14 DAY TRIAL // It seems that the female crabs behave like supermodels when it comes to picking a mate. What could the female crab be thinking of? "Too short", "Too thin"," Too fat", "Too skinny", "Not rich enough".
A study conducted by a biologist at the University of California, San Diego that appears in the August issue of the journal Animal Behaviour found that females of the species Uca crenulata may check out 100 or more male fiddler crabs and their burrows before finally deciding on a mate.
"As far as I know, no other species has been observed sampling nearly as many candidates as the California fiddler crab," said Catherine deRivera, who conducted the study while a doctoral student and a lecturer at UCSD. She is now a research biologist at the Aquatic Bioinvasions Research and Policy Institute, a joint entity of the Smithsonian Environmental Research Center and Portland State University.
deRivera and a group of UCSD students who assisted her conducted their observations in the Sweetwater River estuary in Chula Vista, south of San Diego, near the Mexico-U.S. border. She said previous studies of mate selection in other animals, such as birds and the natterjack toad, found that females of most species typically sampled only a handful of potential mates before making a final selection.
"Most animals sample just a few mates, presumably because search costs override the benefits of lengthy searches," she said in her paper. But female California fiddler crabs are much pickier, she discovered in her study, checking out male suitors and their bachelor pads an average of 23 times before making a final selection. One particularly choosy crab visited 106 male burrows, fully entering 15 of them, during her one hour and six minute search.
Why are female fiddler crabs so picky? The survival of their offspring, deRivera found in her experiments, appears to be strongly linked to the size of their mate and, more importantly, his corresponding abode. "The size of the male's burrow affects the development time of his larvae," she said. "A burrow of just the right size allows larvae to hatch at the safest time, the peak outward nighttime flow of the biweekly tidal cycle."