Tracking Down Nuisance Wildlife in Urban Settings

Editor’s Note: This article was reprinted with permission from Pinto & Associates.

When conducting an inspection for nuisance wildlife like rats, squirrels, raccoons, or bats, look for clues to learn what you're dealing with. It's especially important to know whether you are dealing with rats or mice, or larger nuisance animals that will require trapping and removal or exclusion, or that may even be protected.

Knowing how to find and read the signs of wildlife can: (1) identify the animal(s), (2) tell you how many are present, (3) determine whether young are present, (4) tell you how long the problem has been going on, (5) find the most active sites, (6) assess the degree of damage, and (7) help determine why the animal was attracted to the site and how it got in.

Visual sightings - Even if you don't see the animal, you may find carcasses. If nocturnal animals like raccoons are active during the day, it may mean that the population is very large, or the animal has young and is feeding more often.

Sounds - Vocal squeaks, growls, cries, hisses, chitters, as well as movement noises such as clawing, scampering, and gnawing will confirm that there is an animal present and will tell you where it is active, but it will take practice to identify the animal from its sounds.

Odors - Animals have smells specific to their own breed, especially noticeable when they are denning together. You may key in on the odors of fermenting urine, droppings, or body oils. Experienced inspectors can even tell the odors of mice from those of rats.

Urine - Rodent urine glows under ultraviolet light (see Techletter, Dec. 12, 2010). Other materials do too, so you need practice to discriminate. You may find building materials discolored from large amounts of urine, often from raccoons, flying squirrels, or bats.

Droppings - If you know the animal's travel route or entry points, look for droppings near these sites. If you find large numbers of droppings, you may have just pinpointed major runways, shelters, or entry holes. You can usually identify the animal from its droppings.

Nests and burrows - Animal nest material varies with the animal and what's available but includes hair, string, paper, fabric, leaves, twigs, and grasses. Some animals burrow and some do not. The location of the burrow, its size, the type and number of entrances, and objects located nearby will help you identify the animal.

Food caches and leftovers - Rats, squirrels and other animals often hoard and store food (and sometimes rodenticide bait) in attics, wall voids, closets, etc. You might find the remains of an animal's meal near its den. Identifying what it was eating can tell you whether the animal is a carnivore or herbivore, and even where it is getting the food.

Access routes - Walk around the outside perimeter and try to imagine how the animal got into the building. Are there trees or utility lines near the roof? Could it have crawled under a porch, up a chimney, or along a downspout? These clues can point to likely culprits. Skunks, for example, aren't going to jump onto a roof from a tree branch and squirrels are less likely to wriggle in under a porch.

Entry sites - Look for holes, cracks, gnawed openings, loose siding, rubmarks, etc. usually low around the foundation or high around the roofline and eaves. The location, site, and condition of the entry sites are important clues to the species involved.

Rubmarks - Dark, oily smudges are often seen along the animal's run where it rubs against a surface during its travels, leaving behind dirt and oil from its fur. Look for rubmarks on pipes, beams, against walls, and on the outside edges of entry holes.

Tracks and claw marks - Footprints, tail marks, and wing prints may be found on dusty surfaces, sand, soft soil, and in snow. If the surface doesn't show tracks well, you can apply a nontoxic tracking patch. You may find claw marks on woodwork, trees, or other building surfaces.

Gnawing - Look for evidence of chewing (wood chips, tooth marks, holes, shredded fabrics, frayed wires) wherever wildlife might try to enlarge a crack or gain entry. The size of the tooth marks or the size of a chewed entry hole can help you tell whether you're dealing with rats, squirrels, or mice.

Hair, feathers, or shed skins - You may find tufts of hair on a fence or baseboard, feathers in an attic or above a drop ceiling, or less often, the shed skin of a snake. With practice, you may be able to identify the animal from these signs.

Pet excitement - When cats or dogs hear or smell animals in some inaccessible space such as a wall void, they may become extremely interested with whining, sniffing, and scratching at the spot. Observe any pets and ask your customer about unusual behavior.

The authors are well-known industry consultants and co-owners of Pinto & Associates.