Using canines to detect spotted knapweed : field surveys and characterization of plant volatiles

Abstract

Invasive plants threaten biodiversity as well as the function of ecosystems and cause loss for land users and managers in western North America. Eradication of invasive plant populations is desirable to prevent these impacts. But eradication is difficult to attain due to imprecise detection rates for low density and inconspicuous plants, such as juveniles and small adult plants. In an effort to improve the accuracy of plant detection, we investigated the ability of domestic dogs (Canis familiaris L.) to search for and detect rare occurrences of spotted knapweed (Centaurea stoebe L). The objectives of this study were to (1) compare the performance of trained dogs to human surveyors in detecting new invasions of knapweed, (2) evaluate the ability of the dogs to detect below ground odor produced by knapweed roots, and (3) characterize the above and below ground volatile profiles of spotted knapweed. The accuracy of three dogs was compared to human surveyors on a dryland pasture near Belgrade, Montana in 2005 and 2006. Dog accuracy for large-size knapweed infestations (0.52m ³) was similar to human accuracy and better than humans (94 vs. 78%) for medium-size infestations (0.13 m ³). Dog accuracy (67%) was greater (>81% probability) than humans (34%) for small knapweed targets (plants; 0.02 m ³). In September 2006, controlled odor response experiments were conducted in a livestock barn in Bozeman, Montana to evaluate the ability of the dogs to identify spotted knapweed root material without being previously trained to do so. Mean success rate of the dogs to recognize bare and intact roots were 97% and 87% respectively. In 2005 and 2006, volatile collections were conducted. The main compounds of the foliage were found to be (Z)-3-hexenyl acetate, beta-cis-ocimene, and beta-cubebene, which were not present in the roots. The main constituents of the roots were junipene, beta-caryophyllene, and thujopsene, which were not present in the foliage (exception: beta-caryophyllene), indicating dissimilar volatile profiles between the foliage and the roots. Collectively, these results indicate detection dogs might improve the efficiency and accuracy of plant detection by increasing the likelihood small and inconspicuous plants, including belowground plant targets, will be detected.