Fast Food Joints

Special hinges in their lower jaw enable some skinny little snakes to eat at an astonishing speed.

Story by Adam Summers  ~  Illustrations by Sally J. Bensusen

Threadsnakes (one of three blindsnake families) have three joints in the lower jaw: The jaw joint connects the jaw to the rest of the skull. The intramandibular joint allows the lower jaw to bend in the middle. The interramal joint (see following illustration) permits the tips of the left and right sides of the jaw to rotate relative to each other.

The eating habits of snakes have jump-started many a cocktail conversation among my (admittedly peculiar) circle of friends, and we are always fascinated by the extremes: the python that swallowed a deer, the bull snake that swallowed several lightbulbs, the odd little African snake that crushes bird eggs with special vertebral protrusions at the back of its throat and then regurgitates the shells. All these gustatory achievements are accomplished with deliberate slowness. Recent work on a group of snakes known as blindsnakes has revealed them to be eating champions of a very different sort. These snakes feed on smaller prey-the larvae, pupae, and adults of ants and termites-and they do so remarkably fast.

Found mostly in tropical and subtropical regions, blindsnakes are not well known because they are small and spend much of their lives hidden in underground burrows and foraging in ant and termite mounds. Their tiny eyes can tell light from dark, but little more. These snakes are roughly cylindrical, and if their small forked tongues didn't flick in and out, it would be hard to tell one end from the other.

Ants and termites may be small, but they're not easy pickings. Armed with formidable tactical and chemical weapons, they will swarm an attacker. The "soldiers" of both groups have strong mandibles with which they can inflict a nasty bite. Many ants also sting, and some termites can shoot acid from their bulbous heads. To a blindsnake, an ant or termite nest is a huge, concentrated supply of food but also a serious danger, because given the chance, most colonies could rapidly kill and consume it (most blindsnakes are less than two feet long and thinner than a pencil).

These snakes are not entirely defenseless, however. Some blindsnakes have thick skin as well as scales so smooth that ant mandibles tend to slide right off. Others produce glandular secretions known to repel adult ants. But the snakes' best defense is simply to minimize the time spent exposed to attack. To do so, they pack in the pupae so fast that early researchers thought they must employ suction. 

When the snake is at rest, the teeth on its lower jaw (seen here from below) face forward and upward. When feeding, the snake is able-thanks to its three joints-to rapidly move the two sides of its lower jaw like swinging doors. (During the "in" swing, the teeth are not visible from below.)

Most snakes use their upper jaw to move prey into their mouth, slowly "walking" first the left side and then the right side along the prey item, while their lower jaw slides along passively. Nate Kley, of the University of Massachusetts, has studied ingestion of prey in a family of blindsnakes that have teeth only in their upper jaw. While feeding, these snakes don't just move the upper jaw back and forth, they also rotate it rapidly and extend it partially out of their mouth. The upper jaw shoots in and out of the mouth up to ten times per second, one of the fastest repetitive feeding rates recorded for vertebrates. As a result, the snakes can rake in more than eighty pupae per minute.

Kley has also studied threadsnakes. This blindsnake family has teeth on the lower (rather than the upper) jaw and also an especially well-developed intramandibular hinge joint about halfway along each side of the lower jaw. This joint allows the jaw to bend in the middle, flexing back toward the gullet. (As in all snakes, the tips of the left and right sides of the jaw are connected by a flexible ligament.) A long muscle, running back from the jaw about a tenth of the snake's length, yanks the tips of the lower jaw back in less than one-sixth of a second (long muscles can shorten more quickly than short ones). Springy cartilage in the hinge joints and muscle that runs between the left and right sides of the jaw then snap the jaw back into position. Quickly repeating these jaw movements, the threadsnake ratchets the squirmy prey farther and farther down the hatch.

You can visualize the movements by holding your hands open, with the palms facing you and held at about eye level. Make sure your pinkies are touching. Then flex your wrists to bring your fingertips toward your chest. (If your fingers start to bend, try to keep them still-imagining them, if necessary, in little splints.) In this analogy, your forearms and hands are the lower jaw, your wrist joints the intramandibular hinges, and your fingers the teeth. Now picture doing that while hugging a pillow (a fat little larva), and you get an idea of what it must be like for a threadsnake to eat dinner.

Or look at it this way: to emulate the dining accomplishments of this skinny little snake, we would have to gulp down a whole ballpark frank or a large loaf of bread (depending on the species of blindsnake and the particular ant or termite). Consider Takeru Kobayashi, the world's champion hot dog eater, who ate fifty frankfurters in twelve minutes. A blindsnake could polish off a comparable meal in little more than thirty seconds, and if it continued eating for a full twelve minutes, it would consume the equivalent of more than a thousand of Nathan's finest.

Check out the video!  Click here.

Adam Summers is an assistant professor of ecology and evolutionary biology at the University of California, Irvine, and can fit a billiard ball in his mouth (asummers@uci.edu).