Comparison of two sampling protocols and four home-range estimators using radio-tracking data from urban badgers Meles meles

Radio-telemetry is often the method of choice for studies of species whose behaviour is difficult to observe directly. However, considerable debate has ensued about the best way of deriving home-range estimates. In recent years, kernel estimators have become the most widely used method, together with the oldest and simplest method, the minimum convex polygon (MCP). More recently, it has been suggested that the local convex hull (LCH) might be more appropriate than kernel methods in cases where an animal’s home range includes a priori inaccessible areas. Yet another method, the Brownian bridge (BB), explicitly uses autocorrelated data to determine movement paths and, ultimately, home ranges or migration routes of animals. Whereas several studies have used simulation techniques to compare these different methods, few have used data from real animals. We used radio-telemetric data from urban badgers Meles meles to compare two sampling protocols (10-minute vs at least 30-minute inter-fix intervals) and four home-range estimators (MCP, fixed kernels (FK), LCH and BB). We used a multi-response permutation procedure and randomisation tests to compare overall patterns of fixes and degree of overlap of home ranges estimated using data from different sampling protocols, and a general linear model to compare the influence of sampling protocols and home-range estimator on the size of habitat patches. The shape of the estimated home ranges was influenced by sampling protocol in some cases. By contrast, the sizes and proportions of different habitats within home ranges were influenced by estimator type but not by sampling protocol. LCH performed consistently better than FK, and is especially appropriate for patchy study areas containing frequent no-go zones. However, we recommend using LCH in combination with other methods to estimate total range size, because LCH tended to produce smaller estimates than any other method. Results relating to BB are preliminary but suggest that this method is unsuitable for species in which range size is small compared to average travel speed.

Radio-telemetry is often the method of choice for studies of species
whose behaviour is difficult to observe directly. However, considerable
debate has ensued about the best way of deriving home-range estimates.
In recent years, kernel estimators have become the most widely used
method, together with the oldest and simplest method, the minimum
convex polygon (MCP). More recently, it has been suggested that the
local convex hull (LCH) might be more appropriate than kernel methods
in cases where an animal’s home range includes a priori inaccessible
areas. Yet another method, the Brownian bridge (BB), explicitly uses
autocorrelated data to determine movement paths and, ultimately, home
ranges or migration routes of animals. Whereas several studies have
used simulation techniques to compare these different methods, few have
used data from real animals. We used radio-telemetric data from urban
badgers Meles meles to compare two sampling protocols (10-minute vs
at least 30-minute inter-fix intervals) and four home-range estimators
(MCP, fixed kernels (FK), LCH and BB). We used a multi-response
permutation procedure and randomisation tests to compare overall patterns
of fixes and degree of overlap of home ranges estimated using data
from different sampling protocols, and a general linear model to compare
the influence of sampling protocols and home-range estimator on
the size of habitat patches. The shape of the estimated home ranges was
influenced by sampling protocol in some cases. By contrast, the sizes
and proportions of different habitats within home ranges were influenced
by estimator type but not by sampling protocol. LCH performed
consistently better than FK, and is especially appropriate for patchy
study areas containing frequent no-go zones. However, we recommend
using LCH in combination with other methods to estimate total range
size, because LCH tended to produce smaller estimates than any other
method. Results relating to BB are preliminary but suggest that this
method is unsuitable for species in which range size is small compared
to average travel speed.

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