In the social circles of crustaceans, the claw means everything. Larger claws can be used to signal dominance, staving off unnecessary battles between poorly-matched opponents. However, if two similarly-sized individuals fight it out - it's usually the one with the stronger claw that wins.
Unlike humans, where opponents can assess strength visually (e.g. bicep size), crustacean muscle is contained within a hard exoskeleton. This means that crustaceans can't determine each others' strength without testing it in combat, and it opens the possibility for cheating. Cheating could benefit individuals by gaining them dominance without having to fight; meaning access to better quality food, enhanced mating opportunities, and safer shelters - all without risk of bodily harm in combat or the high metabolic costs associated with maintaining strong claw muscles.
And cheating may be as easy as growing a large, wimpy claw.
By and large, animals are thought to signal their value (i.e. strength, power, dominance) honestly. But Dr. Robbie Wilson of the University of Queensland has found that many crustacean species actually cheat - producing large but weak claws that fool potential competitors.
These are exciting findings, because they show that cheating is likely to evolve under particular circumstances.
As part of his honours research in Dr. Wilson's lab, Gregory Walter found that female crayfish, Cherax destructor, are more likely to benefit from cheating compared with males. In his experiments, he measured claw sizes, body sizes, and claw force for each crayfish, and then observed which crayfish won in competitive, same-sex bouts - and, importantly, whether dominance was gained by signalling or battling.
"We found that having large, wimpy claws was prevalent among both males and females," explains Dr. Wilson. "But only females gained dominance by cheating."
It turns out that male C. destructor tended to fight more often than females, so dominance among males was acquired via claw strength - an unfakeable trait. On the other hand, dominance among female C. destructor was most often determined via signalling alone, leaving claw strength untested and rewarding females with large, but weak, claws.
"In fact, females were pretty bad at judging each others' potential strength [based on claw size]," Dr. Wilson continues. "Giving sub-standard females the chance to be dominant."
This work has just been published as:
Walter G, Van Uietregt V, & Wilson RS. 2011. Social control of unreliable signals of strength in males but not females of the crayfish Cherax destructor. Journal of Experimental Biology. 214: 3294-3299.
You can read more about Dr. Wilson's research on honest signalling here.
Written by Dr. Amanda Niehaus
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| Fighting fiddler crabs - photo by Skye Cameron |
Unlike humans, where opponents can assess strength visually (e.g. bicep size), crustacean muscle is contained within a hard exoskeleton. This means that crustaceans can't determine each others' strength without testing it in combat, and it opens the possibility for cheating. Cheating could benefit individuals by gaining them dominance without having to fight; meaning access to better quality food, enhanced mating opportunities, and safer shelters - all without risk of bodily harm in combat or the high metabolic costs associated with maintaining strong claw muscles.
And cheating may be as easy as growing a large, wimpy claw.
By and large, animals are thought to signal their value (i.e. strength, power, dominance) honestly. But Dr. Robbie Wilson of the University of Queensland has found that many crustacean species actually cheat - producing large but weak claws that fool potential competitors.
These are exciting findings, because they show that cheating is likely to evolve under particular circumstances.
As part of his honours research in Dr. Wilson's lab, Gregory Walter found that female crayfish, Cherax destructor, are more likely to benefit from cheating compared with males. In his experiments, he measured claw sizes, body sizes, and claw force for each crayfish, and then observed which crayfish won in competitive, same-sex bouts - and, importantly, whether dominance was gained by signalling or battling.
 |
| Cherax destructor - photo by Gregory Walter |
"We found that having large, wimpy claws was prevalent among both males and females," explains Dr. Wilson. "But only females gained dominance by cheating."
It turns out that male C. destructor tended to fight more often than females, so dominance among males was acquired via claw strength - an unfakeable trait. On the other hand, dominance among female C. destructor was most often determined via signalling alone, leaving claw strength untested and rewarding females with large, but weak, claws.
"In fact, females were pretty bad at judging each others' potential strength [based on claw size]," Dr. Wilson continues. "Giving sub-standard females the chance to be dominant."
This work has just been published as:
Walter G, Van Uietregt V, & Wilson RS. 2011. Social control of unreliable signals of strength in males but not females of the crayfish Cherax destructor. Journal of Experimental Biology. 214: 3294-3299.
You can read more about Dr. Wilson's research on honest signalling here.
Written by Dr. Amanda Niehaus