Introduction

The genus Lagothrix, the woolly monkeys, contains four closely related species, formerly considered subspecies (Groves, 2005). Lagothrix spp. are known to have femalebiased dispersal (Nishimura, 2003; Di Fiore and Campbell, 2007), but genetic evidence suggests that male dispersal also occurs (Di Fiore and Fleischer, 2005). Through long term field studies, female dispersal has been observed in the wild (Stevenson et al., 1994; Nishimura, 2003; Di Fiore and Campbell, 2007), but to date no observations of male dispersal have been recorded. Solitary adult males of Lagothrix poeppigii have been observed trying to join existing groups, but have been expelled by resident males (Di Fiore and Fleischer, 2005). Here we report the acceptance of a newcomer three-year-old male into an existing group of Lagothrix lagotricha. This observation should be interpreted with caution since it concerns a captive raised individual reintroduced to the wild.

Observations

In 1996, a 5 to 8 month old male woolly monkey (L. lagotricha) that was being kept as a pet was confiscated by local authorities. The monkey's origin is not certain, but may have been the Putumayo region, Colombia. The regional environmental authorities had no adequate infrastructure to house this individual, so the infant was given to Angela Maldonado, who raised the monkey until 1998 in her household, in Bogotá, Colombia. The woolly monkey's lower lip had a scar, presumably generated during its capture from the wild. The monkey's diet consisted of fruit and vegetables, and he was taken every weekend to nearby forests in order to allow the development of normal climbing behavior.

On April 2^nd 1998 Maldonando brought the captive raised woolly monkey to the Caparú Biological Station in Vaupés, Colombia (for a more detailed description of the site refer to Defler and Defler, 1996), where a semi captive free-ranging group of primates was kept for rehabilitation and reintroduction purposes. The group consisted of eight common woolly monkeys (Lagothrix lagotricha: four adult females, one sub-adult female, two infant females, and one juvenile male), two white-fronted capuchins (Cebus albifrons albifrons: one male and one juvenile female), one subadult female long-haired spider monkey (Ateles belzebuth), and three mottled-faced tamarins (Saguinus inustus: two adult females and one sub-adult male). The monkeys there foraged freely in the station area and were fed once daily. On April 3, 1998, a wild group of woolly monkeys passed near the station, and in response, the captive-raised male performed an aggressive display, including branch shaking. Although an adult male stopped and observed the new male, and some other members of the group paid attention to the display, they performed no aggressive displays, and continued on their way, seemingly unperturbed. The captive-raised male followed the group until dusk and then returned to the station.

When first introduced to the primate group of the Caparú Biological Station, the captive-raised male was approximately 3 years old, and interacted normally with the other individuals of the group for his age. He was, however, rejected by one of the adult woolly females, and after this interaction all of the adult females were aggressive to him. On two occasions, this caused the captive-raised male to escape into the forest and remain alone overnight. The most aggressive female was the lowest ranking in the group, had no offspring in the group, and was also the most aggressive towards humans. On April 12, after 3 days of enforced separation by the Caparú staff, the aggressive female and the captive-raised male were allowed near each other again and the aggression continued. This time the male escaped into the forest and did not return to the station. He was observed foraging the next 2 days with a wild group. On the second day (April 14^th) the male responded and approached the observer. On April 26 the same group was encountered, and the male responded when called by his pet name, but he did not approach the observer. Maldonado then left the Amazon station and returned to Bogotá. The male was observed once during the month of May by a field assistant and answered when called but did not approach the observer. It is not known if the group he joined was the same that tolerated the aggressive display on the 3^rd of April, but it is likely, given the group's home range. Just over one year later, on June 26, 1999, Maldonado followed a wild group of woolly monkeys, presumably the same one the captive-raised male had joined. A male came particularly close to her during the observations and responded when called by his pet name, but because he had matured she was unable to recognize him unequivocally. She then followed the male until his identity was confirmed through the scar on his lower lip.

Discussion

The present case shows that a social mechanism exists for the acceptance of a new male into an existing group of Lagothrix lagotricha, and thus supports Di Fiore and Fleischer's (2005) molecular data suggesting some level of male dispersal in woolly monkeys. However, this particular male's upbringing differed significantly from wild individuals, as he remained isolated from conspecifics for an important part of his development. The fact that the introduced male was not an adult might suggest that only juvenile or sub-adults can be accepted into existing groups, but this remains to be determined. Observations of sub-adult or juvenile males dispersing from their natal groups are lacking to confirm the existence of male dispersal in Lagothrix.