The rat that chewed its way in from the cold, right through the wall

The Irish Times - Weekend Review - - OUTDOORS - Michael Viney

In a shad­owy cor­ner of our kitchen, a patch of freshly ce­mented wall gives me, if not plea­sure, then some greater peace of mind. Be­hind the ce­ment are shards of bro­ken glass and be­hind those the metal pot scrub­ber I had pushed deep into a hole be­tween rocks of the old house gable. Such are the des­per­ate me­chan­ics of de­fence when a brown rat de­cides to bur­row in from the cold, through plas­ter walling and all.

Au­tumn is, in­deed, the peak sea­son for re­minders that rats ex­ist. Peanut feed­ers hung up for for the birds can in­vite some sur­pris­ing – and alarm­ing – ro­dent ac­ro­bat­ics.

The first coun­try rat I ever saw was sit­ting on our bird ta­ble in the mid­dle of a sunny day, the very pic­ture of health and well­be­ing. Com­fort­ably poised upon its haunches, it held an oat flake dain­tily be­tween its paws, like a child mak­ing a bis­cuit last. Its eyes sparkled and its whiskers trem­bled in the breeze.

It’s the tail that seems to bother me most, so brazenly naked and hair­less. As well as for bal­ance, it’s the an­i­mal’s heat-loss or­gan, con­trol­ling body tem­per­a­ture by di­lat­ing or con­strict­ing its blood ves­sels. Learn­ing this does noth­ing to quench my dis­taste.

In last week’s col­umn, dis­cussing the eco­nomic costs of Ire­land’s non-na­tive species, I quoted the ¤2 mil­lion lost an­nu­ally in the ce­re­als eaten or spoiled by rats. Even this au­tumn, with yields well down, the pas­sage of grain lor­ries will have set the road­side verges quiv­er­ing with furry life.

In ear­lier years I grew a rood of bar­ley to har­vest for the hens. Once, lift­ing sheaves to build a rick, I was helped by a neigh­bour and his watch­ful dog. The dog had killed 13 rats on such an oc­ca­sion, but now there was only one, which beat the dog to the ditch.

Mis­lead­ing name

Farm­ers talk of “wa­ter rats” as dif­fer­ent from the ev­ery­day kind, but swim­ming rats are the or­di­nary brown (or grey or black) ones, Rat­tus norvegi­cus. The name is mis­lead­ing, per­sist­ing oddly when so many names in sci­ence have changed.

The an­i­mal may, in­deed, have dis­em­barked in these is­lands from Nor­we­gian tim­ber ships, but Rat­tus norvegi­cus was part of the ear­lier spread of the species from the steppes of cen­tral Asia. The ear­li­est ar­rival in west­ern Europe was from a Rus­sian ship reach­ing Den­mark in 1716 and it re­put­edly reached Ire­land in 1722. (Nor­way didn’t get them for an­other 40 years.)

The black rat, Rat­tus rat­tus, al­ready in Ire­land, was na­tive to In­dia and first brought to Bri­tain with the Ro­mans. If the way­ward chron­i­cler Gi­ral­dus Cam­bren­sis can be trusted, it had reached this is­land by 1187, seek­ing out the warmth of hu­man habi­ta­tion.

The black rat is smaller than the brown rat that dis­placed it, with larger ears and a tail even longer than its body. As a ship rat, its fleas brought Black Death to Ire­land in 1348, ini­tially to Howth or Dalkey. The ware­house lofts of the ports housed a long, if ten­u­ous, pop­u­la­tion.

Its only con­firmed colony to­day is on Lam­bay Is­land off Co Dublin, where it win­ters in farm build­ings and can be seen scam­per­ing on the cliff-tops in spring and sum­mer.

The black rat’s vege­tar­ian tastes (in In­dia it climbs trees for fruit and berries) may have hand­i­capped its chances when the brown rat swept in, di­gest­ing al­most any­thing chew­able. But the over­whelm­ing ad­van­tage of Rat­tus norvegi­cus lies in its pro­lific breed­ing.

Lit­ters

Sex­u­ally ma­ture at eight to 12 weeks of age, fe­males can have lit­ters as of­ten as once a month, with about seven or eight ba­bies in each. Ex­po­nen­tial math­e­mat­ics project po­ten­tial an­nual off­spring near to 100 and some 400,000 de­scen­dants per year.

Hu­man use of poi­son baits can rapidly change the odds. But nat­u­ral con­trol comes from lim­its to food sup­ply, smaller

We live in a maze for ro­dent ad­ven­tur­ers, lured in by food aro­mas and the prom­ise of warmth as win­ter closes in

lit­ters, crowded con­di­tions that in­hibit breed­ing, out­breaks of dis­ease. These add to death by fox, owl, stoat, mink, pine marten, do­mes­tic dog and speed­ing 4x4s.

Along with the ma­te­rial costs of dam­age and con­trol come threats to hu­man health. Rats can ex­crete lep­tospiro­sis (Weil’s dis­ease) in their urine, a bac­te­rial in­fec­tion still rare in Ire­land. Find­ing tun­nels in my com­post heaps has some­times made it pru­dent to wear gloves.

The tun­nelling in our gable was not the first. The old house was built of field stones a cen­tury ago and the new bit sits on a plat­form of rocks. We live in a maze for ro­dent ad­ven­tur­ers, lured in by food aro­mas and the prom­ise of warmth as win­ter closes in.

So yes, we set care­ful and cov­ered caches of poi­son – if not, it seems, quite of­ten enough. Once or twice over the years, a ca­su­alty has ex­pired in­doors, in some ob­scure and in­ac­ces­si­ble cav­ity. But that may be more than you wish to think about, at break­fast or any other time.

IL­LUS­TRA­TION: MICHAEL VINEY

Peanut feed­ers hung up for for the birds can in­vite some sur­pris­ing – and alarm­ing – ro­dent ac­ro­bat­ics.

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