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The Animal Science Blog is the place for conversation and discussion about scientific and technological topics related to pets, livestock, and other animals. See how cutting-edge advances help - or hinder - species around the world.

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Snakes: Feeding Time! (Part 2)

Posted May 20, 2010 12:01 AM by Vi Pham

In Part 1, we discussed the different methods that snakes use to find their prey. We also learned about the snake strike. Today, we'll learn what happens after the strike.

A Deadly Bite and a Tight Squeeze

Once a snake grabs hold of its prey, a few things can happen. Venomous snakes begin injecting their victims with venom as they recoil from the strike. Most keep their prey in their mouths, but some release their victims and wait for them to die.

There are two basic types of toxins within snake venom: neurotoxins and hemotoxins. Neurotoxins attack nerve cells. Different neurotoxins affect nerve cells in different ways, but all lead to muscle paralysis. Taipoxin, for example, causes the paralysis of respiratory muscles. The victim dies of asphyxiation.

Hemotoxins destroy blood cells, prevent blood from clotting, and cause organ degeneration and tissue damage. Because hemotoxins destroy both tissue and organs, a snake's prey isn't just killed. It's made easier to digest.

Snakes can have one or both toxins in their venom. The fangs, which are used to administer the venom, can be either hollow or grooved. Some snakes are rear-fanged and others are front-fanged.

Rear-fanged snakes have grooves on the back on their fangs. When a snake bites, its venom sacks contract. This allows the venom to flow down the grooves of the fangs and into the bite wounds. By contrast, front-fanged snakes have hollow fangs that act like hypodermic needles. Venom is injected directly into the animal.

Most front-fanged snakes inject venom directly downward. But some front-fanged snakes have injection openings that point forward. These snakes, commonly known as spitting cobras, can eject their venom as a defensive maneuver. Spitting cobras always aim for the eyes of the creature that threatens them and are very accurate - even from a few meters away. If immediately rinsed from the eyes, this venom causes temporary blindness. Otherwise, blindness becomes permanent.

Constricting snakes coil tightly around their prey. Despite what many people think, constrictors don't crush their prey. Nor do they break any bones. In the past, it was believed that these snakes would coil so tightly that the prey item could not expand its ribcage to inhale, leading to death from asphyxia. It's since been observed, however, that many prey items die in a shorter time than would be possible through asphyxia.

It has been suggested, too, that the increased pressure within the body due to constriction is too much for a victim's heart to handle. This results in immediate cardiac arrest in the prey item. Although this theory has not been confirmed, ongoing research has presented data that suggests it is possible.

One BIG Gulp

Once a prey item is killed, the snake begins to swallow it. Thanks to an extraordinarily flexible skull, liberated mandibles, and very stretchy skin, snakes are able to swallow prey that is much larger in diameter the snake itself.

Snakes use their liberated mandibles and back-pointed teeth to "walk" themselves over their prey. Once the prey item is past the snake's teeth, the snake uses its muscles to push the food down to its stomach.

So how to snakes breathe while they eat? A snake's trachea, or windpipe, opens at the bottom of its mouth. Snakes have the ability to extend the windpipe, moving the opening further forward. This allows a snake to continue breathing while it swallows food.

To see a video of a snake eating a mouse, click here.

The digestive juices of a snake are strong enough to break down the nails, claws, and bones of its prey. But that doesn't mean that snakes eat every part of their victims.

Egg-eating snakes swallow eggs whole, but do not eat the eggshell. As the egg travels down the throat, inward-pointing bony spines protruding from their vertebrae make slits in the shell. The snake squeezes out the contents of the egg and then regurgitates the shell.

Three Meals a…Year?

As I mentioned at the very beginning of my blog series, reptiles are extremely efficient creatures. On average, a reptile uses about 3% of the energy that a similarly-sized mammal uses each day. Because of this, snakes do not need to eat as much food on a daily basis. Coupled with the fact that snakes can eat food much larger than themselves, snakes can survive for many days after eating a meal.

For example, when my snakes were babies they ate one or two baby mice every week. Now that my snakes are a few years old, they eat a few juvenile mice every two weeks. When they are adults they will eat 2-4 adult mice every two weeks. The larger boas and pythons I used to take care of would eat one or two large rats or rabbits each month.

Large snakes that are capable of eating small deer may go for several months without ever feeling hungry!

What's Next?

My next entry will be about the snake life cycle. I will discuss growing, development, and shedding. See you then!

Picture Sources:

animalpicturesarchive.com

freerepublic.com

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Snakes: Feeding Time! (Part 1)

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