Distribution of Four Pinnipeds (Zalophus californianus, Arctocephalus philippii townsendi, Phoca vitulina richardii, and Mirounga angustirostris) on Islands off the West Coast of the Baja California Peninsula, Mexico

In the western region of the Baja California Peninsula, Mexico, four species of pinnipeds are found: the California sea lion (Zalophus californianus), the Guadalupe fur seal (Arctocephalus philippii townsendi), the Pacific harbor seal (Phoca vitulina richardii), and the northern elephant seal (Mirounga angustirostris). Their populations have changed in recent decades as a result of banning their commercial exploitation and government protection. These changes also have impacted their distribution, so it is necessary to have updated information. Herein, we present information about the distribution of the four species on a local scale, on 16 islands off the west coast of the Baja California Peninsula. These data were obtained from boat surveys during the winter and summer of 2009. The California sea lion and the northern elephant seal were found on all the islands except San Roque. New records for the northern elephant seal on the islands of Todos Santos Sur [South], San Jeronimo, and Asuncion are presented. The Guadalupe fur seal was only found on Guadalupe Island and the San Benito Archipelago; however, it is now present in new areas on the island. This expansion is especially noticeable on the San Benito Este and Oeste [East and West] Islands. The harbor seal was found on all the islands in the study area except Guadalupe. This seal has only been recorded on the three San Benito islands in recent years. These changes in the distribution of the four species should be considered in future studies on abundance and other ecological topics, especially those concerning population growth and recolonization.