Everything you (didn't) want to know about rats

The recent concerns about rats which have been raised locally are obviously worrying to the parents who have highlighted the issue, writes Brian Byrne. But the worries are likely based on very little knowledge of the species itself, just an understandable gut reaction.

So the Diary has been prompted to look at rats, in their history and current position, so that at least there's some kind of perspective.

The brown rat (Norway Rat) has only been in Ireland since the 18th century, coming via ships from Britain and Europe, having originated in Asia. It quickly outnumbered the black rat which had been the dominant species here. Today it is the most common rodent species in Ireland, and along with the mouse is the most widespread terrestrial mammal in Ireland.

It likes to live near humans because as an opportunistic feeding animal, it is guaranteed ample food. Cereal crops and seeds are favoured, but also any scraps of meat, fish, vegetables, nuts and fruits. In rural areas rats will travel up to 4km in a night in search of food.

The brown rat is a prolific breeder, a pair producing up to five litters a year, mostly between March and November. Each litter can comprise between one and 10 pups, and a pair can produce a colony of up to 800 rats in a year in ideal conditions. But generally the mortality rate is high, with up to 90 percent dying in their first year.

The key predators are owls and other birds of prey, stoats, and foxes. The brown rat is the main source of food for the barn owl in many parts of rural Ireland.

For humans it is the most serious pest species, with a number of associated diseases carried, the best known being Weil's Disease, coming from the animal's urine and which can be fatal. Mites and fleas on brown rats can transmit other diseases to humans. They can also cause structural damage to buildings and electrical systems, due to their gnawing habits.

Large scale control of the numbers of brown rats have been unsuccessful, as they have both become resistant to poisons and are clever enough to learn to avoid food traps. However, a second generation of anticoagulant poisons is quite efficacious.

Brown rats are vermin, and are not protected under any legislation.

There's an urban myth that nobody is more than 6ft from a rat, but that's probably exactly what it is, a myth. There are expert opinions that put the distance at 164ft.

Rats do not generally attack humans, unless in a tight confrontation where they are themselves under attack. Bites on children, and sleeping homeless, are generally thought to have occurred through the animals trying to eat food residue on those bitten.

Rats are not just in Pinkeen Stream in Kilcullen, they are also regularly visible in other parts of the town for those who look, including the hedgegrows along the main road opposite Nicholastown. Any watercourse, including the banks of the Liffey, likely have rat populations, particularly where food residue litter is thrown, including beer cans.

In some parts of town where there are colonies of feral cats, rats are rarely seen, for obvious reasons.

(We're grateful to Conserve Ireland as the source of some of this information. It may not be of any comfort to those who are worried, but at least now the background is information-based.)