Countershading doesn’t always work

September 19, 2014 • 1:36 pm

[JAC: There was some discussion this morning about why so many mammals have light bellies. Greg answered in the comments, but I’d also direct you to this article on countershading (yes, it’s from Wikipedia, but it’s the best I could find). Greg happens to be our resident expert on animal coloration, and decided to add a short post based on a picture he saw in the local paper.]

by Greg Mayer

As the picture below shows, countershading doesn’t always work– sometimes the hawk does spot the chipmunk.

Immature Cooper's Hawk with chipmunk in Racine, Wisconsin (photo by Diana Hawes, from Journal Times).
Immature Cooper’s Hawk with chipmunk in Racine, Wisconsin (photo by Diana Hawes, from Journal Times).

I saw this just today in my local paper. As was discussed in the comments on the latest set of readers’ wildlife photos, chipmunks being dark above and light below gives them a “flattened” aspect and makes them harder to see, but no protective coloration is perfect. There have been years when hawks nested in trees on my block quite close to my house, and mangled chipmunk remains would appear frequently below the nest. This year, I haven’t seen any hawks near the house, and chipmunks seem more common than usual.

9 thoughts on “Countershading doesn’t always work

    1. Yes! Predators looking down into the ocean depths will have a harder time to see such dorsal colouring while predators looking up will also have a similar difficulty when prey have light ventral coloration.

  1. Dawkins has several pages on countershading in “The Ancestor’s Tale”(pp 327-329 in my edition).

    Among other things, he introduces us to the upside down catfish, which has a dark belly and a whiteish back.

  2. Perhaps I’m a bit slow, but I don’t see how having a dark back and a light belly makes an animal more conspicuous from above than having a dark back and a dark belly.

    Does the light belly adsorb light from the ground, making for less visible shadow as seen from above?

    1. The countershading makes them less conspicuous from above, because they lose their 3-dimensionality (they are “flattened’).Have a look at the Wikipedia article Jerry linked to above, and you’ll see it in action.


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