Western North Pacific gray whales (WGWs), once considered extinct, are critically endangered with unknown migratory routes and reproductive areas. We attached satellite-monitored tags to seven WGWs on their primary feeding ground off Sakhalin Island, Russia, three of which subsequently migrated to regions occupied by non-endangered eastern gray whales (EGWs). A female with the longest-lasting tag visited all three major EGW reproductive areas off Baja California, Mexico, before returning to Sakhalin Island the following spring. Her 22 511 km round-trip is the longest documented mammal migration and strongly suggests that some presumed WGWs are actually EGWs foraging in areas historically attributed to WGWs. The observed migration routes provide evidence of navigational skills across open water that break the nearshore north-south migratory paradigm of EGWs. Despite evidence of genetic differentiation, these tagging data indicate that the population identity of whales off Sakhalin Island needs further evaluation.
This article presents data on frequencies of mitotypes (control region and cytochrome b and ND2 genes) in groups of Gray Whales found off the Chukotka Peninsula, Koryak coast, eastern Kamchatka and Sakhalin Island. From north to south the number of mitotypes decreased dramatically, but mitotypes which were predominant in the south were the same as ones also abundant in northern samples. For the control region sequences only, our data and data presented in the literature suggest that breeding areas in Baja Cali fornia may include diversity of both distant groups of mitochondrial lineages known for the species. On the other hand, the same control region sequences may be found in different mitochondrial genomes, and so con clusions based on this mtDNA fragment only may be incorrect.
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