Why Don’t Cactus Wrens Impale Themselves?
Excerpt from Valley 101: A Slightly Skewed Guide to Living in Arizona, a collection of Clay Thompson’s columns for The Arizona Republic. (Originally published April 30, 2003.)
Q: How is it that cactus wrens don’t impale themselves when they land on or nest in a saguaro or a cholla? Do they possess some kind of tiny body armor to protect against getting poked?
A: Randy Bapp, a biologist at the state Game and Fish Department, said every now and then, the cactus wrens do get impaled on saguaro spines or are found on the ground with a ball of cholla needles stuck in their breast.
I’m not sure why, but I find this kind of reassuring. It’s not that I like the idea of the little creatures suffering or whatever. I don’t know. I guess I just like the idea of them messing up sometimes.
However, for the most part, cactus wrens and other desert animals have learned to live with thorns. Bapp called it “behavioral and functional adaptation.”
It is, as he pointed out, the same reason a coyote can run through a patch of desert where a dog can’t go, or at least not a dog with any sense. Or why a pack rat can carry a cholla ball in its mouth without harm, or why a hawk can perch on a saguaro in perfect comfort. Actually, a hawk has leathery feet and tries to plant its toes between the spines.
And there is the matter of weight. A cactus wren, although good-sized for a wren, is light enough to perch on cactus spines without applying enough force to get impaled.
The cactus wren is a fairly interesting bird. It is, of course, our state bird, but I doubt if that means much to your average cactus wren.
It’s not like you see them wearing little bola ties or anything.