Diving into the past: tools for recovering historic dive traces from film-based time depth recorders using data from Weddell seals
Abstract Background Over the past 4 decades, time depth recorders (TDRs) have become an essential tool for research into the previously unexplored diving behavior of marine organisms. Of the early TDRs invented in the 1970s, the Kooyman–Billups TDR was the first to be placed on a free-ranging animal...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
BMC
2025-07-01
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| Series: | Animal Biotelemetry |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s40317-025-00418-0 |
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| Summary: | Abstract Background Over the past 4 decades, time depth recorders (TDRs) have become an essential tool for research into the previously unexplored diving behavior of marine organisms. Of the early TDRs invented in the 1970s, the Kooyman–Billups TDR was the first to be placed on a free-ranging animal. This device documented behavior for up to 2 weeks using a pressure-sensitive arm that moved an LED light across a rolling window of film, which would later be photocopied and annotated by hand. As TDR technology advanced from film-based instruments to small electronic tags and biotelemetry devices, comparisons of diving behavior measured by the changing devices have been hindered by the difficulty of comparing digital and analog datasets. However, historic analog data from early TDRs contain empirical information on the behaviors of animals that can inform modern studies. Here, we describe a novel computational method for recovering dive records from film-based Kooyman–Billups TDRs deployed on the Weddell seal (Leptonychotes weddellii). Results Our recovery process involved record scanning, image processing, and bias correction. To assess the efficacy of our method, we compared dive statistics from the recovered dive traces with a previous analysis of the same records by hand in 1992, and found no large differences. Our recovery methods are published as open-source code in an R package. Conclusions This tool will assist in recovering dive data from historic Kooyman–Billups TDRs and from similar devices of this time, which recorded data for at least 14 different species. Recovery of these datasets provides a unique opportunity to examine behavioral change over decadal time scales in ecosystems experiencing direct and indirect anthropogenic activity. |
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| ISSN: | 2050-3385 |