A path reconstruction method integrating dead-reckoning and position fixes applied to humpback whales

• Published in: Movement Ecology
• Main Authors: Wensveen, Paul J., Thomas, Len, Miller, Patrick J O
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: Megaptera novaeangliae; Marine mammal; Positioning; Fine-scale movement; State-space model; Bio-logging; Track reconstruction; Archival tag; Focal follow; Humpback Whale
• Online Access: https://risweb.st-andrews.ac.uk/portal/en/researchoutput/a-path-reconstruction-method-integrating-deadreckoning-and-position-fixes-applied-to-humpback-whales(9b1c4eea-98b2-4183-a474-da776189df07).html; https://doi.org/10.1186/s40462-015-0061-6; https://research-repository.st-andrews.ac.uk/bitstream/10023/11976/1/Wensveen_2015_ME_PathReconstructionMethod_CC.pdf

BACKGROUND: Detailed information about animal location and movement is often crucial in studies of natural behaviour and how animals respond to anthropogenic activities. Dead-reckoning can be used to infer such detailed information, but without additional positional data this method results in uncertainty that grows with time. Combining dead-reckoning with new Fastloc-GPS technology should provide good opportunities for reconstructing georeferenced fine-scale tracks, and should be particularly useful for marine animals that spend most of their time under water. We developed a computationally efficient, Bayesian state-space modelling technique to estimate humpback whale locations through time, integrating dead-reckoning using on-animal sensors with measurements of whale locations using on-animal Fastloc-GPS and visual observations. Positional observation models were based upon error measurements made during calibrations. RESULTS: High-resolution 3-dimensional movement tracks were produced for 13 whales using a simple process model in which errors caused by water current movements, non-location sensor errors, and other dead-reckoning errors were accumulated into a combined error term. Positional uncertainty quantified by the track reconstruction model was much greater for tracks with visual positions and few or no GPS positions, indicating a strong benefit to using Fastloc-GPS for track reconstruction. Compared to tracks derived only from position fixes, the inclusion of dead-reckoning data greatly improved the level of detail in the reconstructed tracks of humpback whales. Using cross-validation, a clear improvement in the predictability of out-of-set Fastloc-GPS data was observed compared to more conventional track reconstruction methods. Fastloc-GPS observation errors during calibrations were found to vary by number of GPS satellites received and by orthogonal dimension analysed; visual observation errors varied most by distance to the whale. CONCLUSIONS: By systematically accounting for the observation errors ...