Common Egg Eater|
that is, they're zoophagous. There are no vegetarian snakes. Snakes are carnivorous reptiles. Large snakes eat large animals. Small ones eat small ones. The smallest snakes eat insects and other invertebrates.
Most snakes eat rodents or birds after either killing them with venom or squeezing them to death in constricting coils. They mostly eat small animals because most snakes aren't that big.
What do snakes eat? Garter snake Thamnophis sirtalis ingesting a toad.|
Snake eating chicken
Image: Ryan Somma
But, of course, there are big snakes. The largest snake in the world, the green anaconda, which kills by constricting, can eat animals as large as a human being or a pig.
Many snakes also eat eggs. But eggs, too, are animals, although at an early stage of development. Birds, especially young birds in the nest, are also a target.
Non-constricting, non-venomous snakes generally eat smaller prey such as insects and small rodents that they can easily seize in their mouths and swallow.
There are also snakes that eat other snakes. Well-known examples are the king cobra and the various king snakes (such as the scarlet king snake, which eats rattlesnakes) — king refers to the fact that these snakes dominate and eat other snakes.
Erroneous reports allege that the tentacled snake of southeast Asia (right) eats aquatic plants. While it is in fact the world's only snake with tentacles, it actually eats minnows, not plants. The widespread, mistaken idea that it's the only vegetarian snake stems from an old, incorrect report. In fact, among all snake adaptations, the tentacled snake's methods of predation are among the most highly developed and unusual known (see Catania 2009).
How much do snakes eat? A snake of any given weight eats far less than does a mammal of the same size because snakes are cold-blooded. A mammal must eat more in order to generate enough energy to maintain its body temperature. A snake only uses about 10 percent of the amount of energy used by a mammal of similar size. So they only need about a tenth as much food. Snakes do drink water — but, again, much less than a mammal of equivalent size.
One of the most unusual snake adaptations, and one of the most impressive among reptile adaptations as a whole, is the ability to swallow large animals intact, often ones that are much bigger around than the snake itself (snakes don't chew). Snakes can do this because they can unhinge their jaws to permit the passage of large objects. Digesting a meal of this sort can take a snake weeks, or even months. Once digestion is complete, the snake vomits any bones or other indigestible parts that can't be passed through its system. Not an appetizing sight.