Contests with deadly weapons: telson sparring in mantis shrimp (Stomatopoda)

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Green, P.A. and S. N. Patek. 2015. Contests with deadly weapons: telson sparring in mantis shrimp (Stomatopoda). Biology Letters 11: 20150558.

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Biology Letters

Mantis shrimp strike with extreme impact forces that are deadly to prey. They
also strike conspecifics during territorial contests, yet theoretical and empirical
findings in aggressive behaviour research suggest competitors should resolve
conflicts using signals before escalating to dangerous combat. We tested how
Neogonodactylus bredini uses two ritualized behaviours to resolve size-matched
contests: meral spread visual displays and telson (tailplate) strikes. We predicted
that (i) most contests would be resolved by meral spreads, (ii) meral
spreads would reliably signal strike force and (iii) strike force would predict
contest success. The results were unexpected for each prediction. Contests
were not resolved by meral spreads, instead escalating to striking in 33 of 34
experiments. The size of meral spread components did not strongly correlate
with strike force. Strike force did not predict contest success; instead, winners
delivered more strikes. Size-matched N. bredini avoid deadly combat not by
visual displays, but by ritualistically and repeatedly striking each other’s
telsons until the loser retreats. We term this behaviour ‘telson sparring’,
analogous to sparring in other weapon systems. We present an alternative
framework for mantis shrimp contests in which the fight itself is the signal,
serving as a non-lethal indicator of aggressive persistence or endurance.

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