Some people think that we know everything worthwhile about life on earth. Scientists know better. Not only are we ignorant about even something so basic as to how many kinds of living things there are, but we know little about a number of organisms that have been long known to science. Ord's Kangaroo Rat, one of the more common rodents in the Chihuahuan Desert today, has an enormous geographic range, extending in grasslands and deserts from southern Canada to central Mexico.
In view of the wide variety of climatic conditions met today, we'd
think the Southwestern Ice Age climate wouldn't phase it a bit. But, in fossil
deposits of the Pleistocene, this creature is rare at best, and complete absence is
common. The question becomes, what feature of its biology suppressed it? Certainly not
cold, for even the Ice-Age Southwest couldn't match today's temperatures of the
southern Canadian plains. Water availability is no problem to today's rat. One
possibility is that thick, low plant growth denied it the bare spaces it uses today.
But at best, a lot of guesswork!
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.