WHAT TO EAT?


Garter snake eating toad-1

Gartersnake attempting to feed on an American Toad

All Snakes Are Carnivores

Not many tetrapods are completely carnivorous. Hawks and owls certainly are, and adult frogs and most weasels are, too. But many animals we think of as “carnivores," including bears, coyotes and raccoons, are actually omnivoresthey eat a lot of plant material, from stems and leaves to fruits and their seeds. 

Snakes are obligate carnivores—they survive only by eating other animals. Plant material found inside snake stomachs is thought to have been ingested accidentally, but more research is needed. Like raptors, prey taken by snakes depends on the snake species (including individual age and sex) and also on food availability. You might imagine that the lack of limbs could put snakes at a disadvantage when hunting; however, magnificent adaptations in morphology (especially of the skull and jaws) and behavioral adaptations have given snakes a wide repertoire of feeding mechanisms.

There are three basic evolutionary pathways to procuring a meal: grab-and-swallow, constriction, and venom injection. Examples of all three methods are found in various Western Massachusetts snakes. 


Grab and Swallow Snakes     Constricting Snakes          Venomous Snakes


Gartersnake                  Milksnake                Copperhead

Ribbonsnake                 Eastern Ratsnake     Timber Rattlesnake

Wormsnake                                

Greensnake

Red-bellied

Ring-necked 

Racer (sometimes will “pin” their prey with a loop of their body)

Dekay’s

Hog-nosed (with a delightful hint of venom to their saliva)

Watersnake


Consider the food items taken by each feeding type. The grab-and-swallow snakes eat mostly small, soft-bodied prey, from insect larvae and other invertebrates to adult amphibians. Constricting snakes are able to eat larger vertebrates, from other snakes to squirrels. Of course, they can grab their prey, loop coils around it, hold on until its demise, and then eat it. A chipmunk rarely sits still for this and it’s possible it could break free or even injure the snake in the process. Venom may be the most recently evolved adaptation, allowing snakes to take medium to large vertebrates and, at the same time, minimize contact with struggling, and potentially dangerous, prey.

Some snakes are active hunters. Many feed at night, others in daylight. Thanks to a lot of study in recent years, we’ve seen Timber Rattlesnakes use a “sit-and-wait” strategy, taking advantage of the fact that small mammals use logs as elevated (and quiet) runways through the forest floor. The snakes (presumably) choose a log actively used by small mammals and rest their chins, awaiting the pitter-patter of tiny feet. They just have to strike accurately from their ambush posture and pick up the food at the end of the log. A clever twist on a drive-thru restaurant model; sort of.

There are ample examples of people having toxic reactions from the bite of “harmless” or non-venomous snakes. Over the years I have met a few people who have experienced slight discomfort, minimal swelling, or a skin reaction to some of our local species (particularly Gartersnakes). The first widespread discussion of this topic came from herpetologist Sherman A. Minton in his article Beware:Nonpoisonous Snakes published in Natural History magazine in 1978. See if you can get a copy from your local library. More detail is offered in a recent book “Venomous Bites from Non-Venomous Snakes” that summarizes data from around the world. Another reason to suggest watching snakes: it’s better than catching snakes!

© Tom Tyning 2013