Tests revise image of kangaroo rats

The textbook case of how to survive in a desert may have important details wrong, according to new studies of kangaroo rats.

Species in the genus Dipodomys, nocturnal rodents that scurry through North America’s deserts, have epitomized toughness in punishing climates, says Randall Tracy of the University of Connecticut in Storrs. Earlier researchers, he says, marveled at how the creatures apparently got water by metabolizing seeds and avoided overheating by staying in cool burrows until late at night.

In an upcoming issue of Oecologia, Tracy and Glenn E. Walsberg from Arizona State University in Tempe challenge those views. They made their observations near Yuma, Ariz., in the Sonoran desert.

The animals’ burrows get hotter than expected, the researchers found. For more than 100 days of the year, soil temperatures rose to over 30C at depths of 2 meters.

Yet during most of the summer, the kangaroo rats remained less than a meter deep, where it’s about 35C. Nor did the animals emerge only in the cool part of night; they ventured above ground right after sundown. Also, forget the seeds-only menu. The rodents ate a considerable amount of green plant tissue, presumably a substantial water source during tough times.


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Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.