[FOCUS ON TERMITE CONTROL] Top Dog

How many times have you heard (or said) this: "Do you really think dogs can accurately detect live termites in walls? They’re cute. But I’ve heard so many stories about both how great and how poor the dogs are at termite detection. What should I believe?"

As researchers at the University of Florida, we decided to get to the bottom of the issue by doing some research of our own. Here, we present the first in a two-part series on the effectiveness of canines as termite detectors.

BACKGROUND INFORMATION. As an entomology researcher, graduate student and professor, the authors are well aware of the problems with doing a termite inspection. Visual inspections are still the industry standard. Most pest management professionals take a flashlight, a probe and hopefully a clipboard to write down findings and produce an inspection report. But a significant part of any given structure is "inaccessible" if visual inspection is the only method used and termites often invade a home through inaccessible areas.

On the other hand, dogs rely on olfaction, not vision, to detect a wide array of materials including narcotics, missing people, brown tree snakes, agricultural quarantine items and explosives. Dogs used to detect explosives must be tested to 100% accuracy before being assigned to field operations as "bomb-sniffing dogs," so we knew that dogs could be trained to a high level of accuracy.

So why is there confusion on the effectiveness of termite sniffing dogs? Lack of research data. While there are many testimonials regarding the use of dogs by the pest management industry, there was only one published account on the ability of the dogs to detect termites (Lewis et al. 1997). Five beagles tested in the study were 81% accurate at finding more than five Western subterranean termite workers, which is not bad, considering how difficult termites are to detect in inaccessible areas. However, what was concerning was the high "false positive" rate of 28% in this study. "False positives" in this study meant that the dogs incorrectly indicated there were termites 28% of the time when there were no termites. For a pest management professional that may have to open a wall or drill a slab in preparation to treat because of a "false positive," a rate of 28% was not very reassuring.

What was the cause of this high false positive rate and can it be corrected? We hypothesized that the material used to train many canine termite detectors was contaminated with damaged wood and other nest material. The U.S. Customs narcotics dog training protocol notes that training materials contaminated with non-target odors may teach dogs to respond to both target and non-target odors, increasing the number of false positives. Thus, the purpose of our study was to determine the ability of dogs to detect varying numbers of Eastern subterranean termites (EST) when trained with live EST workers.

MATERIALS AND METHODS. We used six dogs, one German shepherd (Dog A) and five beagles (Dogs B through F) for our study. All were trained, maintained and handled by Jose ("Pepe") and Maggie Peruyero, owners of J&K Canine Academy, Alachua County, Fla. The dogs were trained using the method outlined by the U.S. Customs Service (USCS 1979). Dogs B through F were trained with a combination of USCS method and food reward method to reinforce correct behavior. All dogs, except Dog B, were trained with pure termite samples.

Dog B was trained with a mixture of EST and termite damaged material and debris (1 gram EST to 85 grams of termite-damaged material and debris). Daily training lasted from three weeks to three months depending on the individual dog. Each dog began testing after consistently reaching 100% accuracy in locating approximately 100 termite workers buried under gravel. Training methods are detailed in Brooks (2002).

DETECTION OF VARIOUS NUMBERS OF TERMITES. We wanted to see if dogs could detect decreasing numbers of EST. We tested termites in groups of 160, 80 and 40 workers. Termites from three colonies were collected from the field and placed in plastic cups (1 fluid oz.) with a moistened piece of paper towel (about 1 sq. inch). The plastic cup lids were perforated with 30 holes to allow scent to permeate out. The plastic cups were placed inside 2-inch PVC tubes that were fitted with caps and secured onto a pineboard surface. A 1¼-inch hole was drilled in the center of the PVC cap to allow any termite scent to escape. The PVC tubes were placed onto the boards and allowed to sit for 12 to 14 hours before being inspected by the dogs.

Five PVC containers were placed on the ground linearly, about 1 yard apart. The handler led the dogs to each of the five PVC containers for inspection. The dogs responded to the presence of termites in individual containers by digging. Responses were categorized as "positive indications" which is defined as a dog responding correctly to containers with termites and "false positives" which is defined as the dog incorrectly responding to containers without termites.

