As with other seals, bulls secure territory in sea caves or rocky shores during the breeding season and acquire harems of about 10 females each. Tenure of territorial males lasts from 35 to 122 days. It is thought that reproductive males are faithful to particular sites over a number of years. Young are born from mid-June through July and are weaned after nine months. The fur seal feeds on squid and fish.
Once ranging from Monterey, California to Tapachula, Mexico near the Guatemalan border, the range of this species is now extremely limited along the Pacific Coast of Mexico. Guadalupe fur seals breed on Isla Guadalupe and Isla Benito del Este off the coast of Baja California. They have been sighted infrequently along the California coast at San Miguel, San Nicolas, and San Clemente Islands and range south to the tip of Baja California.
Prior to the 18th and 19th century commercial seal harvests, the Guadalupe fur seal was abundant, with between 20,000 and 100,000 animals ranging from Monterey Bay, California to the Revillagigedo Islands in Mexico. Commercial sealing nearly exterminated the species throughout its range by the early 1900s, and it was thought to be extinct until rediscovered in 1954. With the end of commercial sealing and government protection granted by Mexico and the United States, the Guadalupe fur seal is slowly recovering. There are now around 10,000 Guadalupe fur seals. The recovery of the Guadalupe fur seal, though evident, continues to be slow. While no longer in danger from hunters, fishing-related mortality is now the biggest threat to the species, especially entanglement in the drift and set gillnet fishing gear. This species appears to be easily disturbed by human presence and activities, and offshore mining and oil exploration may present additional threats to its habitat.