For a person, life as a pack rat is one of obsessively collecting, say, newspapers, computer parts, food containers, or maybe all of these. But a literal pack rat gathers plant fragments, bone bits, fecal pellets, and even, occasionally, eyewear.
"A friend of mine lost his glasses to a pack rat," says Kenneth Cole of the U.S. Geological Survey in Flagstaff, Ariz. In the September Geology, Cole and a colleague report that pack rats' fossilized collections, secreted away for millennia in caves and rocky overhangs, can improve the portrait of global temperatures at the end of the last ice age.
Known as the Younger Dryas, this portion of the ice age lasted from about 12,900 to 11,600 years ago. Temperatures in Europe, Greenland, and the North Atlantic Ocean during this time averaged 10°C below today's average temperatures. Scientists have relied on many lines of evidence to reconstruct climate trends. Layers of ice and sea sediment, for example, indicate preci