Rats! Feb 9, 2009 Published in March 2009 issue of Metchosin Muse
Walking into my laundry room late one night in November, flipping on the light switch and seeing a rat streak up the wall and along the rafters at light speed elicited an immediate and visceral response. The scream I produced would have garnered an Oscar at any horror film awards presentation.
I unwillingly shared my home with this impudent house guest for a number of weeks as it continually foiled my attempts to have it removed, dead or alive.
Most rats in our region are Rattus rattus, also known as black, ship or roof rats. Historically they arrived via ships and because they need a warmer climate than Norway (brown) rats (Rattus norvegicus), they are usually confined to coastal areas, although, if they can find suitable winter habitat (inside your home or business) they can be found in Interior urban areas. They are thought to have originated in India or tropical Asia and are the disseminators of the bubonic plague that killed 30-60% of Europe’s population and many more people from Asia, Africa and India in the fourteenth through eighteenth centuries. Actually the true culprit was the oriental rat flea, which killed the rats as well as the human populations. They have also been implicated in a catastrophic decline in songbird populations when they have been introduced on small islands.
In most of North America, the Norway rat is the one you are most likely to encounter. Where the two rat species co-exist the Norway rats will chose to inhabit basements and the roof rat, the upper levels of buildings. The Norway rat is not from Norway, that is the place they were first scientifically described, it is believed that they originated in northern China.
Mike Kennish of PSI, the pest control specialist that I eventually brought in to deal with “Ratty” has been in the business for eighteen years and the stories he told could curdle your blood or at least cause an involuntary shudder or two. He said that in all those years he has only seen one Norway rat.
Around here, Rattus rattus are commonly known as roof rats because of their preference for aerial habitats. They can run up wallpaper, along wires and rafters and often nest in attics or between floors and ceilings; even in trees and they will burrow under homes in the absence of Norway rats. They are noted for their speed and agility. The stronger, larger Norway rats are infamous for their use of basements, sewers and aquatic areas and for creeping along close to walls, leaving an smeared, oily track. These are the legendary and infamous creatures of New York fame.
Roof rats are territorial and have a rather small home range of no more than 100 m, remaining close to their food source. They are omnivorous but prefer fruits, nuts and grains. Apparently they enjoy snails but it is not recommended to encourage them as a “natural” garden pest solution alternative! Their bodies are fifteen to twenty cm in length, with an equally long, hairless tail and on average, they weigh about 200 grams (1/2 lb). Their fur can show a variety of colours, though northern populations are more likely to be black or steel coloured. Rats are nocturnal animals, if you see them during the day it is because they are so overcrowded the rats lowest in status have been forced to seek food and shelter during the day. Not a good sign!
There is speculation that they have evolved for speed selection. I can attest that these creatures are fast! Ratty sped across my basement rafters in the blink of an eye. Females (does) in heat are chased by groups of males (bucks), with the female selecting the fastest male. The resulting litter of two to eight kittens or pups are born in about twenty-one days and are sexually mature in three months. A healthy female can conceivably reproduce five times a year. Most wild rats live only a year, they have a 91-97% mortality rate, whereas rats in captivity can live three to four years. A group of rats is called a mischief, although the things I have called them are not nearly so whimsical!
Despite the fact that most of us feel a deep sense of revulsion when we even think of rats, they are fascinating animals that are highly evolved survivors.
They haven’t developed particularly acute sight but their long whiskers are used to similarly sense their environment. Their whiskers are extremely sensitive to touch, more so than our fingertips, and research is showing that they are also used in hearing, they can pick up the frequencies produced by brushing against objects. Their whiskers read the world like the blind read Braille, if Braille could be in surroundsound. A rat’s world is a smorgasbord of scent, one percent of their DNA is involved in their sense of smell. This helps them find food and discern its edibility with incredible accuracy. They have a secondary olfactory organ, located in their nose, that is responsible for receiving and relaying chemical signals that often relate to reproduction and social standing. Rats have acute hearing, both for soft sounds and high into the ultrasonic range. We might not be able to hear the sound produced if we rub our finger and thumb together, but rats can.
