It is sometimes necessary for men wanting to attract the opposite sex to come out of their shell . Yet it seems that by often choosing the bolder males , women may be missing out on the best possible mate . Researchers have found that the shyest males actually have the most to offer a potential lover - at least in the world of hermit crabs . Hermit crabs , like the ones above , borrow the shells from other creatures to keep them safe and new research has shown that those crabs that stay in their shells more often tend to be a better mate for female crabs . Professor Mark Briffa , a marine animal behaviour researcher at Plymouth University , and his colleagues have found that the most timid crabs tend to more high quality sperm - making them a better option for females looking for a mate . This , they say , is because the crabs that spend more time hiding from the world inside their shells , also have invested the most resources in becoming reproductively fit . Males of a species of hairy chested crab , which has been given a nickname David Hasselhoff , spend their lives largely separate from the females , according to new research . In a study looking at the private life of the deep-sea crab known as the 'Hoff ' have found that the males and females spend separate lives at volcanic vents 1.5 miles deep near Antarctica . This , according to the British research , is because of the conflicting demands of feeding and raising young among the sexes . In 2010 , a British expedition revealed a 'lost world ' of deep-sea animals including the crab named after the Baywatch star thriving on the ocean floor near Antarctica . Using a deep-diving remotely operated vehicle ( ROV ) to examine the distribution , size and sex of these crabs at the vents , Dr Leigh Marsh and colleagues from the University of Southampton have now pieced together their private lives . The researchers found that large male Hoff crabs live highest on the mineral spires of the deep-sea vents , closest to the hot fluids that jet from them . Smaller males tend to mingle with the females at the base of the mineral spires . It is an unusual approach in the animal kingdom , where the boldest , bravest and strongest usually win the right to mate . Indeed , in many species males have to prove their physical fitness with bold and dramatic displays - like in peacocks and birds of paradise - and even mortal combat in some cases . Writing in the journal Proceedings of the Royal Society B , Professor Briffa and his colleagues said : 'It appears that in hermit crabs , high-quality individuals that have invested heavily in reproduction , by making large spermatophores , are the most risk averse . 'Although we did not measure metabolic rate , a key process for the pace of life syndrome , this result seems counter to the idea that the most productive individuals should also be the boldest . ' The researchers examined the 'personality ' of 100 hermit crabs collected from Mount Batten and Hannafore Point in Plymouth . They did this by testing the 'startle response ' of each crab by removing it from its tank , inverting the crab for five seconds , which caused it to withdraw into its shell , and then returning it back into the tank upright . The boldest crabs would then poke their heads back out of their shells far faster than the more timid crabs . On average most crabs emerged within 16 seconds . The researchers then measured the levels of a protein called haemocyanin , which is responsible for carrying oxygen around the crabs bodies . They found crabs that stayed in their shells longer after being startled tended to have higher levels of this protein . Hermit crabs , like the one pictured above , hide in their shells when startled , but it also helps them become better mates . This is because when inside their shell , the crabs are unable to access the oxygen rich sea water around them and so higher levels of this protein helps use the oxygen already in their bodies more efficiently . Next the researchers examined the crustacean 's gonads and measured the size of the tube shaped bundles of sperm there , called spermatophores . Again they found in the timid crabs , those that were slower to reemerge from their shells after being frightened , had larger spermatophores and so more high quality sperm stored . As they grow , hermit crabs like the one above , 'upgrade ' their shells by seeking out larger ones as finding the right home can offer them protection from danger but also give them a way of growing better stores of sperm . Professor Briffa and his colleagues said that hiding in the shell when threatened may allow the crabs to conserve their energy for building up greater sperm reserves . It also reduces the risk of losing a shell in a fight with another crab , something that can increase the amount of stress a crab is exposed to . They said that in hermit crabs less reproductively fit individuals may develop boldness to help them compete with the shier more fertile crabs . They said : 'Low-quality males may emerge more quickly in an attempt to maximize their chance of mating , or because they need to return more quickly to foraging , or through a combination of these causes . '
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 .