Data from: Behavioral responses of individual blue whales (Balaenoptera musculus) to mid-frequency military sonar

This study measured the degree of behavioral responses in blue whales
(Balaenoptera musculus) to controlled noise exposure off the southern
California coast. High-resolution movement and passive acoustic data were
obtained from non-invasive archival tags (n=42) while surface positions
were obtained with visual focal follows. Controlled exposure experiments
(CEEs) were used to obtain direct behavioral measurements before, during,
and after simulated and operational military mid-frequency active sonar
(MFAS), pseudorandom noise (PRN), and controls (no noise exposure). For a
subset of deep-foraging animals (n=21), active acoustic measurements of
prey were obtained and used as contextual covariates in response analyses.
To investigate potential behavioral changes within individuals as a
function of controlled noise exposure conditions, two parallel analyses of
time-series data for selected behavioral parameters (e.g., diving,
horizontal movement, feeding) were conducted. This included expert scoring
of responses according to a specified behavioral severity rating paradigm
and quantitative change-point analyses using Mahalanobis distance
statistics. Both methods identified clear changes in some conditions. More
than 50% of blue whales in deep feeding states responded during CEEs,
while no changes in behavior were identified in shallow-feeding blue
whales. Overall, responses were generally brief, of low to moderate
severity, and highly dependent on exposure context such as behavioral
state, source-to-whale horizontal range, and prey availability. Response
probability did not follow a simple dose-response model based on received
exposure level. These results, in combination with additional analytical
methods to investigate different aspects of potential responses within and
among individuals, provide a comprehensive evaluation of how free-ranging
blue whales responded to mid-frequency military sonar.