No matter how much I can respect and admire a rat’s ability to survive and flourish, I still don’t want it in my home. Rats, despite being clean animals themselves (they spend 1/3 of their time grooming), spread disease through their droppings. They use their urine as scent markers and much like the bar codes on our grocery items, each rat’s urine scent is identifiable to other rats. It records their health, sex, reproductive readiness, social standing and a host of other details important to rat life, kind of a rat’s version of Facebook. If conditions are good, all this advertising results in a proliferation of rats and the need to seek out new territory. Rats seek heat, warm and cozy hiding places to raise their young. According to Mike, the best defense against rat intrusions into your home, is to maintain your home in the best condition possible-build to exclude them and keep your garbage at a minimum and securely contained.
Rats do not have the collapsible skeletons that have been attributed to them but an average sized roof rat can squeeze through a hole the size of a quarter. Vines and pipes climbing up the exterior woodwork allow the agile roof rat easy access to any unnoticed openings, into broken vents in soffits or decaying roofs. Inspect the foundation and see if cracks have developed, my rat gained entry through an open door under the steps and then chewed through a 2 x 4 to enlarge a small hole in the concrete foundation, they can chew through concrete too. Check to make sure that all your vents to the outdoors are strong and in place. Second, make sure you are not attracting rats with the delicious aroma of garbage: slightly rotting fruits, well aged meats, seeds and grains. In the spring, rat colonies can be on the move, hungry from the winter’s depredations, looking for more convivial quarters. Don’t hang out an olfactory sign that says Rat Restaurant!
Pet cats and dogs are not always rat deterrents, although I had a standard poodle once that caught a few rats. Terriers and Jack Russells have been bred to be ratters but they need to be trained from an early age. Don’t leave your cat locked in the basement with a rat, sadly, many times the cat will be the loser.
Mike told me in his matter of fact way of storytelling how he had recently been called to a home of a, shall we say, eccentric client. This person had been feeding the neighbourhood squirrels and wildlife to the point they were coming onto the window ledge. By the time he was called in, the neighbourhood was besieged by rats, they were even seen in the trees during the day. In six weeks he captured 335 rats! They had constructed so many burrows under the house that the foundations were no longer structurally sound and the house had to be torn down.
When the inevitable happens and you find a rat in your home, remember you are not alone. Everyone has a rat story. Mike says that most people first hear a rat in the bedroom wall behind their headboard. I remember a saying from my childhood, “If you can hear it, it’s a rat; if you can’t, it’s a mouse!” I tried to catch mine for a week or two but setting the traps was just too heart stopping and I ran out of friends to call to set them for me! Hence my frantic call to Mike. It took a couple of more weeks but eventually Ratty succumbed to the temptation to take the peanut butter bait. I admit I felt a sense of relief when I finally found his body.
The typical extra-large version of a mousetrap is considered the most humane method of dispatching rats and has the least chance of harming your pets. Poisoned baits or the bodies of poisoned rats can be ingested by other non-target animals or the rats can slowly die in the walls of your home. If that has ever happened to you, you know it is not a sensory delight. Rats are phobic about anything new in their environment and they will initially avoid a new trap or food. There are recommendations on baiting but not setting a trap for several days, until the rat has become conditioned to the trap.
Rats and deer mice are known to transmit the Hanta virus through their droppings or the dust from their droppings. Although it has not been recorded from Vancouver Island, to be safe and to prevent breathing in this toxic dust, wear a mask and spray any droppings you find with a ten percent bleach solution, let dry and then vacuum.
Some people keep roof rats as pets; they are said to be clean, intelligent, friendly and playful. Norway rats have a long history as pets and have been bred for the pet and research market. They have been used in studies on heart disease and cancer, in understanding neurological responses and drug reactions. It is somewhat ironic that one of the most reviled animals is also one that has significantly contributed to our understanding of human health.
Along with humans and some primates, new research has shown that rats possess metacognition, the ability to be “aware of their own strengths and weaknesses, the nature of the task at hand, and available "tools" or skills”. No wonder they have conquered the world and survive almost any threats.
Whatever you think of them, rats live among us, following our trails of garbage and discarded foods, seeking our warm shelters. Their intelligence, fecundity and adaptability makes them survivors that require us to use our ingenuity to keep them out of our homes.
2008 was the year of the Rat in Chinese astrology (1925, 1937, 1949, 1961, 1973, 1985, 1997, 2008). People born under this sign are considered honest, generous, creative, curious, hard-working, charismatic, survivors, ambitious, quick tempered, manipulative and selfish. Alexander the Great, Cleopatra and one of my ex-husbands were notable Rats.
Gillespie, H. and P. Myers. 2004. "Rattus rattus" (On-line), Animal Diversity Web. Accessed February 09, 2009 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Rattus_rattus.html.
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