Detection of frugivory using game cameras

Background/Question/Methods   Typically, frugivory is detected and quantified by examining the presence of seeds in animal feces, an approach that presents a biased, animal-centric picture. This may be valuable for diet studies, but is less useful for studies of seed dispersal, particularly for uncommon to rare plant species whose fruits may be consumed only rarely. We examined the potential to use game cameras to quantify frugivory, and other plant-animal interactions, in an uncommon to rare understory plant, Panax quinquefolius (American ginseng). In 2007 and 2009, we deployed six inexpensive IR/motion-detecting game cameras aimed at berry-producing adult plants in natural populations to capture animals near infructescences over 27 – 45 day periods, yielding a total of 1748 images taken over 212 observation-days. Specifically, we asked; Can game cameras detect animal species in close proximity to American ginseng fruits? Is it possible to distinguish frugivores from incidental co-occurrences of animals and ginseng plants?

Results/Conclusions   Eight mammals, seven bird species, and one amphibian were detected and identified within the field of view. Cameras varied 6-fold in the rate of image capture of potential frugivores; cameras near forest edges and those set with a wide field of view captured more images and more species. Two observations were particularly notable for the information gained that would have been difficult to obtain any other way: First, although indirect evidence of widespread deer browsing in ginseng is frequently noted, one camera captured a sequence of images providing direct evidence of complete defoliation of a large plant by deer. Second, wood thrushes (and other Turdidae) were observed at every monitored plant, and two images at separate cameras captured wood thrushes with ginseng berries in their beaks. Although red berries are frequently thought to be bird-dispersed, no prior association of particular bird species with ginseng had been established. No direct evidence of frugivory was obtained for other species, though candidate dispersers were identified by frequent observations. In conclusion, game cameras do not collect unbiased information on frugivory, however significant insights can be gained from their use and certain types of information may be uniquely accessed by this ‘remote sensing' approach.