Common Rat
Rattus norvegicus
Adult Common Rats are considerably larger than any of our mouse or vole species, but youngsters may be confused with Wood Mouse - though look for the proportionally thicker tail and over-sized hind feet in young Common Rat. Coat colour in the Common Rat is variable and dark-coloured or black (melanic) individuals are not uncommon. Such individuals may be confused with the smaller and more delicate looking Black Rat. The Black Rat is so scarce here now that any 'black' rat is much more likely to be a melanic Common Rat than a Black Rat.
Common Rats may sometimes be seen swimming in water, such as urban rivers, where they may be confused with Water Vole. Look for the prominent ears, pointed muzzle and long tail in Common Rat, which also appears less buoyant when seen swimming than is the case with Water Vole.
Common Rats are resourceful and adaptable. As a consequence, they are found in many different habitats, including gardens. They tend to live in colonies, often comprised of smaller social units or clans. Each of these clans is likely to consist of a dominant male and his partner, together with a wider harem of females and younger individuals, all centred on a single burrow system.
Mainly nocturnal in habits, the Common Rat may also appear during daylight where feeding opportunities are particularly advantageous. During periods of cold weather, diurnal activity often increases.
Common Rats are eaten by owls, stoats and foxes, among other carnivores.
One of the reasons why the Common Rat appears to have been so succesful in interactions with its human neighbours is the fact that it is suspicious of new food sources. A new source of food is sampled over several days, the rat only taking small quantities initially until it is sure that the new food does not pose a risk. Favoured foods are those with a high starch or protein content, but the Common Rat will make use of many different food types, including invertebrates, cereals, meat, bones, fat and suet. If Common Rats are viewed as a problem in your garden, then you will find some useful advice here
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