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FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 resting (which increases an animal’s activity rate and energy demand). For example, a study of grizzly bears (Ursus horribilis) reported that bears disturbed by hikers reduced their energy intake by an average of 12 kcal/min (50.2 x 103kJ/min), and spent energy fleeing or acting aggressively toward hikers (White et al. 1999). Nevertheless, other investigators concluded that when food handling does not require visual attention, a foraging animal can avoid the energetic costs and costs in time associated with vigilance (Bednekoff and Lima 1998, Cowlishaw et al. 2004, Lima 1988). In these cases, however, the foraging animals relied on one sensory modality (vision) to detect food and another sensory modality (hearing) to remain aware of the approximate location and proximity of potential predators. We assume that endangered or threatened marine animals that might be foraging in the Hawai'i Range Complex would be able to remain aware of the number of surface vessels, proximity, speed, and approach vector through acoustic cues while foraging when they are not proximate to the ships (at distances that would normally cause them to avoid rather than evade the ships). At distances that might elicit evasive or escape behavior, however, we assume that endangered or threatened marine mammals would dedicate most or all of their attention on the vessels. Although we cannot discount interrupted foraging caused by vigilance behavior, marine mammals in the Hawai'i Range Complex seems more likely to experience disrupted foraging during attempts to evade approaching surface vessels or received levels of active sonar than because of vigilance behavior. CONTINUED PRE-DISTURBANCE BEHAVIOR, HABITUATION, OR NO RESPONSE (Box B2 of Figure 3). Under some circumstances, some of individuals that are exposed to active sonar transmissions will continue their normal behavioral activities; in other circumstances, individual animals will become aware of the sonar transmissions at lower received levels and move to avoid additional exposure or exposures at higher received levels (Richardson et al. 1995). It is difficult to distinguish between animals that continue their pre-disturbance behavior without stress responses, animals that continue their behavior but experience stress responses (that is, animals that cope with disturbance), animals that habituate to disturbance (that is, they may have experienced low-level stress responses initially, but those responses abated over time), and animals that do not respond to the potential disturbance. Watkins (1986) reviewed data on the behavioral reactions of fin, humpback, right and minke whales that were exposed to continuous, broadband low-frequency shipping and industrial noise in Cape Cod Bay. He concluded that underwater sound was the primary cause of behavioral reactions in these species of whales and that the whales responded behaviorally to acoustic stimuli within their respective hearing ranges. Watkins also noted that whales showed the strongest behavioral reactions to sounds in the 15 Hz to 28 kHz range, although negative reactions (avoidance, interruptions in vocalizations, etc.) were generally associated with sounds that were either unexpected, too loud, suddenly louder or different, or perceived as being associated with a potential threat (such as an approaching ship on a collision course). In particular, whales seemed to react negatively when they were within 100 m of the source or when received levels increased suddenly in excess of 12 dB relative to ambient sounds. At other times, the whales ignored the source of the signal and all four species habituated to these sounds. Nevertheless, Watkins concluded that whales ignored most sounds in the background of ambient noise, including the sounds from distant human activities even though these sounds may have had considerable energies at frequencies well within the whale’s range of hearing. Further, he noted that fin whales were initially the most sensitive of the 216
FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013 four species of whales, followed by humpback whales; right whales were the least likely to be disturbed and generally did not react to low-amplitude engine noise. By the end of his period of study, Watkins (1986) concluded that fin and humpback whales have generally habituated to the continuous, broad-band, noise of Cape Cod Bay while right whales did not appear to change their response. Aicken et al. (2005) monitored the behavioral responses of marine mammals to a new low-frequency active sonar system that was being developed for use by the British Navy. During those trials, fin whales, sperm whales, Sowerby’s beaked whales, long-finned pilot whales (Globicephala melas), Atlantic white-sided dolphins, and common bottlenose dolphins were observed and their vocalizations were recorded. These monitoring studies detected no evidence of behavioral responses that the investigators could attribute to exposure to the low-frequency active sonar during these trials (some of the responses the investigators observed may have been to the vessels used for the monitoring). 5.3.3.6 Stranding Events In what follows, we address the evidence bearing on assertions from several NGOs and scientific investigators that low-frequency active sonar causes marine mammals to “strand.” Some authors seemed to have contradicted themselves by first publishing articles that initially identified low frequency active sonar as the “cause” of marine mammal stranding events in the Canary Islands and the Mediterranean Sea, then later publishing articles that identify mid-frequency active sonar as the “cause” of those stranding events after the Bahamas stranding report became available. These causal claims are incoherent: the beaked whale stranding events had a causal association with either low frequency active sonar, mid-frequency active sonar, a combination of the two, or neither of the two. The earlier claims (for example, Frantis 1998) asserting low-frequency active sonar as causal are not compatible with the revised claims of a causal relationship between the stranding events and mid-frequency active sonar. As of the date of this <strong>Opinion</strong>, none of these authors have published retractions, corrections, or clarifications of their published arguments on whether they believe exposure to low-frequency active sonar, mid-frequency active sonar, or both, caused the stranding events or was a contributing cause of those events. Despite the small number of instances in which marine mammal stranding events have been associated with midfrequency active sonar usage and despite the fact that none of these stranding events involved endangered or threatened species, the amount of controversy that surrounds this issue requires us to address it. For these analyses, we defined a “stranded marine mammal” as “any dead marine mammal on a beach or floating nearshore; any live cetacean on a beach or in water so shallow that it is unable to free itself and resume normal activity; any live pinniped which is unable or unwilling to leave the shore because of injury or poor health” (Gulland et al. 2001, Wilkinson 1991). Marine mammals are known to strand for a variety of reasons, although the cause or causes of most stranding are unknown (Geraci et al. 1976, Eaton 1979, Odell et al. 1980, Best 1982). Klinowska (1985, 1986) correlated marine mammal stranding events and geomagnetism and geomagnetic disturbance. Numerous other studies suggest that the physiology, behavior, habitat relationships, age, or condition of cetaceans may cause them to strand or might predispose them the strand when exposed to another phenomenon. For example, several studies of stranded marine mammals suggest a linkage between unusual mortality events and body burdens of toxic chemicals in the stranded 217
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