SUPER RATS

While talking with a resident in Chicago a while back, he commented to me, "The rats in our neighborhood are as big as alley cats and twice as mean. Our rats," he went on, "are tough, mean, dudes. And, the rat poison the exterminators put out only feeds them."

A few weeks later, upon relating this comment to a pest professional in New York City, the New Yorker replied with a defensive shrug: "Yeah? Tell him to come to the South Bronx if he really wants to see big rats."

It seems people are always willing — even proud — to tell tales of big, no, really big rats they have seen or "been nearly attacked by." But are there "super rats" in size and prowess living in our cities and farms?

BIGGEST OF THE BIG. Wild Norway rats have been recorded over the years by rodentologists, mammalogists and pest management professionals as measuring in varying lengths up to 19 inches (482 mm) and body weights of up to 1.87 ounces (850 g). But how common are such rats? And, are there even bigger rats out there? Is there a "Jaws" rat? Possibly.

Genetic anomalies (i.e., mutants) occur among nearly all animal populations. Occasionally, exceptionally large (or small) rats do occur — the same as is true with exceptionally tall or short people. Too, rats that are well fed from birth and live in environments where food and harborage are plentiful have a good chance of attaining or exceeding their maximal growth potential.

The biggest rats are usually males, as typically males grow larger than females. It is also the larger male rats that emerge as the dominant rats within their colonies. But other behavioral and social factors also contribute towards the status of "King Rat" in rat colonies.

Interestingly, it is to a rat’s advantage not to become large. Being able to remain small enough to hide in crevices and burrows in which their larger predators cannot fit is an important survival advantage, as is remaining lightweight and sleek to enable the rat to escape danger quickly. So it’s not likely even the super rats will constantly be breaking size and weight records.

MORE THAN JUST BIG. The term "super rat" is associated not only with just bigness. After only a couple of decades following the introduction of the effective rat poison warfarin, Norway rats began exhibiting physiological resistance to this poison. Thereafter, the public’s perception of super rats that are immune" to all rat poisons was ingrained in many urbanites. In fact, pest management professionals must constantly face this frustrating argument with urbanites that continue to see rats in their neighborhoods year after year.

Still, when considering a larger-than-normal, dominant, wily, male rat, which also may be resistant to some of the older rat poisons, it actually is not so much an exaggeration to call such rats "super rats."

THE FEAR FACTOR. But, size and resistance together still don’t account entirely for the often-amazing stories of super rats as big as cats and spaniels told repeatedly in cities around the world. Perhaps the most important element contributing to the super rat encounter is fear factor among both people and rats.

A frightened rat, upon being surprised by an intruder or an enemy (e.g., dog, cat, human, etc.), elicits a defensive posture prior to fighting its way out of the confrontation. This involves a ceremonial display of the rat clacking the incisor teeth, arching the back, hissing and raising the body hairs (i.e., raising the hackles). This "show" is an attempt to appear as large and act as fearsome as possible and hopefully frighten the threat away.

As most people who have unexpectedly experienced such a display by a large rat aimed at them can attest, the rat’s technique is usually highly effective. Frightened you are — composed and clear-thinking you’re not. I personally recall one cold, October night in an abandoned Indiana granary. It was very dark, my flashlight was dimming and there were squeals and tooth chatter of rats seemingly all around me. Sure enough, a rat came within inches of my face. No lie. That sucker was big. In fact, I swear it coulda been...

The author is president of RMC Pest Management Consulting and can be reached at rcorrigan@pctonline.com or 765/939-2829.

Editor’s note: This story was excerpted from Bobby Corrigan’s upcoming book, Rodent Pest Management: A Practical Guide for Pest Management Professionals, which will be available this fall from PCT. Call Lori Skala at 800/456-0707 for ordering information, or visit www.pctonline.com/store/productDetail.asp?CatId=2&SubCatId=5&Id=50.