February 2014 - The Brown Rat

Brown rat - Lin's garden

This is the time of year when we feed our local birds with seeds, nuts, fat balls, meal worms and a variety of other foods. But rats are hungry too! Every year in winter we are invaded by these unwelcome rodents. They do damage to property with their incredibly sharp teeth and love of gnawing. They got into our loft one year and set off the burglar alarm in the middle of the night by chewing through the wire cable; that year I also had to replace pipe lagging in the loft which they had destroyed. The same year they broke through the concrete floor of the aviary and took one very old zebra finch away entirely. We never even found her body, blood or any feathers!

The Brown rat has several names including common, street and sewer rat. It is also called the Norway rat as it was thought originally to have come to the UK on ships from Norway. Now the rats are thought more likely to have originated from central Asia, probably China. The rat's tail is as long as its body, and adult's body alone can be as long as 10 inches (25cm) and may weigh 11 oz (300g). Rats are highly resourceful, adapting to any environment and being truly omnivorous, eating just about anything. They are especially fond of cereals. Rats tend to use defined 'rat runs' which extend from the nest to places of potential food and they can climb onto bird tables and up trees (I have seen them climb our Victoria plum tree, happily eating the plums in the late summer).

A female rat can have as many as 5 litters a year. We found a litter in our compost bin last year with 9 babies, a common number for a rat to have. Talk about a population explosion if allowed to go unchecked! Their life span is about three years although most (over 90%) die in the first year due to predation and social conflict. They live in hierarchical groups, usually in burrows and if the the group is put under stress, i.e. by overcrowding or lack of food, the lower ranks are the first to die. If a large proportion of the population is exterminated, the remaining rats will increase their reproductive rate to restore the old population levels.

Brown rats carry a variety of pathogens causing diseases, such as Weil's disease and Salmonella. If you have come into contact with rats and feel unwell, then seek medical advice immediately.



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