The honey possum Tarsipes rostratus, a shrew-sized marsupial endemic to south-western Australia, feeds exclusively upon nectar and pollen. Tarsipes has fewer pouch-young, which remain in the pouch longer, than the young of sympatric insect-feeding marsupials of comparable size. Tarsipes pouch-young were recorded in every month of the year. Of all adult females caught, 68% had pouch-young and 36% of the remainder had recently carried young. This continual reproduction is offset by an average lifespan of only about one year.

Although Tarsipes have four teats, only very few of the largest females reared four young to independence. The number of pouch-young was inversely related to their size, changing, on average, from 3.6 young immediately after birth to 2.4 young at pouch-exit. Larger females gave birth to larger litters than smaller females and appeared more successful in rearing them. Variation in the initial litter size, and any subsequent reduction in litter size, might allow females to optimize offspring production during their short lifetime in relation to an unpredictable and specialized food supply.