Is Bleaching Next? Whales Look at Teeth When Picking Mates

By Boonsri Dickinson | December 17, 2008 6:50 pm

beaked whaleHumans aren’t the only species that use pearly whites to judge the fitness of a mate: Apparently teeth are also important to a certain species of whales. The beaked whales have earned the reputation as the most bizarre whales in the ocean, spending the majority of their lives foraging for food and living in seclusion. For years, scientists have wondered why these strange whales have tusks, especially since it hinders their bite.

It turns out these seeming-unnecessary teeth are important for mating—a discovery that marks the first time scientists have found a secondary sexual characteristic (like antlers) that shaped evolution in a marine mammal.

The tusks, grown externally and only in males, aren’t used for eating, but are useful for scratching (and grabbing the attention) of potential mates. Interestingly, the size and appearance of these tusks varies a good deal throughout the 21 species of beaked whales.

An Australian researcher at the University of New South Wales checked the DNA of 14 beaked whale species, and created a family tree to figure what caused speciation. In contrast to previous theories that tooth shape evolved due to geographic isolation, the newest study shows that the tusks drove species separation. In other words, the males with the teeth that are the most ideal for that particular species were seen as the best mates by females.

Now for the next question: Does bad teeth give Brits an evolutionary advantage?

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MORE ABOUT: mating, sex, whales
  • neil

    a discovery that marks the first time scientists have found a secondary sexual characteristic (like antlers) that shaped evolution in a marine mammal.

    Er, walrus? Elephant seal? Sea lion? Sperm whale? Narwhal? Humpback singing?

  • Rob

    Is it a coincedence that there’s a teeth-whitening ad in the top bar as I’m looking at this article? Is this a wonderful product placement or somebody’s excellent idea for a joke? Either way, I’m very impressed.

  • Boonsri Dickinson

    Neil, the marine mammals are the beaked whales.

  • neil

    Sorry, I didn’t explain myself well.

    The point I was trying to make is that dimorphism of secondary sexual traits is well documented in a variety of marine mammals, including those I listed. These differences arise (at least in part) through sexual selection and, by definition, shape the evolution of the animal in question. However, there have been many studies into the importance of sexual selection in the evolution of marine mammals and it seems unfair/misleading not to recognize this work.

    The claim made by Dalebout et al. (2008) is subtly, but importantly, different. They state that this study documents the first known case of sexual selection driving evolutionary radiation (i.e. rampant speciation) in a “non-ungulate” mammal. I’ll leave it to those with the interest and access to Google Scholar to assess the validity of this statement.

    At any rate, it’s a very interesting paper and I don’t mean to detract from it at all. I just thought it was worth mentioning that beaked whales don’t appear to be unique among marine mammals in this regard (although perhaps they are an extreme case at least among the living fauna).

  • Erika

    I thought that a couple years ago scientists showed that the narwhal’s tusk was essentially an inside-out tooth, that they use for sensing temperature, pressure, etc. in their environment. I wasn’t aware that it was also a sexual characteristic.

    Beaked whales are interesting critters- I didn’t know they were so unusual. Too bad we don’t have more information about them.

  • neil

    @ Erika – the function of narwhal tusks continues to be debated, a sensory function is likely, however tusks are strongly sexually dimorphic being generally absent or small in females.

  • Andy B

    You made some good points there. I did a search on the topic and found most people agree with your blog.


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