. In theory, differences in daily path length of primate groups are determined by several factors such as diet P. R. Stevenson type, food distribution, group size and cohesion, com- Department of Anthropology, State University New York, petition, energetic constrains, cognitive abilities, and Stony Brook, NY, USA predation risk, among others (Janson 1992; Janson and Goldsmith 1995; Boinski and Garber 2000). For in- Present address: P. R. Stevenson (&) Depto. Ciencias Biolo´gicas, Universidad de Los Andes, stance, daily path length for frugivorous primate groups Cr. 1 No. 18a-60, Bogota, Colombia tends to increase linearly with group size (but not for E-mail: [email protected] folivorous animals); this relationship is used as evidence 240 of the importance of intra-group competition when food woolly monkeys there is a foraging advantage for sources are patchily distributed and inconsistent in time dominant individuals. It can be hypothesized that sexual and space (Janson and Goldsmith 1995). In terms of dimorphism is partially related to intragroup competi- group cohesion, socio-ecological models predict that tion for preferred resources, such as fruits. If this idea is small group size or temporal subdivision of group correct, we should expect a positive association between members is feasible when predation risk is low, and less body size, dominance, and foraging efficiency. Further- cohesion is expected under regimes of high intra-group more, if intra-group competition is strong we expect a competition (Janson 1988; van Schaik 1989). Terborgh higher consumption time of defendable resources (fruits and Janson (1986) postulated long ago that the fission– and leaves) for dominant than for submissive individu- fusion social organization was common in the large als, and higher budgets devoted to moving for low spider and woolly monkeys because they may be less ranking than for high ranking individuals. The second vulnerable to predation than smaller New World mon- purpose of this paper is to test these predictions. The keys. Although consistent differences in the social specific questions I will address in this paper are: (1) organization of these two species have been pointed out which kinds of forest types are preferred by the woolly (Peres 1996), qualitative observations suggest that all monkeys at Tinigua Park; (2) is there an association atelines show some plasticity in group cohesion, which between fruit production and variables such as habitat might be related to total community size (Strier et al. use, diet, and activity; (3) are there differences in 1993). We still lack solid quantitative data on cohe- behavioral patterns between age/sex classes that could siveness at group spatial scales, which could be ex- be associated with intra-group competition; (4) what plained by socio-ecological factors. socio-ecological factors are most important to explain The ranging behavior of woolly monkeys varies at differences in daily path length; and (5) is male domi- both regional and local scales. Populations in the central nance related to foraging efficiency? Amazon region, such as the groups studied by Defler (1987) and Peres (1996), range over larger areas than the groups in upper Amazonia (Stevenson et al. 1994; Methods Di Fiore and Rodman 2001; Di Fiore 2003). These dif- ferences in home range size can be up to five times in Study site magnitude, and are associated with variations in popu- lation densities, which are negatively correlated with The study site is located in a tropical lowland forest on fruit production (Stevenson 2001), which in turn could the eastern border of Tinigua National Park be influenced by soil fertility (Defler and Defler 1996). (201,875 ha), west of Sierra de La Macarena, Departa- Similar differences in home range size and path length mento del Meta, Colombia (2°40¢N, 74°10¢W, 350– have even been documented for groups of woolly mon- 400 m above sea level). The study site, Centro de keys living in the same study site, but with different Investigaciones Ecolo´gicas La Macarena (CIEM) is on proportion of good quality habitat (Stevenson and the west margin of the Rı´o Duda. Rainfall is markedly Castellanos 2001). Previous analyses of foraging pat- seasonal in the region, with a 2 to 3-month dry period terns of woolly monkey groups at Tinigua showed sim- occurring between December and March (Stevenson ilar fruit-feeding rates and shorter daily path lengths for 2002). Average annual precipitation for the three study medium-sized groups (Stevenson and Castellanos 2000). years was 2,782 mm. Data from the period of low fruit abundance were not included in these analyses to reduce the variation in path length due to causes other than differences in group size, Data collection because daily path length tends to be larger during periods of fruit abundance (Stevenson et al. 1994). These I collected data on activity, diet, and habitat use using a differences have been explained as an energy-saving combination of instantaneous and continuous sampling strategy that seems common in all atelines (Strier 1992; on focal individual woolly monkeys during three yearly Stevenson et al. 2000; Di Fiore and Rodman 2001). In cycles (April 1990–March 1991, August 1996–July 1997, summary, there is evidence that several ecological and and January–December 2000, hereafter referenced as social factors affect the ranging patterns of woolly 1990, 1996, and 2000, respectively). I analyzed data from monkeys, but we lack an analysis that simultaneously 48 h of focal samples each month, equally distributed takes into account the potential factors affecting daily throughout the day (0600–1800 hours). I sampled four path length (group size, fruit production, and habitat different age/sex classes [adult males, females with quality). dependent infants (less than 1-year-old), adult females Among the atelines, woolly monkeys show the high- without infants, and immature individuals (juveniles and est degree of sexual dimorphism in body size (Ford and subadults of both sexes)], sampling one class each day Davis 1992). This dimorphism may be associated with every month between 0600 and 1800 hours. All group male dominance, but it is unclear why this trait is not members were individually recognized (with the excep- present in the related Ateles and Brachyteles. It is pos- tion of some juveniles and subadult individuals) and sible that in the relatively more cohesive groups of samples were not biased for any particular individual. 241 Genital marks, injuries, particular facial expressions, the two groups were combined, except for the estimates and body size were used to distinguish individuals.