NMFS Biological Opinion on U.S. Navy training ... - Govsupport.us

FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013
Morton et al. (2004) exposed killer whales (Orcinus orca) to sounds produced by acoustic harassment devices
(devices that were designed to harass harbor seals, source levels were 194 dB at 10 kHz re 1μPa at 1 meter). They
concluded that observations of killer whales declined dramatically in the experimental area (Broughton Archipelago)
during the time interval the harassment devices had been used (but not before or after the use). Other investigators
concluded that gray whales and humpback whales abandoned some of their coastal habitat in California and Hawai’i,
respectively, because of underwater noise associated with extensive vessel traffic (Gard 1974, Reeves 1977, Salden
1988).
Nowacek et al. (2004) conducted controlled exposure experiments on North Atlantic right whales using ship noise,
social sounds of con-specifics, and an alerting stimulus (frequency modulated tonal signals between 500 Hz and 4.5
kHz). Animals were tagged with acoustic sensors (D-tags) that simultaneously measured movement in three
dimensions. Whales reacted strongly to alert signals at received levels of 133-148 dB SPL, mildly to conspecific
signals, and not at all to ship sounds or actual vessels. The alert stimulus caused whales to immediately cease
foraging behavior and swim rapidly to the surface.
Several studies have demonstrated that cetaceans will avoid human activities such as vessel traffic, introduced
sounds in the marine environment, or both. Lusseau (2003) reported that bottlenose dolphins in Doubtful Sound,
New Zealand, avoided approaching tour boats by increasing their mean diving interval. Male dolphins began to
avoid tour boats before the boats were in visible range, while female dolphins only began to avoid the boats when
the boats became intrusive (he attributed the differential responses to differences in energetics: the larger body size
of male dolphins would allow them to compensate for the energy costs of the avoidance behavior more than female
dolphins). Bejder et al. (2006) studied the effects of vessel traffic on bottlenose dolphins in Shark Bay, Australia,
over three consecutive 4.5-year periods. They reported that the dolphins avoided the bay when two tour operators
began to operate in the bay.
Marine mammals may avoid or abandon an area temporarily during periods of high traffic or noise, returning when
the source of the disturbance declines below some threshold (Lusseau 2004, Allen and Read 2000). Alternatively,
they might abandon an area for as long as the disturbance persists. For example, Bryant et al. (1984 in Polefka 2004)
reported that gray whales abandoned a calving lagoon in Baja California, Mexico following the initiation of dredging
and increase in small vessel traffic. After the noise-producing activities stopped, the cow-calf pairs returned to the
lagoon; the investigators did not report the consequences of that avoidance on the gray whales. Gard (1974) and
Reeves (1977) reported that underwater noise associated with vessel traffic had caused gray whales to abandon some
of their habitat in California for several years. Salden (1988) suggested that humpback whales avoid some nearshore
waters in Hawai’i for the same reason.
As Bejder et al. (2006) argued, animals that are faced with human disturbance must evaluate the costs and benefits
of relocating to alternative locations; those decisions would be influenced by the availability of alternative locations,
the distance to the alternative locations, the quality of the resources at the alternative locations, the conditions of the
animals faced with the decision, and their ability to cope with or “escape” the disturbance (citing Beale and
Monaghan 2004a, 2004b; Gill et al. 2001, Frid and Dill 2002, Lima and Dill 1990). When animals shift from one
site to an alternative site, we should assume that the costs of tolerating a disturbance have exceeded any benefits of
remaining in the location they are leaving.
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