Your article reminded me that taking a bird’s song and transposing it down four octaves makes it sound like a whale’s song. The opposite is also true. To hear this, go to http://www.mind.net/music/birdwhaleDemo.mp3.

Todd Barton
Ashland, Ore
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The article would imply that the only anomaly to the theory that mass equates to longevity is that large-dog breeds live shorter lives than small ones do. I would suggest that there are many more discrepancies. For example, humans outlive elephants, horses, and cows, and tortoises outliving humans. And amoebas outlive us all.

McClellan Blair
Indiana, Pa
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This is tremendously interesting. The scaling law is evidently expressible in a single formula. Why not present it?

Patrick J. Roache
Socorro, N.M.

Here’s the equation , I = i0 M 3/4 e –E/kT . I is an individual’s metabolic rate , i0 is a normalization constant , M is mass , E is the activation energy , k is Boltzmann’s constant, and T is body temperature in kelvins .—E. Klarreich