Roof Rat

Not only are rats vectors for diseases such as the plague, leptospirosis, and salmonellosis, but they can cause a considerable amount of damage to a home. Rats can gnaw on electrical wire and wood structures such as doors, ledges, corners, and wall material. They can also tear up insulation in walls and ceilings for nesting.

Not all rats are created equally. There are two different species of rats that wreak havoc on homes. The Norway rat and the roof rat. Your home could be providing these pests the resources that they need to thrive. Food, water, and shelter. Though they have the same basic needs, the approach to controlling them will be different.

Below is a profile of the roof rat and ways to prevent this pest from infesting your home or property.

Identification
  • Adults weigh between 3 and 12 ounces
  • They range in color from light brown to gray and black with a smooth coat
  • They have large, thin, hairless ears and a pointed snout
  • Rats can fit through openings the size of a dime.
Behavior
  • Mainly nocturnal, but can be seen during the day if colonies are overpopulated.
  • They prefer to travel along edges, along pipes or rafters, and along overhead utility lines.
  • Are generally wary of crossing open spaces that provide no cover. Hedges and other dense vegetation in landscaping or against buildings provide cover for rodent trails.
  • Are usually extremely wary of new objects in their environment; however this is only a temporary hesitation.
  • They also have amazing physical abilities that allow them to climb vertically in pipes, walk horizontally along wires, and jump from a standstill vertically at least 24 inches and horizontally at least 4 feet. They can also drop from heights of 50 feet without injury.
  • All rats can swim.
  • Rats will gnaw through almost any material with an exposed edge including, wood, chip board, lead pipes, cinder blocks, aluminum, sheet metal and glass.
  • Rats feed on all kinds of human and pet food.
  • Roof rats prefer fresh plan material such as fruits, vegetables, nuts, seeds and tree bark. They are frequently associated with avocado and citrus trees. Roof rats will also eat insects, slugs and snails.
Habitat
Life Cycle
  • Adults are polyestrous (multiple breeding cycles)
  • The average litter size is between 5 and 12.
  • They can have up to 9 liters per year depending on food availability. Roof rats have an average of 5 litters per year.
  • The gestation period is 20-25 days.
  • Lifespan is generally under 1 year.
Seasonality
  • In subtropical climates rats can reproduce year round.
  • In cooler climates populations peak in spring and fall.
Favorable Conditions
  • Poor sanitation provides rats with ample quantities of food to sustain large numbers of rats.
  • Improperly stored food and waste allows another food resource for rat populations to flourish on. Pet foods are a common meal for rats and should be stored properly as well.
  • Clutter and improper storage practices provide abundant hiding places, nesting sites, and travel routes for rats.
  • Dense vegetation and ground cover can act as excellent nests and rat highways.
Health Concerns
  • Rats contaminate food and eating utensils
  • Rats can transfer diseases bite, from vectors like fleas or mites on the rat, or contamination from feces or urine.
Signs of an infestation
  • Sightings of live or dead rodents
  • Rodent droppings, urine stains and rub marks
  • Gnaw marks on wires, food packages, wood and other parts of the structure
  • Nesting material like paper, cotton, or other fabrics
  • Biting pest symptoms from ectoparasites

What You Can Do To Prevent A Roof Rat Infestation

  • Store bags of pet food, bird seed, and grass seed in rodent-proof containers, or at the very least, inspect them often for any signs of gnawing.
  • Pick up fallen fruit and nuts from trees daily.
  • Never leave uneaten pet food inside or outdoors for any length of time. You cannot count on dogs or cats to keep rats away.
  • Fix leaky plumbing and eliminate any unnecessary standing water.
  • Dispose of all garbage in dumpsters or garbage cans with tight fitting lids that are kept closed.
  • Reduce clutter and debris by using proper storage techniques.
  • Trim tree branches 3 to 6 feet away from the building and trim vines, bushes, grass, and weeds at least 2 feet from all buildings to decrease cover for rodent runways, to prevent hidden access.
  • Eliminate dense plantings or break them up with pathways, stretches of lawn, or very low groundcover.
  • Avoid large expanses of low groundcover that could allow rats to run for long distances without being seen.
  • Seal large and small holes both inside and out. Also seal where pipes and wires enter the structure. Seal small holes with steel or copper wool and caulk.
  • Seal vents with ¼ inch hardware cloth.

What You Can Do When Roof Rats Are Inside Your Home

  • Use snap traps and place them along walls, rodent pathways, and in other protected areas like behind objects.
  • For bait, use food the rats are already eating or for roof rats use nuts, dried fruit, apples, bananas, candy, marshmallows, raisins or peanut butter.
  • Move objects around to funnel rats into traps.
  • Monitor traps regularly and frequently, and keep bait fresh. Rats avoid old or rancid bait.
  • Exclusion methods are favored over any chemical means. Rodenticides can pose hazards to non target animals, including children and dogs. Poisoned rodents may also die in inaccessible places and cause odor and fly problems.