Pit Viper

Reviewed by: BD Editors

Pit vipers have pits on their face they use to detect prey, as well as venomous fangs.
A Pit Viper

Kingdom Animalia
Phylum Chordata
Class Reptilia
Order Squamata
Family Viperidae
Genus 22 genera in the subfamily Crotalinae
Species 150+ Species
Niche Ambush Predator
Length From 1 to 13 feet (30 cm – 4 m)
Weight Up to 15 lbs (7 kg)
Lifespan Varies by species
Social Structure Typically solitary
Conservation Status Least Concern to Endangered
Preferred Habitat Variety of Habitats, depending on the species
Average Clutch Size Between 2 and 86, depending on the species
Main Prey Species Smaller rodents, reptiles, birds
Predators Some mammals, large birds, humans

The Basics

Pit viper is a common name used for species in the subfamily Crotalinae which share the defining feature of having infrared-sensing organs on the front of their face. “Pit viper” actually refers to over 150 different species that are found around the world and occupy habitats as diverse as the desert and the jungle – from Australia to Arizona. This group includes rattlesnakes, cottonmouths, copperheads, moccasins, the white-lipped pit viper, and many other pit vipers.

A pit viper uses pit organs on its upper lip to find and identify prey. Much like eyes, pit organs detect electromagnetic radiation. However, these specialized organs sense infrared light instead of light in the “visible spectrum” – the wavelengths humans can see. Scientists studying pit vipers think that pit organs give them the ability to “see” body heat, and allows these snakes to judge the size and type of their prey.

The large pit organs on this rattlesnake are used to sense the heat that small mammals and birds give off.
The Rattlesnake – a Desert Pit Viper

Interestingly, pit vipers also have special muscles around their fangs that allow them to better inject venom into their prey. Pit viper venom is different based on the species, and in many cases, it has evolved to be most effective on the prey species that the pit viper normally preys upon. Depending on the species, different components of pit viper venom include neurotoxins that cause paralysis, metalloproteinases that destroy tissue, and proteins that stop the blood from coagulating. Even for humans that are much larger, a bite from a pit viper can easily lead to death if untreated.

Interesting Insights from the Pit Viper!

Whether the pit viper fills you with fear or fascination, it is a perfect animal to help explain some important biological concepts. Let’s take a look at a few ways these snakes can help scientists understand other parts of biology.

Pit Organs

Pit organs are not only found in pit vipers. In fact, these special organs are also seen in boas and pythons. However, superficial analysis and genetic analysis both confirm that these organs evolved multiple times. The pit vipers seem to share a single genetic origin – all pit viper pit organs are similar in shape and structure.

The bushmaster is the largest species of pit viper, and it can reach lengths of over 12 feet long!
A Bushmaster – the Largest Pit Viper

The pit organs of pit vipers consist of a deep pit, with a highly innervated membrane stretched across the opening. This highly sensitive area contains a large number of neurons, which receive a number of signals from the environment. Boas and pythons also have these pits, though there is no stretched membrane and the back of the pit is simply highly innervated. Boas and pythons typically have several pits on their upper lip, whereas pit vipers generally only have two large pits – one on each side of the head.

These pit organs are so sensitive that a pit viper could be completely blinded and still have the ability to hunt and strike prey. In fact, this has been shown in lab experiments where pit vipers were temporarily blind-folded. All snakes were still able to accurately strike prey. This is one piece of a large body of evidence that suggests that pit vipers create a mental image with the information from its pit organs – making them as or more sensitive than eyes. The snakes may also use this sense to determine which areas are best for basking or for cooling off.

Cottonmouths are one of the most dangerous snakes in the US, and a juvenile like this is often more dangerous because it can deliver more venom that necessary.
The Cottonmouth – A Semiaquatic Pit Viper


Unlike most species of snakes that lay eggs, pit vipers are most commonly ovoviviparous. This means that eggs remain inside the female and develop for several months. When they are fully developed, the eggs hatch inside of the female, then wiggle their way out into the world. This method of reproduction carries several advantages over laying eggs.

First off, the female can protect her eggs easily, since she carries them with her at all times. For snakes without powerful defenses, this might not be a great strategy. For example, if the female is eaten, all of her offspring die with her. But, pit vipers are not like other snakes. They have extremely powerful venom and are often decorated with warning coloration – or in the case of the rattlesnake a warning rattle. In concert with their powerful venom, this helps pit vipers scare off dangerous predators and making it safer to carry her eggs with her.

The white lipped pit viper can be very dangerous, though it commonly hunts birds among the canopy.
A White Lipped Pit Viper

Second, (because pit vipers are excellent at controlling their body temperature) the female can perfectly control the temperature of her eggs at all times. Laying eggs in a nest can be risky. Though the female may identify a nest site with the proper temperature before she lays her eggs, many different events can cause that site to become unsuitable long after the female has laid her eggs and left. That makes ovovivipary a beneficial strategy for the pit viper.

Cite This Article

Biologydictionary.net Editors. "Pit Viper." Biology Dictionary, Biologydictionary.net, 23 Jul. 2020, https://biologydictionary.net/pit-viper/.
Biologydictionary.net Editors. (2020, July 23). Pit Viper. Retrieved from https://biologydictionary.net/pit-viper/
Biologydictionary.net Editors. "Pit Viper." Biology Dictionary. Biologydictionary.net, July 23, 2020. https://biologydictionary.net/pit-viper/.

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