These crabs swap sex for favors
November 5, 2009, Thursday
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IN the world of fiddler crabs, the best form of protection is, apparently, prostitution, according to an Australian study published yesterday.
Researchers from The Australian National University in Canberra found that male fiddler crabs will happily defend a female neighbor against intruders - partly because the females will dole out sex in return.
"The fact that the neighbor comes over and helps to defend another territorial individual is pretty unusual," said Michael Jennions, who conducted the study published in the Biology Letters journal.
Jennions and fellow ANU researchers Richard Milner and Patricia Backwell studied the behavior of fiddler crabs living in mud flats off the African country of Mozambique in October and November 2008. Male fiddler crabs have giant claws, but the researchers wanted to see how female crabs, with only two small feeding claws, protect their homes.
Fiddler crabs are territorial and live in burrows. The researchers gathered crabs from distant parts of the mud flats and tethered them near new, occupied burrows. In 21 trials involving male intruders, the researchers found that male crabs would scuttle over to fight off the invaders on a female neighbor's territory 95 percent of the time. But in 20 trials involving female intruders, the males crabs only fought off the invaders 15 percent of the time.
That suggests the male crabs preferred to keep females nearby, largely because they will almost always have sex with their male neighbors, Jennions said.
Swapping sex for favors is not unheard of in the animal kingdom. Antarctica's Adelie penguins exchange sex for highly coveted stones used for nest building.
Researchers from The Australian National University in Canberra found that male fiddler crabs will happily defend a female neighbor against intruders - partly because the females will dole out sex in return.
"The fact that the neighbor comes over and helps to defend another territorial individual is pretty unusual," said Michael Jennions, who conducted the study published in the Biology Letters journal.
Jennions and fellow ANU researchers Richard Milner and Patricia Backwell studied the behavior of fiddler crabs living in mud flats off the African country of Mozambique in October and November 2008. Male fiddler crabs have giant claws, but the researchers wanted to see how female crabs, with only two small feeding claws, protect their homes.
Fiddler crabs are territorial and live in burrows. The researchers gathered crabs from distant parts of the mud flats and tethered them near new, occupied burrows. In 21 trials involving male intruders, the researchers found that male crabs would scuttle over to fight off the invaders on a female neighbor's territory 95 percent of the time. But in 20 trials involving female intruders, the males crabs only fought off the invaders 15 percent of the time.
That suggests the male crabs preferred to keep females nearby, largely because they will almost always have sex with their male neighbors, Jennions said.
Swapping sex for favors is not unheard of in the animal kingdom. Antarctica's Adelie penguins exchange sex for highly coveted stones used for nest building.
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