The Reproductive Cycles of Three Species of Opossums and Other Mammals in the Panama Canal Zone

Abstract

Data on the reproductive cycles of Didelphis marsupialis, Marmosa robinsoni , and Philander opossum in the Panama Canal Zone are presented, and the reproductive patterns of an additional 42 species of Panamanian mammals representing seven orders are reviewed. The three species of opossums breed seasonally, and females of D. marsupialis, P. opossum , and possibly M. robinsoni are polyestrous. Breeding in D. marsupialis and P. opossum began in late January and in M. robinsoni in late March in 1967. Females of each species are anestrous in October through January or longer in the case of M. robinsoni . Litter size is largest in M. robinsoni and smallest in P. opossum . Adult males of each species probably are reproductively active throughout the year. Considering all 45 species, reproductive activity, as evidenced by the presence of pregnant or lactating females, is highest in March and April (the latter part of the dry season) and lowest in August through November (middle to late wet season). Twenty-three species are known to breed seasonally, and in these species major periods of copulation occur in November and January and major birth peaks in March–April and July–August. In many species, initiation of reproductive activity appears to be stimulated by the cessation of heavy rains. Most species probably produce their young when food resources are highest. There is no evidence that closely related species stagger their breeding seasons to avoid interspecific competition for limited resources.