Figure 4.1 Hypothetical movements of an animal overlaid on five (numbered) habitat types. Habitat selection is often assessed in terms of relative use compared to availability. In this example, habitats 1, 3, and 4 were used and thus also available. Habitat 2 (depicted as a swamp) appears to have
been traversed, possibly just to get from habitat 1 to habitat 3; if it was used simply because of its
location, not because of its habitat-related attributes, a question arises as to whether it should be
considered in the analysis. Conversely, although habitat 5 was not used, it may or may not be considered available. Judged within the context of the home range boundaries, point A in habitat 5
appears to be unavailable, yet this point is closer to known locations of the animal than points B or
C, which are both within the apparent home range. Habitat availability is a nebulous concept, and
thus may be difficult to measure. Similarly, although the figure depicts a travel route, from which relative use of habitats might be deduced, most analyses deal with relative time, not distance, in each
habitat (partly because telemetry data are generally comprised of point locations); it is unclear which
is really a better measure of use.