WEBVTT - How Can Pit Vipers 'See' Heat?

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<v Speaker 1>Welcome to Brainstuff, a production of iHeart Radio, Hey brain

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<v Speaker 1>Stuff Lauren vocal bom Here. The rattlesnakes depicted on yellow

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<v Speaker 1>Gadsden flags and Craig Ferguson's coffee mug are all American

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<v Speaker 1>pit vipers noted for their venom. Vipers make up a

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<v Speaker 1>wide spread snake family that's represented on most of the

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<v Speaker 1>world's continents, Australia and Antarctica being the two exceptions. All

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<v Speaker 1>vipers carry venom in twin glands behind their eyes. The

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<v Speaker 1>toxic brew is delivered through movable fangs that can be

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<v Speaker 1>folded up against the roof of the snake's mouth. Rattlesnakes

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<v Speaker 1>bring something extra to the table, though they belong to

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<v Speaker 1>a viper subfamily called Crotolina, or the pit vipers. Such

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<v Speaker 1>reptiles come with an amazing built in tool that they

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<v Speaker 1>used to locate prey and predator alike. We don't call

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<v Speaker 1>them pit vipers because they hang out in ditches or

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<v Speaker 1>attend the University of Pittsburgh. Instead, that name to drives

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<v Speaker 1>from the heat sensitive holes, that is, pits located between

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<v Speaker 1>their eyeballs and nasal openings. But we spoke via email

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<v Speaker 1>with herpetologist Emily Taylor. She explained pit vipers are distinguished

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<v Speaker 1>by the two infrared sensing pits on their faces. Other

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<v Speaker 1>vipers lack these pits and also lack the ability to

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<v Speaker 1>sense infrared radiation. Other sneaks like boa and pythons, also

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<v Speaker 1>do have pit organs, though the structures are different. I'm

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<v Speaker 1>discovered in the year eighteen hundred. Infrared radiation, also called

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<v Speaker 1>i R or infrared light, is a type of radiant

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<v Speaker 1>energy on the electromagnetic spectrum that's invisible to the human eye,

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<v Speaker 1>but you're giving off infrared radiation right now. Every object

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<v Speaker 1>in the universe with a temperature above absolute zero that

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<v Speaker 1>is negative four hundred and fifty nine point eight degrees

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<v Speaker 1>fahrenheit or negative two hundred and seventy three point one

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<v Speaker 1>five degrees celsius emits some amount of infrared radiation. Shin

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<v Speaker 1>things that are physically warmer give off more infrared radiation.

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<v Speaker 1>We can sense that energy as heat like night vision goggles.

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<v Speaker 1>Pit vipers facial pits are also used to detect infrared radiation.

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<v Speaker 1>But we also spoke via email with wildlife biologist Andrew Derso,

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<v Speaker 1>who explained that these structures are quote essentially very simple

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<v Speaker 1>eyes that see in the infrared spectrum. They have a

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<v Speaker 1>narrow opening leading to a wider cavity in the middle

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<v Speaker 1>of which a membrane filled with infrared receptors is suspended

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<v Speaker 1>away from the body, acting as a retina. This lets

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<v Speaker 1>snakes see thermal images of nearby animals. Since many pit

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<v Speaker 1>vipers go hunting after dark for rodents, birds, and utter

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<v Speaker 1>creatures that are warmer than themselves. It's a helpful superpower,

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<v Speaker 1>and Taylor said their real eyes do not sense this radiation. However,

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<v Speaker 1>the sensory information from their eyes of photo reception and

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<v Speaker 1>their pits thermo reception is likely merged in their brain

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<v Speaker 1>in some way. It's impossible to know for sure what

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<v Speaker 1>it looks like to the snake, but it's likely that

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<v Speaker 1>they combine the input from their eyes and from their

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<v Speaker 1>pits into some sort of dual image. When dinner's insight,

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<v Speaker 1>vipers lash out with sophisticated fangs, hinged and capable of

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<v Speaker 1>moving independently. These are long, tubular teeth, and they're hollow too.

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<v Speaker 1>Venom is released through a slit near the tip. Taylor

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<v Speaker 1>said snake venoms are cocktails of thousands of chemicals, mostly

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<v Speaker 1>proteins that disrupt physiological pathways in the prey. Biological toxins

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<v Speaker 1>fall into a number of different categories. Two of the

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<v Speaker 1>major groups are known as hemotoxins and neurotoxins, and Taylor

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<v Speaker 1>explained hemotoxins disrupt the coagulation of blood and cause internal bleeding.

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<v Speaker 1>Neurotoxins interfere with the normal nervous system functions at multiple levels,

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<v Speaker 1>for example by blocking neurotransmitter release or reuptake, or by

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<v Speaker 1>preventing neurotransmitters from binding. The result is that muscles cannot contract,

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<v Speaker 1>and envenomated prey often die when their diaphragm, which is

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<v Speaker 1>the main muscle used for breathing, can no longer contract.

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<v Speaker 1>Many venomous snakes, including pit vipers, have multiple hemotoxins and

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<v Speaker 1>neurotoxins in their venoms. Ambush hunting is a pit viper specialty.

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<v Speaker 1>Most of the time, the snakes wait for their prey

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<v Speaker 1>to come to them instead of chasing it down y

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<v Speaker 1>waste energy. When a pit viper lashes out, the reptile

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<v Speaker 1>can strike with up to half of its total body length.

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<v Speaker 1>Some have been clocked moving their heads at eight feet

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<v Speaker 1>or over two meters per second in the process. That's

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<v Speaker 1>not to say that they always hit the target. Experiments

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<v Speaker 1>involving a Chinese pit vipers showed that adults strike more

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<v Speaker 1>accurately than juveniles. Halfway around the world, Kangaroo rats can

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<v Speaker 1>use a vase of maneuvers to dodge mojave rattle snakes

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<v Speaker 1>in mid strike. Ironically, road runners actively goad rattlesnakes into striking.

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<v Speaker 1>The birds eat small rattlers despite having no natural resistance

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<v Speaker 1>to their venom. A road runners first move is to

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<v Speaker 1>pester one of these snakes until the reptile tries to

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<v Speaker 1>strike back. Then, while the snake's body is fully extended,

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<v Speaker 1>the bird will grab the head before our rattler can react,

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<v Speaker 1>its attacker whips the skull against the ground. Red tailed

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<v Speaker 1>hawks employ a similar strategy. Pit Vipers are also killed

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<v Speaker 1>by non venomous king snakes, who swallow rattlers, cotton mouths,

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<v Speaker 1>and copper heads whole. People would do well to keep

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<v Speaker 1>their distance, though, While snake bite fatalities are rare in

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<v Speaker 1>the United States, with only five to six human deaths

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<v Speaker 1>occurring per year, pit viper in venomation may lead to shock, swelling, bruising, blistering, paralysis,

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<v Speaker 1>and other delightful symptoms. Many pit vipers reside in the Americas,

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<v Speaker 1>though the subfamily also extends into parts of Southeast Asia.

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<v Speaker 1>Besides rattlers, the list of pit vipers includes cotton mounts,

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<v Speaker 1>copper heads, and the bushmaster snakes. There are two hundred

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<v Speaker 1>and sixty species currently recognized. Today's episode was written by

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<v Speaker 1>Mark Mancini and produced by Tyler Clang. For more in

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<v Speaker 1>this and lots of other striking topics, visit how stuff

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<v Speaker 1>works dot com. Brain Stuff is production of iHeart Radio

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<v Speaker 1>or more podcasts. My heart Radio visit the i heart

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