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Woodrat Midden

Neotoma sp.


Large nest made of wood and debris from surrounding area. The Woodrat lives in these nests which can be thousands of years old. "The vast majority of the materials will be from a radius of several dozen yards of the nest. Woodrats often urinate on the debris piles; sugar and other substances in the urine crystallize as it dries out, creating a material known as amberat, which under some conditions can cement the midden together. The resilience of the middens is aided by three factors. The crystallized urine dramatically slows the decay of the materials in the midden; the dry climate of the American Southwest further slows the decay; and middens that are protected from the elements under rock overhangs or in caves survive longer."


Mixed Oak forest of Daley Ranch. These are two different nests. One was on flat ground surrounded by trees. The other is on a rocky hillside also surrounded by trees. There are also nests found high up in the trees.


"A packrat midden is a debris pile constructed by a woodrat. A packrat midden may preserve the materials incorporated into it for up to 50,000 years. The middens may thus be analyzed to reconstruct their original environment, and comparisons between middens allow a record of vegetative and climate change to be built. Examinations and comparisons of pack rat middens have largely supplanted pollen records as a method of study in the regions where they are available." - Wikipedia

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Hi Seema, this home is for Woodrats only. If all of the rats were exterminated, I suppose another organism could make it home but I have yet to hear of that. Here's a great reference regarding the debrit dating scientists do from Midden's:

Seema 6 years ago

Are these twig mounds winter home of woodrats only?
I saw a few of them in Laguna coast wilderness...
Can it be of other animals too?

Oh goodness, how did I forget? Thanks for the reminder, Ava! :)

Ava T-B
Ava T-B 7 years ago

Beautiful! Please consider adding this spotting to the Animal Architecture mission at

San Diego, California, USA

Lat: 33.17, Long: -117.05

Spotted on Feb 9, 2013
Submitted on Feb 10, 2013

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