The double migration of elephant seals

HSWRI researchers discovered that adult northern elephant seals, who both breed and molt on California’s Channel Islands, go to sea twice each year during which they range widely in the northern Pacific Ocean. Using new tracking technology, we found that elephant seals returned to the same foraging areas during post-breeding and post-molt movements, documenting the first double migration for any animal. We also showed segregation by sex during both migrations, the causes of which are unknown. Seals travelled linear distances of up to 21,000 km during days they were at sea. These were the longest annual migrations yet recorded for any mammal, until a gray whale was recorded migrating 22,500 km in 2015.

Stewart, B.S. and R. L. DeLong. 1996. Double migrations of the northern elephant seal. Journal of Mammalogy. 76:196-205.