Troop fission in female Lemur catta at Berenty Reserve, Madagascar

A-Troop of Lemur catta at Berenty Reserve, Madagascar, divided in July-August 1992. We observed the daughter troops-A1 and A2-between Aug. 15 and Nov. 15. The subordinate female subgroup of A-Troop (A2) had been harassed for at least 3 years previously. After fission, it suffered high conflict and energy demands, wounding, and socially induced infant mortality. Costs of fission may be a pressure for remaining in large troops. In September, A2 ranged widely, was chased by all neighbor troops, but then it challenged the previously dominant subgroup, Al, and by late October occupied a portion of the previous A-Troop range in which if was consistently successful in confrontations. A2's acquisition of range may relate to its high affiliation and low conflict between females of the subgroup. Unlike previously reported fission in L. catta there was no male involvement in defense, and the females that lost infants became more aggressive. This may be interpreted as female competition for resource control.