Feb 23, 2007 2:54 pm US/Eastern
CBS 2 Guide: Detecting Rat Infestations
NEW YORK (CBS) ―
Rats can be a serious problem in New York City, a problem made all too vivid by CBS 2 video Friday that showed a rat infestation at a Greenwich Village KFC/Taco Bell restaurant (4th Street and 6th Avenue). So how can you tell if there's a rat infestation nearby? Here are the signs, as detailed in the National Park Service Integrated Pest Management Manual:Periodic surveys of buildings and grounds can reveal the existence of rat infestation. Inspection visits should be made every other week and increased or decreased according to the severity of the problem. Evening inspection using a powerful flashlight is the best way to see rats, but there are many signs of rat infestation besides the animals themselves. Rat sounds, droppings, burrows, urine stains, smudge marks, runways, tracks, gnawing damage, nests, food caches, pet excitement, and rat odors are all signs of rat activity.
Sounds. Squeaks, gnawing sounds, clawing, and scrambling in walls are typical sounds of a rat infestation.
Droppings. A single rat may produce 50 droppings daily. Norway rat droppings are larger (3/4") than roof rat droppings (1/2"). Determine if an area is currently infested by sweeping up old droppings, then reinspect after a week. Fresh droppings have a putty- like texture; old droppings crumble easily.
Burrows. Estimates of relative abundance in a limited area can be made by counting, mapping, and loosely plugging burrow entrances on a weekly basis. Burrows which are reopened the following week are active.
Nests. Roof rat nests are often visible in attics, or they may be found when vegetation is trimmed.
Urine Stains. Under ultraviolet light (blacklight), rat urine will glow blue-white.
Runways. Rats regularly travel the same routes. Outdoor runways appear as beaten paths in the ground. Grass will be worn down.
Smudge Marks. Oil and grease that rub off a rat's fur build up on well-used runways.
Tracks. An adult rat's footprint is about 3/4" long. Rats may also leave a drag line (from their tail) in the middle of their tracks. A "tracking patch" can help determine the location and extent of rat activity. Place a light dusting of clay, unscented baby powder, or powdered limestone in suspected runways and near rat signs. Typical patch sizes range from 12"x4" to 6"x18". Examine the patch for tracks at regular intervals.
Gnawings. Rats constantly gnaw on hard surfaces. Gnawed holes may be 2" or more in diameter.
Food Caches. Rats may store surprisingly large quantities of food in protected areas.
Pet excitement. Cats and dogs often probe an area of floor or wall where rats are active, particularly if the rats only recently invaded.
Odor. Heavy infestations have a distinctive odor. Experienced pest managers can smell the difference between a rat and a mouse infestation.
Evaluation of population size. Rat signs may be interpreted visually as follows.
• Rat-free area or low rat population: no sign of rat presence.
• Medium population: old droppings and gnawing common, one or more rats seen by flashlight at night, none during the day. Each rat seen at night usually indicates 10 or more elsewhere.
• High population: fresh droppings, tracks, gnawing evident, three or more rats seen at night, one or more in daylight.
Estimates of rats present can also be made by placing premeasured, ground, nontoxic cereal bait in various locations to determined how much is eaten each night. Double the amount each night until the amount taken in one night levels off. Divide the amount by 1/2 oz. This will provide a very rough estimate of the minimum number of rats present.
(© MMVII, CBS Broadcasting Inc. All Rights Reserved.)
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