Image credits to Wikipedia
Fact file
Latin name
Rattus norvegicus
Threat status
Least Concern (Global)
Least Concern (Europe)
Least Concern (UK)
Etymology
The brown rat’s Latin name ‘Rattus norvegicus’ translates to Norwegian rat as it was believed that the rat colonised the UK from timber imports from Scandinavia. However, when the rat was becoming common in the UK, it had yet to colonise Norway and the rest of Scandinavia. It is now believed to have originated from Central Asia hence the change in the name to the brown rat due to the rats notable brown fur colour.
Identifying features
Most notable for its brown fur colour, the brown rat is much larger and wider than its smaller cousin the Black rat (Rattus rattus) with smaller ears and eyes.
Habitat
They are commonly found in association with human settlements due to the ease of finding anthropogenic foods. They can also be found around agricultural buildings as well as around hedgerows and some coastal areas.
Numbers
Minimum estimates are around 7 million from the Mammal Society Review of the Population and Conservation Status of British Mammals.
Distribution
Found throughout Europe, central Asia and Eastern Asia as well as parts of the Middle East and Northern Africa. They are found throughout the British Isles but are less common in more ‘wild areas’ which includes much of the Scottish Highlands.
Diet
Brown rats are opportunists so will feed on any food source that is available to them. In urban environments they tend to eat any scraps that they can find whereas in rural environments they tend to focus more on cereals and vegetables.
Size
Total head and body length of between 150-270mm but with many individuals, mostly males, being much larger and a tail length which is similar in length to the body at 110-240mm. They can weight between 150-500g but individuals have been recorded at over 1kg.
Life span
The maximum life span of wild rats is around three years but is rarely that long due to very high mortality rates of nearly 95%. Often rats will only last a single year with more dominant individuals living longer.
Breeding
Brown rat are rapid breeders and can breed throughout the year allowing females to have around 5 litters per year which contain on average 9 young with larger females producing more offspring. Females are pregnant for around 22 days and the offspring are born pink and blind. After 6 days they are able to open their eyes and by 3 weeks are fully weaned. It then takes the offspring about 3-4 months before they are fully sexually mature and can breed themselves.
Survey techniques
Rats are surveyed often using large catch traps but due to their size and aggressive behaviour require experience to handle.
A real rat race
Image credits to Wikipedia
Due to the rats amazing sense of smell, they are often used as ‘sniffer rats’ for various different applications, for example in forensics. A Belgian non-government organization, APOPO, trains Gambian pouched rats (Cricetomys gambianus) to sniff out land mines and tuberculosis.
Also due to the small size of rats, they can run through small tunnels which can be used to help lay internet wires under the group.
Good pets
Over many years, people have kept domesticated rats and over time have selectively bred them to become ‘fancy rats’. They now have various different colour such as white, Berkshire, hooded, capped, blazed and variegated.