Galápagos Fur Seal, Arctocephalus galapagoensis

The Galápagos fur seal (Arctocephalus galapagoensis) is native to the Galápagos Islands. It is thought that there is one colony in northern Peru. This species prefers a habitat on the western ends of the islands with rocky shores. It is the smallest member of its family, with males reaching an average body length of nearly five feet and females reaching a body length nearly four feet. Males weigh an average of 140 pounds, while females weigh less at only 62 pounds. Its fur is brownish grey in color, and it spends up to seventy percent of its life on land, a trait unique to its species.

The breeding season for the Galápagos fur seal occurs between the months of August and September During this time, females will form territories separate from the main colony. This species has the lowest reproductive rate of all seal species. Females give birth to only one pup, which they do not leave for the first week of its life. After about one week, the mother seal will leave the pup periodically to hunt for food, returning to nurse the pup every few days. Mothers and pups can identify each other using scent and call recognition, which is very important because if an unknown pup approaches a mother, she will greet it with violence. Orphaned pups typically perish after just one month.

Weaning typically occurs after eighteen months, but can be delayed until the pup is two or three years old if conditions do not support weaning. When this occurs, the new pup faces competition with the older pup when nursing. In years with good conditions and abundant food, the mortality rate for younger pups is only at five percent, which is the average for single pups, but in bad years, this number increases to eighty percent. This process serves as a buffer in bad times, and keeps population numbers stable in good years. When mothers are caring for two pups, aggression within the “family” does occur. When the older pup nurses more than the younger pup, the mother often intercedes in an aggressive manner, sometimes wounding the older pup. Older pups sometimes cause younger pups to die of starvation, because they only allow the younger pup to nurse once completely satisfied, leaving little milk behind. During times when food is scarce, particularly after major flooding caused by El Niño weather patterns, older pups cause their mother’s to neglect the younger pups in order to delay weaning longer.

The diet of the Galápagos fur seal consists of fish cephalopods like squid and cuttlefish. This species hunts primarily at night at depths of up to 554 feet, although it is more commonly seen near the shore. During harsh times, especially those associated with El Niño, adults will eat before feeding their young, and young pups experience high death rates. Although this species does not have main predators, killer whales or sharks can hunt it if any individuals of these two species stray out of their normal hunting range.

The population numbers of the Galápagos fur seal declined in the 1800’s, when poachers overhunted it. In 1959, Ecuador established laws to help protect the seals and designated the Galápagos Islands a protected area. There has not been any major poaching since the designation of the islands as a national park. Between the years of 1982 and 1983, an El Niño weather patterns caused most pups from the previous breeding season and thirty percent of adults to die. After this tragedy, the population has been on a slight increase. The Galápagos fur seal appears on the IUCN Red List with a conservation status of “Endangered.”

Image Caption: Galápagos Fur Seal (Arctocephalus galapagoensis), male, Santiago Island, Ecuador. Credit: D. Gordon E. Robertson/Wikipedia  (CC BY-SA 3.0)