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Common Rat

Common Rat © northeastwildilfe.co.uk

Disease-carrying vermin, habitué of sewers and other filthy places, promiscuous, a despoiler of food, the shudder-inducing nightmare of so many horror films: or, a remarkably successful, wonderfully adaptable, world-colonising rodent, able to live almost anywhere and eat almost anything, an affectionate pet and as a laboratory animal indispensable to medical research. Everyone knows the Common Rat Rattus norvegicus and few wild animals have so intimate a place in human perceptions.

Once called the Norway Rat in the mistaken belief that it entered the UK from Norway (hence the scientific name), the Common Rat is thought to have its probable origin in the steppes of Central Asia, spreading out and colonising Europe including the British Isles in the 18th century (Harris and Yalden, 2008). The first Common Rats reached Britain around 1720 in Russian ships from the Baltic and by 1776 it was recorded in Selkirk in Scotland (Twigg, 1975). As it spread it supplanted the UK’s only other rat, another non-native, the Black Rat or Ship Rat Rattus rattus. By the second half of the 19th century the Common Rat was living up to its name with descriptions such as “swarms in all the reclamation embankments constructed by the Tees Commissioners” (Lofthouse, 1887).

There is no need to describe the morphology of the Common Rat: TV and film have made it one of the best known mammals in the world. Male Common Rats tend to be bigger than females with a head and body length of around 280 mm and weighing around 500 g: the tall tales of rats the size of cats just aren’t true. The bare, scaly tail is usually a little shorter than the body length and is a useful aid to identification. Otherwise known as the Brown Rat they are generally grey brown in colour above and grey beneath (Harris and Yalden, 2008).

The Common Rat by Thomas Bewick

Common Rats are colonial rodents, living in territorial clans, each clan having a home range and a system of burrows and dens used for shelter and breeding. Breeding can be continuous throughout the year in sheltered environments with good food sources, but is limited to summer and autumn in less productive and harsher environments. Rat populations can reach very high numbers in late summer and early winter but adult mortality is high with few rats reaching one year old, and by the spring numbers are usually much reduced. Rats will eat almost anything but they do prefer protein rich foods, especially cereals, a diet which has probably always brought them into conflict with humans. The rat’s catholic taste and its ability to adapt and exploit changing food opportunities are well illustrated in a tale told by James Hardy of Gateshead:

On February 24, taking a walk with a companion, as we went along the side of the mill race at Swalwell, near Newcastle upon Tyne, we noticed a common house-rat making its way close by the edge of the water among the coarse stones that formed the embankment. Curious to know what it could be doing there, we watched its progress downwards, until it reached the outlet of a drain, into which it had just turned, when it gave a sudden plunge, and as quickly reappeared in the stream with a middling-sized eel in its mouth. (Harting, 1892, in Twigg, 1975).

In the UK the Common Rat can be found almost anywhere with the exception of some exposed mountain areas and some offshore islands. It is widespread in Durham and Northumberland occupying habitats from the coast to the upland moors, but is likely to be common only where humans provide all-year-round food and shelter. Away from the human resource, occupation of the wider countryside may be limited to the summer months including the early autumn when harvesting cereal crops in arable areas. Our post-2000 distribution map is probably limited by observer bias but the indication of an abundance of Common Rats around the urban conurbations of Teesside and Tyneside, places where rats can find food, shelter and places to breed all year round, may well be an accurate one.

MARS Brown Rat

Rats and humans must always have been in conflict primarily over food, although they are a human food item themselves in some parts of the world. More recently rats were also recognised as a vector of disease in humans. The history of rats and humans is a long one described mostly in terms of vermin control with trap and poison.

Rats were included in the 1566 Act for the “Preservation of Grayne” with a bounty of one penny for three dead rats, to be paid by the churchwarden of the parish. The rat referred to in the Act would be the Black Rat and possibly also the Water Vole Arvicola terrestris, still commonly referred to as the Water Rat. Historically rats rarely actually appear in the churchwardens’ lists of vermin paid for and this may well be because there was already a long established tradition of professional and domestic rat control (Lovegrove, 2007). The Common Rat is exempt from the Hunting Act 2004 and can still be legally hunted with terriers and ferrets; unfortunately the ignorance or carelessness of the hunters often extends the prey species to include the Water Vole.

As agricultural pests rats are supreme, and inventing ways to get rid of them was and is a perpetual challenge. Before modern traps and poison, anything would be tried to get rid of rats and attempts at the charming away of rats as in the “Pied Piper of Hamelin” story was resorted to. In 1953 the journal Folk-lore printed a letter recounting a tale, told to the writer by an Irish farming lady, of an itinerant rat-man who visited their farms to rid them of rats. His method was to play a tune through the infected steadings and stackyards, placing a written incantation in the rat holes as he went. As a result the lady informant assured the letter-writer that the rats gathered together in a body and left that place (MacGregor, 1955). The same technique was formerly employed in Northumberland: Neasham (1893) records a Mr Dand of Hauxley Cottage showing him a letter to quit, written to rats. The letter on a sheet of quarto paper was “To all the Ratts in the house, Barns, Biers, stabls and Outhouses belonging to Robert Milburn of Ulgham”. The body of the text reads:

“A Billet For Ratts. This is to Discharge you all, in the Name of Tibract, Price of Catts, to begon from this Place, as you are bad Neighbours, and Disturbers of our peace; but you must go and Lodge with William Tweedy of Ulgham Park, which are not above a mile to the Nor west from this place. There you will have good quarters, and Plenty of Food; so adue, bad Neighbours, adue.”

The postscript to the letter gives instructions for use and shows that this attempt was not a once-only one: “Be shour you Lay this Billet wheare the Ratts Resorts. After it is sealed up it is not to be look’d on by no person, as they may likely taked [take it] from the place you lay it in. This has been well tried in sindry [sundry] places.” What is not recorded is whether music was part of the process.

Mass migrations of rats are occasionally recorded, like the one reported by a scared policeman in 1976 to the habitués of a pub in Clayton Street, Newcastle upon Tyne, of a river of rats migrating across the road between basements; or the horse rider in late summer 2008 reporting the strange and dreadful noise of the hundreds of rats she watched crossing a stubble field and heading in the direction of Kirkheaton (Ruth Hadden, pers. comm., 2012).

Rats were also a threat as a vector of Weil’s disease or leptospirosis, a disease of agricultural workers, sewer workers and – more pertinent to the northeast of England – coal miners, with miners at risk of illness and occasionally death (Broom, 1951). Drift mines allowed Common Rats to walk in and colonise the piles of waste rock, subsisting on the food of the pit ponies stabled underground and on discarded scraps of the miners’ food. Particularly in wet mines, rat urine would spread the disease which was contracted by miners through abrasions and cuts (Twigg, 1961). Even deep mines were not always free from rats but here, once they were in, the rats would starve if food sources were removed. Robert Stephenson MP of engineering fame recounts the tale of Walker Colliery, near Killingworth, where rats depending on pit pony food for their existence had reached great numbers. When the pit closed for the miners’ holidays the ponies were brought to the surface and the rats deprived of their food. On re-opening the pit after the holiday the first man down the shaft was attacked, killed and eaten by the starving rats (Bell, 1874).

Improved hygiene and the introduction of effective anticoagulant poisons in the 1950s gave humans a temporary upper hand in the war with rats, but there is now evidence that some rat populations have developed resistance to anticoagulants through an inherited trait (Harris and Yalden, 2008) and it seems that the Common Rat is likely to continue to live up to its name.

References

Written by Terry Coult (last updated Nov 12)