Several species of shrews inhabit the Chihuahuan Desert Region, though all but one kind are limited to the relatively moist and cool highlands. All shrews, lowland or highland, have in common their small size and a voracious appetite for their animal prey. These two characteristics are not unrelated. An important principle in science is that as size increases, volume increases more rapidly than surface area; and, of course, the opposite is true: as size decreases, the relative amount of surface area increases. This has profound biological effects for warm-blooded creatures such as birds and mammals. When there is a relatively large surface through which to lose body heat, the rate at which fuel is burned has to be much higher than in larger animals.
In shrews, among the smallest of mammals, food is consumed at such a
rate that death from starvation can occur within a day or less. Needless to say,
stoking the furnace requires herculean effort. Tyrannosaurus rex as a super predator?
Forget it—ounce for ounce, a shrew puts that icon of terror to shame.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.