Available online at www.sciencedirect.com The effects of claw regeneration on territory ownership and mating success in the fiddler crab Uca mjoebergi LEEANN T. REANEY, RICHARD N. C. MILNER, TANYA DETTO & PATRICIA R. Y. BACKWELL School of Botany and Zoology, The Australian National University, Canberra (Received 9 July 2007; initial acceptance 15 August 2007; final acceptance 23 September 2007; published online 19 November 2007; MS. number: 9450) Underlying male quality is often reflected in the condition of sexually selected traits. In fiddler crabs, male success in both intra- and interspecific interactions is highly dependent on the size of the major claw. However, males are often forced to autotomize their major claw. Claw regeneration significantly altered the structure of a males’ major claw in Uca mjoebergi. We found, however, that claw regeneration did not affect signal quality. Both males and females were unable to visually distinguish a regenerated claw from an original claw. Although regenerated males were inferior fighters, males were able to compensate for this fighting disadvantage by avoiding fights with other males. Regenerated males were, however, less likely to acquire and defend high-quality territories and consequently suffered a decrease in mating success. Ó 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Keywords: claw regeneration; fiddler crab; mating success; signal quality; territory ownership; Uca mjoebergi Sexually selected signals are notoriously costly to produce (Andersson 1994). In many species, only high-quality males can produce and maintain costly signals, allowing conspecifics to rely on these traits to honestly signal competitive ability or mate quality (Zahavi 1975). The re- lationship between signal costs and signaller quality, how- ever, can be disrupted by several factors including disease (McGraw & Hill 2000), a change in resource availability (Kotiaho 2000) or a temporary loss of quality (e.g. a loss of competitive ability due to moulting or a loss of mate quality due to sperm depletion; Adams & Caldwell 1990; Kendall & Wolcott 1999). In some species, the relation- ship between signal costs and sender quality may be disrupted after the regeneration of a sexually selected trait. Many invertebrates possess the ability to self-amputate (autotomize) major appendages. While autotomy can be hugely beneficial in terms of survival, the subsequent regeneration of a major appendage can be very energeti- cally costly (e.g. Naya et al. 2007). Regrowing a lost appendage often requires a large shift in resource alloca- tion that can affect somatic and reproductive growth (e.g. Niewiarowski et al. 1997). When an individual loses and regenerates a costly sexually selected trait, they may experience a reduction in overall condition that may be reflected in the quality of the regenerated trait. Append- ages that have been regrown are also often structurally different from their nonregenerated originals (for review see Maginnis 2006). Consequently, regeneration can po- tentially affect maleemale performance ability, competi- tiveness and mating success. In male wolf spiders, for example, regenerated legs are smaller than original legs and lack the conspicuous decorative tuft used in courtship and aggressive displays. As a result, leg regeneration nega- tively affects both male competitive ability and mating success (Uetz et al. 1996). Male fiddler crabs (Uca spp.) produce one greatly en- larged major claw that can make up as much as 40% of their body mass (Crane 1975). They use their claw both as a weapon in agonistic encounters with other males and to attract mate-searching females. The length of the major claw is important in the assessment of fighting abil- ity before physical contact (Jennions & Backwell 1996; Morrell et al. 2005) and as a predictor of male mating success (Backwell & Passmore 1996; Reaney & Backwell 2007). Males also attract females to their burrows by wav- ing their major claw, often in synchrony with neighbour- ing males. Females have been shown to preferentially visit males with faster wave rates (Backwell et al. 1999, 2006). Although the major claw is extremely important to males, they occasionally need to autotomize it during Correspondence: P. R. Y. Backwell, School of Botany and Zoology, The Australian National University, Canberra, ACT 0200, Australia (email: pat.backwell@anu.edu.au). 1473 0003e 3472/08/$34.00/0 Ó 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. ANIMAL BEHAVIOUR, 2008, 75, 1473e1478 doi:10.1016/j.anbehav.2007.09.021