Opportunistic breeding in the polyandrous honey possum, Tarsipes rostratus

Abstract

Honey possums, Tarsipes rostratus, tiny (7–12 g) flower-dependent marsupials, were trapped in three areas of south coastal heathland in Western Australia on 5–8 occasions each year from 1984 to 1995. Mark–recapture estimated annual mortality at 86%, with only a few individuals living for more than one year. Most females breed for the first time while not yet fully grown and may produce up to four litters in a year. Maximal litter size is four, but usually only two or three young are reared. The small litter size and relatively slow growth of pouch young is attributed to the time needed for the mothers to harvest pollen, upon which T. rostratus relies for its nitrogen requirements. Females with pouch-young were recorded in all months, but with a higher frequency over winter when nectar was most abundant, and at a lower frequency (in some years, none) when food was scarce in autumn. Young are in the pouch for about 60 days and some females give birth to the next litter soon after pouch exit, presumably from delayed blastocysts. We suggest that T. rostratus females are polyandrous and that the smaller males compete by searching for females in oestrus. The multiple paternity of several litters, confirmed by single-locus microsatellite profiling, supports this model.