Hooker Crabs Swap Sex for Safety
Male crabs rewarded with sex for defending neighbors
By Rob Quinn,  Newser Staff
Posted Nov 4, 2009 4:17 AM CST
Two male fiddler crabs fight on a beach on Inhaca Island, Mozambique.    (AP Photo/The Australian National University, Tanya Detto)

(Newser) – Selling sex is the key to survival in the seedy world of fiddler crabs, according to Australian researchers. Scientists studying the burrow-dwelling, highly territorial creatures found that male fiddler crabs fought off intruders to protect female neighbors—who lack the male's huge claw—far more often than they would aid male neighbors, and apparently received sex in return.

"Males protected their female neighbors in 95% of instances where the intruder was male, and only 15% of instances where the intruder was female," one researcher said. "This suggests that males don't care who their neighbor is, as long as they are female." Trading sex for benefits has been observed in several other species, including birds and monkeys, but this is the first time such behavior has been seen among crabs.