Wednesday, April 4, 2007

Bottlenose Dolphins in New Zealand Displays Unique Rituals for Mating

Species of bottlenose dolphins in New Zealand displays unique sexual rituals.

They may be the gentlemen of the sea.A small group of male bottlenose dolphins in waters off the southern tip of New Zealand has been found to take a unique, more egalitarian approach to wooing prospective mates. David Lusseau, a socio-ecologist at Dalhousie University in Halifax, discovered after two years of studying the population that the male dolphins allowed the females to choose their sexual partners, unlike many other dolphin species that coerce them into sex."There's a greater choice for females to actually select their mates and the males have to compete by sticking close to these females," he said Tuesday, a day before his findings were published in the scientific journal PLoS ONE."It opens new avenues of thinking about the full extent of the benefits of having complex social relationships in males."Lusseau tracked the population of about 65 dolphins in Doubtful Sound, New Zealand, from 1999 to 2001, spending more than 600 hours watching them and trying to qualify their sexual practices and social networks.By observing them from a boat and underwater with cameras, he identified all 65 dolphins and could monitor their behaviour as they began their mating rituals.He found that like other bottlenose dolphins, these ones fought amongst themselves to win over female partners, but unlike similar dolphins in Florida and Australia, they refrained from forcing the females to have sex.The discovery led to a broader understanding of the mammalian species that is thought to have highly sophisticated social relationships similar to humans.Lusseau said this population differed greatly from other groupings because they formed alliances with other males but with no immediate, short-term benefit. For example, male dolphins usually form coalitions with other dolphins because they need help in overpowering a sexual partner or fending off male rivals.But in this case, there is no upfront benefit because they are not using other males to coerce females into sex."The underlying implication is that there is some benefit to forming a group," he said. "The long-term benefit might be the maintenance of a group of males and having that social cohesion."Lusseau, who has worked with dolphins since 1991, said the research indicates the animals might seek a sort of companionship for the sake of belonging to a group that can be relied on for a variety of tasks."What we see is the formation of these bands and the maintenance of that social cohesion but without that short-term benefits," he said. "And from what we know of the social interactions in males, this should not be and flies in the face of 20 years of sociobiology."The scientist said it's not clear why the bottlenose dolphins differ in their sexual practices or why they form tight social networks, but he speculates there could be something in their environment that has resulted in these behavioural traits.Source:

No comments: