Black-tailed Jackrabbit:  Big Ears are Good for Living in Hot Deserts!

Dr. James J. S. Johnson

For the sun is no sooner risen with a burning heat, but it withereth the grass, and the flower thereof falleth, and the grace of the fashion of it perisheth: so also shall the rich man fade away in his ways.   (James 1:11)

The sun can provide a burning heat, especially in a hot desert — such as the 3 hot deserts located in America’s Southwest  —  the Sonoran Desert, the Mojave Desert, and the Chihuahuan Desert (the last of which Big Bend National Park is part of).  Yet the Black-tailed Jackrabbit, famous for its gargantuan ears, lives in all of those deserts quite nicely.   So what about those huge ears?  Do they help it to live in hot deserts?

BLACK-TAILED  JACKRABBIT:   El Paso, Texas:  Big Bend Nat’l Park

Yes!  The jumbo-sized ears of the jackrabbit are not primarily for hearing desert noises, although the rabbits’ ears are used to hear with, of course.  Rather, the most critical importance of having huge (and relatively thin) ears, for the Black-tailed Jackrabbit, is how it providentially equips him (or her) with a heat-shedding advantage  —  a very practical trait for such desert-dwelling lagomorphs.  In short, thanks to God’s bioengineering wisdom, the Black-tailed Jackrabbit controls its body temperature by radiating out excess heat over the relatively large surface areas of its ears!

“These large, floppy-eared rabbits inhabit not only the deserts of the [American] southwest, but also large reaches of midwestern prairie. At one time it was supposed that the large ears were used to enhance their hearing ability, but it has been found that their ears perform a far more important function. Laboratory investigations on heat-stressed jackrabbits have indicated that the blood leaving the ear is significantly cooler than the blood entering the ear. During heat stress, a jackrabbit can increase ear blood flow to very high levels through expanded blood vessels. The research indicates that the large, nearly bare ears serve as efficient heat radiators! Thus, even in mid-day heat, this animal may sit in the shade of a bush with its ears erect, and radiate sufficient heat toward the cool portion of the sky (away from the sun) to prevent it from reaching uncomfortable temperatures. Studies on a number of large mammals possessing permanent horns with high blood circulation, have shown that these structures also are used for heat regulation.” [Quoting John Meyer & Kenneth Cumming, “Biology of Grand Canyon”, in GRAND CANYON: MONUMENT TO CATASTROPHE (Santee, CA: ICR, 1994), pages 158-159.]

Thankfully, those gigantic ears really take the heat off those desert jackrabbits!   ><> JJSJ

PHOTO CREDITS:

featured image of standing Black-tailed Jackrabbit: Pinterest

Black-tailed Jackrabbit at Big Bend Nat’l Park:  Fred Wasmer