The adder is Britain's only venomous snake and is declining nationally, facing threats from habitat fragmentation, persecution, and the loss of the heathland and grassland it depends on.
Adder welfare is shaped primarily by persecution and habitat loss. Deliberate killing of adders - which is illegal - occurs when people encounter them in gardens or on paths and react with fear. Even non-lethal disturbance during winter hibernation, when adders are in temperature-torpor, can be fatal - disturbed hibernating adders cannot escape cold exposure and may die from cold stress. Adders bitten by dogs or cats face significant welfare consequences from wounds even where venom is not the primary injury mechanism. The conservation welfare case is strong: genetically isolated small populations on fragmented heathland face inbreeding depression that reduces reproductive success over generations.