- Lifespan
- 10–15 years in the wild, up to 20 years in captivity
- Size & Weight
- 50–90 cm (females larger than males); 40–180 g
- Habitat
- Heathland, moorland, woodland edges, and south-facing slopes with dense ground cover and shelter.
- UK Distribution
- Found throughout England, Wales, and Scotland north to the Scottish Highlands; resident year-round but range has contracted significantly in recent decades.
- Diet
- Carnivorous, feeding on small vertebrates and invertebrates including lizards, small mammals, birds, and insects.
- Prey
- Slow worms, common lizards, shrews, voles, nestling birds, insects (particularly grasshoppers)
- Predators
- Buzzards, kestrels, grass snakes, badgers, foxes, and hedgehogs; humans also pose a threat through persecution.
- Mating Season
- April to June
- Breeding
- Ovoviviparous (live-bearing); 3–20 live young born August–October, typically 6–8; no parental care after birth.
- Behaviour
- Solitary and relatively sedentary. Adders are venomous but docile; they only bite when threatened or accidentally stepped on. They basking in spring and autumn to thermoregulate, and remain inactive during winter hibernation (November–March).