CÁCERES, N.C. 2000. Population ecology and reproduction of the white-eared opossum Didelphis albiventris (Mammalia, Marsupialia) in an urban environment of Brazil. Ciência e Cultura Journal of the Brazilian Association for the Advanced of Science 52(3):171-174.
Abstract. The seasonal variation in numbers of individuals, causes for death, breeding season and litter size of the white-eared opossum, Didelphis albiventris, were studied in two small urban forest fragments of southern Brazil. In order to trap opossums, 30 live traps were used once a weak in a forest fragment (5 ha) between February 1995 and January 1996. In addition, 10 traps were used twice a month in another area (2.5 ha) between Novemeber 1996 and February 1997. Individuals trapped were sexed, aged, and released. Females with litter had their pouch young counted. The bait used was banana with codfish liver oil. As results after an effort of 1770 traps set, 37 opossums were captured (20 females and 17 males) with the sex ratio being significantly equal (p > 0.40). Juvenile individuals were captured seasonally during the wet season (spring and summer). Since juveniles represented the most common individuals trapped, total abundances were heigher during the wet season. Immigrations (plus births) rather than emigrations were thought to be the main factor for abundance variations. Moreover, road kill by cars and fights with dogs were the main causes for death of opossums. Based on time of captures of recently weaned opossums and females with litters, the breeding season showed mainly two periods of births (between August and November), though two litters were seen in April of two years. The mean litter size was 9.0 young (N = 14 litters). The white-eared opossum revealed a great potential to colonize urban environments where there are forest fragments, with its higher numbers of juveniles compensating adult deaths mainly by anthropical factors.
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