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
Other species experience the same phenomenon when they vocalize in the presence of high levels of background
sound. Brumm (2004) studied the songs of territorial male nightingales (Luscinia megarhynchos) in the city of
Berlin, Germany, to determine whether and to what degree background noise (from automobile traffic) produced a
Lombard effect in these birds. Based on his studies, the birds increased the volume of their songs in response to
traffic noise by 14 dB (their songs were more than 5 times louder than birds vocalizing in quiet sites). Cynx et al.
(1998) reported similar results based on their study of zebra finches (Taeniopygia guttata) exposed to white noise.
Although this type of response also has not been studied extensively in marine animals, Scheifele et al. (2005)
reported that beluga whales in the St. Lawrence River increased the decibel levels of their vocalizations from 80.46-86.76
dB in conditions without noise to 91.74-99.10 dB when confronted with vessel noise.
Holt et al. (2007) reported that endangered southern resident killer whales (Orcinus orca) in Haro Strait off the San
Juan Islands in Puget Sound, Washington, increased the amplitude of their social calls in the face of increased
sounds levels of background noise.
3. Adjust temporal structure of vocalizations (Box C1.2 of Figure 3). Animals responding this way adjust the
temporal structure of their vocalizations by changing the timing of modulations, notes, and syllables within
vocalizations or increasing the duration of their calls or songs.
Cody and Brown (1969) studied the songs of adult male Bewick wrens and wrentits that occupied overlapping
territories and whose songs had similar physical characteristics (similar song lengths, frequency structure, and
amplitude). They reported that wrentits adjusted the timing of their songs so they occurred when the songs of the
Bewick wrens subsided.
Ficken et al. (1974) studied vocalizations of ten red-eyed vireos (Vireo olivaceus) and least flycatchers (Empidonax
minimus) at Lake Itasca, Minnesota (a total of 2283 songs). They reported that flycatchers avoided acoustic
interference from red-eyed vireos by inserting their shorter songs between the longer songs of the vireos. Although
there is some mutual avoidance of acoustic interference, the flycatcher tends more strongly to insert its short songs in
between the longer songs of the vireo rather than vice versa. Indeed, most of the overlap occurred when the
flycatcher began singing just after the vireo had begun, suggesting that the flycatcher had not heard the vireo begin
singing.
A few studies have demonstrated that marine mammals make the same kind of vocal adjustments in the face of high
levels of background noise. Rendell and Gordon (1999) reported that long-finned pilot whales (Globicephala melas)
in the Ligurian Sea made several vocal adjustments in call whistles when putatively exposed to active sonar transmissions
at frequencies of 4-5 kHz (reference and received levels were not reported).
Miller et al. (2000) recorded the vocal behavior of singing humpback whales continuously for several hours using a
towed, calibrated hydrophone array. They recorded at least two songs in which the whales were exposed to lowfrequency
active sonar transmissions (42 second signals at 6 minute intervals; sonar was broadcast so that none of
the singing whales were exposed at received levels greater than 150 dB re 1µPa). They followed sixteen singing
humpback whales during 18 playbacks. In nine follows, whales sang continuously throughout the playback; in four
follows, the whale stopped singing when he joined other whales (a normal social interaction); and in five follows,
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