REPRODUCTION OF 2 SPECIES OF CONGENERIC FRUIT BATS (CYNOPTERUS) IN BRUNEI, BORNEO

Reproduction and growth of two species of congeneric fruit bats, Cynop terus minutus and C. brachyotis, were studied in Brunei, northern Born eo. C. minutus is smaller and inhabits rainforest; C. brachyotis is la rger and inhabits non-rainforest habitats (secondary forest, mangrove forest, deforested zone). The two species were sympatric only at Batan g Duri, a village near rainforest. The climate of the study area is ch aracterized by uniformly high temperatures and rainfall, but relativel y there are two seasons of more rain and two of less rain. Reproductio n of both species is seasonal with continuous bimodal polyoestry. With in each species, the females are in reproductive synchrony, with young born in two distinct seasons (3-4 months each) of parturition 5-7 mon ths apart. Each parturition is followed by postpartum oestrus. For eac h species, gestation spans about 5-6 or 5-7 months, with embryonic dev elopment delayed in the early stages. Births of neither species were t imed to the seasons of greater rainfall or to the general season of fl owering/fruiting of trees. Instead, births were centred about the two seasons of less rainfall and probably timed to the fruiting of certain species of trees, including mangoes for C. brachyotis. The weight dat a for C. brachyotis indicated a difference in diet between adult males and females. The bimodal pattern of weight increase/decrease for adul t males corresponded to the bimodal cycle of ripened mangoes in Brunei . Although weight increase/decrease for adult females did not correspo nd to the bimodal cycle of ripened mangoes, none the less the two birt hing seasons did, following shortly after or beginning at the two time s of abundant ripened mangoes. Similarly, adult males and females of C . minutus appeared to have different diets and/or different foraging p atterns. Both sexes of C. minutus (and probably also of C. brachyotis) attain maturity at about 7 months, with females giving birth for the first time at about 12 months. Females conceive shortly upon attaining sexual maturity and are thereafter in states of essentially continuou s reproduction with two young born annually (2 litters/yr, 1 neonate/b irth). Relative to other fruit bats (Mickleburgh, Hutson & Racey, 1992 ), C. minutus and C. brachyotis have high rates of reproduction.