Pest Control for Norway Rats

Latin Name for Norway Rats: Rattus norvegicus

Location of Norway Rats

The Norway rat reached the Americas between the 17^th and 18^th century¹. Currently Norway rats exist all over the world.

Biology of Norway Rats

The Norway rat is a more highly developed species than the roof rat. The Norway rat has adapted to dry, treeless, and grassy areas.² Norway rats range from 13-18 inches and weigh nearly 11 ounces. The roof rat has a litter range from 6-12 young, and lives less than 1 year.³

Foods of Norway Rats

In the wild, Norway rats eat grains, nuts, vegetation, seeds, insects, slugs, snails, and occasionally small birds and fish. When necessary, roof rats will cannibalize their young.⁴

Habitat and Range: Norway Rats

The Norway rat is the most important rat in urban areas. The Norway rat is a ground-dwelling species that is partially dependent on people for food and shelter. Rats are very adaptable, so it is habits vary from place to place. However, rats generally have two peak periods of activity, near sunset and dawn.⁵

Predators of Norway Rats

Just some of the many predators include hawks, owls, ferrets, weasels, coyotes, skunks, raccoons, and snakes. Contrary to popular belief, cats and dogs do not maintain control of mice and rats.⁶

Health Issues: Norway Rats

Rats can carry a variety of diseases, if in contact with a rat or bitten by one contact your doctor immediately. Historically, urban plagues have been spread by roof rats and Normway rats bitten by fleas.⁷ In recent years the plague has been a non-factor due to sanitation and antibiotics. To minimize the risk of plague, use insect repellant, and when handling wild animals, wear protective gloves.⁸ An additional disease carried by rodents is the Hantuvirus. Rodents can pass the Hantuvirus to humans through 3 main processes;

• Direct bites
• Coming in contact with something that has been contaminated with rodent urine, droppings, or saliva, and then by touching your nose or mouth.
• Food becoming contaminated through rodent urine, droppings, or saliva.⁹

Although only marsh rice rats and the hispid cotton rat carry the Hantuvirus, the untrained eye may have difficulty discerning these from other rodents. Luckily, neither type of rat is found in California.¹⁰

Pest Control for Norway Rats

Identification: A Norway rat is larger and thicker than the roof rat. The roof rat has larger ears and a more pointed nose as well.¹¹ Ten (10) signs a rodent may have infested include:

• Feces(droppings)
• Gnawing damage
• Burrows
• Runways
• Tracks
• Smudge marks
• Urine stains
• Visual sightings of live or dead rodents
• Rodent sounds
• Rodent odors¹²

Non-Chemical control of Norway rats: The Norway rat is susceptible to rodent proofing and perimeter baiting due to its dependence on humans.¹³ Norway rats have adapted to dig burrows for shelter, because of this, blocking Norway rats out of buildings alone will not substantially reduce their numbers.¹⁴ Once control is attained, non-toxic monitoring can be achieved through bait blocks and the use of non-toxic foods.¹⁵ This can determine whether the infestation is still present. Rodent proofing (exclusion) and sanitation are effective ways to prevent future entry of rodents. Mechanical and glue traps are currently available, but mechanical is the safest and most effective method.¹⁶ Chemical control of Norway rats: Rodentcides exist, but there are many reasons mechanical traps are generally preferred including:

• It can take 3 to 10 days to kill a rodent with rodentcide baits, during which the rodent will continue to contaminate the area with fecal pellets, urination, hairs, and gnawing. With mechanical traps the rodent is captured once and prevents this problem.
• Rodenticides are toxic and can be spilled, carried away, or blown into the wind, all of which could transfer the chemical to non-target sites and possibly contaminate food.
• When used correctly, captured rodents will not die inside a wall, which prevents odors and other types of infestations..
• In most cases, rats can be eliminated using only traps and without the use of rodenticides.¹⁷

