The Shark Bay mouse is a long-haired, robust rodent, with the nickname ‘shaggy mouse’, due to its shaggy fur, which is pale yellow-fawn and gray on its back, giving it a grizzled look, fading into buff on its sides and white below. Its tail is slightly longer than its head and body and is gray on top and white below, and on the tip is a dark tuft of hair.
The Shark Bay mouse is currently found only in Western Australia on Bernier Island in the Shark Bay area, and two translocated populations on North West Island and Faure Island. It lives mainly in sandy areas such as coastal dunes, sheltered by coastal daisy and beach spinifex, where there are abundant flowers, leaves, spiders and insects to eat. It is sometimes also found further inland among the spinifex and wattle heath.
Shark Bay mice are nocturnal and solitary. Apart from during the breeding season, it does not appear to make use of burrows as often as other native mice species, but instead builds runways and tunnels amongst vegetation, to use as daytime refuges. Some mice have been seen using the hollows in mangrove trees for daytime refuges, as well as sites among rocks.
Not much is known about the mating behavior of Shark Bay mice, and what we do know is due to behavior observations of captive animals. Mating on Bernier Island mostly takes place from May to November, with gestation lasting around 28 days. In captivity, up to five in a litter have been recorded, although three is considered to be more common. Offspring are born without. Their eyes remain closed for four more days. They are weaned by the time they are four weeks old and they reach their full adult size at about 100 days.
The major threats to this species are unknown. Several factors may be responsible for their disappearance from the mainland, including predation by foxes and feral cats, habitat changes (soil compaction, grazing and vegetation trampling) due to introduced hooved herbivores; and the competition of introduced pests such as rabbits. Altered fire regimes are also a possible reason for their decline. As this mouse builds its tunnels in vegetation rather than constructing substantial burrow systems underground, it is especially exposed and vulnerable, more than many other rodents.
According to the IUCN Red List, the total population size of the Shark Bay mouse is less than 2,000 individuals. This includes a few hundred individuals on Bernier Island, under 200 mice on Faure Island, and under 1,000 mice on North West Island. Overall, currently Shark Bay mice are classified as Vulnerable (VU) but their numbers today are increasing.
Being herbivores, Shark Bay mice may have a role in the structuring of plant communities. They may also affect predator populations, as items of prey.