Caption A captive desert woodrat, also known as a packrat, stands on a rock near branches from a toxic creosote bush. A new University of Utah study shows how microbes in the gut play a key role ...

When climate warming eliminated juniper trees from what is now the Mojave Desert between 18,700 and 10,000 years ago, packrats there had to eat much more toxic creosote bushes, which replaced juniper.