Comment permalink

Beaked Whales: First Marine Mammal to Use Secondary Sexual Selection in Mating

The rarely seen beaked whales have scientists talking. Mostly found only as carcasses washed ashore leading to their discovery in the first place, researchers have been doing some testing pertaining to their teeth and the connection with breeding. Scientists presume that their teeth have evolved as secondary traits to help females select males of the right species. These whales are identical and the only difference in gender is teeth or tusks. Females can distinguish breed as well as gender since each breed of beaked whales has their own distinctive set of teeth and tusks.
Teeth in the beaked whales are something worth researching as it is since it is not known exactly why they have them in the first place which led to this study. A beaked whale's diet seems to mainly consist of squid making their particular tooth structure and tusks unnecessary for their survival. In some species of the beaked whale their teeth actually make it more difficult for them to eat since they can wrap around the upper jaw only allowing them to open their mouths slightly. Female beaked whales however do not show their teeth at all.
The research team on this project took DNA samples from 14 beaked whale species to create a family tree showing just how the various species had developed over time. The timeline closely showed how the female beaked whale was the deciding factor in who was going to continue family line, choosing only to mate with male beaked whales that met certain criteria. Studies showed that the female beaked whales used the shape of the teeth to select their males of the right species to mate with. It is speculated that they may also choose mates based on the size or shape of the individuals teeth or of the scars they bear.
Beaked whales, when choosing their females, will fight if needed. Through these mating battles, the males are left with massive scars marking them and giving them another distinguishing mark for females to tell them apart from the others. Scientists think that these scars are also a determining factor in the females choice in a mate as well as the shape and size of their tusks. Beaked whales that had a fair amount of scaring seemed to have a better chance at winning over the female. As most species go, only the strongest survives and the beaked whales prove no different when it comes to choosing the very best for reproduction in their line of species.
Once the family tree was laid out in a timeline for researchers to look at, the data showed that the more successful males were the ones with the shape of teeth most characteristic of that particular species ensuring that the shapes are preserved and even enhanced over evolutionary time making this a secondary sexual characteristic. This is amazing to researchers as this is the first time that secondary sexual selection has been shown to have shaped the evolution of any marine mammal on earth.