2.2 Estimation of home range, cumulative distance travelled and
site fidelity
We estimated annual and monthly home-ranges using the 95% kernel
density estimator contours (KDE) and the cumulative distance travelled
for each tagged individual using the “amt” package (Signer et al.,
2019). Cumulative distance travelled per month were measured as the
total length of each track (in km) (Edelhoff et al., 2016). Individuals
with less than ten fixes per day were discarded (n=4 cases).
We measured the individual home-range fidelity by calculating the
percentage of overlap between consecutive monthly home-range (Fieberg &
Kochanny, 2005). We selected the 95% KDE as an estimator of home-range
to evaluate differences in foraging areas. The percentage of overlap was
quantified using the Bhattacharyya coefficient, which ranges between 0
(complete segregation) and 1 (perfect overlapping; Fieberg & Kochanny,
2005; Winner et al., 2018).