Fiddler crabs have the largest relative weapons yet rarely fight
Evidence
What he found was they wave them. Up and down, up and down, again and again they raise their claws high and drop them. Dozens of times each minute, thousands of times per hour, hour after hour. When contests get intense, claws clearly function as weapons—dangerously strong claspers capable of inflicting real harm. Yet they also appeared to serve as signals. In fact, for every few minutes of outright fighting, males spent dozens of hours waving. Most of the time, fiddlers were employing their claws as warnings rather than instruments of battle. They were using them for deterrence. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 366 (
#expands, via linked claim)
Imagine the beachscape from the vantage of a wandering crab, eyes perched on stalks a mere inch above the sand. Everywhere he looks are claws jerking up and down, bursting above the horizon and back again. Over and over they rise and fall, surrounding him with an incessant barrage of motion. The wandering male doesn’t simply march up to the first burrow he encounters. Nor does he approach at random. As he weaves between waving males, he sizes them up—bigger claws reach higher than smaller claws—advancing only toward burrows guarded by males whose claws are equal in size or just a bit smaller than his own. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 375 (
#corroborates, via linked claim)
- Masatoshi Matsumasa and Minoru Murai were able to measure the energetic costs of fiddler crab claws in action by tracking changes in blood glucose (a sugar used to power activity) and blood lactate (a chemical by-product of metabolism and an indication of energy burned) as animals performed various behaviors. By measuring baseline lactate levels in resting animals, and comparing this to the elevated levels they detected during fights, Matsumasa and Murai showed that the energetic cost of waving a claw was substantial. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 767 (
#complicates, via linked claim)
Categorization
- XREF: connects to: Fiddler crabs use their oversized claws far more as signals than as weapons — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 366; Fiddler crabs assess rival claw size and only approach equally-matched opponents. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 375; Waving a fiddler crab claw incurs measurable energetic costs — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 767 (+1 more)
Related
- Fiddler crabs use their oversized claws far more as signals than as weapons (similarity 0.95)
- Fiddler crabs assess rival claw size and only approach equally-matched opponents. (similarity 0.93)
- Costly claw muscle raises male fiddler crab resting metabolism nearly twenty percent (similarity 0.90)
- Waving a fiddler crab claw raises blood lactate measurably. (similarity 0.89)
- Waving a fiddler crab claw incurs measurable energetic costs (similarity 0.88)
- Even resting male crabs pay high energy costs for big claw muscles (similarity 0.86)
- Weapon size honestly signals fighting ability because growth tracks health and nutrition (similarity 0.85)
- Sexual weapons sometimes protect rather than burden their bearers from predators (similarity 0.79)
- The same three ingredients trigger weapon evolution across wildly divergent animal clades (similarity 0.78)
Broader Connections
- Fiddler crabs use their oversized claws far more as signals than as weapons
#expands(0.80) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 366 - Fiddler crabs assess rival claw size and only approach equally-matched opponents.
#corroborates(0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 375 - Waving a fiddler crab claw incurs measurable energetic costs
#complicates(0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 767 - Costly claw muscle raises male fiddler crab resting metabolism nearly twenty percent
#expands(0.55) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 303