Over the past 60 years, the population of cephalopods—octopuses, squids, and cuttlefish—has been steadily growing. This is particularly remarkable because many types of marine life have been dying out as carbon levels in the oceans rise, making the water more acidic. So even as numbers of crabs, sea stars, and coral reefs are shrinking, the tentacled creatures of the deep are thriving.

Writing in Current Biology, a large group of marine biologists describe how they discovered this trend. Looking at the past 61 years of fisheries data from all major oceans, they examined numbers of cephalopods that are bycatch, or accidentally caught along with target fish. Using these numbers as a proxy for cephalopod populations as a whole, they discovered a steady increase over the decades, across all cephalopod species. The question is why.

The researchers say it's likely a function of a cephalopod's ability to adapt quickly. "These ecologically and commercially important invertebrates may have benefited from a changing ocean environment," they write. Most cephalopods have very short lifespans and are able to change their behavior very quickly during their lifespans. Indeed, octopuses are tool-users who can learn quickly, leading to many daring escapes from tanks in labs as well as brilliant forms of camouflage at the bottom of the ocean. All these characteristics add up to a set of species who can change on the fly, as their environments are transformed.

If trends continue, cephalopods may be among the species who are poised to survive a mass extinction in the oceans, leading to a future marine ecosystem ruled by tentacles.

Current Biology, 2016. DOI:10.1016/j.cub.2016.04.002