Male bottlenose dolphins in Australia have been found to offer large, opulent sea sponges to females, possibly as love tokens.
A male bottlenose dolphin pushes a large sponge toward a female. [Photo by Simon Allen]
Human males may offer a bouquet of flowers or a box of chocolates to their object of affection, and it turns out that bottlenose dolphins may not be too different from us. Researchers have spent 10 years observing Australia’s bottlenose dolphins present large sea sponges to females--a behavior that may be part of a courtship ritual. It has long been known that dolphins use sea sponges as tools to forage for food, but this was the first time that they’ve been observed to proffer the sponges to the females of their species.
Of course, the possibility that these dolphins were trying to impress the opposite sex wasn’t what’s surprising. “A display to impress a female is not unusual, but using an object in that display is very unusual,” says Simon Allen, one of the researchers in a study detailing the curious behavior.
Bottlenose dolphins are known for using sponges as protection against injury while foraging, as shown by the young female above. [Photo by Ewa Krzyszczyk]
Though humans are known to bring forth love tokens in courtship, the same behavior is unheard of among non-human mammals. And yet, here are dolphins doing something quite similar to how humans court potential mates.
Tool use is a well-known ability among cetaceans, but it has only been observed in situations involving foraging for food. The bottlenose dolphins in Australia’s Shark Bay, in particular, are known to use sponges to protect their beaks from injury as they forage for food on the rocky seafloor. Thus, this makes this new discovery quite interesting. Are dolphins capable of using tools for purposes outside of searching for food?
Allen and his colleagues managed to observe 17 instances of male bottlenose dolphins offering possible love tokens to members of the opposite sex. The behavior occurred in five different pods, and the objects of affection were sexually mature females who have already had calves that were of weaning age. Thus, these females were usually ones that were ready to mate again.
However, the researchers still aren’t certain that this is indeed a courtship ritual, especially since they don’t know how the females react to the offerings. They want to observe the courtship process underwater to get more information. Also, the researchers aim to do DNA testing on dolphin calves to see if males that used love tokens were more successful at mating.
A male striking the enigmatic banana pose [Photo by Simon Allen]
According to the researchers, this behavior is also associated with what they call the “banana pose”. To strike this pose, a male will arch his back, putting his head and tail above the surface of the water. Researchers still don’t actually know why male dolphins pose this way in the vicinity of the female. “We don’t yet know what he’s doing—whether he’s flexing or sporting an erect penis, we have no idea,” Allen relates. “But sometimes he’s just lying there for a while posing near the female, and at other times moving along in the water just behind her.”
If anything, this tells us that dolphins have a rich world that we’re only just starting to understand. The use of sponges as love tokens may just be the tip of the dolphin beak.
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