Preliminary findings on social and ecological correlates of a polyspecific association between a golden-headed lion tamarin (Leontopithecus chrysomelas) and Wied's marmosets (Callithrix kuhlii).

The advantages of living in a group include feeding benefits and/or predation avoidance, while the disadvantages are typically related to competition. One way to avoid competition while maintaining the benefits of living in a group is to form interspecific associations with species with relatively little dietary overlap. Here we report a stable association between a male golden-headed lion tamarin (GHLT), Leontopithecus chrysomelas, and a group of Wied's black-tufted-ear marmosets (WBTMs), Callithrix kuhlii. We collected ecological and behavioral data on a duo of GHLTs from May to August 2008, totaling 62 h of observations. On 19 August 2008, the radio-collared GHLT dispersed alone and was located on 28 August in association with WBTMs. To examine possible changes in GHLT ecology and behavior, we monitored the mixed-species group between September and December 2008, totaling 122 h of observations. We found that the GHLT's home range and daily path length decreased by about ten and three times, respectively, after joining the WBTM group, suggesting adaptations to the WBTMs' use of space. All non-agonistic behaviors recorded in the mixed group were directed from GHLT to the WBMTs, whereas all agonistic interactions were directed from the WBMTs to the GHLT, indicating a subordinate position of GHLT in the mixed group. In golden lion tamarins, reproductive success of subordinate adult males that remain in the group is higher than that of those that disperse and "prospect" for a breeding opportunity. If dispersing individuals are unable to find a mate and defend a territory, they will likely die within a year. The dispersing GHLT in this study assumed a subordinate role in a mixed-species group outside a GHLT territory. Apparently, the benefits of waiting for a dispersing female in a relatively safe situation may exceed the costs of prospecting elsewhere or being a subordinate.