V-Track: software for analysing and visualising animal movement from acoustic telemetry detections

Abstract

The tagging of aquatic and semi-aquatic animals with acoustic transmitters and their detection by passive underwater receivers has gained huge popularity over the past decade. This technology offers researchers the opportunity to monitor the finite- to broad-scale movements of multiple individuals over many years; however, the sheer scale and spatial complexity of these datasets are often beyond the capabilities of routine database and spread-sheet applications. In the present paper, we describe software (V-Track) that greatly facilitates the assimilation, analysis and synthesis of animal-location data collected by underwater passive acoustic receivers. The principal features within V-Track are the behavioural event qualifier (BEQ) and the receiver-distance matrix (RDM) calculator. The BEQ identifies and catalogues horizontal movements from receiver detection data, or vertical movements from transmitter sensor data (depth or temperature). The RDM is generated from the geographical location of the acoustic receivers and is utilised by V-Track to illustrate the behavioural event information in a spatial context. V-Track is a package written within the R-programming language, and a graphical user interface is also provided. Here, we feature two case studies to demonstrate software functionality for defining and quantifying behaviour in acoustically tagged marine and freshwater vertebrates.

An open Web-based system for the analysis and sharing of animal tracking data

“…An additional step to further facilitate the development of new tools may be to offer the R source code to users as an optional output, together with the raw and edited data, and model results (e.g. [8]). This increased transparency would also facilitate the development and implementation of new analysis tools by the wider biotelemetry community.…”

“…Telemetry devices now routinely generate datasets that are larger than off-the-shelf software tools or spreadsheet applications can handle [7,8]. While dedicated, proprietary software platforms for processing these tracking data are available directly from the tag manufacturers, many largescale and long-term studies utilise tags sourced from multiple manufacturers (e.g.…”

DIVING IN A WARMING WORLD: Thermal constraints on the diving capacity of estuarine crocodiles (Crocodylus porosus)

“…Adjusting for body mass brings this value to 0.08 ml O2 min -1 kg -1 . Figure A5.1: Sensitivity analyses used to parameterise the behavioural event qualifier in VTrack (Campbell et al, 2012). Total number of dives (A) and maximum dive duration (B) extracted from the acoustic data set across a range of time thresholds (i.e.…”

“…Wet-dry sensors did not operate in freshwater and satellite fixes of animals were used to confirm when animals entered freshwater river reaches, allowing real zeros in dive frequency counts to be distinguished from zeros arising from freshwater inactivation of tags. Dive depth profiles were extracted from the acoustic fixes in R-Studio (version 3.1.3; R Core Team, 2012) using the behavioural event qualifier (BEQ) function in V-Track (Campbell et al, 2012); where a dive was defined using a minimum depth threshold (≥ 0.5 m) and a maximum time between detections threshold (60 min), to ensure animals did not leave the field of detection before resurfacing. The termination depth threshold was set to ≤ 0.5 m to qualify the end of a dive event.…”

“…Data analyses were performed in R Studio (version 3.1.3; R Core Team, 2012) using the mgcv (mixed GAM computation vehicle; Wood, 2000), nlme (linear and nonlinear mixed effects models; Pinheiro et al, 2012), lattice (Sarkar, 2008), cosinor (Sachs, 2014) and V-Track (Campbell et al, 2012) packages. Time stamps for dive events were adjusted from coordinated universal time (UTC) to Australian Eastern standard time (AEST) and converted into radians.…”