Importance of weapon size in all stages of male–male contests in the hermit crab Pagurus minutus

Yasuda, Chiaki I.; Koga, Tsunenori

doi:10.1007/s00265-016-2221-0

Cited by 20 publications

(15 citation statements)

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“…First, as noted above, guarding pair sampling assured a high reproductive motivation in all contestants. For Pagurus males, mature females are a critically important resource (Suzuki et al, 2012; Yasuda & Koga, 2016b; Yasuda et al, 2012), but at the end of trial–1 no losers possessed a female, regardless of their initial role. Therefore, in trial–2, both prior owners and prior intruders may have no difference in motivation to attempt to take over mate from an opponent.…”

Section: Discussionmentioning

confidence: 99%

“…Since weapon size (CL) is a more reliable indicator of the outcome of male–male contests in P. minutus than is body size (SL; Yasuda & Koga, 2016b), we used CL as a male RHP proxy in this study. To minimize the asymmetry of RHP between contestants related to the physical attribute, based on the variation of CL difference between males in all contests (Figure A1b in Appendix S1), we excluded the four sets of contests from the statistical analyses in which the absolute CL difference in one or both trials was more than 3 mm.…”

Section: Methodsmentioning

confidence: 99%

“…In this study, we aim to examine (a) whether resource ownership and female value (i.e., her body size and the number of days until spawning, reflecting maturity) affect the contest outcomes and (b) whether the probability of winning after losing differs depending on the initial role of the loser (i.e., owner or intruder) in P. minutus . According to Yasuda and Koga (2016b), male–male contests in this species are settled based on the asymmetry of male weapon size rather than body size and not based on resource ownership and female body size. However, this previous study did not examine the effects of female maturity, and more importantly, it was performed with randomly chosen (i.e., random‐sized) contestants, meaning that factors other than male size may have been masked.…”

Section: Introductionmentioning

confidence: 99%

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Does prior residency interact with loss? A study of male–male contests in the hermit crab Pagurus minutus

2020

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Residency is an important predictor of success in contests with ownership asymmetries. Residency often can interact with a winning experience. However, given that some residents lose a contest even when showing an ownership advantage and that the process leading to loss often determines the loser's subsequent success, prior ownership might also interact with a loss. Here, we staged experimental contests between males of the hermit crab Pagurus minutus with a similar‐sized weapon (i.e., cheliped) to examine this possibility. Male–male contests in this species occur between a solitary intruder and an owner guarding a mature female. We evaluated (a) whether resource ownership and female value affect the contest outcome and (b) whether the probability of winning after losing differs depending on the initial role of the loser (i.e., owner or intruder) by using precopulatory guarding pairs of P. minutus collected from the field. In the first fighting trial, we found an ownership advantage and increasing owner success as the body size of his partner increased. Although some owners lost the fight, in contrast to our prediction, the frequency of losing in the second fighting trial did not differ between prior owners and prior intruders. Because losers from the first fighting trial of male–male contests have no female regardless of their initial role, this shared solitary status might be related to the lack of difference in success in the second fighting trial. Moreover, unlike in other animals, resident status might not always assure greater fighting ability in P. minutus males because guarding Pagurus males can avoid male–male contests by climbing up objects in the field. Losers in the first trial, therefore, may have been weaker contestants based on traits other than size, regardless of whether they were owners or intruders.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Does prior residency interact with loss? A study of male–male contests in the hermit crab Pagurus minutus

2020

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“…Kawaminami and Goshima (2015) suggest that climb-up behavior by a guarding male helps to sequester a guarded female from rival males and hence to avoid male-male contests. Yasuda and Koga (2016)r e p o r t e dt h a tm o s t solitary P. minutus males (>80%) initiate a contest against the guarding males they encounter, and more than half the intruders may succeed in takeover of a guarded female from her original 'owner' during escalated male-male contests. This indicates that prior guarding position (owner advantage) is less effective in this species than in other Pagurus species (e.g., P. middendorffii,W a d ae ta l .1999).…”

Section: Discussionmentioning

confidence: 99%

Seasonal change in sexual size dimorphism of the major cheliped in the hermit crab Pagurus minutus

Yasuda

Otoda

Nakano

et al. 2017

Ecological Research

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Sexual size dimorphism is a common phenomenon in the animal kingdom, and its seasonal change has been reported in some species that possess traits dimorphic only in males and specialized for male mating success. However, few studies have examined seasonal change in sexual dimorphism of traits possessed by both sexes. Here, we examined the reproductive biology of the hermit crab Pagurus minutus, at a sandflat in the Waka River estuary, Japan, with special reference to seasonal changes in sexual dimorphism of the large claw (major cheliped) size by conducting population and precopulatory guarding‐pair sampling. Previous investigation demonstrated that the major cheliped is used as a weapon, and its size, more than body size, determines the winner in male–male contests of this species. We found ovigerous females from November to April, peaking in January, when 80% of females were ovigerous. Sexual size dimorphism of the major cheliped was observed; the degree of dimorphism increased in the reproductive season, when only males possessed an enlarged major cheliped. In addition, in the reproductive season, precopulatory guarding males had a larger body and larger relative size of the major cheliped than did solitary males, although the major cheliped size in guarding males seemed to reach an upper limit. These results suggest that seasonal change in sexual dimorphism of the major cheliped size in P. minutus strongly reflects sexual selection favoring the development of this natural weaponry, and that the degree of the dimorphism might be limited through natural selection.

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“…A particular aspect of behavioural display that has clear effects is intensity, often signalled by the willingness to initiate a display and by its rate or magnitude [1 -7]. Display intensity can be transmitted by visual and non-visual signals alike, with the benefit that longer-ranging signals can alert several contenders and reduce future conflicts [3][4][5][6][7]. Yet, some types of long-ranging signals also have the further capacity to harbour information in their structure, such as vocalizations that vary markedly in complexity [8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Signal complexity communicates aggressive intent during contests, but the process is disrupted by noise

et al. 2019

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Contestants use displays to signal their aggressive intent and settle disputes before they escalate. For birds, this is often in the form of song, which can vary in structural complexity. The role of song complexity in signalling aggressive intent has not been fully established, and its efficacy could be influenced by background noise levels. Using playback experiments, we found that in European robins, Erithacus rubecula, song complexity signalled sender aggression and affected receiver response. However, increased noise impacted the ability of contestants to adjust response based on opponent song complexity. These findings provide new evidence regarding the use of acoustic signal complexity for assessing opponent aggression and that noise can influence contest behaviour by interrupting this process, which could impose fitness consequences.

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Importance of weapon size in all stages of male–male contests in the hermit crab Pagurus minutus

Cited by 20 publications

References 62 publications

Does prior residency interact with loss? A study of male–male contests in the hermit crab Pagurus minutus

Does prior residency interact with loss? A study of male–male contests in the hermit crab Pagurus minutus

Seasonal change in sexual size dimorphism of the major cheliped in the hermit crab Pagurus minutus

Signal complexity communicates aggressive intent during contests, but the process is disrupted by noise

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