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Vipera berus


The adder is one of the very few snakes in which males and females are colored differently. Males are cream, dirty yellow, silvery or pale gray, or light olive, with a distinct, dark "zig-zag" pattern on their backs and sides. Females have the same distinct pattern along their sides and back, but their ground color is usually red, reddish brown, or gold. The throat of the male is black or whitish with scales spotted or edged with black, while the female's throat is yellowish-white, sometimes tinged with red. Both sexes sport a pair of dark bands forming an "X" or "V" on the head. Black varieties in which all patterning is obliterated are common. Juvenile adders are usually reddish.

The average fully-grown male is about 21 inches long, the female 24 inches.



black adder

Distribution and Habitat

Adders are found from the United Kingdom (except for Ireland) to the Pacific coast of Asia, as far north as the Arctic Circle and as far south as the Mediterranean Sea. They inhabit a variety of woodlands, moorlands, heathlands, and wetlands, as long as there are open, sunny places suitable for basking and relatively dense ground cover for shelter.


Adult adders feed primarily on lizards, mice, voles, and shrews; young adders feed on insects and worms.

Adders have two different hunting techniques. The first is to wait for prey to pass close enough for the snake to strike and inject venom, after which it will follow the animal (by smell) until it succumbs. The other involves actively seeking out prey. Which technique is used depends primarily on how hungry the adder is.


Adders mate in the spring, usually April, soon after emerging from hibernation. The males emerge first and stay close to the hibernation site in an area referred to as the mating ground. As females emerge, males swarm around them and allow females to choose a mate with whom to copulate. When two males try to court the same female, fighting can occur during which males raise the upper half of their bodies off the ground and attempt to wrestle each other to the ground. More than two males can be involved in these fights.

The male generally remains with the female for several hours after mating, and then goes off in search of another receptive female.

Egg development takes place inside the mother's body, and takes 3-4 months. The young (5-20 per clutch) are born coiled up in a membrane which is ruptured by their convulsive movements. Six to eight inches long at birth, the young are capable of independent existence almost immediately, but appear to stay close to mother for some time (exact length unknown).

mother adder with day-old young
mother adder with day-old young

Sexual maturity is reached at 2-3 years, and adders generally live for 10 to 15 years.

Other Habits and Behaviors

Adders escape cold weather by hibernating, beginning when the shade temperature falls below 49 F, and ending when the average air temperature is above 46 F. It is not uncommon for adders to come out hibernation during the winter if the temperature is high enough, even if there is snow on the ground, and to return to hibernation when the temperature falls again. Unlike most other snakes, adders prefer crevices and holes to burrows for hibernation. It is very common for as many as 40 adders to hibernate en masse, along with an assortment of toads and lizards. Masses tend to return to their respective hibernation spots year after year.

Adders live solitary lives, with the exception of mating and hibernation.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Reptilia
order Squamata
suborder Serpentes
family Viperidae
genus & species Vipera berus

Animal Diversity Web

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The Robinson Library >> Science >> Zoology >> Reptiles and Amphibians >> Suborder Serpentes

This page was last updated on March 23, 2018.