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Rodent poop gauges ancient rains

Size of chinchilla pellets reveals past desert environment

IGUASSU FALLS, Brazil — The size of fecal pellets in ancient rodent middens can provide clues about the abundance of rainfall in times past, new analyses suggest.

Middens are, in essence, rodent latrines shared by a family or social group. Abandoned middens are composed of large numbers of fecal pellets cemented together by crystallized urine, reported Claudio Latorre Hidalgo, a paleoecologist at Pontificia Universidad Católica de Chile in Santiago, on August 9 at the Meeting of the Americas. Besides containing the DNA of the creatures that deposited them, the pellets contain pollen and undigested bits of plants, a trove of ecological data for the region surrounding the midden.

But new analyses by Latorre Hidalgo and his colleagues focus on nothing more than the size of the pellets. The larger the fecal pellets, the larger the creatures that deposited them, the researchers suggest, and the lusher the climate conditions at the time.

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