Such outlier positions have a disproportionate influence on MCP area; an effect that
increases with time and complicates comparisons of MCP estimates made during periods of
unequal duration. To counter this, outlier positions were excluded using a peeled polygon core
method excluding 0, 5% and 10% of positions furthest from the harmonic mean centre (the
point where inverse reciprocal mean distance to all the other fixes is a minimum) to obtain
100%, 95% and 90% peeled polygon cores. Autocorrelation or independence of fixes is an
important consideration when calculating home-range using conventional radio-telemetry
(Kenward 2001). However, this is not considered to be a problem in the use of GPS-PTT units so
long as positions are recorded at regular intervals during the animal’s normal activity cycle, thus ensuring unbiased temporal coverage of the animal’s movements during the study period (Otis
and White 1999).