How mantis shrimps spar

ANCHORAGE, Alaska — Mantis shrimps famed for their murderously fast punches don’t dance around much before they start swinging at each other.

In about a third of 34 disputes over territory staged in a lab, a Neogonodactylus bredini mantis shrimp’s first move was slamming a raptorial club into a rival, says Patrick Green of Duke University. And all but one of the rest of the clashes eventually came to blows, Green reported June 11 at the annual meeting of the Animal Behavior Society.

A mantis shrimp can accelerate its club with the same order of magnitude as bullets exploding out of the muzzle of a gun. Based on face-offs among other well-armed animals such as deer, Green and coauthor Sheila Patek, also at Duke, had predicted that mantis shrimps would start combat with harmless displays that give opponents a chance to assess each other.

Instead, mantis shrimp punches themselves can allow for some nonfatal assessment. The animal on the receiving end curls its rear forward between its legs so the last body segment rises in front of it like a bumpy shield. Patek’s lab had previously found that the last segment, or telson, works like a punching bag, dissipating much of the impact energy of the wallop.

The winner of sparring rounds is often the combatant delivering the most blows, Green found. One combatant often just stops, unsmashed, but the loser by one or more punches. When same-species sparring escalates to real fighting, N. bredini often stops punching and starts spearing.

Editor’s Note: This brief was updated June 23, 2015, to correct how many  territorial disputes staged in a lab began with a mantis shrimp throwing a punch without warning. It was a third, not half.