Collecting Fossils from Harvester Ant Mounds

Abstract

Fossilized remains of small vertebrates, seeds, and other items of paleontological or anthropological interest have been gathered for many years from mounds made by harvester ants. The methods of collecting these specimens have ranged from picking the individual specimens, one by one, from the surface of a mound to shoveling the complete mound, including the ants, into a container and subsequently separating the desired specimens from the collected mass of twigs, rocks, ants, silt, and other debris. Certain objections to these two extremes in collecting methods prompted me to devise a method that would recover most of the fossils from a mound with a minimum of time, labor, and expense, while preserving the ant colony as a source of future fossils. By collecting and keeping separate the component parts of several mounds, I learned that practically all of the fossilized material occurred in the one-halfto one-inch-thick outer layer of the mound' and in a surrounding zone where wind and rain leave bone fragments and silt eroded from the cone. Consequently, by using a small hand-scoop with a flat lip, it is possible to skim off the surface of the mound and the surrounding area and have most of the fossils concentrated in less than one-half cubic foot of silt and matrix.