Dolphins
Methods Summary
Identified dolphin acoustic events include echolocation clicks from Risso’s and Pacific white-sided dolphins, and whistles from unidentified dolphin species
Triton software is used for the following:
Long-term spectral averages (LTSAs) are calculated from Channel 1 recordings with a 200 Hz, 5 second resolution
For continuous recordings (ADRIFT dataset), the start and end times of dolphin acoustic events are identified by manually scanning LTSAs in 1 hour windows
For duty-cycled recordings (CCES and PASCAL datasets), the presence of dolphin acoustic events is identified within 2-minute bins
Step-by-Step Instructions
Generate Long Term Spectral Average (LTSA)
See methods in “Data Prep” section. Use 5 s 200 Hz resolution.
Start Triton Logger Remora
- Launch Triton within Matlab. Open the LTSA for the data you want to analyze.
- In the Triton “Control” window, select the Remoras menu, choose Logger and then start a new log. You will need to re-start Triton if this is the first instance of using the Logger remora. See more info on Triton Remoras on the Marine Bioacoustic Research Collective wiki.
Annotate the presence dolphin acoustic events
Risso's dolphins (Grampus griseus) and Pacific white-sided dolphins (Lagenorhynchus obliquidens) produce echolocation clicks which can be identified to species by distinct spectral features observable in the LTSA and spectrogram (Soldevilla et al. 2008). There is some varation in the spectral features of echolocation clicks for Risso’s dolphins (Soldevilla et al. 2017) and Pacific white-sided dolphins (Soldevilla et al. 2008). The analysts noted the presence of different click types within each encounter, when possible. Some dolphin species produce echolocation clicks which cannot currently be classified from the LTSA; those species are not included in this analysis, but their presence may be captured by the dolphin whistle events.
[INSERT SCREENSHOT SHOWING START AND END TIME OF RISSO’S DOLPHIN ECHOLOCATION EVENT]
[INSERT SCREENSHOT SHOWING START AND END TIME OF PACIFIC WHITE-SIDED DOLPHIN ECHOLOCATION EVENT]
<!--# Potential unidentified dolphin species within the California Current include common dolphins (Delphinus spp.), bottlenose dolphins (Tursiops truncatus), Northern right whale dolphin (Lissodelphus borealis), and striped dolphins (Stenella coeruleoalba).
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Dolphin whistles appear in the LTSA as scattered, yet distinct pockets of energy between 2-20 kHz. There are no established methods to identify dolphin species by their whistles in the LTSA alone; therefore dolphin whistle events are all attributed to “Unidentified Odontocetes”.
[INSERT SCREENSHOT SHOWING START AND END TIME OF DOLPHIN WHISTLE EVENT]
Dolphin acoustic events are defined with an encounter granularity (including start and end time) for continuous acoustic data, and with a 2-minute binned granularity (presence-only within a 2-minute bin) for duty-cycled acoustic data.