Some Crabs Crabbier Than Others

A common European hermit crab outside its shell. CREDIT: Mark Briffa.

Is one crab more crabby than another? It could be true.

Crabs apparently can have different personalities from one another, the first discovery of personality in crustaceans.

People consistently differ from one another in behavior, differences known as personalities. The same is known to hold true in many other animals, such as dogs or cats.

The vast majority of investigations of animal personality focus on animals with backbones. Although there is no reason in theory why personalities should not also exist in creatures without backbones, "this is often assumed to be the case," said researcher Mark Briffa, a behavioral ecologist at the University of Plymouth in England.

Briffa had a conversation with a colleague at a Christmas party about animal personalities "and straight away realized hermit crabs would be really good for looking at this," he recalled.

Scientists have long experimented with how these crabs respond to being startled, to gauge how they behave in combat and other activities. Briffa reasoned that how crabs recover after startling could help measure boldness — how much risk each crab was willing to take.

The researchers investigated the common European hermit crab (Pagurus bernhardus) for boldness. They flipped more than 100 hermit crabs upside down and recorded how long it took for each to emerge from the protective snail shells they had made their homes.

They found there was a significant pattern of individual consistency in behavior. Some crabs generally proved bold, while others were more timid.

"Now I think it's not surprising that invertebrates show personalities," Briffa told LiveScience. "A personality or consistent behavior is just one strategy to cope with a variable environment. There's no reason why such a strategy should evolve only in one small group of animals such as vertebrates."

Curiously, hermit crabs from one beach proved more timid than those at two other beaches the scientists examined. Briffa and his colleagues speculated that perhaps those crabs experienced different levels of predation or different waves than the others.

Previous research had shown that jumping spiders also displayed personalities, by showing "consistent individual levels of boldness," Briffa said.

He added that personalities might perhaps be found even in organisms with very simple nervous systems. "Maybe vertebrates or even humans aren't as special in this respect as people often assume," Briffa said.

Briffa and his colleagues detailed their findings March 12 in the journal Proceedings of the Royal Society B.

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