Why whales get no bigger

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Carl Zimmer reports that it might be a function of physics. Bigger whales have proportionality bigger mouths, but at some point the biological engineering runs up against constraints:

s they report today in the Proceedings of the Royal Society, Goldbogen and his colleagues found that big fin whales are not just scaled-up versions of little fin whales. Instead, as their bodies get bigger, their mouths get much bigger. Small fin whales can swallow up about 90% of their own body weight. Very big ones can gulp 160%. In other words, big fin whales need more and more energy to handle the bigger slugs of water they gulp. As their body increases in size, the energy their bodies demand rises faster than the extra energy they can get from their food.

If the scientists are right, they may have discovered one of the big ironies in evolution. Lunge-feeding may have allowed whales to become the biggest animals ever to roam the planet. But this was not an open-ended invitation. Once whales got large enough, lunge feeding itself became so costly it prevented them from getting any bigger. Perhaps some day another animal will evolve a new strategy that will let it get even bigger than a blue whale. But for the animal kingdom as we know it, we may be sharing the planet with the biggest species it can offer.

Given enough time and a large population one can imagine that evolution might be able to figure out a solution, or back out of the adaptive dead end.

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  1. I find this argument difficult.  
    Anyway, there has also been question about why very large animals dont suffer more from cancer. Armand Leroi considers this a serious paradox and in commented in Nature News about someone’s theoretic paper on the subject. I’m not sure I believe the theory. I wonder if whales dont just form fewer significant tumors in the first place, by just spending more energy day by day on antitumor defense. But its hard to see how you would find out; youre not going to MRI a blue whale.

  2. I sneer at the tiny whales.

  3. That reminds me of something I heard about relatively short falls being very dangerous for elephants. It’s an inverse of the jumping ability of fleas. Nature is not scale invariant. 
    I didn’t know there were giant lobster. They should use that for a horror movie.

  4. Just another example of the square-cube law. 
    As for cancer, calculate the effect of adding a couple of extra tumor suppressor genes. Works in Down’s.

  5. Obligatory link to the all-time classic on the subject. For the two or three people on Earth who might not have read it yet. 
    Also, I believe “scaling laws” is the general term. Of course, square-cube laws, which point out that volume and mass necessarily grow faster than area (with all kinds of biomechanical/evolutionary consequences), are by far the most common example.