Friday, January 7, 2011

Detector Dogs Used to Locate Brown Treesnakes


Finding reptiles can be a challenge. In the 1970's Elizabeth and Charles Schwartz used Labrador Retrievers to find Box Turtles on their study site in Missouri. Recent news stories report researchers using a Labrador to find Indigo Snakes at the Nature Conservancy's Apalachicola Bluffs and Ravines Preserve in Florida (Halley, 2010).

USDA Snake Detector Dog
Now, Julie Savidge and colleagues (2010) report that detector dogs have been used by the USDA since 1993 to inspect cargo leaving Guam that may contain Brown Treesnakes (Boiga irregularis). In experimental trials dogs averaged 62% for snakes in escape-proof containers planted in cargo without the knowledge of the dog's handlers. Savidge et al. investigated if dogs could be used for finding Brown Treesnakes in the wild on Guam as a way to ascertain if eradication efforts had been successful. The snakes are primarily nocturnal and although humans can detect them at night detection probabilities by humans is only 0.07 per search. During the day, brown treesnakes are hidden making visual detection by humans exceptionally difficult. However, trained dogs rely on odors and they may be more successful at locating snakes. The researchers investigated canine teams (dogs and their handlers) on Guam as a potential tool for finding Brown Treesnakes in the wild. Canine teams searched a 40 × 40 m forested area for a snake that had consumed a dead mouse containing a radio-transmitter. To avoid tainting the target or target area with human scent, no snake was handled or closely approached prior to searches. Trials were conducted during the morning when these nocturnal snakes were usually hidden in refugia. A radiotracker knew the snake's location, but dog handlers and search navigators did not. Of 85 trials conducted over four months, the two canine teams had an average success rate of 35% of correctly defining an area that was about 5 × 5 m that contained the snake with the transmitter; the team with more experience prior to the trials had a success rate of 44% compared with 26% for the less experienced team. Canine teams also found 11 shed skins from wild snakes. Although dogs alerted outside the vicinity of snakes carrying transmitters, only one wild, non-transmittered snake was found during the trials. This article can be found on-line (see below).

Literature



Schwartz, C. W. and E. R. Schwartz. 1974. The three-toed box turtle in central Missouri: its population, home range, and movements. Terrestrial Series No. 5. Jefferson City, MO: Missouri Department of Conservation. 28 p.

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