Have you ever smelled a garter snake? A foul, sweetish odor permeated the screen porch and clung to my hands as we passed the small snake around. The scent is a defense mechanism that makes garter snakes less appetizing to potential predators.
The twelve middle-school kids on our field trip were not deterred, though, and the snake calmed down as we examined it. One student in particular was reluctant to pass the snake on, and watched, mesmerized, as the yellow and black creature twined around his hands, and even slithered up his sleeve.
My first clear memory of a garter snake is from fourth grade, when Clayton County Iowa Naturalist, Karen Newbern, gave a program in the school library. There, on the pea-green, low-pile carpet, the snake pooped. It reminded me of a cheeseburger.
Snake feces is a lot like other animal waste. It smells, it is often brown, and it happens as often as the animal eats. Because snakes only have a single utilitarian opening called a cloaca, their poop combines with urea from their kidneys. It is the same with bird poop, where you see the purple berry seeds mixed with white urea. This particular snake had yellow urea that looked just like melted cheese, along with a brown chunky center.
Today, as we examined the garter snake, retired zoologist and Museum volunteer, Ed Moll, reminded the kids to hold the snake carefully with two hands. Garter snakes are not constrictors, so they don’t squeeze your hands and hold on like bull snakes or fox snakes.
Constrictors have strong muscles they use to squeeze their prey to death and then eat it, but garter snakes simply seize prey in their mouth and work it down. This is where their poop starts – as a rodent, frog, slug, earthworm, leech, lizard, amphibian, ant, cricket, frog egg, or toad. Garter snakes are carnivores and generalists. They will eat almost anything they can overpower.
While their musk protects garter snakes from predators, three features of their mouths make it easier for them to be the predator. First, garter snakes have an extra bone between their skull and lower jar. That bone allows their mouth to open one hundred and eighty degrees. Second, the two halves of their lower jaw are not fused, and can move independently. Finally, their teeth point down their throat.
So, a garter snake can open up wide enough to let a toad in, then walk the critter down their throat by using one side of their jaw at a time. Then their ribs flare and their skin stretches to accommodate the breakfast bulge.
If attempting this with a live and wiggling prey sounds daunting, you may be interested to know that garter snakes (although often thought of as non-venomous) have a little venom to assist with the process. The venom is in their saliva, and seems to flow only after a bit of chewing. The mild toxin helps to stun their prey, and is not usually dangerous to humans, unless you are bitten repeatedly and develop an allergy.
After prey is in their belly, snakes will go into a dormant mode, and expend as little energy as possible on things other than digestion. Optimal digestion occurs at 86 degrees Fahrenheit, as stomach enzymes break down all but the bones, teeth and feathers of their prey. These hard parts will be excreted as waste, and evidently, sometimes look like a cheeseburger.
Despite the musky smell on Ed’s screen porch, the students sat mesmerized by the snake and its amazing adaptations. Until, that is, one parent chaperone called it a garden snake. “There is no such thing!” exclaimed Ed, breaking their trance with a good-natured shout. Hopefully that lesson will linger as long as the garter snake’s smell.