Of packrat poop, creosote bush and juniper-fed lamb

Scientists find that gut bacteria can help animals digest toxic plants.


How can herbivores survive munching on poisonous plants? A new study helps prove something that scientists have long suspected -- that it’s not just enzymes in an animal's liver that break down toxic compounds in plants, but that bacteria in its guts also play a major role.

As an aside, if you’re wondering why an animal would deliberately eat a naturally toxic plant, that happens for several reasons – perhaps the plant contains a lot of nutrients, or it tastes good, or both (for example, larkspur and locoweed, which plague Western cattle growers). Or maybe better-quality forage isn’t available and the animal is desperate.

The new University of Utah study focused on the woodrat (Neotoma lepida, also called packrat), found in Western deserts. In desert areas where creosote bushes grow, the bushy-tailed rodents eat it and thrive, despite a toxic resin in the leaves that can cause kidney cysts and cancer. Apparently the creatures acquired this talent some 17,000 years ago, according to a press release about the study:

“In a natural climatic event at the end of the last glacial period, the Southwest dried out and our major deserts were formed,” the study’s senior author, Denise Dearing, professor and chair of biology, says. Creosote, which was native to Mexico, moved north into the Mojave Desert and replaced juniper there, but did not go farther north into Great Basin deserts. Desert woodrats in the Mojave started eating creosote bushes, while desert woodrats in the Great Basin kept eating toxic juniper, to which they had adapted earlier."

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