Male sea otters nap in the sun, clasping each other’s paws for stability. Female otters float with their young perched on their chests. Newborn otters, even more buoyant than adults, bob alongside like corks. This can mean only one thing. Southern sea otters are making a comeback in California!

But wildlife experts aren’t doing a victory dance yet. In fact, they’re scratching their heads.

People hunted southern sea otters for their fur for hundreds of years. (And it’s no wonder. Sea otters have the densest fur in the world! It keeps them—and people—seriously warm.) By the 1930s, only 50 of the creatures remained. Laws were put in place to protect the near-extinct species. And now otters are on the rebound at more than 3,000.