The Longest Mammal Migration Ever

How a Russia-to-Mexico journey complicates everything we know about gray whales.

A female from a group of gray whales has been observed traveling from Russia to Mexico and back, a journey that astonished the scientists who tracked her. Watch the video above to see how the record 14,000-mile, 172-day trip upends some long-held beliefs about gray whale populations and could mean a historic group is actually extinct.