Kernel Home Range Estimation for ArcGIS, using VBA - Fish and ...

equal to or smaller than the distance typically traveled in the given sampling interval
(displacement distance)(Figure 7.2.a.), then in theory, the animal would have left the area by the
next sampling event (Figure 7.2.b.). Resightings in that area should only occur if the animal
chose to stay in the area instead of moving its typical interval distance, or if it subsequently
returned to the area (Figures 7.2.c-e). In both cases it is fair to assume that a high density of
location estimates may reflect biological importance to the animal.
a b c d e
Figure 7.2. Appropriate choice of smoothing parameter based on the structure of the location
data (sampling schedule) and the movement behavior of the species (displacement
distance).
ABODE provides a smoothing selection function in which the user can enter the sampling interval
for the given dataset. This is the smoothing function “Displacement”. If ancillary data that include
the day, month, and year of each location are provided, then ABODE will search the dataset and
find all consecutive location estimates for the given interval. The distance traveled between the
locations will be calculated, and the arithmetic mean thereof will be used as the smoothing
parameter for the dataset. In reality, not all studies will have the luxury of a generally consistent
sampling interval. Many data are collected opportunistically, and will thus have an irregular
sampling schedule. In such cases, ABODE can look for a sampling interval that best represents
the data. The user should decide which measure of central tendency would best represent the
data. ABODE can look for the median, mean and mode sampling interval. Before making a
selection, the user should understand the implications that outliers in the data will have on each
estimate. It may be best to run all three analyses and choose a method that seems most
appropriate.
Sample size considerations dictate that ABODE uses a range of values for its search criteria.
The mean sampling interval may not even be represented in the dataset, or may, at best, be
represented by only a few actual data pairs. To base a travel distance on such a small sample
size may produce undesirable results. Similarly, the median sampling interval may only be
represented once in a dataset, and the mode, at least twice. ABODE will search for sampling
intervals within a range that operates on an increasing scale (Table 1.). If the interval ABODE is
searching for is less than 7 days, then the tolerance (on either side) is 0 days. If the interval is
38