Behavioral response of northern elephant seals and California sea lions on San Nicolas Island, California, to loud impulse noise

Abstract

Breeding northern elephant seals (Mirounga angustirostris) and California sea lions (Zalophus californianus) on San Nicolas Island, California, were exposed to loud impulse noise created by a carbide pest control cannon. Distance of seals from the sound source varied from 5–50 m. Sound pressure levels varied from 145.5 dB(A) re 20 μPa and 146.9 dB(flat) re 20 μPa 5 m from the cannon to 115.6 dB(A) and 125.7 dB(flat) 50 m from the cannon. The intensity and duration of behavioral responses of each species to sonic stimuli varied by sex, age, and season. Responses to visual stimuli (humans) also varied seasonally and differed from responses to sonic stimuli. Habitat use, population growth, and pup survival of both species appeared unaffected by periodic exposure to carbide cannon impulse noise during the 1981 breeding seasons.