This species of "packrat" is nicknamed for its habit of gathering wood, cactus parts, stones, cow dung, bones, beer cans, candy wrappers - just about every movable object in the vicinity - to build its large nest. Woodrat collections provide us with an important window into the past. Preserved inside ancient nests found in the desert are acorns, pine sticks, and other items which suggest a cooler, wetter climate. Using carbon dating, scientists have determined that 10,000 years ago areas such as Tonto National Monument were covered by oak woodlands. As the climate gradually grew warmer and dryer, woodrats began filling their nests with cacti and other desert plants we find today.