Effects of underwater noise on migrating gray whales off the coast of California

The potential effects of man‐made underwater noises on the behavior of gray whales (Eschrictius robustus) off the Coast of central California were studied during their southern and northern migration in 1983. In January, two shore‐based theodolite tracking sites recorded whales' swimming patterns as well as behavioral activities while underwater sounds (production platform, drilling platform, semisubmersible, drillship, helicopter, or killer whale, Orcinus orca) were transmitted from a vessel anchored in the middle of the nearshore migratory pattern. In April and May, when the majority of whales were mother‐calf pairs, three theodolite tracking sites recorded swimming patterns, behavior, and respiration times for individuals. Experimental noise sources consisted of either a seismic vessel operating a 40‐gun array, a vessel operating a single air gun or a stationary vessel broadcasting either drillship or killer whale sounds. The behavioral measures used to assay disturbance included deflection of normal m...