Longest mammal migration: Grey Whale covers 1400 miles across North Pacific

It is well known that the gray whales cruise along California’s coast during their annual fall migration. Yet there is another tiny, strange group of related whales off the Russian coast, the western north Pacific grey whale (Eschrichtius robustus)¬†population considered to be critically endangered for many years on the IUCN Red List of Threatened Species.

Scientists believed that this group is separate from its eastern Pacific counterpart. However the new findings has changed that view, and has documented a female in that population who completed the longest migration on record for a mammal.

Scientists from the US and Russia has recorded the longest migration of a mammal: a round-trip of nearly 13,988 miles in 172 days by a nine-year-old female western grey whale, Varvara. Varvara swam from Sakhalin island, Russia to Cabo San Lucas, Baja California and back starting in November 2011.

To understand their migratory patterns, researchers from Marine Mammal Institute, Oregon State University used satellite tags to follow 7 western Pacific gray whales. Only 3 tags lasted long enough for researchers to track the migrating animals.

All the 3 headed east from Sakhalin, with two joining the southward migration of eastern Pacific gray whales to Baja California. Researchers surprisingly spotted Varvara off the coast of southern Oregon with a group of eastern Pacific gray whales.

Experts elaborate that, as calves follow their mothers from breeding areas to foraging grounds, they all stick to the same routes as they get older. Thus the appearance of western gray whales in the eastern Pacific shows that western gray whales were born there.

This finding could flip over the idea of an isolated western gray whale population. However genetic experts say that they eastern and western population are separate.

The results are published in the journal, Biology Letters.

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Arunima Maiti

Arunima Maiti

Biomedical scientist with special interest in reproductive biology.

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