Research Summary:

Noise impacts on cetaceans from industrial activities, shipping, and other acoustic disturbances

Noise associated with industrial development, including oil and gas exploration, and other activities may adversely impact gray whales by: 1) interfering with or disrupting communications, feeding, breeding, or other vital functions; 2) causing animals to avoid or abandon important feeding area, breeding areas, resting areas, or migratory routes; 3) causing animals to use marginal habitat or to concentrate in undisturbed areas which in turn may result in crowding, over-exploited food resources, increased mortality, and decreased reproduction; 4) stress animals and make them more vulnerable to parasites, disease, and/or predation; and 5) attract animals making them more vulnerable to oil spills, hunting, or harassment (Swartz and Hofman 1991).

Avoidance behavior has been reported for gray whales in response to decibels
greater that 120dB for continuous noise and 160-170 dB for pulsed sounds
(Tyack 1988). In experiments using the underwater playback of sounds from a
Bell 212 turbine helicopter projected at random intervals of 10 seconds to 2
minutes, Malme et al. (1983, 1984) reported significant course changes in
apparent avoidance of the sounds. Malme et al. (1984) found a 50 percent
probability of an avoidance response of 2.5 km off central California for a
seismic airgun array, 1.1 km for a drillship, and 400 m for a single airgun.

Reactions to noise by gray whales were more pronounced on their
breeding/calving grounds. These impacts included whales vacating the study
area during the projection of industry noises (Jones et al. 1991) and
changes in the acoustical and observed surface behavior and distribution
(Dahlheim 1988). In response to vessels and to playbacks of vessel noise,
Dahlheim (1988) found that gray whales: 1) increased calling rates; 2)
received an increase level of sound; 3) increased the frequency modulation,
number of pulses per series, and repetition rates; and 4) changed their
movements both away from and toward the sound source. In response to the
playback of oil drilling noise, calling rates were reduced, direct movements
away from the sound source were documented, milling rates decreased, and
major changes in distribution and a decrease in local whale abundance were
documented (Dahlheim 1988, 1988a; 58 FR 3129). In his study of the impact
of noise on gray whales in the San Ignacio Lagoon in 1983 and 1984, Jones et
al. (1994) concluded that gray whales left the lagoons, at least
temporarily, in response to underwater playback of noises from boats,
industrial activities, and other sources." Such results caused the MMC to
suggest that "noise associated with coastal development and related
activities could cause whales to avoid and, if exposure to the noise is
prolonged, to abandon areas that may be essential to calving, nursing, and
breeding (MMC 1994).

On its feeding grounds, Malme et al. (1986) estimated that there was a 50
percent probability of gray whale avoidance when the average pulse level of
the received noise was approximately 173 dB and a 10 percent probability of
avoidance at 163 dB. Noise impacts on the gray whales feeding grounds may
temporarily cause the animals to abandon productive feeding areas if
excessively disturbed (NMFS 1993). Because such exploration activities
occur from June to September when gray whales are on their feeding grounds,
the adverse impact of such disturbance could force whales to use
less-productive areas potentially affecting their body condition and ability
to successfully migrate and reproduce.

Because noise from oil and gas activities occurs at frequencies that overlap
gray whale calling frequencies, however, it may influence other behavior
causing interference with socialization, reproductive behavior, and
communication (NMFS 1993).