Mantled Howler Monkeys (Alouatta palliata) in a Costa Rican Forest Fragment Do Not Modify Activity Budgets or Spatial Cohesion in Response to Anthropogenic Edges.

Forest fragmentation increases forest edge relative to forest interior, with lower vegetation quality common for primates in edge zones. Because most primates live in human-modified tropical forests within 1 km of their edges, it is critical to understand how primates cope with edge effects. Few studies have investigated how primates inhabiting a fragment alter their behaviour across forest edge and interior zones. Here we investigate how anthropogenic edges affect the activity and spatial cohesion of mantled howler monkeys (Alouatta palliata) at the La Suerte Biological Research Station (LSBRS), a Costa Rican forest fragment. We predicted the monkeys would spend greater proportions of their activity budget feeding and resting and a lower proportion travelling in edge compared to forest interior to compensate for lower resource availability in the edge. We also predicted that spatial cohesion would be lower in the edge to mitigate feeding competition. We collected data on activity and spatial cohesion (nearest neighbour distance; number of individuals within 5 m) in forest edge and interior zones via instantaneous sampling of focal animals. Contrary to predictions, the monkeys spent equal proportions of time feeding, resting and travelling in forest edge and interior. Similarly, there were no biologically meaningful differences in the number of individuals or the distance between nearest neighbours in the edge (1.0 individuals; 1.56 m) versus the interior (0.8 individuals; 1.73 m). Our results indicate that A. palliata at LSBRS do not adjust their activity or spatial cohesion patterns in response to anthropogenic edge effects, suggesting that the monkeys here exhibit less behavioural flexibility than A. palliata at some other sites. To develop effective primate conservation plans, it is therefore crucial to study primate species' responses to fragmentation across their geographic range.

The fourth level of social structure in a multi-level society: ecological and social functions of clans in hamadryas baboons.

Hamadryas baboons are known for their complex, multi-level social structure consisting of troops, bands, and one-male units (OMUs) [Kummer, 1968. Social organization of hamadryas baboons. Chicago: The University of Chicago Press. 189p]. Abegglen [1984. On socialization in hamadryas baboons: a field study. Lewisburg, PA: Bucknell University Press. 207p.] observed a fourth level of social structure comprising several OMUs that rested near one another on sleeping cliffs, traveled most closely together during daily foraging, and sometimes traveled as subgroups independently from the rest of the band. Abegglen called these associations "clans" and suggested that they consisted of related males. Here we confirm the existence of clans in a second wild hamadryas population, a band of about 200 baboons at the Filoha site in lowland Ethiopia. During all-day follows from December 1997 through September 1998 and March 2005 through February 2006, data were collected on activity patterns, social interactions, nearest neighbors, band fissions, and takeovers. Association indices were computed for each dyad of leader males, and results of cluster analyses indicated that in each of the two observation periods this band comprised two large clans ranging in size from 7 to 13 OMUs. All band fissions occurred along clan lines, and most takeovers involved the transfer of females within the same clan. Our results support the notion that clans provide an additional level of flexibility to deal with the sparse distribution of resources in hamadryas habitats. The large clan sizes at Filoha may simply be the largest size that the band can split into and still obtain enough food during periods of food scarcity. Our results also suggest that both male and female relationships play a role in the social cohesion of clans and that males exchange females within clans but not between them.