Bizarre teeth of male whales help females choose their mates

December 16th, 2008 - 5:21 pm ICT by ANI  

London, Dec 16 (ANI): A new research has suggested that the bizarre teeth of male beaked whales have evolved to help females choose their mates.

Beaked whales are a family of about 21 species that make up the least known group of whales or dolphins.

They are typically about four meters long and spend most of their time deep in the ocean foraging for food, surfacing rarely and briefly.

The male will need to fight with other males for access to a female group, and to be attractive to the females for them to choose him

It has been observed that the males do not seem to use the two teeth on the outside of their jaws for eating, but for scratching each other.

Now, according to a report by BBC News, scientists have used DNA analysis to show the teeth probably evolved as secondary sexual traits to help females select males of the right species.

Beaked whales are among the least known, least understood and, frankly, most bizarre whales in the ocean, said Scott Baker, associate director of the Marine Mammal Institute at Oregon State University in the US.

They are the only cetacean species with tusks, and scientists have long wondered why, since their diet primarily is squid, he added.

The shape of the teeth, or tusks, varies markedly between different species.

In some, they actually appear to hinder feeding, as they wrap over the upper jaw, preventing it from opening fully.

Females do not show teeth; and this difference between the sexes, or sexual dimorphism, is virtually the only way to tell them apart.

The research team took DNA samples from 14 beaked whale species and used it to construct a family tree depicting how the various species had developed.

One of the theories of beaked whale evolution is that different groups emerged in ocean canyons that were more or less isolated from the wider oceans, and that this pattern of evolution was responsible for different shapes of tooth.

But, the genetic work suggests this is unlikely.

It turns out that tusks are largely an ornamental trait that became a driver in species separation, said Dr Baker. The tusks help females identify males within their species, which could otherwise be difficult as these species are quite similar to each other in shape and coloration, he added.

So, females use the shape of the teeth to select males of the right species to mate with. They may also choose mates based on the size or shape of the individuals teeth or of the scars they bear. (ANI)

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