Sex ratio and breeding of white-lipped peccaries Tayassu pecari (Artiodactyla : Tayassuidae) in a Costa Rican rain forest

White-lipped peccaries are non-seasonal breeders in South America, but litt le is known about their reproduction in Central America. There are few stud ies about the sex ratio of this species in the field. We studied the reprod uction and sex ratio of white-lipped peccaries during 200 hours of field ob servation of four radiomarked and two unmarked herds, from July 1996 to Apr il 1997, in Corcovado National Park, Costa Rica. Sex ratio data of three ad ditional, radiomarked herds observed in 1998 were also included. We recorde d numbers of mountings, presence of newborns and numbers of nursing interac tions. The peccaries showed a distinct reproductive seasonality, with one m ating peak in February and another in July. The greatest number of newborns and the peak in nursing activity were observed during July and August, whe n fruit availability for the peccaries was high. The adult sex ratio was si gnificantly female biased (1.4:1 - 1.8:1), also in contrast with South Amer ican populations.