Abstract
Daily travel distance (DTD), the distance an animal moves over the course of the day, is an important metric in movement ecology. It provides data with which to test hypotheses related to energetics and behaviour, e.g. impact of group size or food distribution on DTDs. The automated tracking of movements by applying GPS technology has become widely available and easy to implement. However, due to battery duration constraints, it is necessary to select a tracking-time resolution, which inevitably introduces an underestimation of the true underlying path distance. Here we give a quantification of this inherent systematic underestimation of DTDs for a terrestrial primate, the Guinea baboon. We show that sampling protocols with interval lengths from 1 to 120 min underestimate DTDs on average by 7 to 35 %. For longer time intervals (i.e. 60, 90, 120 min), the relative increase of deviation from the “true” trajectory is less pronounced than for shorter intervals. Our study provides first hints on the magnitude of error, which can be applied as a corrective when estimating absolute DTDs in calculations on travelling costs in terrestrial primates.
Highlights
Spatial information is crucial for many questions in ecological and behavioural research, e.g. species or resource distribution, habitat utilisation and estimates of home ranges or daily travel paths
Travel distance (DTD), the distance an animal moves over the course of the day, is an important metric in movement ecology
The increase of deviation from true Daily travel distance (DTD) followed an exponential function, indicating that the average relative error increase is larger at shorter sampling intervals than at larger ones, which is in agreement with findings from Rowcliffe et al (2012)
Summary
Spatial information is crucial for many questions in ecological and behavioural research, e.g. species or resource distribution, habitat utilisation and estimates of home ranges or daily travel paths. Programming fewer GPS fixes results in longer battery life but at the price of lower data density. It might not be a big problem if one is interested in the area an animal uses within a year, which one can probably estimate fairly well with just 2 or 3 fixes day−1 (Cagnacci et al, 2010). It can be problematic if one is interested in daily travel distance (DTD), where, optimally, a quasi-continuous recording of the travel path would be best, Published by Copernicus Publications on behalf of the Deutsches Primatenzentrum GmbH (DPZ)
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