A tiny crab species, commonly known as flotsam crabs, have quite the luxurious lifestyle. They spend most of their lives hitching free rides on loggerhead sea turtles, catching views of the open ocean as they travel safely nestled between their carapaces and tails. Here, they’re offered safety from predators, and typically ride along with a mate to reproduce and have a friend.
Previously assumed to be faithful for life to both their turtle host and mate, a study recently published in the Journal of Experimental Marine Biology and Ecology shows that these crabs may not actually be that monogamous. The study found that some male flotsam crabs don’t stick with one crustaceous lover for life, leaving their mate and host when they have the chance.
Scientists are calling this “risky behavior,” since switching hosts leaves these poor swimmers exposed and vulnerable in the ocean. And once they find a new turtle host (the scientists think they may do this when loggerheads converge each year to mate and feed), they’re not even guaranteed asylum: These tiny crabs sometimes have to fight off current male residents to earn the new spot alongside females.
Previous research shows that tiny, monogamous organisms should have similar body sizes to their mates. So, when the study authors found that flotsam crab body size data didn’t match data of a committed lifestyle, they discovered that these crabs may not be so faithful after all. Scientists studied crabs on loggerhead sea turtles in Japan, Mexico, Peru, and Brazil to reach this conclusion, says Smithsonian Science.
While these risk-takers may not engage in the long-term relationships as previously assumed, this behavior clues scientists into the relationship between ecology and mating patterns in crustaceans, says the study.