I was at Chester Zoo, walking through a rainforest exhibit, and I saw a fish tank up ahead. It was beautiful, glowing green as a light above illuminated all of the plants. As I approached, I noticed a strange thin branch or tube or something, I wasn’t sure what it was. The top of it seemed almost furry, like dark green hair was growing on top of it, I was intrigued. What I was not expecting as I got closer was for it to start moving, swimming even. What was it? Some kind of hairy eel? No, that’s ridiculous. Though the reality was perhaps even stranger. I’ve never been as confused and amazed then when I realised that it was a snake with hair-like algae growing on its back. As I stood with my face practically pressed up against the glass, it only got stranger. It had two small tentacles coming from its snout! Just as I noticed this another one suddenly swam past, THERE WERE MORE! The tank had many of these amazing animals and as I got around to the sign, I learned that they were aptly named Tentacled Snakes (Erpeton tentaculatum).
This is the tentacled snake I saw, well one of them.
Photo by Smithsonian's National Zoo "Tentacled snake baby" 2012, access via Flicker.
After returning from out trip to the zoo I threw myself into google to learn more about them and what I learned only made me love them more. Tentacled snakes (Erpeton tentaculatum) are small aquatic snakes ranging from 50 to 75 cm (20 to 30 inches) and are the only species belonging to the Erpeton genus. They are native to Southeast Asia and are found in stagnant and slow-moving water bodies of Thailand, Cambodia, and Southern Vietnam. They are almost totally aquatic but they have been seen digging burrows into the mud until the return of the rainy season. Although they are aquatic, they do not have gills and still have to breathe air using their lungs. They can hold their breath for approximately 30 minutes before surfacing to breathe, usually through their nostrils which have a special tissue that allows them to close whilst underwater. Tentacled snakes are also viviparous, meaning they produce eggs inside their bodies, allow them to develop fully, and give birth to live young whilst underwater. They have a diet made exclusively of fish and have many behavioural and physiological adaptations to help with hunting. The most obvious of these are their two tentacles which are not well understood but are believed to work as mechanoreceptors that can sense the movement of nearby fish to aid in hunting. It’s believed that a combination of the tentacles and the snake's eyesight help them hunt.
The aspect of their hunting that I find the most fascinating is that they seem to have an innate hunting technique that is known from birth, something that would usually be a learned behaviour in other species. Tentacled snakes hunt fish by forming a C like shape using their body. They then wait for a fish to move into this C shape where they are able to move the lower section of their body to elicit a flight response from the fish which they are able to predict and use that predicted movement to catch the fish. The figure below from Catania (2010) illustrates this tactic.
Section A from Figure 2. from Catani 2010. Illustrating the C-start hunting style of tentacled snakes.
Catania (2010) explains further in their article “Predicting the future position of a moving object is common, and equivalent to a batter striking a baseball based on brief visual information about its initial trajectory. Extending this analogy to tentacled snakes–it would be as if the batter could estimate the position of the ball in time and space without ever seeing the pitch. Moreover, the present study of naive snakes shows they can do this without ever seeing any pitches. Of course, the situation is simplified for the tentacled snakes because they elicit a specific pitch (the C-start), providing the basis for their precisely timed strike. Nevertheless, the fact that ‘‘knowledge’’ of C-starts is innate and therefore inherited by tentacled snakes is remarkable and seems to be unparalleled.”
The idea that Tentacled Snakes are somehow born with this knowledge is absolutely astounding to me. There is a lot we don’t know about nature, a lot we don’t know about brains specifically, and I love that we still have so much to learn. But this is a totally different level of wow to me. The idea that their brains could somehow be coded from birth to hold certain information even this simple, makes me feel like we are stepping over into sci-fi territory and I love it. I hope that one day it will be a well understood phenomenon but for now it remains a mystery of the natural world. With nature, wonders truly never cease.
Sources:
Catania, K., 2010. Born Knowing: Tentacled Snakes Innately Predict Future Prey Behavior. PLoS ONE, [online] 5(6), p.e10953. Available at: <https://www.proquest.com/docview/1292303793?parentSessionId=aIU%2F9WM1BBhcNYA%2FKv6r%2BYGCNGjXvca2eEdOgE%2F7gLU%3D&pq-origsite=primo&accountid=10910> [Accessed 30 January 2022].
Catania, K., Leitch, D. and Gauthier, D., 2010. Function of the appendages in tentacled snakes (Erpeton tentaculatus). Journal of Experimental Biology, [online] 213(3), pp.359-367. Available at: <https://journals-biologists-com.ezproxy.flinders.edu.au/jeb/article/213/3/359/10003/Function-of-the-appendages-in-tentacled-snakes> [Accessed 30 January 2022].
Chester Zoo. 2022. Rare Asian snakes given pregnancy scans | Chester Zoo. [online] Available at: <https://www.chesterzoo.org/news/rare-asian-snakes-given-pregnancy-scans/> [Accessed 31 January 2022].
Smithsonian's National Zoo. 2022. Tentacled Snake. [online] Available at: <https://nationalzoo.si.edu/animals/tentacled-snake> [Accessed 31 January 2022].
Toronto Zoo. 2022. Tentacled snake. [online] Available at: <https://www.torontozoo.com/animals/Tentacled%20snake> [Accessed 31 January 2022].
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