This species is mainly diurnal, especially in the north of its range.
Further south it is said to be active in the evening, and it may even be active at night during the summer months.
It is predominantly a terrestrial species, although it has been known to climb up banks and into low bushes in order to bask or search for prey.

Adders are not usually aggressive, tending to be rather timid and biting only when cornered or alarmed.
People are generally bitten only after stepping on them or attempting to pick them up.
They will usually disappear into the undergrowth at a hint of any danger, but will return once all is quiet, often to the same spot.
Occasionally, individual snakes will reveal their presence with a loud and sustained hissing, hoping to warn off potential aggressors.
Often, these turn out to be pregnant females.
When the adder is threatened, the front part of the body is drawn into an S-shape to prepare for a strike.

The species is cold-adapted and hibernates in the winter.
In Great Britain, males and females hibernate for about 150 and 180 days, respectively.
In northern Sweden hibernation lasts 8–9 months.
On mild winter days, they may emerge to bask where the snow has melted and will often travel across snow.
About 15% of adults and 30–40% of juveniles die during hibernation.
This species is mainly diurnal, especially in the north of its range. Further south it is said to be active in the evening, and it may even be active at night during the summer months. It is predominantly a terrestrial species, although it has been known to climb up banks and into low bushes in order to bask or search for prey.
Adders are not usually aggressive, tending to be rather timid and biting only when cornered or alarmed. People are generally bitten only after stepping on them or attempting to pick them up. They will usually disappear into the undergrowth at a hint of any danger, but will return once all is quiet, often to the same spot. Occasionally, individual snakes will reveal their presence with a loud and sustained hissing, hoping to warn off potential aggressors. Often, these turn out to be pregnant females. When the adder is threatened, the front part of the body is drawn into an S-shape to prepare for a strike.
The species is cold-adapted and hibernates in the winter. In Great Britain, males and females hibernate for about 150 and 180 days, respectively. In northern Sweden hibernation lasts 8–9 months. On mild winter days, they may emerge to bask where the snow has melted and will often travel across snow. About 15% of adults and 30–40% of juveniles die during hibernation.
Vipera berus