Be ready for that panicked call from clients who suddenly find they’re sharing their home with a member of the wildlife community.

Before homeowners can take action regarding wildlife that has entered a home, they need to know what kind of critters they’re dealing with. It may be that your clients haven’t actually seen an animal but have heard telltale sounds coming from the walls, ceilings, or attics.

Be sure to check out the feature in our March/April issue on the impact wildlife can have on your clients’ homes, as well as on real estate transactions. Here are some additional tips for identifying and dealing with some of the most common home intruders.

Bats. Indications of a bat inside a home include noises that sound like fluttering or squeaking, most often at night and high up in a room or wall, as well as black droppings known as guano. Despite their reputation for carrying rabies, only around 1 percent actually do, according to a study by the University of Calgary. However, they can easily carry other diseases, so it’s critical to remove them promptly from a home.

Extermination is not the best solution because bats make a valuable contribution to the ecosystem by eating flies and mosquitoes. Moreover, several species are legally protected. Adding a bat house outdoors provides an alternate place to nest, says Brian Ogle, an anthrozoology instructor at Beacon College in Leesburg, Fla. Because bats tend to reproduce in the spring, homeowners should be especially vigilant against offering entry points at that time of year. Bats are creatures of habit that roost in the same place over and over again (typically in spring or summer), so it’s important to get them out and seal off access areas, says bat expert Neil Tregger, co-owner of Hudson Valley Wildlife Solutions in Troy, N.Y. His firm does so with one-way doors that allow bats to leave but not reenter. Homeowners should work with a specialist who knows an area’s rules regarding proper removal, which varies by area and state.

Squirrels. Squirrels are one of the most common and invasive nuisance wildlife animals nationwide. “More people visit our website looking for a solution to squirrels than any other wildlife animal,” says Cindy Mannes of the National Pest Management Association in Fairfax, Va. Squirrels can cause structural damage to a home; they often gnaw at framing to create holes through which they can enter. They may also chew away at wires and insulation, causing major damage that requires expensive repairs.

Homeowners will likely have to hire a professional to humanely remove squirrels and seal access points. Homeowners should cut down tree limbs that extend within 8 to 10 feet of a roofline to discourage easy access inside.

Rodents, mice, and roof rats. According to the NPMA, rodents seek shelter in more than 21 million homes across the country, with the house mouse being the most common species. Some common signs of rodents include droppings, particularly near where food is stored; gnaw marks, tracks, or rub marks; and strange noises in walls, especially at night and in attics where the dark makes for a welcome environment for them to build nests. If there’s one rodent, it’s likely there are others, as they breed rapidly. A house mouse can have up to a dozen offspring every three weeks.

Because rodents are known to spread more than 35 diseases, homeowners should contact a licensed pest control expert for periodic inspections, treatment, and removal if they are spotted. It can be very difficult for a typical homeowner to locate where rodents are coming into the home, where they are nesting and breeding, and the true extent of infestation. That’s because mice can squeeze through openings as small as a dime, and rodents could be residing in more than just one location inside a home. The NPMA says experts can also help seal up entry points and suggest where to prune foliage and branches that may be good hiding spots for these creatures.

Raccoons. These nocturnal animals are often found near watering areas. Evidence of their presence includes structural damage to attics—since they often try to enter a home that way—and noises at night. Raccoons are one of the most common hosts of rabies, which is why it’s important that homeowners work with a pest control professional to remove them for good rather than do it themselves and risk being bitten, according to the NPMA.

To keep them away, homeowners should repair damaged screens, install chimney caps, replace loose mortar and weather stripping, keep garbage cans secured and with tight-fitting lids, keep attics and basements well ventilated and dry, remove ripe fruit from trees, and keep pet food indoors to avoid attracting these critters and others.

Deer. Deer, active in almost every region of the country, are often found in areas near water, trees, vines, shrubs, and grasses. Telltale signs are droppings that resemble a cluster of marbles and hoof prints that look like a heart with a line down the middle. They also often cause damage to property at waist height or higher. Homeowners might also notice trees with rubbed bark, since deer like to leave a scent in that manner.

Commercial deterrents and shiny ornaments can be effective, says Brian Ogle, lead anthrozoology instructor at Beacon College. Many plants, such as hostas, will attract them, so if these appeal to you, ask your local nursery or pest exterminator what local plants they’ve found can discourage nibbling. Homeowners should also know that some plants generally won’t appeal to deer looking for food, such as anything that smells like rosemary, lavender, sage, or mint, says landscape designer Michael Glassman. If homeowners want to add a fence, advise them to build it tall enough since deer can leap quite high.

Groundhogs. They burrow in (sometimes 5 to 6 feet down), build complex tunnels, and stay for the long haul, destroying lawns and consuming vegetation. Telltale signs include gnaw marks on plants, the lower branches of trees, wood, tubing, and wires. You may also see burrows bordered by mounds of soil.

To remove them, New York–area licensed specialist Jason Gagadorn likes to bait a trap with Brussels sprouts, cantaloupe, or apples. “It may require multiple efforts to coax them in,” he says. He cautions that local regulations vary regarding removal and extermination of these intruders.