The adder is Britain's only venomous snake and faces welfare pressures from deliberate persecution, habitat loss, and predation, leading to population declines across its range.
Deliberate killing of adders is illegal but continues in some areas due to fear of venomous bites. Disturbance of basking adders causes stress and loss of thermoregulation opportunities. Habitat fragmentation prevents normal ranging behaviour and gene flow between populations. Predation by pheasants released in high densities is a documented welfare pressure.