Fiddler Crabs Will Boink for Survival

Nov 05, 2009 • Research


Male fiddler crabs will gladly rise in defense of a strange female of their species when an intruder crab comes around. Chivalry? Not so much. Researchers from the Australian National University in Canberra have found that female fiddler crabs bestow sexual favors on males to ensure their own safety.

“This study shows, for the first time, that in exchange for sex and other benefits, males protect their female neighbors from territory-seeking male intruders. The paper provides the first evidence of ‘defense coalitions’ between territorial males and females,” says Michael Jennions, who assisted with the study, which was published in the journal Biology Letters.

Jennions, along with researchers Richard Milner and Patricia Backwell, studied the crabs living in mud flats off the African country of Mozambique late last year. Fiddler crabs are territorial and live in burrows; while the males have large claws to protect themselves, the females do not. The researchers took crabs from other parts of the mud flats and placed them near occupied burrows.

Male invaders did not fare well with the male residents. In 21 trials, resident males fought off the male invaders 95 percent of the time.

Of course, in 20 trials involving female intruders, the males residents only fought 15 percent of the time. Jennions theory? Male crabs prefer to keep females nearby, because they will almost always have sex with resident males.

Image by barloventomagico. Information from The Associated Press.