Peromyscus nesodytes

The giant island deer mouse[1] (Peromyscus nesodytes) became extinct approximately 8000 years BP and lived during the late Pleistocene on California’s Channel Islands.[2]

Peromyscus nesodytes Temporal range: Late Pleistocene- Early Holocene
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Cricetidae
Subfamily:	Neotominae
Genus:	Peromyscus
Species:	P. nesodytes
Binomial name
Peromyscus nesodytes Wilson 1936

Overview

In 1934, Robert W. Wilson designated P. nesodytes as a new species after discovering a mouse bone (a right ramus of the mandible).[3] 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.”[3] The only larger mice known are the extant mice of the genus Megadontomys found in Mexico and Central America.[3]

The mouse “generally considered ancestral to P. nesodytes” is Peromyscus anyapahensis.[4] Another relative, P. anyapahensis, is also extinct; it is smaller in body size than P. nesodytes.[5]

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.[6]

Habitat

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.[6]

Extinction

P. nesodytes probably became extinct following the possibly accidental introduction of a smaller mouse, Peromyscus maniculatus, by the Chumash people, who lived in the Santa Barbara area.[6] The Chumash traded on the northern Channel Islands and could have been unknowing transporters of P. maniculatus to the islands. It has been noted that, on occasion, individuals of P. maniculatus could have secreted themselves in baskets of food and been unintentionally conveyed by boat to the islands for trading purposes.[7]

P. maniculatus probably fared better at avoiding the most frequent mouse predator on the islands, the barn owl, than did P. nesodytes. A possible example of this appears in Daisy Cave, an archaeological site on San Miguel Island. Cave floor layers show fewer P. maniculatus remains in the older, deeper levels than in the newer, upper levels. Barn owls may have preferentially preyed on the larger species, P. nesodytes, rather than on the smaller P. maniculatus. [2]

Further information

For behavior and information on deer mice in general, see the Wikipedia entries for Peromyscus and Peromyscus maniculatus.

References

1. Ainis, Amira F. and Rene L. Vellanoweth (2012). Expanding the Chronology for the Extinct Giant Island Deer Mouse (Peromyscus nesodytes) on San Miguel Island, California, USA. Journal of Island & Coastal Archaeology 7:146–152.
2. Guthrie, D.A. (1993). New information on the prehistoric fauna of San Miguel Island: in F.G. Hochberg, ed., Third Channel Islands symposium, Santa Barbara, CA, Santa Barbara Museum of Natural History, p. 405-416.
3. Wilson, R. W. (1936). "A New Pleistocene Deer-Mouse from Santa Rosa Island, California" (PDF). Journal of Mammalogy. 17 (4): 408–410. doi:10.2307/1374408.
4. Guthrie, D.A. (1998). Fossil Vertebrates From Pleistocene Terrestrial Deposits on the Northern Channel Islands, Southern California: in Weigand, P.W., ed., Contributions to the geology of the Northern Channel Islands, Southern California: American Association of Petroleum Geologists, Pacific Section. MP 45.
5. White, J.A. (1966). A new Peromyscus from the late Pleistocene of Anacapa Island, California, with notes on variation in Peromyscus Nesodytes: Los Angeles County Museum Contributions in Science no. 96, p. 1-8.
6. Wenner, A.M. and D.L. Johnson (1980). Land vertebrates on the California Channel Islands: Sweepstakes or Bridges? in D.M. Powers, ed. The California Islands, proceedings of a multi-disciplinary symposium, Santa Barbara, CA, Santa Barbara Museum of Natural History, p 497-530.
7. Walker, P. (1980). Archaeological evidence for the recent extinction of three terrestrial mammals on San Miguel Island: in D.M. Powers, ed. The California Islands, proceedings of a multi-disciplinary symposium, Santa Barbara, CA, Santa Barbara Museum of Natural History, p. 703-717.