A swimming rudder , thermal regulator , ice breaker , arm , foraging puppet , sensor — that ’s thelistof ideasso farthat scientist have proposed the iconic narwhal tusk could be used for . But due to modified observations , it ’s been difficult to be sure-footed about any of these explanation . Now , scientist have thrown yet another idea into the mix : it could have acquire as a condition sign used by female to channelise mate choice . The swelled the tusk , the more attractive the male person . This does n’t necessarily discredit the other mind , but suggests that the tusk may indicate fertility to females , much like brightly gloss bird plumage or telling deer antlers . The workplace has been published inMarine Mammal Science .
Narwhals , sometimes discover as the “ unicorns of the sea , ” are toothed whale related to bottlenose dolphins , orcas and belugas . These arctic dwellers possess justtwo teeth ; in males , the left cuspid protrudes through the jaw into a sword - same helical ivory that can hand almost three meters in length . Some femalesalso produce tusks , but they ’re not as salient .
The function of this tusk has been a subject of debate for some time now and many different ideas have been hold around in the past . male have been observed using them asweaponsto fight over females , and some logical argument of grounds have advise they may be used to stir up sediment in search of intellectual nourishment . More latterly , one study proposed that they may actually provide asensory part . But given that most females do n’t have one , it’sunlikelythat they are essential for survival of the fittest . Now , freshly gathered evidence suggests that they could wait on as a “ Hey madam , I ’m a good mate , ” sign , much like Inachis io feathers .
To make this find , a team of investigator took various body part measurements from almost 150 narwal legally kill in the Canadian Arctic between 1997 and 2008 . They discovered a significantassociationbetween manful ivory length and testes mass , which is an index of fertility rate . This indicates that the tusk may be an important factor in female mate alternative and is thus sexually selected for . Bigger tusk in all likelihood point to the female that the male is more fertile and a well mate , and would also have the added fillip of helping the male to win a fight over potential mates .
The researchers acknowledge that the tusk probably plays other use as well , such as acting as an environmental detector . However , since the correlation between testicle size and tusk duration is only honour in mature males andnot juvenile person , it seems potential that it does play an important role in mating .
alas , being well endowed also comes at a price as those with large tusk are target by hunters . This could potentiallydisturb narwhal coupling ecology , so the researchers are cutting to look into the importance of tusk duration in distaff first mate pick further .
[ ViaMarine Mammal Science , io9andScience ]
