How does a lizard go vegetarian? By growing its gut

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How does a lizard go vegetarian? By growing its gut

“Eat your greens. They won’t kill you!” That’s good advice for human children, but what about for lizards? Plants are full of hard-to-digest fiber and low in protein, and only 4% of lizards and snakes are full-on herbivores. So scientists have wondered whether it’s even possible for most lizards to go veg. To find out, researchers took a lizard that usually has a balanced diet of insects and plants, Ruibal’s tree iguana (Liolaemus ruibali, closely related species pictured), and raised it on a diet of almost all alfalfa-based rabbit chow instead. Forty days in, those vegetarian iguanas managed to keep the same weight as iguanas given a balanced diet. Dissections revealed a possible reason: Vegetarians’ small intestines had grown 17% longer. Plus, their guts harbored a more diverse community of microbes than lizards on the typical diet, including higher numbers of a few microbe groups suspected to break down fiber, the team reports today in the Journal of Experimental Biology. Together, these two adjustments probably help vegetarians make the most of a bad situation by keeping food in their guts longer, and ramping up the speed at which they break down and absorb food. Lizards, it seems, are more flexible in their diets than some scientists give them credit for. If only the same were true of picky kids.