Passing the Smell Test

Dogs that have been trained to detect an invasive weed are better at finding the plants than humans, a new report says.

Invasive plant managers often face the tough task of wiping out an entire species from an area. But small or rare plants can elude notice, thwarting efforts at eradication. To track down those pesky hold-outs, researchers suggest, why not recruit dogs? After all, so-called detection dogs have been trained to find everything from land mines to cadavers.

A team trained dogs to recognize the smell of spotted knapweed (Centaurea stoebe), an invasive plant in North America. Three of the dogs – Nightmare, Tsavo, and Rio – were then let loose in a Montana pasture containing knapweed during four trials in 2005 and 2006. For each trial, three people familiar with the species also scoured the area.

The dogs found knapweed plants or patches 124 times, whereas humans only had 90 hits, the study in Invasive Plant Science and Management says. And dogs had an accuracy rating of 81 percent, compared to 59 percent for people. The animals were especially good at finding individual plants and smaller patches, as well as detecting knapweed over long distances.

The dogs’ performance wasn’t perfect: they tended to issue more false alarms than humans. And one of the animals, Tsavo, was prone to “distraction by ground squirrels,” the authors note. But overall, the results suggest that dogs could be valuable additions to teams on the hunt for invasive plants. – Roberta Kwok

Source: Goodwin, K.M., Engel, R.E. and D.K. Weaver. 2010. Trained dogs outperform human surveyors in the detection of rare spotted knapweed (Centaurea stoebe). Invasive Plant Science and Management 3(2), 113-121. DOI: 10.1614/IPSM-D-09-00025.1.

Image © straga,



  • Gary J Sibio June 26, 2010 at 1:16 am

    This is not particularly surprising but considering what my dog does to the plants I’m sure I don’t want any contact with it.


  • Rebecca June 29, 2010 at 2:28 pm

    Just want to tell you, nice article! A friend of mine (with her own garden) told me that she keeps squirrels away by sprinkling her dog’s hair sheddings around her plants… I wonder if the same technique might be useful in this endeavor that you mentioned?
    Anyway, cool article either way!! 🙂


    • roberta June 30, 2010 at 10:34 am

      Hi Rebecca,

      Thanks for the comment! I’m not sure the dog-hair shedding would be useful here since they’re trying to find the plants, not keep animals away from them. Glad you enjoyed the story.



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