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Record long mammal migration raises questions about distinct species

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Posted April 23, 2015

A team of scientists from the United States and Russia have documented the longest migration of a mammal ever recorded. The western North Pacific gray whale travelled nearly 14,000 miles (approximately 22,531 km). This unexpected behaviour challenges view towards status of this whale, as this species have been previously identified as critically endangered.

The longest mammal migration ever recorded challenges view towards status of endangered western North Pacific gray whales. Photo by Craig Hayslip, OSU Marine Mammal Institute

The longest mammal migration ever recorded challenges view towards status of endangered western North Pacific gray whales. Photo by Craig Hayslip, OSU Marine Mammal Institute

The researchers used satellite-monitored tags to track three western North Pacific gray whales. They travelled across the Pacific Ocean rom their primary feeding ground off Russia’s Sakhalin Island down the West Coast of the United States to Baja, Mexico. One of the whales, called Varvara, visited the three major breeding areas for other species of whales – eastern gray whales, which are found off North America and are not endangered.

This interaction between western and eastern gray whales puzzles scientists over the status of critically endangered animal. Scientist Bruce Mate from Oregon State University said that these two species of whales have been identified as separate, but this new information suggests that closer look is needed. Western gray whales were already thought to have gone extinct by the 1970s, but then a small aggregation was discovered in Russia off Sakhalin Island. It is estimated that there are about 150 of western gray whales.

Eastern gray whales were announced to be endangered as well. However, conservation efforts led to their recovery and now there are more than 18,000 animals. Now one author of the study, Valentin Ilyashenko of the A.N Severtsov Institute for Ecology and Evolution, says that these are not two different species of whales. Western and eastern gray whale populations are not isolated from each other and gray whales found in Russian waters could be simply a part of an eastern population that is restoring its former historical range.

This new record of migration of nearly 14,000 miles shows that these whales have ability to navigate across open water over tremendously long distances and suggests that some western gray whales might actually be eastern grays. But whether it means that western gray whales went extinct or there are some of them remaining is still unanswered question. However, if this is true, population of true wetern gray whales is even smaller than previously believed.

Protecting western gray whales has been a difficult task. Five of them have died in Japanese fishing nets within the last decade. Their feeding areas became fishing areas, shipping lanes, and oil and gas production sites. Despite their ability to navigate and travel for very long distances, their migration routes are full of other hazards as well. Therefore, protection of already small population was a difficult job for the scientists. Now they compared pictures of both groups and identified dozens of western gray whales from Russia matching whale photographs taken in British Columbia and San Ignacio Lagoon in Baja California, Mexico. It could mean two things – scientists were not accurate enough about distinguishing two species of whales and real western gray whales have much smaller population than previously believed or are already extinct.

This story illustrates how one discovery can change whole perception of the object of scientific investigation. Even though tremendously long range of migration was the longest of ever recorded in mammals, now it challenges the view of what exactly these mammals are and what is real situation of endangered species of whales.

Source: Oregon State University

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