Northern elephant seal tracking and diving – processed data

Northern elephant seals (Mirounga angustirostris) have been integral to the development and progress of biologging technology and movement data analysis. Adult female elephant seals at Año Nuevo State Park and other colonies along the west coast of North America were tracked annually from 2004 to 2020 for a total of 653 instrument deployments and 561 recoveries. These high-resolution diving and location data have been compiled, curated, and processed. This repository has netCDF files containing the raw tracking and diving data. The raw data are available in a second repository (https://doi.org/10.7291/D10D61).

Methods
These data were collected from biotelemetry devices attached to adult female northern elephant seals (Mirounga angustirostris) from 2004 to 2020. The instruments collected locations (Argos and/or GPS) and continuously recorded depth throughout the animals' trips. Data were processed in MATLAB and R using custom code, the IKNOS package for dive data processing, and the aniMotum package for track processing. The details of data collection and processing are documented in the data descriptor paper associated with this dataset. In addition, all code used to process the data are available on GitHub and Zenodo.

The data presented here are freely available for use under the CC0 (Creative Commons Zero), with attribution highly encouraged given to the data descriptor (DOI: 10.1038/s41597-024-04084-4) and this Dryad repository. We encourage users to reach out to the data owner for richer insight into the dataset. Subsets of this dataset have been made available through other projects and data portals and we caution users that these are not independent northern elephant seal datasets. This includes the AniBOS/MEOP data portal (https://www.meop.net/database/meop-databases/), the Animal Tracking Network (ATN) (https://portal.atn.ioos.us/), Movebank (https://www.movebank.org/cms/movebank-main), and MegaMove (https://megamove.org/data-portal/).

Additional data about the instrumented animals, such as morphometrics, demographics, and other biologging data (e.g., acceleration, jaw motion, temperature), are available for many of these animals but are beyond the scope of this dataset. For more information, contact the data owner.

Sampling Biases

Generally, we have been careful to select healthy animals for sedation and instrumentation. For animals deployed at Año Nuevo (most of the tracks), typically individuals with known site fidelity to the colony were selected and if age was known it was usually restricted to 4- to 12-year-olds. Furthermore, the data reported here span two decades of work. During this time, different studies prompted additional non-random population sampling. Examples include focusing on one age for a year, repeat tracking the same individuals two trips in a row, and intentionally selecting previously tracked females who had used a coastal foraging strategy. Many individuals in the dataset have been tracked multiple times. We strongly encourage researchers to evaluate the metadata provided carefully and contact the data owner with inquiries.

Code Availability

All the code written for data processing and NetCDF data import code for MATLAB, R, and Python are available at GitHub (https://github.com/rholser/NES_TrackDive_DataProcessing) and Zenodo (https://doi.org/10.5281/zenodo.12511548). Extensive documentation of functions and scripts is also provided there. In addition, the authors have provided code in Python, R, and MATLAB for basic access to the netCDF files (GitHub link). They should serve as a model to enable users unfamiliar with the format to access the data.