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Handedness in fiddler crab fights

Perez, D. M.; Heatwole, S. J.; Morrell, L. J.; Backwell, P. R. Y.


D. M. Perez

S. J. Heatwole

P. R. Y. Backwell


Asymmetric weapons are common in bilateral animals and, in some species, they can occur on either the left- or the right-hand side of the body (lateralization). Fiddler crabs (Uca spp, Decapoda: Ocypodidae) have an enlarged claw that is used in male–male combat over territories and in courtship displays. Males can be either right- or left-handed, and most species have a 1:1 ratio. Past studies have found little effect of handedness on fighting success, fight duration or other measures of combat. Here we show that, while handedness per se, does not affect fighting, handedness matching has a significant effect. In Uca mjoebergi, fights between different-handed males were more likely to escalate to grappling, suggesting that it is harder for the combatants to determine the winner. We suggest that the positioning of the claws during fighting creates distinct forces that result in different outcomes for same- versus different-handed fights. This can represent a strong selective pressure in populations with an uneven handedness distribution where the handedness minority will often engage in different-handed fights. We discuss these results in light of the selective forces that may act on handedness distribution in fiddler crabs.


Perez, D. M., Heatwole, S. J., Morrell, L. J., & Backwell, P. R. Y. (2015). Handedness in fiddler crab fights. Animal behaviour, 110(December), 99-104.

Journal Article Type Article
Acceptance Date Aug 24, 2015
Online Publication Date Oct 23, 2015
Publication Date Dec 1, 2015
Deposit Date Oct 23, 2015
Publicly Available Date Nov 23, 2017
Journal Animal behaviour
Print ISSN 0003-3472
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 110
Issue December
Pages 99-104
Keywords Body asymmetry; Fight costs; Fight outcome; Handedness distribution; Handedness matching
Public URL
Publisher URL
Additional Information Authors' accepted manuscript of article published in: Animal behaviour, 2015, v.110, December.


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