DETERMINANTS OF AGGRESSION IN 9-BANDED ARMADILLOS

Potential determinants of aggression in nine-banded armadillos, Dasypu s novemcinctus were identified by comparing the sex, age, and reproduc tive status of initiators and recipients of aggression in a marked pop ulation in southern Texas. Males and females were equally likely to in itiate and receive aggression. Adults initiated most aggression, direc ting it towards younger animals. Adult males directed aggression prima rily at 1- and 2-year-old males and did so most frequently during the breeding season (June-November). Most adult males exhibiting aggressio n were previously or subsequently seen paired with females, suggesting that male aggression may function to maintain exclusive access to rec eptive females. Adult females directed aggression primarily at juvenil es of both sexes and at other adult females, mostly during a 4-month p eriod corresponding to late pregnancy and lactation (February-May). Th ese findings suggest female aggression may function in defending curre nt litters and in promoting the dispersal of last year's young. Examin ation of other potential influences on agonistic behavior showed that heavier individuals were more likely to win encounters and that escala ted contests (i.e., fights) were more likely between evenly matched op ponents.