Meet the new species of pit viper found in Arunachal Pradesh

Itanagar, May 10: India now has a fifth brown pit viper with a reddish tinge, a venomous snake with a unique heat-sensing system - from a forest in West Kameng district of Arunachal Pradesh.

The discovery, published in the March-April volume of the Russian Journal of Herpetology, makes the Arunachal pit viper (Trimeresurus arunachalensis) the second serpent to have been discovered after the non-venomous crying keelback in the State's Lepa-Rada district in 2018.

The new species also makes Arunachal Pradesh the only Indian state to have a pit viper named after it.

What does heat sensing ability means?

They have special pits located between their eyes and nostrils that can sense minute temperature changes as infrared rays, as an aid in locating warm-blooded prey such as rodents. Snakes use the radiation to generate 'thermal images' of predators or prey, but the underlying physiology has been unclear.

The more advanced infrared sense of pit vipers allows these animals to strike prey accurately even in the absence of light, and detect warm objects from several meters away.

It is found on the sensory nerve fibres that stimulate the snakes' pit organ, the highly specialised facial structure that initially detects radiant heat and consists of cavities located on each side of the head.

Also called 'heat vision', the infrared rays have longer wavelengths than those of visible light and signify the presence of warm-blooded prey in three dimensions which helps a snake aim its attack.

A pit has two chambers. The interior chamber is naturally the internal temperature of the snake itself. The exterior chamber heats up when it is close to a heat source.

The snake is then able to detect the temperature difference between the two chambers. This system is so accurate that pit vipers are actually able to detect temperature changes as little as 0.002 degrees centigrade.

Types of snakes with pits

As snakes evolved, they branched out into vipers and constrictors. The vipers further evolved to include pit vipers (part of the scientific sub-family in Viperidae called Crotalinae). Not all vipers have pits, and not all boa constrictors and pythons do either. Pit vipers are found worldwide and are all poisonous, just as all vipers are poisonous.

India had four brown pit vipers - Malabar, Horseshoe, Hump-nosed and Himalayan - before the Arunachal Pradesh discovery.

Other uses of the pits

Snakes also use pit organs to help them find cool places to regulate their internal temperatures. Snakes are reptiles and cold-blooded, which means they have to warm up in the sun. When they get too warm, they have to find a cooler area to use for bringing down their temperatures. The pits on their faces help them find these cool places. When the loreal pits are blocked or otherwise covered, the snake has trouble finding these places when needed, as if blind.