Supreme fitness is a trait males of many species might show off when searching for a mate. Peacocks display their tails, the more elaborate of which require more energy to grow and carry around. Human men might strip off and strut down the beach. The fiddler crab, new research shows, flexes its muscles by waving a brightly colored claw and then drumming it on the ground, a behavior that also seems to indicate the size of its home.
If you look at a banana fiddler crab, both its major claw and the reason for its name are hard to miss. Research has shown these creatures are willing to go to some extreme lengths to find a mate, with a study last year revealing that some will wait until a female enters her burrow and then trap her in there.
The latest research reveals a much less coercive mating strategy. Researchers at the UK's Anglia Ruskin University studied the behavior of male banana fiddler crab, finding that they will initially catch the attention of a female crab by waving their big yellow claw about, and then drumming it on the ground when they come in for a closer look.
These rapid vibrations communicate information to the female about the male's stamina and appears to be a physically exerting activity. The team knows this because it had the crabs sprint along a special race-track. Those that had recently engaged in courtship rituals performed more poorly, indicating that all that drumming had tuckered them out.
The team also discovered that the frequency of the drumming had a positive relationship with the size of the male's burrow, but say that further study is needed to really pin down its specific function. It did find, however, that the drumming can continue even after the female follows the male to the burrow, suggesting that it could convey information through the acoustic properties of the abode. This might be of interest to the female, because it is where she will stay to incubate her eggs.
"Male fiddler crabs that wave and drum their claws rapidly during courtship were found to have high physical fitness, despite the fatiguing nature of this display," says Dr. Sophie Mowles, who led the research. "Therefore, by choosing a vigorously displaying male, a female can ensure she selects a good quality mate who can offer her good genes for her offspring."
The research was published in the journal Royal Society Open Science, and you can see the crab in action in the video below.
Source: Anglia Ruskin University