Gray whale

Bruce Mate, Leigh Torres

Latin name: Eschrichtius robustus

We began doing research with gray whales in 1978 when the species was still ESA listed as endangered and have been part of the documentation of their recovery leading to delisting in 1996. By radio tagging and satellite tracking, we tracked mothers with calves from Scammon's Lagoon on the western Baja Peninsula to the high Arctic, where the recovering population expanded its foraging activities in apparent response to larger numbers in the Bering Sea (their previous main habitat during recovery) beyond those that could be supported by the available Bering Sea benthic amphipods.

The rediscovery of what was thought to be an extinct Western Gray Whale population off Sakhalin Island, Russia, where oil and gas are being developed, led to concern for this IUCN-listed critically endangered species. Whales in this area were equipped with Argos-monitored radio tags, allowing us to track four of them crossing the Bering Sea and the Gulf of Alaska into the normal range of the fully recovered Eastern North Pacific (ENP) gray whale. One female was tracked from Russia almost to the tip of Baja, visiting offshore all three of the major ENP breeding areas and returning to Russia after an absence of 5.5 months. This was the longest migration known for any mammal and adds doubt as to whether the population off of Russia is really a different stock or merely an extension of the ENP foraging range far to the west.

Western North Pacific gray whales are listed as critically endangered with unknown migratory routes and reproductive areas. Conventional wisdom held that this population would migrate south in winter from Sakhalin Island, Russia, to the South China Sea to breed/calve. Sponsored by the International Whaling Commission, we attached satellite-monitored tags to three western gray whales off Sakhalin Island in 2010-2011 and they subsequently migrated to Eastern North Pacific regions occupied by non-endangered eastern gray whales. A female with the longest-lasting tag visited all three major eastern gray whale reproductive areas off Baja California, Mexico, before returning to Sakhalin Island the following spring. Her migration strongly suggests that some presumed western gray whales are born in traditional eastern gray whale calving areas and leads to conjecture how western gray whales might maintain their own (possibly genetic) separation from the eastern stock or if they are merely the westerly most extension of the eastern stock. 

Did you know? Gray whales in Oregon exhibit multiple foraging strategies.