Which is the only poisonous snake that is native to Britain?

The adder is the only poisonous snake that is native to Britain. It is also known as the common viper and can be found in a variety of habitats across the country, including woodlands, heathlands, and grasslands. Adders are recognized by their distinctive zigzag pattern along their backs, although their coloration can vary.

The adder's venom is not typically life-threatening to humans, but it can cause pain and swelling, and in rare cases, it may provoke severe allergic reactions. Awareness of their habitat and behavior is important, especially for outdoor enthusiasts, as encounters can occur in their preferred environments.

The other snakes mentioned, such as the rattlesnake and the grass snake, do not reside naturally in Britain. The rattlesnake, for instance, is primarily found in the Americas, while the grass snake is non-venomous. Recognizing the adder as Britain's only venomous snake highlights its unique status within the country's fauna.