2 research outputs found
The Relationship Between GPS Sampling Interval and Estimated Daily Travel Distances in Chacma Baboons (Papio ursinus)
Modern studies of animal movement use the Global Positioning System (GPS) to estimate animals’ distance traveled. The temporal resolution of GPS fixes recorded should match those of the behavior of interest; otherwise estimates are likely to be inappropriate. Here, we investigate how different GPS sampling intervals affect estimated daily travel distances for wild chacma baboons (Papio ursinus). By subsampling GPS data collected at one fix per second for 143 daily travel distances (12 baboons over 11–12 days), we found that less frequent GPS fixes result in smaller estimated travel distances. Moving from a GPS frequency of one fix every second to one fix every 30 s resulted in a 33% reduction in estimated daily travel distance, while using hourly GPS fixes resulted in a 66% reduction. We then use the relationship we find between estimated travel distance and GPS sampling interval to recalculate published baboon daily travel distances and find that accounting for the predicted effect of sampling interval does not affect conclusions of previous comparative analyses. However, if short-interval or continuous GPS data—which are becoming more common in studies of primate movement ecology—are compared with historical (longer interval) GPS data in future work, controlling for sampling interval is necessary
Estimation of baboon daily travel distances by means of point sampling – the magnitude of underestimation
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