How Snakes Find, Capture, And Swallow Their Prey

Hello Friends,

Spring is upon us and wildlife is beginning or already has begun to be come active. One group of animals in particular that are enjoying the warm weather are snakes! Snakes are reptiles that are commonly misunderstood and feared. Learning more about them can help get people pass the fear and even gain an appreciation for them. We are about to learn some really cool things about snakes that are just few of the many reasons why I love them!

For starters, snakes are animals that are completely lacking in arms and legs, and yet they manage to survive quite well with out them. Have you ever wondered how snakes even find, capture and swallow their prey? Well, you are about to find out...

E. Cottonmouth attempting to eat a ribbon snake. Photo by ME. 

So, What Do Snakes Eat?

Well, snakes are carnivorous, which means they prey on other animals. A neat thing about snakes is that some species of snakes' diets are different from others. In fact, some snakes are what scientists call Specialists, which according to Michael Dorcas and Whit Gibbon's book, Snakes of The Southeast, are snakes that "focus on one or a few prey types." In other words, they dine on specific prey items.

One such example is the Eastern Hognose, which primarily eats toads. The neat thing about them is that they use the pointed end of their nose (hence the name) to occasionally dig up such prey items.

Eastern Hognose Snake. Photo by ME

Another example of a specialist is the Rough Green Snake. This species primarily eats insects and spiders, though they will take a treefrog from time-to-time. (Dorcas and Gibbons)
So not all snakes eat rodents.

Pictured below is a Rough Green Snake. Photos by ME.

            

In addition to snakes that specialize in a specific prey item to eat, there are also snakes that are called Generalists. Such snakes "eat a wide variety of animals..." (Dorcas and Gibbons).

One example of a generalist is the Eastern Kingsnake. These snakes are commonly known for eating other snakes; even venomous ones. Though they will occasionally do that, they mostly eat small rodents, small turtles, and eggs, among other critters.

Kingnsnake eating another snake. Photo from internet, taken by Pierson Hill.

Another example of a generalist is the Northern Water Snake. Now these snakes will go after small rodents on the occasion as well as insects, but these snakes also "eat a greater variety of fish and amphibians than any other North American snake." (Dorcas and Gibbons). In addition to being active foragers, northern watersnakes will wedge themselves among rocks and move back and forth with the mouth open ready to catch unsuspecting fish, and they sometimes corral fish in shallow water with a body coil. All prey items are swallowed alive." (Dorcas and Gibbons)

How cool is that?

N. Water Snake eating fish. Photo from Internet

Now that we have an idea of what snakes eat, the next question we will take a look at is, How Do Snakes Find Food?

Well, snakes primarily find their food through use of sight, scent, and for some species, heat sensing pits. In regards to hearing, snakes have very poor, to little hearing so that is not a factor in finding prey. As far as I know.
Some snakes, such as Black Racers are known for having excellent vision and use this to their advantage to find food. (Dorcas and Gibbons)

Black Racer. Photo by ME.

In regards to scent, this is a very important sense that snakes rely on to find food. You may be wondering how a snake exactly is able smell? What a snake does is flick its tongue, which gathers odor elements from the environment and is sent up into the root of the mouth to be identified by what is called the Jacobson's Organ.

A rough sketch by me showing you where the Jacobson's Organ is located on a snake. 

Below is an Eastern Garter Snake flickering its tongue to pick up odor elements from its environment.

Eastern Garter Snake. Photo by ME.

So, sight and scent are important in helping a snake find its prey. There are some snakes that in addition to sight and scent, also have heat sensing pits. Some( I say "some" because Emerald Tree Boas among some other snakes have labial pits and are not considered pit vipers.) of these snakes are called Pit Vipers; which includes Copperheads, Cottonmouths, and Rattlesnakes.

These pits are located on both sides of the pit viper's head; in between the eyes and nostrils.

According to David Badger's book, Snakes, "Each pit have 2 chambers; separated by a thin membrane equipped with nerve endings. The nerves in this membrane are extraordinarily sensitive to the slightest change in temperature." The snakes that have pits, uses them to detect the body heat from any potential mammalian prey.  It's awesome!

Pictured below is a Tropical Rattlesnake and if you look closely, you can see one of its pits. It is the "hole" between the eye and nostril.

A rough sketch by me showing where the heat-sensing pit is located on a pit viper.

Can you find the pit on the snake below?

Photo by ME

As you can see, snakes have the means to find food, now the question is, How Do Snakes Capture Prey?

Snakes are just about as diverse in their methods of capturing prey as their diets. Often times, people think of boa constrictors constricting a capybara or some kind of large prey item.  Constriction is one way many snakes captures, kills, and swallows their prey for sure. The snake will strike at prey item, wrap its body around it and then constricts until the prey is dead.
Kingsnakes constrict their prey; even other snakes! Rat Snakes are also constrictors and will constrict a variety of prey items, which makes them generalists. What's neat about them ( and Corn Snakes too) is that they are good climbers and will climb up into trees for bird eggs and even birds if they get the chance to capture one.

Black Rat Snake climbing. Photo by ME.

Another method, once the prey item is found, is to strike, hold and then swallow, in some instances, swallowing the prey alive. Black racers are an example of this, as they track down their prey and strike it, followed by swallowing it.

