Giant island deer mouse
The giant island deer mouse (Peromyscus nesodytes ) became extinct approximately 8000 years BP and lived during the late Pleistocene on California’s Channel Islands.
In 1934, Robert W. Wilson designated P. nesodytes as a new species after discovering a mouse bone (a right ramus of the mandible). He writes, “The outstanding character of P. nesodytes is its large size, which is greater than any living species of Peromyscus native to the United States.” The only larger mice known are the extant mice of the genus Megadontomys found in Mexico and Central America.
The mouse “generally considered ancestral to P. nesodytes ” is Peromyscus anyapahensis.P. anyapahensis is also extinct; it is smaller in body size than P. nesodytes.
The extreme size of P. nesodytes follows Foster's rule of insular gigantism and dwarfism, in which some rodent species attain greater body size following their occupation of islands lacking a multitude of predators.
The habitat of P. nesodytes was confined to the northern Channel Islands. Remains of P. nesodytes have been found on San Miguel Island and Santa Rosa Island. The northern Channel Islands once comprised a “super-island” called Santa Rosae; increased sea levels have separated the islands for thousands of years.
