It has been a challenging start to field work for the 2018 Atlantic Behavioral Response Study. Windy conditions have kept us off the water on several days and when we have been offshore, our study animals have not been very co-operative. But despite these challenges, we managed to complete our first Controlled Exposure Experiment (CEE) of the field season on May 15th.
Just to recap – our objective in the Atlantic BRS is to study the behavioral responses of Cuvier’s beaked whales (Ziphius cavirostris) and short-finned pilot whales (Globicephala macrorhynchus) to U.S. Navy sonar operations off Cape Hatteras. We had a very successful field season in 2017, deploying 26 satellite-linked tags on both focal species, including 14 beaked whales. We conducted a CEE with 10 animals using full-scale mid-frequency active sonar and a CEE with simulated sonar on 11 animals, including beaked and pilot whales tagged with high-resolution acoustic tags (DTAGs).
So far in 2018, we have encountered both our focal species off Cape Hatteras – successfully deploying a satellite-linked dive recorder on an adult male pilot whale on May 11th. Unusual for us, we missed a tagging attempt on a Cuvier’s beaked whale on May 12th, but fortunately recovered the tag. We have seen large groups of common and bottlenose dolphins off Hatteras, typical for the study area this time of year. We have also encountered five sperm whales while searching for beaked and pilot whales. One of the beaked whales we encountered was Rakes-08, our most frequently sighted beaked whale off Cape Hatteras.
On May 14th we successfully tested the scaled source, which we use to play back the sounds of a simulated sonar system when Navy vessels are unavailable. The plan for May 15th was to find our tagged pilot whale and conduct a CEE to this animal with the scaled source. This might seem like looking for a needle in an offshore haystack, but we are fortunate to be able to track the animal via satellite, getting position updates every few hours. This allows to determine the general area to search and then home in on the tag’s transmission signals using a special receiver. Despite less-than-perfect sea conditions, we managed to find our tagged whale and conduct a CEE. We also collected three biopsy samples from pilot whales in the tagged animal’s group. Ph.D. student Jillian Wisse will analyze concentrations of cortisol and other stress hormones in these tiny samples of skin and blubber to look for a physiological response to the sound exposure.
So, all in all, it’s been a good start to the 2018 work, despite the usual challenges of field work 50 nautical miles from shore. We have a little more calibration work to do with the scaled source and then it’s back to appeasing the weather gods.