Paleo Slide Set: Packrat Middens: Vegetation & Climate Variability in the Southwestern United States
Neotoma cinerea, the bushy-tailed woodrat sitting on den, Chaco Canyon, New Mexico.

About the size of a laboratory rat, packrats or woodrats gather plant materials at close range 
(100 meters at most) and accumulate them in dry caves and crevices. There, the plant remains and 
other debris (including insect and vertebrate remains) are cemented into large masses of crystallized 
urine (referred to as amberat), that can persevere for tens of thousands of years. There are 20 species 
of packrats in the genus Neotoma in North America, distributed from Nicaragua to Canada. Several of these 
species produce middens in arid and semi-arid environments. 

Photo Credits:
Ken Cole 
USGS