Marsupial rats and mice are a diverse group of about 40 species of small, native carnivores of Australia, Tasmania, and New Guinea, in the family Dasyuridae. The young of marsupial rats and mice, as with those of all marsupials, are born while still in a tiny, embryonic stage of development. The almost helpless babies migrate to the belly of their mother, where they fix on a nipple and suckle until they are ready to lead an independent life. Unusual among the marsupials, the females of some species of marsupial rats and mice do not have a belly pouch (or marsupium) that encloses their nipples and protects their young. Other species do have a permanent pouch, or they have one that develops only during the breeding season.