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 CITES Appendix I, which prohibits commercial trade. Despite breeding easily, they are rarely kept in captivity. The Duke Lemur Center coordinated the captive breeding of an imported collection of the northern species, which rose from six individuals in 1982 to 62 individuals by 1989, but the population fell to six by 2009 and was no longer considered a breeding population.
Taxonomy
The first species of giant mouse lemur was described by the French naturalist Alfred Grandidier in 1867 based on seven individuals he had collected near Morondava in southwestern Madagascar. Of these seven specimens, the lectotype was selected in 1939 as MNHN 1867–603, an adult skull and skin. Naming the species after the French entomologist Charles Coquerel, Grandidier placed Coquerel's giant mouse lemur (M. coquereli) with the dwarf lemurs in the genus Cheirogaleus (which he spelled Cheirogalus) as C. coquereli. He selected this generic assignment based on similarities with fork-marked lemurs (Phaner), which he considered to also be members of Cheirogaleus. The following year, the German naturalist Hermann Schlegel and Dutch naturalist François Pollen independently described the same species and coincidentally gave it the same specific name, coquereli, basing theirs on an individual from around the Bay of Ampasindava in northern Madagascar. Unlike Grandidier, they placed their specimen in the genus Microcebus (mouse lemurs); however, these authors also listed all Cheirogaleus under Microcebus and based the classification of their species on similarities with the greater dwarf lemur (M. typicus, now C. major).