Male Dolphins Give Sponge Gifts to Females so They'll Have Sex With Them

A baby bottlenose dolphin swims beside his mother at the Hakkeijima Sea Paradise aquarium in Yokohama, suburban Tokyo, on July 20, 2015. Some dolphins like to give gifts to ladies who they are trying to woo. TOSHIFUMI KITAMURA/AFP/Getty Images

Like humans, dolphins have complex mating rituals. They sing, jump in the air, and now it appears that some dolphins will give sponges as gifts in order to attract a sexual partner.

In many animals, males try to display their fitness to females before mating. That can mean displaying bright feathers, building elaborate nests, croaking loudly and repetitively, and fighting other males. The gift-giving may be an indirect way of proving strength. Males only do this in the presence of sexually mature females.

After 10 years of observations, a team of marine biologists from the University of Western Australia has described repeated incidents of Australian humpback dolphins engaging in this display of sponge-gifting.

Sponges are firmly attached to the sea floor and harder to pick than a bouquet of flowers. The male dolphin, with no hands to grab the sponge, must bite down on it and swim upwards as quickly as possible to dislodge it. Sponges also have chemical defenses, making it uncomfortable for anyone trying to take them. Furthermore, a sandy sea sponge tastes about as good as you'd imagine.

Because it's so hard to gather the sponges, it appears that the more a male has, the fitter and stronger he is. After gathering one or several sponges, the male dolphin then throws the sponge to a female (or, at her), presumably to prove that his genes are the best. These signals are useful to the female, who wants to mate with the fittest male to maximize the chances that her offspring will survive long-term. Research on the different ways that male dolphins woo females was published in October in the journal Scientific Reports.

However, the sponge-gathering activity might be less of a gentle wooing and more a form of intimidation. One researcher noted that, after posing and singing to a female, one male dolphin threw his sponge at a female, in apparent frustration. Similarly, biologists believe that chimps will drag branches and throw rocks to intimidate females into mating.

Either way, it isn't clear whether or not these displays actually lead to more successful pairings. Researchers haven't yet compared how often sponge-giving dolphins have sex versus those who don't bother.

Perhaps female dolphins prefer chocolates or teddy bears, anyway.