I wanted to share a package I've been using to visualize fine-scale movements of fish - T-LoCoH. It can be used in any situation for which you have positional data (i.e. discrete locations), that are common with satellite, gps, and more recently acoustic tags. I have found the package to be intuitive, relatively easy-to-use, and has a GREAT tutorial. In addition, the package's developers are very helpful and quick to respond to issues. T-LoCoH stands for "time local convex hull" which is a specific method for exploring spatial habitat use, and although I am still wrapping my head around some of the concepts, I do think this method can have a lot of value in assessing variability in movements across BOTH space and time.
However, my current use of the package is not for analysis, but simply for visualization. To me, a map is worth a thousand words, and so I get real excited when I can create animations using maps. The package allows you to create an animation to show the movements of an animal through time. The package's ability to create simple but effective animations is really impressive and was relatively straightforward. Some of the nice features/possibilities for animating your movement data include:
- depict the movements of multiple individuals simultaneously
- adding geospatial data (both rasters and vector shapefiles) to act as a backdrop for animal locations.
- Adding a date and time label on the animation as it runs.
- Similarly, a date bar that shows both the temporal extent of the animation and the relative time currently being shown.
- coloring the point of the current animal location by time of day (really nice for diel patterns!).
- ability to explort the animation in mp4 format, as well as export the individual frames so you can create your own gif later.
Below is what I was able to come up with (relatively quickly, although I did need some help from the package developers for a couple of the finer points) - the animation shows some movements of a single bull trout at a lake-river edge in British Columbia. The grey points represent all points the fish visits, with the current location in black (night), yellow (day), or early morning (orange). The map depicts water depth (blue = deep, green = shallow). You might notice the fish's use of the northern part of the screen at night, and a small area that is used with little movement during the day.
To read more on the package, and the T-LoCoH method, see this paper by Lyons et al. in BMC Movement Ecology.
As the field of movement ecology grows, so does the need to have the proper tools to fully analyze and understand the data we collect. In addition, being able to visualize complex data for both scientists and the public alike to communicate science is important. I think T-LoCoH is great for both.