IMMIGRATION IN WILD GROUPS OF GOLDEN LION TAMARINS (LEONTOPITHECUS-ROSALIA)

Seventeen territorial groups of wild golden lion tamarins were monitor ed for periods of 10-76 months. Immigration into established groups wa s rare (0.48 immigrating individuals per group per year) and occurred mostly in the context of replacement of breeding individuals. Nonrepla cement immigration events usually occurred in conjunction with some ot her change in group composition (e.g., an emigration or another immigr ation). Aggression by resident tamarins toward potential immigrants ap peared to be the proximate factor limiting movement into groups. Most such aggression was intrasexual, but potential female immigrants were sometimes chased by male as well as female residents. Immigration was highly male biased (85% of individuals). Factors possibly contributing to this bias were inheritance of breeding positions by adult daughter s (reducing female and increasing male immigration opportunities), abi lity of males but not females to join groups already containing a same -sex breeding individual, and the fact that potential female immigrant s appeared to face some intersexual as well as intrasexual aggression. Male and female roles in the maintenance of a monogynous mating syste m are considered in light of these results. Contrasts with data from i ntruder studies on captive golden lion tamarins [French & Inglett, Ani mal Behaviour 37:487-497, 1989] are discussed. (C) 1996 Wiley-Liss, In c.