Snakes Recycle Poison

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Snakes recycle poison according to reports in news@nature, New Scientist 29 January 2007, and New York Times and Science Frontline, 30 January 2007. Scientists studying the Japanese grass snake Rhabdophis tigrinus have discovered it can eat poisonous toads and store their poison in glands on the back of its neck. Female snakes also transferred poison to eggs, therefore offspring have some poison already stored when they hatched. Researchers also found snakes with poison already stored behaved differently towards predators such as hawks, compared with snakes that had not acquired toad poison. When attacked, snakes with stored poison adopted an arch-necked defensive posture, so the predator was more likely to strike the region containing the glands and cause poison to leak out. Snakes without stored poison tended to slither away and hide when confronted by predators.

This snake is the first vertebrate found to sequester poison from another vertebrate. Some poisonous frogs are known to get their poison from insects in their diets, and some invertebrates, e.g. sea slugs, make themselves unpalatable for predators by storing chemicals obtained from food.

Editorial Comment: This Japanese snake is a rear fanged snake, i.e. it does not have poisonous front fangs to attack prey with. It does secrete saliva, but this is injected into its food from its back teeth as an aid to digestion. Therefore, it is not dangerous or poisonous except to anything it is already swallowing. Snakes do not chew their food, so being able to inject digestive chemicals in their food using their teeth is good design.

Toads use their skin to excrete waste products. In a 'very good' world, where all animals ate plants, nothing would try to eat toads, so toxic waste products in the skin would not threaten anyone. It was only after the world degenerated because of human sin and God's judgement that animals began to prey on one another and defence mechanisms were selected for. Therefore, some characteristics, such as digestive chemicals in snake saliva and waste products in toad skin gained a secondary use as 'weapons'.

It is interesting in the study described above that the snakes' behaviour changed when they had the extra poison so they do seem to have an understanding of what the results of eating toads achieves. Predators and poison are issues raised by sceptics to challenge the Biblical story of the Garden of Eden where there were no predators, and the world was "very good", but this snake reminds us poison is one result of the increasing degeneration occurring as the world continues to go from good to bad to worse.

Evidence News 9 February 2007

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