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Guadalupe fur seal

The precise historic range of the Guadalupe fur seal (Arctocephalus townsendi) is not known because early fur traders did not distinguish it from the northern fur seal. It may have extended from the Revillagigedo Islands of Mexico north to Monterey Bay, California and possibly the Farallon Islands. Historic breeding colonies likely existed on California’s San Miguel and San Nicolas Islands.

The pre-exploitation population size was between 20,000 and 100,000 [1], but collapsed rapidly under European hunting pressure. In the three years between 1808 and 1810, 130,000 seals were killed [3]. By the end of the nineteenth century numbers sufficiently depleted that just 5,575 seal were killed in a 16 year period (1876-1892) [3]. The species was extirpated from California by 1825 and from Isla Benito del Este sometime in the 19th century [4]. Only seven were found on its Guadalupe Island stronghold in 1892. All known seals (15) were killed on Guadalupe in 1894, 35-60 were rediscovered in 1926, but were virtually all killed in 1928. It was thought extinct until a bull was seen on San Nicholas Island, California in 1949, and 14 seals were found on Guadalupe in 1954 [3].

The population has grown steadily since 1954, reaching approximately 12,000 on Guadalupe Island in 2003 [2]. Isla Benito del Este was recolonized by the Guadalupe population sometime between 1984 and 1988 when several bulls were observed hauling out but not breeding [2]. Breeding was first record 1997 when 9 pups and 247 non-pups were observed [4]. By 2004, the Isla Benito de Este popuation reached 648 [2]. They have also recolonized the United States, being seen in the Channel and Farallon Islands with increasing regularity since the 1980s. In 1997, a pup was born on San Miguel Island. Individuals are now occasionally sighted as far south as Tapachula near the Mexico/Guatemala border, as far north as the Point Reyes National Seashore in California, and in the Gulf of California.

[1] NOAA Fisheries. 2000. Stock Assessment Report: Guadalupe Fur Seal (Arctocephalus townsendi), revised December 15, 2000. National Oceanic and Atmospheric Administration, Washington, D.C.
[2] Gallo-Reynoso J.P., M.O. Maravilla Chávez and A.L. Figueroa Carranza. 2004. La población del lobo fino de Guadalupe, Arctocephalus townsendi, en México. VII Congreso Nacional de Mastozoología, 8-12 de Noviembre de 2004. San Cristóbal de Las Casas, Chiapas. México.
[3] Gilbert, L.R. and R. Hilborn. 2001. Catastrophic events and recovery from low densities in populations of otarriids: implications for risk of extinction. Mammal Review 31(2):131-150.
[4] Gallo-Reynoso, J.P. 2005. Personal communication with Juan Pablo Gallo-Reynoso, Laboratorio de Ecofisiologí, CIAD, Unidad Guaymas.

Banner photo © Phillip Colla