Analyzing potential acoustic differences between different bowhead demographics in the Beaufort Sea.

Abstract

Most bowhead whales from the Bering-Chukchi-Beaufort stock migrate westward from Arctic Canadian waters through the Alaskan Beaufort Sea each year from late August to late October. Since 2007 both aerial sighting and acoustic call data have been collected during these fall migrations, as part of a long-term monitoring effort to assess the potential impacts of North Slope oil industry activities on bowhead whales. The aerial sighting efforts recorded the position of bowhead individuals or groups, designating the animals as subadults or adults, and noted whether a calf was present. A five-site array of seven directional autonomous seafloor acoustic recorders (DASARs) each recorded the acoustic data. An automated detection algorithm was used to isolate individual bowhead whale calls and estimate their locations. Here simultaneous acoustic and visual data from 2007, 2008, and 2010 were merged to determine whether potential variations in calling behavior exist between subadults, adults, and adults with calves. Visual measurements of animal course and direction were used to place bounds on call times and locations that may be associated with that animal versus other animals sighted nearby. Potential differences in call rate and call type were statistically examined. [Work supported by the Shell Exploration and Production Company.]