The cave-dwelling grotto salamander, Eurycea spelaea, lives in Oklahoma and likes to eat poop. Coincidence? Well… yeah, probably.
We typically think of poop-eating as a big no-no. We yell at the dog for doing it and consider it a sign of mental illness or college fraternity membership in people. However, coprophagy, the fancy scientific word for this curious behavior, is commonly observed in nature. One reason that animals ingest their own feces or the feces of others is to extract nutrients from it that were not absorbed during the first round of digestion. Some animals produce fairly nutritious waste because they have inefficient digestive systems.
Bats are a good example. Bats have adaptations that reduce their energy consumption during flight. These adaptations include weight-saving features like a short digestive tract that passes food through quickly. Bat poop, known as guano, is rich in nitrogen, phosphorus, other important nutrients, and calories. Guano is used as fertilizer by humans and provides nutritious, if not delicious, sustenance for many cave-dwelling organisms.
Cave-dwelling critters live in places where “normal” sources of food are often scarce. Caves are typically isolated from the energy and nutrient cycles of the surface world, which rely on sunlight and plant growth to keep things rolling. Cave-dwelling species exist in habitats that are lightless wastelands compared to those above ground. But where there are bats, there are piles of guano. Impressive mounds of the stuff build up beneath bat roosts. So if you are an animal living in a wasteland, you might as well make use of all that waste…
Back to our salamander, Eurycea spelaea (my best guess at the pronunciation is YOO-rih-SAY-uh speh-LEE-uh). It was recently reported that the aquatic larvae of this species, which live in subterranean streams, slurp up guano that drops into the water (Fenolio et al 2005). The biologists who made this discovery also analyzed guano for its nutritional content. It turns out that guano packs about as much nutritional and caloric punch as a McDonald’s Big Mac hamburger (the analysis literally compared samples of guano to samples of Big Macs! So don’t be surprised if the next time you roll into Micky D’s you see the Crispy McBat-turd Sandwich on the menu. I’m lovin’ it!).
This is the first well-documented case of an amphibian that is coprophagous. Salamanders are normally carnivorous, so biologists have presumed that cave-dwellers like Eurycea spelaea munch strictly on the invertebrates that skitter around in caves. It seems that larval Eurycea spelaea skip down a trophic level and go straight to the primary energy source available in their habitat. It remains uncertain whether adult salamanders also partake of the poo, although it seems possible. Fenolio et al (2005) note that coprophagy may be more common among cave-dwelling vertebrates than previously thought. So there might be more poop-eaters out there than anyone ever could have possibly imagined in their wildest, most ludicrous dreams. Oh, the wonders of nature.