Saturday, March 23, 2013


There are a lot of snakes called "boas," and what they all have in common is they wrap themselves around their prey and squish it until it is dead.  After that, they swallow it whole, like all snakes do with their food.  The boa constrictor is in the family Boidae, which lives in North, South, and Central America, plus also in some islands of the Caribbean.  The scientific name of the most common boa constrictor is Boa constrictor constrictor, which is easy to remember because it's the same as its common name, with an extra "constrictor" on the end.

The yellow parts show
the range of the boa constrictor.
Anyway, this type of boa constrictor does well in many different habitats, including deserts, rain forests, open savannas, and cultivated fields.  What they don't like very much is water, even though there are other kinds of boas that do like water.  Mostly, boa constrictors live in places like hollow logs and abandoned animal burrows.

Cleveland Metroparks Zoo
Boa constrictors can be several different colors such as tan, green, red, or yellow.  The color they are usually depends on where they live and what sort of background they need to blend into.  Boas all have markings that might be jagged lines, ovals, diamonds, or circles.  There are more markings towards the tail, which is why this species of boa constrictor is also called a "red-tailed boa."

You can tell a female boa from a male one because the females are bigger around and longer.  This is probably so they have room inside them for a whole bunch of baby snakes.  An adult female is usually between 7 and 10 feet long, and a male is 6 to 8 feet.  Really large boa constrictors can weigh as much as 60 pounds, but the more usual weight for the bigger females is between 22 and 33 pounds.

Killing a rat
The favorite foods eaten by boa constrictors are rats, squirrels, lizards, birds, opossums, mongooses, and bats.  The way boas catch bats is by hanging in trees or at the mouths of caves, and then when a bat flies by, the boa grabs it and squeezes it to death.  Some boas eat even bigger prey, such as monkeys and wild pigs.  In my opinion, boa constrictors are nicer to their prey than cobras are, because boas at least wait until their food is dead before they start swallowing it.

Starting to swallow
A boa constrictor's bite is not poisonous, but the boa has a bunch of small, hooked teeth that grab and hold its prey while the boa is killing it.  There are some cells in a boa's lips that help it sense heat.  This is useful if you are looking for prey in the dark, which is when boas like to hunt.  Mostly, a boa constrictor will stay by itself unless it wants to mate.  The only times boas come out in the daytime is when it's too cold at night, and they want to bask a little in the sun.

Almost got it all down!
Usually, boa constrictors hunt by waiting in ambush until something tasty comes by that they can grab. But if there is not much prey around, they might go out looking for something.  Like all snakes, they can open their jaws really wide and swallow really big things.  It takes between 4 and 6 days to digest a meal, depending on its size and also how warm the weather is.  After that, the boa might not eat again for several weeks or months, because of its slow metabolism.

Photo by Joel Sartore
Many kinds of snakes only have one lung, but boa constrictors have two.  The left one is very small, and it doesn't do anything, but at least it's there.  The right lung is what boas use when they breathe.  Another thing boa constrictors have is pelvic spurs.  Pythons also have these.  Pelvic spurs are all that's left to show that once upon a time, snakes had real pelvises and hind legs.

Female boas usually like to breed during the dry season, which is from April to August.   When they are in the right mood, they give out a scent that attracts males, and then they mate with several of them.  This is called being polygynous.  The sperm might stay inside the female for a while before she actually ovulates and becomes pregnant, but after she does, the baby boas will be born in 100-120 days.

Newborn boa constrictors.
A group of snakes is called a bed or knot.
Boa constrictors are what's called ovoviviparous, which means the babies are born live instead of inside eggs.  Well, actually, what happens is that the eggs hatch inside the mom, and then the babies are born. A female boa can have a litter of anywhere between 10 and 65, but the average number is 25.  Luckily, she doesn't have to take care of them because they can already take care of themselves.  When baby boas are born, they are about 15-20 inches long.  They grow really fast at first, and have to shed their skins every month or two.  By the time they are 3 or 4 years old, they will be 6-10 feet long, and they can start having babies of their own.  They will keep growing more slowly for the rest of their lives, and they will only have to shed about every 2-4 months.

In many areas of the tropics, people like to keep boa constrictors around their homes, sort of like pets, because they kill off the rats and mice that might eat the grain.  They are also kept in captivity in lots of zoos and private collections, where they seem to be happy and are bred pretty often.  In captivity, boas are fed mice, rats, rabbits, chicks, and chickens.

Some people like to eat snake for dinner.
I wonder if it tastes like chicken.
If you want a boa constrictor of your very own, just remember that they can live 20 to 30 years, so it is a long-term commitment to have one.  Also, you have to give it enough space and yummy food, plus the right temperature and humidity.

Personally, I don't want us to have any snakes living here in our house, because I think that would be creepy, and Mom feels the same way.  So for once, we are in total agreement about something, and I'm very glad of that!


  1. The photo below the newborns is of an Eunectes Murinus, not a Boa constrictor.

    1. Thanks for the correction. When I find these photos online, they are sometimes mislabeled!