The Guadalupe fur seal (Arctocephalus townsendi) is one of eight members of the fur seal genus Arctocephalus. They are the northernmost members of this genus. Sealers reduced the population to just a few dozen by the late 19th century, but the species had recovered to about 10,000 individuals by the late 1990s. Many individuals can be found on Mexico's Guadalupe Island. Adult Guadalupe fur seals are dark brown or dusty gray with yellowish silver manes, called guard hairs, on the back of the neck. Guadalupe fur seals are sexually dimorphic in size, as males are much larger and heavier than females; males can grow to about seven feet in length and weigh upwards of 400 pounds, while females are typically only five feet long and weigh about 110 pounds. Additionally, males usually have a larger head and are lighter brown in color. Both males and females have a twenty-year lifespan. Guadalupe fur seals have distinctive ear flaps and large flippers for walking on land, confirming that they are not phocids (true seals) but are more closely related to sea lions. Guadalupe fur seal pups are born with black coats similar to those of adult Guadalupe fur seals, but it is difficult to distinguish juvenile Guadalupe fur seals from juveniles of California sea lions and Northern fur seals due to physiological similarities.
Guadalupe fur seals create caves on land which can cause social pressures amongst the individuals. The seals that do not breed often play with each other by barking, lunging at each other, and pushing each other into the water. Other behaviors of the species consist of waving their hind flippers in the water while face down in the water. Additionally, when interacting with humans, these seals are not typically aggressive. They are often seen with their heads under the water and pay little attention to the observer. Guadalupe fur seals are members of the “eared seal” family, Otariidae. Their breeding grounds are almost entirely on Guadalupe Island, off the Pacific coast of Mexico, with recent re-colonization of the islands comprising the San Benito Archipelago. A small number of Guadalupe fur seals have also been reported on the northern Channel Islands off California. Commercial sealers heavily hunted Guadalupe fur seals in the 1700s to the 1800s until they were thought to be extinct in the early 1900s. Dr. Hubbs and Dr. Bartholomew from the University of California rediscovered them breeding in a cave on Guadalupe Island in 1954. The Guadalupe fur seal population has continued to increase from the small remnant group on Guadalupe Island due to protection by the Mexican Government. Guadalupe fur seals are listed as threatened under the Endangered Species Act and depleted under the Marine Mammal Protection Act.
