The latest Nature (Nov. 24) highlights an interesting nutritional comparison found in an article by D. B. Fenolio et al. in Proc. R. Soc. Lond. B. A Big Mac is 23% protein and 33% fat. Bat guano, on the other hand, is 54% protein and only 1 % fat. This is good news for cave salamanders, which do not have access to fast food franchises.