Reproduction of two species of congeneric fruit bats (Cynopterus) in Brunei, Borneo

Abstract

With 12 figures in the text)Reproduction and growth of two species of congeneric fruit bats, Cynoprerus minutus and C. brachyotis, were studied in Brunei, northern Borneo. C. minutus is smaller and inhabits rainforest; C. brachyotis is larger and inhabits non-rainforest habitats (secondary forest, mangrove forest, deforested zone). The two species were sympatric only at Batang Dun, a village near rainforest.The climate of the study area is characterized by uniformly high temperatures and rainfall, but relatively there are two seasons of more rain and two of less rain. Reproduction of both species is seasonal with continuous bimodal polyoestry. Within each species, the females are in reproductive synchrony, with young born in two distinct seasons (3-4 months each) of parturition 5-7 months apart. Each parturition is followed by postpartum oestrus. For each species, gestation spans about 5-6 or 5-7 months, with embryonic development delayed in the early stages. Births of neither species were timed to the seasons of greater rainfall or to the general season of flowering/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 data for C. brachyotis indicated a difference in diet between adult males and females.The bimodal pattern of weight increase/decrease for adult males corresponded to the bimodal cycle of ripened mangoes in Brunei. Although weight increase/decrease for adult females did not correspond to the bimodal cycle of ripened mangoes, none the less the two birthing seasons did, following shortly after or beginning at the two times of abundant ripened mangoes. Similarly, adult males and females of C. minutus appeared to have different diets and/or different foraging patterns.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 continuous reproduction with two young born annually (2 littedyr, 1 neonatehirth). Relative to other fruit hats (Mickleburgh, Hutson & Racey, 1992), C. minutus and C. brachyotis have high rates of reproduction.

Dispersion and site fidelity in a tent-roosting population of the short-nosed fruit bat (Cynopterus sphinx) in southern India

“…Conception appears to occur shortly after parturition, as lactating females sampled during the postpartum oestrus period had implanted embryos while the contralateral uterine horn was still distended (Krishna & Dominic 1983, Sandhu & Gopalakrishna 1984. Similar evidence from congeneric species and other cynopterine fruit bats indicates that conception can occur within several days or weeks of parturition (Heideman 1988(Heideman , 1989Heideman & Powell 1998, Kofron 1997. In peninsular India, postpartum conceptions apparently occur within a particularly compressed window of time, as the interval between the onset of parturition in the dry season (March/April) and wet season (July/August; Krishna & Dominic 1983, Sandhu 1984 closely approximates the estimated duration of gestation in C. sphinx (115-125 days;Gopalakrishna 1969, Moghe 1956, Sandhu 1984.…”

Reproduction of the long‐tongued nectar bat Macroglossus minimus (Pteropodidae) in Brunei, Borneo

“…Delayed embryonic development has been reported previously for approximately 18 species of bats (Racey and Entwistle 2000), including seven in the Pteropodidae: Cynopterus sphinx (Krishna and Dominic 1983), C. brachyotis (Kofron 1997, Bumrungsri et al . 2007, C. minutus (Kofron 1997), Eidolon helvum (Mutere 1965), Haplonycteris fischeri (Heideman 1988), Otopteropus cartilagonodus (Heideman et al 1993) and Ptenochirus jagori (Heideman and Powell 1998).…”

“…These two birth seasons appear correlated to the two seasons of greater rainfall in Brunei: October to December, and April to July However, the two birth seasons of C. brachyotis and C. minutus at the same study site (both which eat fruit, nectar, pollen and flowers ;Lim 1970;Payne et al . 1985) are centred about the two seasons of lesser rainfall (Kofron 1997). Reproduction of the latter two species, likewise, is characterized by seasonal bimodal polyoestry.…”

“…At the Kuala Belalong Field Studies Centre in Ulu Temburong, approximately 17% of the trees are dipterocarps and 3% are Eugenia , but with many more of the latter present as shrubs (Cranbrook and Edwards 1994). The proportion of trees with flowers/fruits in the rainforest was not the same each month: the proportion of trees with flowers/fruits was least during February (9%); and most during April (57%; Kofron 1997).…”

Social structure of a polygynous tent‐making bat,Cynopterus sphinx(Megachiroptera)

“…Why should harem maintenance be a year-round endeavor if opportunites for mating are limited to such sharply defined periods of the annual cycle? One possible explanation is that mating activity is spread over an extended period, so the highly synchronous timing of parturition could be achieved via sperm storage, delayed implantation, or post-implantational delays in embryonic development (Heidemann, 1988(Heidemann, , 1989Heideman, Cummings & Heaney, 1993;Kofron, 1997;Heideman & Powell, 1998). However, seasonally bimodal peaks in spermatogenic activity in males (Krishna & Dominic, 1984;Sandhu, 1988) and the timing of conceptions in females (Krishna & Dominic, 1983;Sandhu, 1984) indicate well-defined periods of mating for C. sphinx in peninsular India.…”