What are packrat middens and why are they important to understanding the vegetational history of Arizona
and the Southwest in general?
They are assemblages of plant remains: twigs,leaves, etc. that were collected by the pack rat Tecoma, and used in nest building. The pack rats urinate on the middens, which preserves them in the desert. They demonstrate that the modern zonation in Arizona today was not as strict as it was in the past, and that plants of cooler clines today had more southerly distribution.