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Measurement error causes scale-dependent threshold erosion of biological signals in animal movement data

Bradshaw, Corey J.A., Sims, David W. and Hays, Graeme C. 2007, Measurement error causes scale-dependent threshold erosion of biological signals in animal movement data, Ecological applications, vol. 17, no. 2, pp. 628-638, doi: 10.1890/06-0964.

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Title Measurement error causes scale-dependent threshold erosion of biological signals in animal movement data
Author(s) Bradshaw, Corey J.A.
Sims, David W.
Hays, Graeme C.ORCID iD for Hays, Graeme C. orcid.org/0000-0002-3314-8189
Journal name Ecological applications
Volume number 17
Issue number 2
Start page 628
End page 638
Total pages 11
Publisher Ecological Society of America
Place of publication Tempe, Ariz.
Publication date 2007-03
ISSN 1051-0761
1939-5582
Keyword(s) Argos satellites
Fastloc
first-passage time
foraging
fractal dimension
geolocation
GPS
Levy flight
radiotelemetry
random walk
spatial scale
VHF
Summary Recent advances in telemetry technology have created a wealth of tracking data available for many animal species moving over spatial scales from tens of meters to tens of thousands of kilometers. Increasingly, such data sets are being used for quantitative movement analyses aimed at extracting fundamental biological signals such as optimal searching behavior and scale-dependent foraging decisions. We show here that the location error inherent in various tracking technologies reduces the ability to detect patterns of behavior within movements. Our analyses endeavored to set out a series of initial ground rules for ecologists to help ensure that sampling noise is not misinterpreted as a real biological signal. We simulated animal movement tracks using specialized random walks known as Lévy flights at three spatial scales of investigation: 100-km, 10-km, and 1-km maximum daily step lengths. The locations generated in the simulations were then blurred using known error distributions associated with commonly applied tracking methods: the Global Positioning System (GPS), Argos polar-orbiting satellites, and light-level geolocation. Deviations from the idealized Lévy flight pattern were assessed for each track after incrementing levels of location error were applied at each spatial scale, with additional assessments of the effect of error on scale-dependent movement patterns measured using fractal mean dimension and first-passage time (FPT) analyses. The accuracy of parameter estimation (Lévy μ, fractal mean D, and variance in FPT) declined precipitously at threshold errors relative to each spatial scale. At 100-km maximum daily step lengths, error standard deviations of ≥10 km seriously eroded the biological patterns evident in the simulated tracks, with analogous thresholds at the 10-km and 1-km scales (error SD ≥ 1.3 km and 0.07 km, respectively). Temporal subsampling of the simulated tracks maintained some elements of the biological signals depending on error level and spatial scale. Failure to account for large errors relative to the scale of movement can produce substantial biases in the interpretation of movement patterns. This study provides researchers with a framework for understanding the limitations of their data and identifies how temporal subsampling can help to reduce the influence of spatial error on their conclusions.
Language eng
DOI 10.1890/06-0964
Field of Research 069999 Biological Sciences not elsewhere classified
Socio Economic Objective 970106 Expanding Knowledge in the Biological Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2007, Ecological Society of America
Free to Read? Yes
Persistent URL http://hdl.handle.net/10536/DRO/DU:30058349

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Every reasonable effort has been made to ensure that permission has been obtained for items included in DRO. If you believe that your rights have been infringed by this repository, please contact drosupport@deakin.edu.au.