Household Pests: Rats

Wild animals are part of what makes nature so magical, and watching them can be highly enjoyable. While it’s important to coexist with animals in relative peace, they can cause countless problems when they take up residence in our homes or gardens. In this series, our Wildlife Management Specialist, Shawn Weeks, will educate us about some common household pests, and share some strategies for keeping them under control without dangerous chemicals.

Today we’ll look at rats.

Habitat and History

The two rat sub-species that North Americans are generally concerned with are the Norway rat and the roof rat, also known as the brown rat and black rat, respectively. The roof rat is said to have come here with the first settlers from Europe, while the Norway rat is said to have come by ship around 1775. They live and breed anywhere humans are, because they prefer habitat that is shared with humans. Unlike most other rodent species, rats don’t do well in grassy or wooded habitats, where there is too much competition from native species, and too many predators.

Rats are phenomenal climbers, excellent swimmers, and very agile. And, despite its larger size, a grown, full-size rat can enter into a hole the size of a quarter. They can scale poles and electrical conduits, jump three feet high, and up to four feet horizontally.

A rat’s range is typically only about 75-500 feet, depending on habitat conditions such as food and water sources, and competition. Norway rats have been known to travel up to a half mile daily to access a food source, however. Norway rats build and live in dens and burrows that are usually around eighteen inches deep and three feet long. These dens have more than one opening for escape and sometimes these openings are loosely covered over for concealment. In buildings they will live inside walls, under cabinets, in plumbing voids, and under cluttered materials. Roof rats are commonly known to live up off the ground. They travel on above ground objects such as utility and phone lines, as squirrels do. If they are found to be living in a building or structure, it is generally high up, such as in an attic, or in voids and walls in the upper levels of a home. Outside, they tend to nest in trees and other high objects.

Both species are primarily nocturnal. Day sightings of rats can usually be attributed to high density populations, low food sources and juveniles not being able to compete at night with adults.

Diet

Rats will eat basically any food source. They are omnivorous, eating both animal and plant matter. Norway rats are known to eat more animal matter than roof rats. They will also consume insects, bird eggs, and even mice when their food supply is low. Adults require approximately one ounce of food per day in addition to a good water source.

Reproduction

Rats breed year round. Breeding age is usually reached at two to three months, with average litter sizes ranging from eight to twelve offspring for the Norway rat and five to six for the roof rat. One female can generally wean twenty young per year.

Problems, Solutions and Health Concerns

There are many problems and health concerns associated with rats. They transmit more diseases to humans than any other insect or animal, including the bubonic plague, salmonella, hantavirus, tularemia, and leptospirosis. More than fifteen thousand rat bites occur annually in the United States, usually to the elderly, incapacitated individuals, and children. All rat bites should be treated by a doctor.

Rats contaminate human food by spreading their urine and feces, and cause structural damage to buildings. They can gnaw through most any material, including lead pipes, and often cause electrical shorts and even fires by gnawing through electrical wires.

There are many preventive methods used to reduce the risk of rats from becoming your tenants or personal guests. Wire mesh, expansion foam, lumber, caulking and sheet metal are commonly used to seal up possible entry points to buildings. Check for openings along foundations, including places where conduits enter structures, heating vents, rotted soffits and roof liners, chimney caps, fill and vent pipes for your home heating oil tank, etc. Basically, rats can enter anywhere, high or low, with an opening of half an inch or more. It can be time consuming, and almost mind numbing, to find and seal all possible points of entry, but it beats the alternative.

As with most other animals covered in this series, it’s important to practice preventive maintenance to ensure you do not become a full time rat cop or exterminator on your own property. Keep your place free of debris and clutter, both inside and out. Keep animal feed and dog food in strong, clean, secure containers. Keep your grass mowed and weeds down, especially around buildings. Make sure to clean up bird feed areas and don’t let used up materials from seeds pile up. Also, remember to keep your garbage cleaned up and hauled out regularly.

There are many different methods for removing rats from a dwelling or building, and the most effective will depends on your own specific situation. The two most common approaches rats are poison and traps. Both methods can be effective, if implemented properly. The main concern with poison is, of course, protecting young children and pets. If you plan to use poison, it should always be placed in closed and secured bait stations installed in areas that are not accessible to children or pets. Traps are generally a safer option and have the added benefit of keeping the rat in place, so it doesn’t expire in an inaccessible location, such as inside your walls, creating a smell. If you prefer, and if you’re sure you’ve sealed off all possible re-entry points into your home, you could also try a live trap, and free the rat outside. Chances are, however, that if there is one rat, there are many.

Remember, rats are the second most successful animal on this planet, with the potential to become the first. Stay diligent and proactive and your chance of having a problem with rats will be minimized.