Hundreds of thousands of individual bones lie in one ice-age fossil deposit within Dry Cave, west of Carlsbad, New Mexico. The natural reaction of students is that animals must have been more plentiful than today. This, though, ignores several things.
For one, each individual animal contains many bones, so the number of
individuals is far fewer than the number of bones. Also, in cave faunas, often many
animals have been brought to the site as stomach contents of owls; owls that famously
regurgitate the fur and bones of their prey. Thus often the smaller creatures have been
collected over some square miles and deposited in a few square meters. A third factor
is tremendously important and difficult to estimate. That is, over what span of time
did the remains accumulate? Ten thousand animals is a lot of animals—but if
deposited over a thousand years, averages out to only 10 animals being deposited each
year. Just a few nights a year of owl regurgitation may well be commemorated by what
appears to be a vast killing field.
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.