Does Plan B work? Home range estimations from stored on board and transmitted data sets produced by GPS-telemetry in the Colombian Amazon.

Jaime Andres Cabrera,Eduardo Molina,Tania Gonzalez,Dolors Armenteras

doi:10.15517/rbt.v64i4.22176

Jaime Andres Cabrera, Eduardo Molina + Show 2 more

Open Access

https://doi.org/10.15517/rbt.v64i4.22176

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Abstract

Telemetry based on Global Positioning Systems (GPS) makes possible to gather large quantities of information in a very fine scale and work with species that were impossible to study in the past. When working with GPS telemetry, the option of storing data on board could be more desirable than the sole satellite transmitted data, due to the increase in the amount of locations available for analysis. Nonetheless, the uncertainty in the retrieving of the collar unit makes satellite-transmitted technologies something to take into account. Therefore, differences between store-on-board (SoB) and satellite-transmitted (IT) data sets need to be considered. Differences between SoB and IT data collected from two lowland tapirs (Tapirus terrestris), were explored by means of the calculation of home range areas by three different methods: the Minimum Convex Polygon (MCP), the Fixed Kernel Density Estimator (KDE) and the Brownian Bridges (BB). Results showed that SoB and IT data sets for the same individual were similar, with fix ranging from 63 % to 85 % respectively, and 16 m to 17 m horizontal errors. Depending on the total number of locations available for each individual, the home ranges estimated showed differences between 2.7 % and 79.3 %, for the 50 % probability contour and between 9.9 % and 61.8 % for the 95 % probability contour. These differences imply variations in the spatial coincidence of the estimated home ranges. We concluded that the use of IT data is not a good option for the estimation of home range areas if the collar settings have not been designed specifically for this use. Nonetheless, geographical representations of the IT based estimators could be of great help to identify areas of use, besides its assistance to locate the collar for its retrieval at the end of the field season and as a proximate backup when collars disappear.

Highlights

The analysis of animal locations, allow the estimation of its home range considered as “the area traversed by the individual in its normal activities” (Burt, 1943)
Since 1960s, very high frequency (VHF) telemetry enabled the monitoring of animal locations in a way it was impossible with the old traditional tracking methodologies, which required the permanence of researchers in the field for long periods of time
Global Positioning Systems (GPS) technology implies technical and economic challenges. It presents the serious drawback of equipment cost, which result in the reduction of the number of individual equipped with collars

Summary

Introduction

The analysis of animal locations, allow the estimation of its home range considered as “the area traversed by the individual in its normal activities” (Burt, 1943) This knowledge provides information to understand how animals interact with their environment and how they use the available resources in heterogeneous landscapes (Cagnacci, Boitani, Powell, & Boyce, 2010). The high proportion of collars that fail and/or get lost in the field because the always challenging field conditions present in some environments like the tropics (Tobler, 2009; Castellanos, 2013), make satellite transmitted data a very desirable characteristic This way, no matter what happen with the collar, at the end of a field season some data will be available. The potential bias due to the technique itself, as the differences between store-on-board (SoB) and satellite-transmitted (IT) data from the same individual have not been considered

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