These dogs are smart. They learn quickly what will please their handler, so to eliminate a testing pattern, we mixed up how many PVC containers held termites. We tested the dogs where more than one, one or none of the PVC containers held termites. We even rearranged the order of the PVC containers with termites for each replicate. However, data presented here are for the situation where one PVC container held termites. Testing was conducted over a period of several months. The dogs’ level of proficiency was maintained by daily training sessions.

In summary, to evaluate the dogs’ ability to detect varying numbers of termites, six dogs were tested using three densities of termites with 15 repetitions.

RESULTS. Dogs trained daily for three weeks to three months with the method previously described were able to accurately locate EST workers in 95.93% (see chart above) of PVC containers for all termite groups tested. All dogs performed at a high level and were statistically not significantly different from each other in their ability to detect termites. The dogs’ ability to detect 40 termites was not significantly different than their ability to detect 160 termites (see chart below).

What was encouraging to us is that dogs trained with the U.S. customs and food reward method also had a low false positive rate. Dogs were also able to discriminate containers with termites from empty containers, falsely indicating the presence of termites in only 2.69% of the empty containers (see chart, page 34). Statistically, there was a significant difference between individual dogs’ responses to empty PVC containers. Dog E had a significantly lower proportion of false positives than Dog D (see chart, page 34).

SUMMARY. The value of detector dogs is defined by their ability to locate hidden objects when the target odor is present and to not respond when the target odor is not present. Our study has shown that dogs can be trained to reliably locate EST with positive indication rates more than or equal to 95% and false positive rates less than or equal to 6%. Target odors that meet or exceed a threshold concentration will elicit a response from dogs trained to respond to that odor (Moulton 1975a, Moulton 1975b, Waggoner et al. 1997, Johnston et al. 1998). The olfactory threshold for dogs trained to locate termites is less than 40 termites.

Lewis et al. (1997) reported a positive indication rate of only about 60% for dogs tested with five termites compared to a positive indication rate of about 98% when termite numbers were increased from five to more than 50. The results from our study are similar to Lewis et al. (1997) with more than 50 termites. We did not test the dogs’ ability to locate fewer than 40 termites because termites rarely forage in small numbers and can have foraging populations of about 200,000 to 5 million individuals (Su et al. 1993).

Stay tuned for part II of this story, where our objectives were to determine whether dogs could differentiate between five species of termites, discriminate termites from termite-damaged wood, and distinguish American cockroaches and the Florida carpenter ant from ESTs.

Authors’ note: We thank Dr. David Oi for review of the manuscript.

Editor’s note: This is the first article in a two-part series.

The authors are a research entomologist, a graduate research assistant and the Margie and Dempsey Sapp Endowed Professor of Entomology at the University of Florida, Gainesville, respectively.

References:

Brooks, S. E. 2002. Canine Termite Detection. M. S. Thesis. University of Florida, Entomology and Nematology Dept.

Johnston, J. M., M. Williams, L. P. Waggoner, C. C. Edge, R. E. Dugan, and S. F. Hallowell. 1998. Canine detection odor signatures for mine-related explosives. Proc. SPIE. 3392: 490-501

Lewis, V. R., C. F. Fouche, and R. L. Lemaster. 1997. Evaluation of dog-assisted searches and electronic odor devices for detecting western subterranean termite. For. Prod. J. 47: 79-84.

Moulton, D. G. 1975a. Factors influencing odor sensitivity in the dog. Air Force Office of Scientific Research, Bolling AFB, Washington D.C., Grant
#AFOSR-73-2425.

Moulton, D. G. 1975b. Laboratory methods for obtaining olfactory discrimination in Rodents, pp. 1-32. In D.G. Moulton, A. Turk, and J.W. Johnston Jr. [eds.], Methods in Olfactory Research. Academic Press, New York, New York.

Su, N. Y., P. M. Ban, and R. H. Scheffrahn. 1993. Foraging populations and territories of the eastern subterranean termite (Isoptera: Rhinotermitidae) in southeastern Florida. Environ. Entomol. 22: 1113-1117.

United States Customs Service (USCS). 1979. U.S. Customs narcotics detector dog training. U.S. Customs Service, Washington D.C.

Waggoner, L. P., J. M. Johnston, M. Williams, J. Jackson, M. Jones, T. Boussom, and J. A. Petrousky. 1997. Canine olfactory sensitivity to cocaine hydrochloride and methyl benzoate. Proc. SPIE. 2937: 216-226.