The Guadalupe fur seal was declared extinct in 1882, but these days, you can find thousands of them swimming off the coast of Mexico. A small handful of the scrappy creatures had clung to life, hiding in island caves and evading human detection for decades. And it’s not the only creature to return from seeming annihilation: A survey of the world’s mammals reveals that more than a third of creatures declared extinct later reappear, the Guardian reports.
On average, these creatures were unseen for 52 years. One critter, the Bahian tree rat, disappeared in 1824 and wasn’t seen again until 2004—a record 180 years later. All of which is good news. But here’s the scary part: Even with all those species returning from the great beyond, the number going extinct is still rising, according to one conservation survey, which advocates spending more resources hunting the species most likely to still be alive.