Forget a bouquet of flowers or box of chocolates, it seems sea sponges are all the rage amongst West Australian male dolphins looking for a possible mate.
University of Western Australia researchers have captured unusual evidence of adult male Australian humpback dolphins offering "gifts" to their female counterparts, in an apparent effort to convince them to mate.
The study observed an interaction between a male, female and her calf off the WA coast where the potential dating technique was used.
"The male dolphin dived down to remove a large marine sponge fixed to the seafloor, balanced it on his beak and pushed it toward the female," the report said.
The study's lead author doctor Simon Allen told Radio 6PR's Simon Beaumont he'd been documenting dolphin behaviour in the wild for nearly ten years and the behaviour has never been documented before.
"As we know, boys tend to like girls in the dolphin world, in the wild animal world it's about getting as many mating opportunities as possible," he said.
"We were working off north-west Australia when we saw this unusual behaviour. What we've been seeing is sponge presentation and it turned out to be only adult male dolphins towards female dolphins.
"Here we have some of the most socially complex animals on the planet using sponges, not as a foraging tool, but as a gift, a display of his quality, or perhaps even as a threat in the behavioural contexts of socialising and mating."
But before the men of WA go out diving for some sea sponges, Dr Allen said it didn't seem female dolphins were particularly fazed by the gift.
"They were generally ignored," he said.
"In one context you could understand the apparent frustration of the males - unrequited love often results in frustration.
"In this case, when he was being ignored, he tossed the sponge in the direction of the female."
Dr Allen said sea sponges were often difficult to dig out of the sea floor and some could sting.
"So essentially the response is - 'I've got this big stinging thing and if you ignore me, I'm going to throw it at you'," he said.
It's not the first time WA dolphins have led the way, with researchers in the Peel-Harvey coastal waters noting another unusual behaviour from its local dolphin population earlier this year.
Murdoch University researcher Krista Nicholson said it seemed the dolphins could have been using blowfish in order to get "high".
She said in Australia, scientists had seen juveniles mouthing blowies in the Leschenault estuary in WA's South West and a sub-adult dolphin carrying an inflated blowie for a few hours in the Kimberley.
Blowies have a lethal toxin called tetrodotoxin, present in their skin, flesh and internal organs, and WA dolphins have been observed chewing on a blowie and "passing the puffer fish around".
Other research by Dr Allen has also found dolphins in the Pilbara deliberately seek out and follow fishing trawlers for days, weeks or even years hoping for a free meal.
