Biologists at Plymouth University studied how males reacted when startled . They found that crabs had larger packets of sperm than the bolder ones . It contrasts with many species where bold displays tend to attract mates . Males in other species must prove their fitness by fighting or showing off . Scientists aggressive hiding allows crabs to invest more energy in attracting sperm .
Biologists at Plymouth University studied how crabs reacted when startled . They found shyer crabs had larger packets of sperm than the bolder ones . It contrasts with many species where bold displays tend to attract mates . Males in other species must prove their fitness by fighting or showing off . Scientists say hiding allows crabs to invest more energy in making sperm .