Along with this method, many snakes employ the technique of ambush. We have already learned about how northern water snakes will sometimes ambush and even corral fish. Rough greens will ambush and then grab, hold, and swallow prey.

A really cool method of ambushing prey some snakes use, is by luring them in. Such examples of this is by neonate (baby) Copperheads and Cottonmouths. These neonates "wiggle a brightly colored tail tip to attract potential prey, such as frogs or lizards, within striking range." (Dorcas and Gibbons)
They do inject venom into their prey, which kills it and then the snakes tracks their prey down. I will write more about venom in a bit. Anyway, these tails are a greenish to yellow color and will fade and get darker as they get older.




Neonate Copperhead. Note the yellow tail. Photo from Internet.

Ok, now onto to venom. As I talked a little bit about pit vipers and the pits early on, these snakes use the pits to pick up the body heat from mammals to find them. Sometimes, they will simply pick up the mammal's body heat and find a place where the prey frequents and will lie in wait to ambush prey. As for venomous snakes that do not have pits, they will usually forage for food or wait until something comes by. Coral snakes grab their prey and chew on it, and releases venom until the venom takes a hold. (Dorcas and Gibbons)

Eastern Copperhead eating a Cicada. Photo by ME. 

There are some snakes that are what scientists call rear-fanged, which means they have fangs in the back of their mouth. As far as I know, only 2 species of rear-fanged snakes are known to be dangerous to people, but a bite from other species can cause unpleasant symptoms too. An example of a rear-fanged snake is the Eastern Hognose Snake we learned about earlier in the blog. Toads, their main prey item, in defense, will puff themselves up in order to look bigger and tougher. Hognose snakes will grab on the toad and "deflate" the toad using the fangs, and perhaps release a mild venom to subdue the toad. Hognose snakes are considered harmless as they rarely, if ever, bite and their fangs are in the back of their mouth.


As you can see snakes have different methods in finding and capturing their food. It is so cool how animals without limbs can be so diverse in surviving! Now we will learn about something even neater about them; How Do Snakes Swallow Their Food?

It is even more amazing how animals lacking limbs can still manage to eat. According to Harry W. Green's book, Snakes: The Evolution of Mystery in Nature, in regards to eating:"Most snakes engulf prey with alternating, side-to-side head movements, made possibly by mandibular liberation, free-swinging quadrates and highly mobile upper jaws." In other words, snakes have expandable jaws that allow them to adjust accordingly so they can grab and swallow large prey items. During the swallowing process, they grab a hold of the prey item with their teeth and then they "walk" their heads over and around it and then they begin to swallow.

Emerald Tree Boa Swallowing a prey item. Note: The Labial Pits around the face. Photo by ME.

Then, "once the prey has entered the throat, peristaltic contractions of the esophagus and sinuous curves in the trunk push it backward to the snake's stomach." (Greene)
Greene also goes on to say that "Snakes lack shoulder girdles and a sternum, the ends of their ribs are separated ventrally, and large food items can pass unobstructed."
On top of that, once the prey item is swallowed, their are some enzymes in the stomach that immediately start breaking the prey item down.

Pretty cool stuff! Of course, during the swallowing process, you may wonder, can the snake still breathe? If so, how?

Let's find out...

Well, first off, snakes, unlike many other terrestrial animals, their windpipe, called the trachea, opens up anteriorly; rather than far back in the throat. (Greene)  Also, snakes have a snorkel-type thing near their tongues called a glottis. Chris Mattison, author of the book The Encyclopedia of Snakes, writes about how it ( the glottis) is " pushed forward and held open during swallowing in order to maintain a passage for air." So, it is sort of like a snorkel that they breathe through, while their prey is being swallowed.  Pictured below is the anatomy of a snake. You can see where the trachea and glottis are located.

Photo from Internet

If you look closely at the picture below, you can see this Cottonmouth's glottis (the snorkel- looking thing; look for the tiny hole in the snake's mouth)

Eastern Cottonmouth. Photo by ME.

Another cool thing about how snakes are able to breathe, while swallowing prey is that their right lung ( which, interestingly enough, is longer than the left one) stores a lot of oxygen that decreases significantly during the swallowing process. (Greene)

Also due to the fact that snakes are not nearly as active as other animals and that they have low metabolisms, they can go a few minutes in between taking some breathes.
Cool huh?

Another thing to know is that once a snake has swallowed the prey item, the snake will readjust its jaw. If you ever seen a snake "yawn", it is actually readjusting its jaw after having a meal.


Below is a video of my corn snake eating. As you watch, you can see it as it works its head over the rodent, its jaws are expandable and moving around. You can also see, though the video quality is not great, the glottis is " pushed forward and held open." (Mattison) At the end of the video, you can see the snake readjust its jaw.






Well, I hope you have learned a lot in this blog; I know I have learned a lot over the year that I have worked on this project. I hope you see this project on a professional poster someday, as an educational tool. As always, feel free to ask me questions you have or even any observations you may have made regarding snakes eating.









I would like to thank the North Carolina Museum of Natural Sciences, in particular the Terrestrial Exhibits and Library Department for the opportunity to work on this project and the use of the great books and other resources that was super helpful in bringing this work together. A big thanks to Phil Bradley, Jeff Mette, Henry Wood, Nick Allen, Sarah McGrath, My family, and everyone else who helped me and encouraged me throughout the time I worked on this project.