Animal Scats And Exterior Bait Stations

Because of cases such as this one, it is important for pest management professionals to know basic, “on-the-job” aspects of scatology (the study and identification of feces), at least for those animals that commonly interact with exterior bait stations. The case above is not an everyday occurrence, but it is not rare either. Periodically, thousands of dollars and man-hours are wasted in chasing either the wrong rodent species or rodents that do not exist.

SCATOLOGY 101. Let’s take a look at scatology as it applies to properly identifying different yet similar looking animal scats commonly found in exterior stations or along foundation walls. These include mice, rats, toads, bats, crickets, large cockroaches and snakes.

First, professionals often rely only on size and/or color to identify scats. But used exclusively, these qualities are misleading. Large cockroach and cricket scats may be similar in size and shape to mouse scats, and thus are sometimes mistaken for them in exterior stations. To distinguish between large insect and mouse scats, first note the general shape of the scats. Mouse scats are typically about ¼ inch long and pointed at one or both ends. Often the mouse’s scat is black or dark in color, but the color can vary significantly from light brown to blue-green (as a result of feeding on dyed rodenticide bait). Rodent scats more than a few hours old are usually hard and compressed and do not easily disintegrate when pressed with a stick or other object (do not use your pencil, pen or fingers). When viewed beneath a hand lens or microscope, mouse and rat scats will reveal hair fragments, which are a result of the coat hairs being passed through the rodent during the grooming process.

The scats of large insects, on the other hand, are usually blunt on both ends resembling a box-shaped pellet. This is because insects do not possess a sphincter muscle. Insect scats range from yellow to black in color. Cricket scats are often tan and usually disintegrate easily when pressed. Other identifying characteristics may also be involved. For example, American cockroach scats contain distinct ridges.

BAT AND RAT SCAT. Bat scats are also commonly misidentified for mouse scats. Although bats do not interact around our bait stations, they commonly hang on the outside walls of commercial structures. This results in bat scats being found on the ground below, which is incorrectly interpreted as mouse activity. Bat scats are similar in size, shape and color to mouse and young rat scats, but the bat scats are made up of mostly shiny insect fragments that are clearly visible to the naked eye. Because of these fragments, bat scats easily disintegrate when pressed.

The two animals most often confused with rats around building exteriors because of their scats are toads and certain snakes — especially some of the larger toads, as they produce scats the same size and shape as rats. Again, it is fairly easy to distinguish toad and snake scats from rat scats. The Norway rat produces scats that are the largest of the commensal rodents, ranging up to ¾ inch long and ¼ inch in diameter. Most Norway rat scats are rectangular shaped with either blunt ends, or they contain a slight point. The roof rat produces scats similar to that of the Norway rat, but they generally are a more curved, sausage-shape scat, measuring about ½ inch in length and less than ¼ inch in diameter.

The larger toads and smaller snakes that visit our bait stations feed on insects, resulting in scats resembling large bat scats — they contain insect fragments and easily disintegrate when pressed. Snake scats are typically elongated and very narrow, and may be twisted at some point.

CHECK YOUR SURROUNDINGS. Keep in mind that many anomalies may exist in feeding and thus in scats. Therefore, analyze scats in groups as opposed to studying just one. Also consider the location. Is there abundant vegetation concealing toads or snakes nearby? Are sewers, foundation cracks, expansion joints and voids harboring large cockroaches or crickets nearby?

When identifying scats inside bait stations, always inspect the bait for feeding patterns. When fed upon by rodents, bait blocks usually exhibit the impressions made by the rodent’s incisor teeth. Insects however, nibble away at bait blocks, resulting in only a general depression into the block or block corners. Finally, when still in doubt, collect the scats and have them confirmed by a specialist.

Dr. Robert Corrigan, one of the country’s leading rodent experts, is president of RMC Pest Management in Richmond, Ind. To contact Dr. Corrigan, call 765/939-2829.