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October 4, 2009

What to Do About Wild Rats

Norway and black rats can be a source of major conflict in urban settings and proper trash management is key to dealing with them

Adapted from the book Wild Neighbors

rat brown

istockphoto

Rats are incredibly hardy animals who have never shown any problem adjusting to change. Usually that change is the introduction of a new poison, as humans constantly work harder and harder to exterminate these animals. But perhaps no other animal resists such attempts better than the rat.

Rather than looking for more powerful and potentially dangerous ways to kill rats, the only real answer to people’s conflicts with these animals is to alter the habitats in which they choose to live to make them less attractive and acceptable.

Common problems and solutions

Public health concerns
Resources

Common conflicts and solutions

Food: Rats will eat anything a human will, and more.  But worse damage is done by their urine and feces which are left behind on any uneaten food.

Burrows: Although rats may create damage with their borrowing, it’s usually more superficial than structural.

Chewing: Since their front teeth grow all their lives rats, chew on things to keep them worn down. This can be dangerous when they gnaw on electrical wiring.

Public Health: Rats can carry many diseases that are harmful to people.

Tolerance

Tolerating rats is not something many people want to do. For many reasons people and rats are unlikely to coexist peacefully. But coexist we will, as perhaps more than any other wild animal, rats have adapted to living among humans. That we do not generally tolerate their presence does not mean that we need to use dangerous and inhumane methods to destroy them—or accept a no-holds-barred way to controlling their numbers.

The best way to control rats is to discourage them from taking up residence in the first place. Typically, conditions that support high rat populations are left until there is a real crisis at hand. Then the poisons are used or trapping employed to reduce the population, only to leave unaddressed the cause of the problem in the first place. Any effort to limit rat populations must be followed by taking the necessary steps—exclusion and sanitation—to make sure the same problems never happen again.

Identifying rat signs

Inside

  • Droppings.
  • Gnawed holes up to two inches wide in baseboards or at doorframes (indicates they’ve been there a while).
  • Smudge marks (body oils) on walls. 
  • Sounds of movement in walls and attics.
  • The family pet staring intently at a blank wall.

Outside

Burrows may indicate the presence of rats, but could also indicate other burrowing animals such chipmunks. Never attempt to control a wildlife problem without being sure what species of wildlife you are dealing with.

To find out if the burrow is in current use, loosely fill it with soil or leaves and check it in a day or two to see if it has been reopened.

Keeping rats out

Rats can enter buildings through many openings:

  • Holes as small as 1 inch wide (about the size of a quarter). 
  • Heating vents.
  • Gaps anywhere electrical conduits, utility or air conditioning lines, or water pipes enter a building.

Suggested techniques

  • Seal holes and other appropriate openings with heavy-weight material (1/4-inch hardware cloth or heavy-gauge screening is recommended).
  • Plug gaps in walls and floors with copper mesh like that used for scouring pads.
  • Finish sealing openings with caulking or foam insulation. Because rats can gnaw through these, though, combine them with wire mesh.

Repellents

Varpel Rope® is registered as a repellant for mice and rats. The active ingredient is used in making mothballs. No repellent has ever been found to work permanently on rats, so in using any that is sold for that purpose, keep this in mind. 

Modifying habitat

Good sanitation is the best and most economic way to control rats. Follow these steps to keep rats away or to keep their numbers in check:

  • Clear away any rubbish piled close to buildings to expose burrows and openings that rats might use to get in.
  • Store food in rat-proof containers, such as galvanized cans with tight-fitting lids. This includes birdseed, grass seed, and other possible foods kept in garages and/or outbuildings. 
  • Store and dispose of garbage properly, so that rats can’t get into it.
  • If you feed your pets outside, leave the food out for just long enough to be eaten, and then remove it.
  • Clean up pet droppings from the yard every day.
  • Remove old wood or rubbish from the property since these are regular rat hangouts.

Where rats continue to be a problem around buildings, you can use an L-shaped barrier of either hardware cloth or concrete to prevent burrowing along foundations long-term. Bury the footer about 12 inches deep and extend it out from the foundation about 12 inches. When a rat tries to dig into the foundation he won’t be able to get past the barrier.

Lethal control

There are no truly humane ways to kill rodents, only methods that are less inhumane. Rats are killed with poisons, snap traps, glue boards, and maze-type traps that drown them. Based on what is known about these methods, the traditional snap trap, and perhaps the newer traps that use an electrical charge to stun and kill, seems to be the least inhumane. This doesn’t mean that rats won’t suffer in these traps—they almost certainly will. 

With the use of lethal control, animals will suffer. So keep in mind, the need to control rats is a largely the result of lack of cleanliness in the immediate environment.

Public health concerns

Rats are considered as carriers or transmitters of more human diseases than any other life form, except maybe the mosquito. More than 15,000 rat bites are reported each year in the United States. All rat bites should be treated by a doctor. Some of the diseases that can be spread from rats to people are bubonic and pneumonic plague, murine typhus, salmonella, leptospirosis, Hantavirus, and tularemia.

Resources

» S. Anthony Barnett, The Story of Rats (2001, Allen & Unwin)
» Robert Sullivan, Rats: Observations on the History and Habitat of the City’s Most Unwanted Inhabitants (2004, Bloomsbury)
» Purchase a copy of Wild Neighbors; the go-to guide for useful, humane solutions to conflicts with wildlife
» If you are located within the D.C. Metro Area, take advantage of our wildlife conflict resolution service. Learn More

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