You may already know that I have a deep-seeded distrust of fiddler crabs (despite this story I made up about one), but this next bit of science takes the cake. Few animals in the animal kingdom are monogamous. Hey, they all can't be like the mantis shrimp, right? But female fiddler crabs take this idea of polygamy to a whole new level! Female Uca mjoebergi will mate outside of their burrows on the sand flat for all the world to see. This rather public display with a male fiddler crab will secure that male's devotion in protecting her burrow. She trades sex for protection!
However, this broad's not finished with getting her, er, crab on. She'll next mate with a male inside her burrow, which is protected by her first mate. So the first male gets to mate, but it's the last male that will likely fertilize the majority of her eggs!
"There's nothing going on behind MY back, right? Right?"
The Slatyer et al. (2012) paper observed that the neighboring males were significantly more inclined to help after mating, so really the males are just as sleazy as the females.
cute, but still sleazy
Thanks to Meghan Garrison for telling me about this incredible crab behavior!
Slatyer, R.A., M. D. Jennions, and P. R. Y. Blackwell. 2012. Polyandry occurs because females initially trade sex for protection. Animal Behviour 83: 1203-1206.