Reptiles
File Snake
Acrochordus · also called file snake, elephant trunk snake, wart snake
A file snake looks like a snake that has been left in the bath too long: its skin is loose and wrinkled, far too big for its body, and its scales feel like coarse sandpaper. Both features are tools. The baggy skin and rasping scales let it grip a thrashing fish underwater, where it spends its entire life. Put one on dry land and it can barely move.
Overview
File snakes are the three species of Acrochordus, fully aquatic, non-venomous snakes of the rivers, estuaries, mangroves, and inshore seas from India to northern Australia. They eat almost nothing but fish, caught in a loose coil and held fast by the skin, then swallowed underwater. A big meal can last one for weeks or months.
Skin and scales
The loose, folded skin and the file-like, non-overlapping scales work as a gripping system: the snake wraps the prey, the slack skin presses in from all sides, and the bristled scales stop the fish sliding free. File snakes have no broad belly scales, so they cannot crawl properly and are nearly helpless on land — everything about them, from top-mounted nostrils to a paddle tail and oxygen uptake through the skin, is built for staying submerged.
Slow lives, live young
File snakes have a very low metabolism, can stay under for over an hour, and grow so slowly that a female may breed only once every few years. They give live birth in the water.
Status
Least Concern — all three species are widespread and the little file snake is abundant, though it is one of the most heavily traded snakes in the world for its distinctive pebbled “elephant trunk” leather.
File Snake: common questions
Is a file snake venomous or dangerous?
No. File snakes have no venom and no fangs, only small gripping teeth, and they are placid, slow, and completely harmless to people. They do not bite defensively in any meaningful way and would rather sink to the bottom and stay still. The main hazard around them is to fish, which they catch and constrict loosely while their rough skin holds the prey in place. Fishers and prawn farmers in parts of Asia and Australia handle them routinely when clearing nets.
Why does a file snake have such loose, baggy skin?
The slack skin and the rough, non-overlapping scales work together as a fish-gripping system. When the snake wraps a coil around a fish, the loose skin lets it fold tightly around the prey and press in from all sides, while the file-like scales dig in and stop the slippery fish from sliding free. A smooth-scaled snake struggles to hold a fish underwater, and the file snake's sandpaper surface solves that. The baggy look also breaks up the snake's outline and may help it blend in with waterlogged debris.
Can a file snake move on land?
Barely. File snakes have lost the wide belly scales that other snakes use to grip the ground and push themselves forward, so on land one can only flop and shuffle awkwardly and is very vulnerable. They essentially never leave the water voluntarily. Everything about them, from the position of the eyes and nostrils on top of the head to the paddle-like flattened tail and the ability to absorb oxygen through the skin, is built for a life spent entirely submerged or floating.
What is elephant trunk snake leather?
It is tanned file snake skin, mostly from the little file snake, and it is prized in the leather trade for its unusual texture, a fine, closely pebbled, slightly rough surface produced by the many small separate scales, quite different from the tile-like pattern of most snakeskin. It is turned into watch straps, wallets, belts, purses, and shoe uppers. The trade is centred on Indonesia and neighbouring countries, where the snakes are caught by hand and in nets in coastal waters, and it is one of the largest commercial harvests of any wild snake.