Adder

The common European adder, known scientifically as *Vipera berus*, is a venomous snake belonging to the family Viperidae.

This species is incredibly widespread across the Eurasian landmass. It can be found in much of Europe and stretches as far east as East Asia. In fact, it is the snake species that lives the farthest north of any other snake in the world. While it is venomous, it is not considered especially dangerous to humans. The adder is not an aggressive animal. It usually only bites if it is provoked, stepped on, or picked up. Although bites can be very painful, they are rarely fatal.

The physical structure of the adder is quite distinct. Adults typically grow to a total length of 50 to 60 centimeters. However, size can vary by region. The largest specimens, reaching over 70 centimeters, are found in Scandinavia. The mass of an adder generally ranges from 100 to 500 grams. Their bodies are relatively thick. The head is large and distinct with sides that are almost flat and vertical. Most adders feature a dark V or X marking on the top of their heads. A dark streak also runs from the eye down to the neck.

Coloration is a major way to identify different adders. Most snakes have a zigzag pattern on their backs that runs along their bodies and tails. Light-colored snakes have small, incomplete dark crossbars. Darker specimens show faint or clear brown markings. Some individuals are melanistic, meaning they are completely black and lack a pattern. Interestingly, you can often tell the sex of the snake by its color. Males are typically a uniform grey with black markings. Females are usually brown with dark brown markings. Melanistic individuals are often female.

The adder has a unique way of reproducing called ovoviviparity. This means the females give birth to live young rather than laying eggs. Females usually breed once every two or three years. In the Northern Hemisphere, litters are typically born in the late summer or early autumn. A single litter can contain anywhere from three to 20 young snakes. These young stay with their mothers for a few days after birth. This reproductive cycle is a vital part of their life history.

Habitat complexity is essential for the survival of *Vipera berus*. They require diverse environments to support behaviors like basking, foraging, and hibernation. They can live in many places, such as rocky hillsides, sandy heaths, and woodland edges. They are also found in meadows, coastal dunes, and even stone quarries. If dry ground is nearby, they may visit wetlands like stream banks or ponds. In the Swiss Alps, they can be found at altitudes of about 2,000 meters. In southern Europe, they often live in low-lying wetlands or high altitudes.

There are three recognized subspecies of the common adder. The first is the nominate subspecies, *Vipera berus berus*. This subspecies lives in many places, including Great Britain, Germany, and Russia. The second is the Balkan cross adder, *Vipera berus bosniensis*. This subspecies is found in the Balkan Peninsula. The third is the Sakhalin adder, *Vipera berus sachalinensis*. This subspecies lives in the Russian Far East, North Korea, and Northeast China. Some recent publications have even regarded the latter two as full species.

The history of the adder's name is quite old. The word "adder" comes from *nædre*, an Old English word for snake. In the 14th century, the term "an adder" emerged in Middle English. Scientists have worked to categorize these snakes for centuries. Carl Linnaeus described the nominate subspecies in 1758. Boettger described the Balkan subspecies in 1889. Zarevskij described the Sakhalin subspecies in 1917. Today, the species is listed as "least concern" by the IUCN, though populations are decreasing. This decline is caused by habitat loss, agriculture, and collection for the pet trade or venom extraction.