Capturing Smart Rats Requires Common Sense And New Ideas

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December 1, 1997

Have you ever had a rat you couldn’t capture? Most pest management professionals encounter this problem every so often. On one occasion, for example, it took me three weeks to take out a single rat from a granary. And recently one rat on a commercial jet liner cost nearly a half million dollars in downtime for the airline because the rat did not respond to any control strategy, and the plane had to be fumigated. The industry is full of similar elusive rat stories.

SMART BY NATURE. But what is it about some rats which makes them so challenging and difficult to control? Are these troublesome rats “smarter” than the rest of their colony members, and do they “know” how to avoid lethal devices and baits? Let’s examine the “smart rat” phenomena a bit closer. The avoidance of strange objects as well as strange animals of the same and other species is actually common throughout the animal kingdom, including among people. This behavior is called neophobia (fear of new). Neophobic behavior serves rodents as a survival strategy. In their natural world, rats are subject to predation once they leave the nest. Their principle means of avoiding predators is their use of familiar pathways under cover and quickness to get to a burrow or other place of concealment. Thus, the rat depends on its previous experience of being able to move quickly and accurately around its living space. In this way, it can run from one point to another using the shortest route and in the least possible time, minimizing its exposure time to predators and danger. So as you might imagine, any sudden changes in the living space is met with suspicion and caution, at least for a time until the rat re-habituates to the changes. Even a new hole (e.g. a bait station) which suddenly appears in a rat’s runway will initially be approached very cautiously. From the rat’s perspective, the hole may be already occupied by a snake or some other predator. In short, neophobia protects the rat from the consequences of careless curiosity.

Neophobic behavior can also play a part in a rat’s feeding behavior, but is somewhat a function of resource availability. For example, if food is abundant and easily accessible, the rodent can afford to ignore the new food for varying lengths of time. Fortunately for pest control programs, most rats overcome their neophobic reactions to new foods usually in less than a day. But in some granaries, zoos and warehouses where rats and rat colonies have been feeding on the same food for years, it is common for some rats to totally ignore all new baits and traps.

FOOLPROOF TECHNIQUES. So how do we control the elusive, neophobic rat? Below are nine techniques which have worked for myself and other professionals over the years:

1. When possible, eliminate the food source, even for just one night. When a rat’s available food resource disappears (i.e. via sanitation) or when a rat population exceeds the food availability, the rats no longer have the option of ignoring foods, new or old. With an instant food shortage, the rats are more likely to turn to your bait or to the bait on the trap.

2. Play the gourmet option. Entice the rat to a new bait station or rat trap by presenting a delectable food item such as fresh meat, fish, shrimp or some similar high quality food. This is no time to go cheap with your baits; callbacks are expensive. Place the bait in a small trail leading toward the bait station or snap trap, as well as on the edges of the device. As the rat habituates to the trail and area, it should eventually interact with the control device.

3. Pre-condition the rat. Leave small pieces of food on both sides next to and on top of an unset trap. In this way, the rat will learn to associate food with the new object. Once feeding has begun, then set the trap. When using a bait station, place a small amount of the enticing food in the entry way, smear a little on the door area, and place some of the bait within the station.

4. Try a natural bait. For elusive rats using both exterior and interior areas of buildings, try reducing the rat’s neophobic response by offering it one of its natural foods. For Norway rats, American cockroaches can be tied to the traps using dental floss. For roof rats, pieces of snails, or snail shells also tied to the triggers have proven effective.

5. Disguise your traps. Disguise a snap trap by filling an empty soda cardboard carton (which holds four six-packs) with sawdust. Bury an unset rat trap beneath the sawdust. Place an enticing food trail leading to the box, and place the food on top of the sawdust including directly over the trigger. Once the rat has habituated to the box and is actively taking the food, install only one food piece directly to the trap trigger and set the trap. When using glue trays, use the large size and install the trays along rat runways, but keep them covered or use plastic wrap over the glue. Once rat tracks are obvious over the covered glue trap, remove the cover. Be sure to secure the glue trap to the surface in some manner.

6. Identify the rat’s scarcest resource. Does the rat have plenty of food, but not much obvious water? Install liquid baits. Or perhaps soft nesting materials (very important to a rodent) are not abundant. Nesting materials (strips of cloth) can be used as baits around traps in the manner as mentioned previously for food baits.

7. Install a sharpshooter. A sharpshooter quietly lying in wait at night is often used to take out the troublesome rat. In persistent cases this is actually one of the most cost-effective approaches.

8. Use tracking powders. Tracking powders have one of their greatest utilities against neophobic rats. The tracking powder can be applied in suspected runways, possible burrow openings, and other areas the rat might travel. Be sure to use only those tracking powders labeled for use around buildings against rats.

9. Use a video camera. Video cameras with low light options and wide angle lenses can be installed overnight in those areas where the elusive rat is suspected to be active. The camera may record the rat’s secretive behaviors and provide the clues needed to trap the rat, or have the sharpshooter stake out an optimal position. With elusive rats, it is wise to invest the time up front. Otherwise, these rats will cause expensive callbacks. The techniques discussed above are more work than smearing peanut butter or tying a piece of hot dog to a trap, and hoping for the best, But they are often your only tools for outsmarting that last “smart” rat.

Certainly, innovative professionals over the years have devised other techniques of eliminating a wily rat. If you have an elusive rat story or technique you’d like to share, I’d love to hear it.

Dr. Robert Corrigan, a contributing editor to PCT magazine, is president of RMC Pest Management Consulting, 5114 Turner Road, Richmond IN 47374, 317/939-2829.