[tlocoh-info] Dealing w/ multiple datasets

Wayne Getz wgetz at berkeley.edu
Wed May 28 01:37:20 CEST 2014

Hi Tom:

I am sure that Andy will respond when he gets a chance, but here are some comments:

> Andy,
> My name is Thomas Janke. I am a graduate student at Sul Ross State University in west Texas working for the Borderlands Research Institute. Over the past 3 years, I have been monitoring the movements and survival of reintroduced desert bighorn sheep to part of their historic range. Now comes time for the analysis and writing.
> After diving into past research and methodology, I knew I wanted to do more than just create and compare MCPs or KDEs to begin describing my research. Which brings me to you and your T_LoCoH software. I believe it is great y'all were able to create a software package that incorporates time into the analysis.
> I am new to this software, but am willing to do what it takes to become more familiarized with it and be able to incorporate it into my data analysis. I have read your dissertation, your Home Range Plus publication, and the overview of the T_LoCoH program, along with following through with the example sets. Now its time for me to start analyzing my data.
> We conducted 2 consecutive releases (2010 & 2011) for this restoration effort. I currently have data from 54 GPS collars, with data collection ranging from <1wk to >2yrs. Over the course of the study, we used 3 different types of collars (all of which have differing data formats). The 2010 released collars collected data in Lat/Long and were programmed to obtain a location every 3 hours. The 2011 released collars collected data in UTMs and were programmed to collect a location every 5 hours.

If you are going to collect data in future, it would be good to have finer resolution, depending of course on the problems you want to address.  But information on diurnal activity cycles would best be served by data at least 2-3 fixes per hour, and more if possible.  At this time, all you can compare are averages across 24-25 hour periods.

> I would ultimately like to compare the movements and UDs by release year, sex, and time of year (ecological seasons).

Again, to see how with diurnal cycle patterns may vary across seasons, finer sub-hourly data would be good.

> I would also like to use the GPS data to see if there are any preferred habitats (e.g. slope, aspect, terrain ruggedness, etc.) for the previously mentioned comparisons. It would also be great to be able to delineate ‘travel corridor(s)' from the GPS data (esp. the sheep that were documented crossing international borders).

I would suggest that you begin with at T-LoCoH analysis with fixed k and large s, where k=6 (this would give you points that are 25 hours apart using your 5 hour data) and s is large enough to give you consecutive points in time.  You can then look at area and elongation of hulls, as well as revisitation rates to hulls and correlate these revisitation rates with your habitat variables.

> How do I need to go about entering and analyzing all of my data? Is there a way to compute an ’s', and an 'a or k' value that can be used on all of the sheep, or will I have to determine individual values?

Use a k=6 for sheep that are monitored every 5 hours and a k=9 for sheep monitored very three hours. Then you will get 24-25 hour use kernels if s is large enough.  So just make s large enough to ensure all neighbors are consecutive in time.  Then, if you want home ranges, take a small s so that points 6 months apart add a component that is about the same as the spatial extent of data (i.e. s*6 months = the greatest spatial distance apart).  You can then try an s half the size or twice the size to see what you get.

> If I am able to combine the data sets, how to I need to go about the different coordinate systems? How do I deal with differing data set sizes (e.g. 1 month compared to 2 years) or collars that had different acquisition rates?

If you are comparing diurnal values at a particular time of the year, you can use all values for that time of the year, but you cannot compare home range constructions based on 1 month versus 6 month data etc.
> Any help you're able to give would be most appreciated.
> Thanks and have a good one,
> Thomas
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Professor Wayne M. Getz
A. Starker Leopold Professor of Wildlife Ecology
Department Environmental Science Policy & Management
130 Mulford Hall
University of California at Berkeley
CA 94720-3112, USA

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