Coincidentally, I just came across this interesting article about a successful project using camera traps to map animal populations in new york state... http://scientistatwork.blogs.nytimes.com/2011/02/07/more-animals-found-in-urban-forests/
<http://scientistatwork.blogs.nytimes.com/2011/02/07/more-animals-found-in-urban-forests/> --- Tim Brown http://Time-science.com - Innovative Image Technologies http://www.gigavision.org - Gigapixel timelapse systems t...@time-science.com Toll-Free: 866.411.3836 Cell: 801.554.9296 On Fri, Mar 4, 2011 at 8:36 AM, Greta Gramig <greta.gra...@ndsu.edu> wrote: > Hello All, > > Many ECOLOG readers requested that I summarize the responses I received to > my question about whether or not game cameras could be used to estimate > population density or abundance for small mammals without the requirement > to > identify individual animals. So, following is a summary of the responses I > received. I hope the summary will be helpful. If anyone decides to > experiment with any of these methods I would love to hear about your > experiences and viewpoints. > > Cheers, Greta > > "This will likely be an unsatisfying answer, but occupancy modeling > techniques could help you quantify the proportion of area occupied (PAO) by > each species or multiple species. Anyway, there are several models that > come to mind from the book (4.1.6 being one relevant example) Hierarchical > Modeling and Inference in Ecology by Royle and Dorazio. The authors > provide > code for most of the models and the text is well written. > > Potentially you could set the cameras to take pictures at regular > intervals, > in this case the pictures could be similar to doing an aerial survey, point > count or numerous other population survey methods. The pictures or even > videos (the longer the video the longer the exposure the higher the > probability of detection) could be treated as repeat visits, which would > then facilitate a hierarchical modeling approach to separate the > observation > and process error. Using the hierarchical formulation covariate estimates > related to occurrence could then be used to map the species distribution > and/or density. You would have to do some reading, thinking about > assumptions and the like, but at first blush I think this idea may have > merit. > > Track plate arrays would also be a nice addition to your existing data." > > "Most likely the small mammals you see in your seed patches don't have any > unique marking for individual identification. What you might want to do is > trap and mark them (using a sharpie or fur clipping) at the side or top. If > you can mark them uniquely, then you might even be able to monitor > visitation rates of individuals in patches. One of my profs (Douglas > Morris, > Lakehead University) used to fur clip small mammals in Canada and use video > recording to study their foraging behavior. I my doctoral research on > desert > gerbils, I marked them with PIT tags and had special readers under their > foraging patches. I carried out some food augmentation experiments to look > at how that affects coexistence among two species of gerbils, and their > anti-predator behaviors. I hope this helps." > > "You need be able to identify individuals. With large mammals, usually with > cats, this is generally based on strips or dots fur patterns. In general > two cameras are used to get pictures from both sides of an individual. > Since > with small mammalls fur patterns may be homogeneus I believe that you would > have to catch them at least once and come up with some visible marker which > could rest for all the study period. > > Since you would need investments on traps anyway I am not sure if it would > be an advantage to invest on cameras as well, rather than run a traditional > recapture with traps. But if funds are available the use of cameras could > be > possible. I would borrow some and run a trial experiment first if > possible." > > "If you are just interested in getting just an estimate of abundance of the > small mammals, you could use activity as a surrogate for density. Activity, > can be measured directly from the number of visits in the camera traps. A > simpler and cheaper method is to use tracking plots. Clear small (e.g. > .5x.5m) plots on the ground, and sprinkle some soft soil/sand on it, and > then just count the # of crossing of small mammals on these plots, or > estimate what percentage of the plot is covered by their tracks. This > should > give you a good estimate of density, because usually activity and density > are highly correlated. > > It might actually be even better to measure activity because, since small > mammals hoard seeds, even though the actual density maybe small (i.e. you > might not see a change in density with your treatments), but the overall > activity of the residents might increase because now there is more food in > the system." > > > Citations for relevant papers: > > Journal of Applied Ecology 2008,45:1228–1236 Estimating animal density > using > camera traps without the need for individual recognition J. Marcus > Rowcliffe, Juliet Field, Samuel T. Turvey, and Chris Carbone > > Using Counts to Simultaneously Estimate Abundance and Detection > Probabilities in a Salamander Community > Author(s): C. Kenneth Dodd, Jr. and Robert M. Dorazio > Source: Herpetologica, Vol. 60, No. 4 (Dec., 2004), pp. 468-478 > > Wildlife Research, 2010, 37, 456–465 > A comparison of the effectiveness of camera trapping and live trapping for > sampling terrestrial small-mammal communities Natasha De Bondi, John G. > White,C, Mike Stevens and Raylene Cooke > >
