Chicago Wildlife Watch Talk

scent bag, or what's that black thing?

  • ForestPreserve by ForestPreserve moderator

    Most of the images show a black "scent bag" or lure, usually attached to a tree or fence. Sometimes the scent bag gets mistaken for a bat, bird, or other animal. Sometimes the scent bag has a shiny disk in the center, other times you can see what looks like a black zip tie sticking out. Sometimes the scent bag is attached to a tree stump or the ground, and sometimes the scent bags go missing....

    The scent bags contain phenylacetic acid,

    Collection of scent bag images (sometimes with animals): CCHS0000c9


  • abdullahmoh by abdullahmoh

    I think they are trapped cameras


  • mason_UWI by mason_UWI scientist

    Yes. We use scent lures to increase the probability of detection for our urban species. Even with a lure, the probability of detecting these mammals each day is pretty low (about 10-20%). Because our species are detected imperfectly we need to account for this statistically. If our main variable of interest is whether or not a species is at a site, a species absence in or data could either mean that it was not there or it was there and we failed to detect it. Lures help increase our chances of detecting species. Here is a figure from a poster a coworker and I presented a while back showing about how many days we need to have a camera trap active in order for us to be certain we sampled the entire community at a site. The model predicted species richness at each site, and we subtracted what we observed in our dataset from that prediction. Thus, when the predicted value equals the observed value the y-axis is 0. The x-axis is the number of days a camera trap was functioning. It looks like if we have about 10 days of sampling (out of a potential of 28), the likelihood of detecting every mammal present is pretty high!

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