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10-year study suggests male dolphins charm females with gifts

Only the big male dolphins put on this show

(CNN) - Romance isn't dead yet -- at least not in waters off the western coast of Australia.

Scientists have recently observed humpback male dolphins in the region presenting females with large marine sponges in the hope of impressing them.

They also observed male humpback dolphins acting as "wingmen" for each other-- this type of male cooperation is unusual in dolphins given that paternity can't be shared.

This is the first time this level of social complexity has been observed in dolphins.

Not just foraging

While previous research has shown bottle-nose dolphins using sponges and sometimes shells as foraging tools, this was clearly different.

"This is a sexual display involving object carrying by humpback dolphins," said Simon Allen, the lead author of a study on the phenomenon that was released last month.

The research was carried out across the north-western Australian coastline, with sites in Coral Bay, the North West Cape, Dampier Archipelago, Cygnet Bay and Cone Bay.

"This is incredibly rare in mammals, except of course, in our own species," Allen, from the University of Western Australia, told CNN.

There are three possible reasons for this behavior, he said: "It's gift giving, it's a signal of his fitness (so) quality as a mate, or it's a threat to coerce her into mating with him."

Big boys only

Only the big male dolphins put on this show, and almost always, it's for the benefit of the female dolphins.

In their decade long study, published in the journal Scientific Reports, researchers from the University of Western Australia, the University of Zurich and Murdoch University recorded sponge presentation, and sometimes, tossing the sponge towards the female.

Some male dolphins even adopt the "banana pose," whereby a big male will lie at the water surface with his head and tail arched up -- almost as if he is flexing his muscles.

An essential for any good first date, the male dolphin might also provide music: a kind of trumpeting "toot!" sound out of his blowhole.

Friendship first

Some big males will even pair up with a friend, acting as a wingman of sorts, helping each other out when it comes to social interactions.

The pairing might try to secure the affections of the female, to prevent her from escaping their attentions, beat up on other males, or even defend the female against a potential attack from other males.

"The formation of alliances between adult males for the purposes of coercing females is uncommon, since mating success cannot be shared," said co-author Stephanie King, a Research Fellow at the Centre for Evolutionary Biology, University of Western Australia. The only other species that form alliances for mating purposes are lions and a few other primates.

Previous research conducted on the bottle-nose dolphins of Shark Bay indicates "these male alliances are generally very tight units, and even when they are following a female, they spend most of their time petting and touching each other, reinforcing that love is love, no matter what the sex or the species," said Allen. This is the first time a similar bond was seen between humpback males as well.

Less is known about such behavior in humpback dolphins, but the team hopes to research this further.

Allen also said the team would next like to collect biopsy samples in order to assess paternity success, to partly answer the question of whether courting behavior by male dolphins actually works.

Dolphins are thought to be one of the globe's smartest species, possibly even having developed their own spoken language. This study suggests they might be the most romantic too.


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