Grey whale
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Gray whale makes record migration

15 April 2015 Last updated at 16:47 BST

Scientists tracking gray whales have found that the mammals swim further than they expected.

One female gray whale, called Varvara, swam all the way from the east coast of Russia to Mexico and then back again in the summer.

The journey clocked up 14,000 miles and is the longest recorded migration of any mammal, according to the scientists.

Every year, lots of whales migrate to warmer areas to eat and breed.

Watch Hayley's piece on whales migration and other animals long journeys.