Paleo Slide Set: Packrat Middens: Vegetation & Climate Variability in the Southwestern United States
Paul Martin, University of Arizona, next to Pleistocene midden.

In 1960, lack of knowledge about former plant distributions in North American deserts was reversed by 
the discovery of plant-rich deposits or middens in caves and rock shelters in the arid interior of North 
America. These so-called middens, an amalgamation of plant and animal remains encased in crystallized packrat 
(Neotoma spp.) urine, were noted by military and scientific expeditions across the West as early as 1849. But, 
it was not until 1960 that paleoecologists fully recognized their potential for reconstructing past environmental change. 

Photo Credits:
W.G. Spaulding