Found solely on the Islas Marías archipelago off the Mexican Pacific coast, an enclave that for decades also housed a federal penal colony whose human activity transformed much of the original vegetation on which it relies. Like many small island mammals, generations of complete isolation surrounded by sea have led it to develop a size and traits slightly different from those of its mainland relatives. It shares these islands with other equally endemic species, including a bat unique to the same archipelago, making the Islas Marías a small natural laboratory of island evolution. Its future is now linked to how the conversion of the former penal colony into a space with other uses is managed.
Small rodent with greyish-brown fur on the upperparts and white on the underparts, large eyes and well-developed ears. The Tres Marías Deermouse is distinguished from other Peromyscus species of the Mexican Pacific coast by its distribution being restricted to the Islas Marías archipelago, with no overlap with mainland populations.
Small track, 1.3-1.8 cm, with 4 fore toes and 5 hind toes. Small, elongated droppings, 3-5 mm long, left scattered along runs through the island vegetation. Digs shallow burrows beneath rocks, logs or roots, with the entrance semi-concealed among dense vegetation.
Dry tropical forest and coastal scrub vegetation of the Islas Marías, in island lowlands. Endemic to this archipelago off the Pacific coast of Nayarit state, Mexico, with no natural presence outside these islands.
Omnivorous, feeding on seeds, fruit, leaves and invertebrates from the island vegetation where it lives.
Solitary and nocturnal, with a home range centred on shelters among dense vegetation and rocks on the islands where it lives.
Its populations are considered to be in decline due to historical island habitat alteration associated with human activity from the former penal colony, and to the introduction of invasive species on some of the islands.
Introduction of cats, rats and other invasive species to the Islas Marías, and island habitat alteration from human activity and infrastructure.
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