The giant mouse lemurs are members of the strepsirrhine primate genus Mirza. Two species have been formally described; the northern giant mouse lemur (Mirza zaza) and Coquerel's giant mouse lemur (Mirza coquereli). Like all other lemurs, they are native to Madagascar, where they are found in the western dry deciduous forests and further to the north in the Sambirano Valley and Sahamalaza Peninsula. First described in 1867 as a single species, they were grouped with mouse lemurs and dwarf lemurs. In 1870, British zoologist John Edward Gray assigned them to their own genus, Mirza. The classification was not widely accepted until the 1990s, which followed the revival of the genus by American paleoanthropologist Ian Tattersall in 1982. In 2005, the northern population was declared a new species, and in 2010, the World Wide Fund for Nature announced that a southwestern population might also be a new species. Giant mouse lemurs are about three times larger than mouse lemurs, weighing approximately , and have a long, bushy tail. They are most closely related to mouse lemurs within Cheirogaleidae, a family of small, nocturnal lemurs. Giant mouse lemurs sleep in nests during the day and forage alone at night for fruit, tree gum, insects, and small vertebrates. Unlike many other cheirogaleids, they do not enter a state of torpor during the dry season. The northern species is generally more social than the southern species, particularly when nesting, though males and females may form pair bonds. The northern species also has the largest testicle size relative to its body size among all primates and is atypical among lemurs for breeding year-round instead of seasonally. Home ranges often overlap, with related females living closely together while males disperse. Giant mouse lemurs are vocal, although they also scent mark using saliva, urine, and secretions from the anogenital scent gland. Predators of giant mouse lemurs include the Madagascar buzzard, Madagascar owl, fossa, and the narrow-striped mongoose. Giant mouse lemurs reproduce once a year, with two offspring born after a 90-day gestation. Babies are initially left in the nest while the mother forages, but are later carried by mouth and parked in vegetation while she forages nearby. In captivity, giant mouse lemurs will breed year-round. Their lifespan in the wild is thought to be five to six years. Both species are listed as endangered due to habitat destruction and hunting. Like all lemurs, they are protected under