When chemical treatments must be used, anticoagulants are commonly the method. Anticoagulants cause death as a result of internal bleeding.¹⁸The most used non-anticoagulants are:

• Zinc phosphide: Attracts rodents and causes them to die from heart failure from within 17 minutes to several hours. It is commonly implemented as bait against roof rats and mice. (Hearts Pest Management does not use zinc phosphide, as it has no antidote)!
• Bromethalin: Causes death within 3 days due to a decrease in cellular energy production, which causes the animal to become weaker over several days. On rare occasions secondary hazards have been reported in cats, however if non-lethal doses are consumed the toxic effects are reversible.
• Cholecalciferol: Disrupts kidney functions. Cats and Dogs are susceptible to its effects, so when an animal is present this is not a potential choice.¹⁹

Notes

¹ Lawrence M. Sullivan, “Roof Rat Control around Homes and Other Structures,” University of Arizona, AZ1280 (March 2002): 22-26. ag.arizona.edu/pubs/insects/az1280.pdf (accessed June 4, 2008). ² Mallis, Arnold, “Handbook of Pest Control: The Behavior, Life History, and Control of Household Pests”, 9th ed. (2004), 27. ³ University of Illinois Extension, “Prevention and Control: Norway Rats”, Illinois Department of Public Health, www.idph.state.il.us/envhealth/pcnorwayrat.html. (accessed 6/4/2008). ⁴ Mallis, Arnold “Handbook of Pest Control”, 34. ⁵ Mallis, Arnold “Handbook of Pest Control”, 29-30. ⁶ Mallis, Arnold “Handbook of Pest Control”, 49-50. ⁷ Mallis, Arnold “Handbook of Pest Control”, 28. ⁸ Mallis, Arnold “Handbook of Pest Control”, 18. ⁹ Lynne F. Bachleda, “Dangerous Wildlife in California and Nevada (Birmingham: Menasha Ridge Press)”, 259. ¹⁰ Lynne F. Bachleda, “Dangerous Wildlife”, 260. ¹¹ R.E. Marsh, T.P. Salmon, and R.M. Timm, “Rats: Integrated Pest Management in the Home and Landscape”, Pest Notes: University of California Agriculture and Natural Resources, ed. B. Ohlendorf 74106 (Jan 2003): 1-2. ¹² Mallis, Arnold “Handbook of Pest Control”, 51. ¹³ Mallis, Arnold “Handbook of Pest Control”, 20. ¹⁴ Mallis, Arnold “Handbook of Pest Control”, 31. ¹⁵ Mallis, Arnold “Handbook of Pest Control”, 58. ¹⁶ R.E. Marsh, T.P. Salmon, and R.M. Timm, “Rats”, 4. ¹⁷ Mallis, Arnold “Handbook of Pest Control”, 74. ¹⁸ Mallis, Arnold “Handbook of Pest Control”, 76. ¹⁹ Mallis, Arnold “Handbook of Pest Control”, 80-82.

Sources

Bachleda, Lynne F. “Dangerous Wildlife in California and Nevada”. Birmingham: Menasha Ridge Press, 259. Mallis, Arnold, “Handbook of Pest Control: The Behavior, Life History, and Control of Household Pests”, 9th ed. University Park: GIE Media, Inc. 2004. 20-82. Marsh, R.E., Salmon, T.P., and Timm, R.M. “Rats: Integrated Pest Management in the Home and Landscape”. “Pest Notes: University of California Agriculture and Natural Resources”, ed. B. Ohlendorf 74106 (Jan 2003): 1-4. Sullivan, Lawrence M. “Roof Rat Control around Homes and Other Structures”. University of Arizona, AZ1280 (March 2002): 22-26. ag.arizona.edu/pubs/insects/az1280.pdf. (accessed 6/4/2008). University of Illinois Extension, “Prevention and Control: Norway Rats”, Illinois Department of Public Health, www.idph.state.il.us/envhealth/pcnorwayrat.html. (accessed 6/4/2008).