Implementation of Acoustic Dosimeters With Recoverable Month-Long GPS/TDR Tags to Interpret Controlled-Exposure Experiments for Large Whales
Obtaining extended and detailed information from instrumented whales is important for understanding whale behavior and interpreting responses to anthropogenic noise but has been difficult to achieve with tags because of short attachment times, poor spatial/temporal resolution, or lack of adequate acoustic data. In 2007–2008, sperm whales were tagged in the Gulf of California with Wildlife Computers TDR-PAT-MK-10 tags. While attached, the tags sent Fastloc-GPS locations and summary dive data (shape, duration, and depth) via ARGOS after dives >10 min and >10 m. Tags released from the whales floated to the surface and were recovered. Downloaded data revealed high-resolution time-depth recorder (TDR; 1-s and 2-m dive-depth increments) and GPS data within 60 m (Mate 2008). The tags provided insights into resting, foraging, and traveling behaviors, diving to depths over 1,200 m for periods of up to 28 days. Fast zigzag patterns during dives likely represented foraging attempts on Humboldt squids. Despite coordinated travels, whales in the same social unit did not usually dive synchronously or to the same depth and displayed considerable variability at the same position and time.