A farewell to arms: males with regenerated claws fight harder over resources

Callander, Sophia; Bolton, Jessica; Jennions, Michael D.; Backwell, Patricia R. Y.

doi:10.1016/j.anbehav.2012.06.017

Cited by 12 publications

(3 citation statements)

References 38 publications

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“…Although regenerated (leptochelous) claws grow to similar sizes compared to the original (brachychelous) claws, they lack morphological features like dactyl teeth and tubercules and are comparatively weaker (see Backwell et al, 2000;Lailvaux et al, 2009;McLain et al, 2010). Claw regeneration among male fiddler crabs can be widespread, and between 10% and 45% of a crab population bear regenerated claws (Bywater and Wilson, 2012;Callander et al, 2012;McLain et al, 2010). Backwell et al (2000) also established that the morphology of regenerated claws never develops to the original quality, even after multiple moult cycles.…”

Section: Introductionmentioning

confidence: 99%

Building a dishonest signal: the functional basis of unreliable signals of strength in males of the two-toned fiddler crab,Uca vomeris

Bywater

Seebacher

Wilson

2015

Journal of Experimental Biology

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Males of many species use signals during aggressive contests to communicate their fighting capacity. These signals are usually reliable indicators of an individual's underlying quality; however, in several crustacean species, displays of weapons do not always accurately reflect the attribute being advertised. Male fiddler crabs possess one enlarged claw that is used to attract females and to intimidate opponents during territorial contests. After the loss of their major claw, males can regenerate a replacement claw that is similar in size but considerably weaker. As this inferior weapon can still be used to successfully intimidate rivals, it represents one of the clearest cases of unreliable signalling of strength during territorial contests. We investigated the functional mechanisms that govern signal reliability in the two-toned fiddler crab, Uca vomeris. Male U. vomeris exhibit both reliable and unreliable signals of strength via the expression of original and regenerated claw morphs. We examined the morphological, biomechanical and biochemical characteristics of original and regenerated claws to establish the best predictors of variation in claw strength. For a given claw size, regenerated claws have less muscle mass than original claws, and for a given muscle mass, regenerated claws were significantly weaker than original claws. The mechanical advantage was also lower in regenerated claws compared with original claws. However, the activity of three catabolic enzymes did not differ between claw types. We conclude that the structural and physiological predictors of force production influence the frequencies of reliable and unreliable signals of strength in U. vomeris. This study furthers our understanding of the proliferation of unreliable signals in natural populations.

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Section: Introductionmentioning

confidence: 99%

Building a dishonest signal: the functional basis of unreliable signals of strength in males of the two-toned fiddler crab,Uca vomeris

Bywater

Seebacher

Wilson

2015

Journal of Experimental Biology

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“…), and male fiddler crabs ( Uca annulipes ) with regenerated claws (weaker competitors) sometimes fight harder over resources than intact males (Callander et al. ). However, in our study, there was no correlation between the birds’ aggressiveness and their body mass index, not supporting the above idea.…”

Section: Discussionmentioning

confidence: 99%

Does Innovation Success Influence Social Interactions? An Experimental Test in House Sparrows

et al. 2015

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In group‐living animals, individuals may benefit from the presence of an innovative group‐mate because new resources made available by innovators can be exploited, for example by scrounging or social learning. As a consequence, it may pay off to take the group‐mates' problem‐solving abilities into account in social interactions such as aggression or spatial association, for example because dominance over an innovative group‐mate can increase scrounging success, while spatial proximity may increase the chance of both direct exploitation and social learning. In this study, we tested whether the individuals' innovation success influences their social interactions with group‐mates in small captive flocks of house sparrows (Passer domesticus). First, we measured the birds' actual problem‐solving success in individual food‐extracting tasks. Then, we manipulated their apparent problem‐solving success in one task (by allowing or not allowing them to open a feeder repeatedly) while a new, unfamiliar group‐member (focal individual) had the opportunity to witness their performance. After this manipulation, we observed the frequency and intensity of aggression and the frequency of spatial associations between the focal individuals and their manipulated flock‐mates. Although flock‐mates behaved according to their treatments during manipulations, their apparent problem‐solving success did not affect significantly the focal individuals' agonistic behaviour or spatial associations. These results do not support that sparrows take flock‐mates' problem‐solving abilities into account during social interactions. However, focal individuals attacked those flock‐mates more frequently that had higher actual problem‐solving success (not witnessed directly by the focal individuals), although aggression intensity and spatial association by the focal birds were unrelated to the flock‐mates' actual success. If this association between flock‐mates' actual innovativeness and focal individuals' aggression is not due to confounding effects, it may imply that house sparrows can use more subtle cues to assess the group‐mates' problem‐solving ability than direct observation of their performance in simple foraging tasks.

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“…These results are consistent with our hypothesis that regenerated males would surrender when the fight escalates. Callander et al (2012) reported that regenerated U. annulipes males fight harder during the mating period to compensate for the physical disadvantage of having a less-robust claw. Uca lactea have mating and non-mating periods during the breeding season (Yamaguchi 2001;Muramatsu 2010b); however, we did not discriminate between mating and non-mating periods in the present study.…”

Section: Fighting Stagesmentioning

confidence: 99%

Fighting with an unreliable weapon: opponent choice and risk avoidance in fiddler crab contests

Muramatsu

Koga

2016

Behav Ecol Sociobiol

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Current signaling theories predict that animal signals are generally honest, but each signaling system allows some admixture of deception. Male fiddler crabs fight aggressively through use of their greatly enlarged major claw, which grows on the left or right side. Some males have fragile regenerated claws (regenerated males) and others have robust original claws (original males), but crabs cannot visually discriminate between the two types. In the present study, we conducted field observations in a population of Uca lactea to investigate how regenerated males fight with their inferior weapons, and how other males deal with the potential deception. Regenerated males employed bluffing tactics; they pretended to be aggressive to deter opponents, but surrendered when the fight escalated. Regenerated males tended to choose smaller and opposite-handed opponents, probably because claws can be grappled tightly in same-handed fights. The bluffing tactics seemed to be partially successful, because regenerated males were not selectively challenged by other males and defeated original males in 41.7% of the cases. However, original males developed counter-bluff tactics, such as choosing same-handed opponents and persisting in contests even when the opponent was larger. Consequently, original males defeated regenerated males equipped with a longer claw in 42.9% of the cases. In the most striking case, an original male evicted a resident male from his burrow despite the 42.7% longer regenerated claw. This counter-bluff tactic decreases the reliance on the signal of strength (weapon size) and limits the benefit of bluffing.

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A farewell to arms: males with regenerated claws fight harder over resources

Cited by 12 publications

References 38 publications

Building a dishonest signal: the functional basis of unreliable signals of strength in males of the two-toned fiddler crab,Uca vomeris

Building a dishonest signal: the functional basis of unreliable signals of strength in males of the two-toned fiddler crab,Uca vomeris

Does Innovation Success Influence Social Interactions? An Experimental Test in House Sparrows

Fighting with an unreliable weapon: opponent choice and risk avoidance in fiddler crab contests

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