Oceans of noise - Whale and Dolphin Conservation Society

anthropogenic factors that make their existence difficult (e.g. high contaminant loads, overfishing,sewage-contaminated habitats etc.). The effective loss of important habitats (e.g. feedinggrounds) could deteriorate these populations ever further, leading to increased morbidity andmortality.There is a vast collection of evidence of cetacean reactions to boat traffic and shipping noise.Reviews of the scientific literature documenting these reactions are summarised in Annex A3.Fright, avoidance and changes in behaviour and vocal behaviour, have been observed in bothMysticeti and Odontoceti over a range from tens to hundreds of kilometres (Gordon et al. 1998).These effects have also been documented in some fish and invertebrates (Swan et al. 1994). Othermarine species have been shown to react to human-induced noise (seismic airguns) at similarlevels to cetaceans, including green Chelonia mydas and loggerhead Caretta caretta sea turtlesand squid Sepioteuthis australis (McCauley et al. 2000).It should be noted that even where there is no measurable behavioural response, it can not beassumed that no biological consequences are resulting from exposure to loud noises. Gordon etal. (1998), for example, found no measurable response from sperm whales to ATOC-like soundsbased on blow rate patterns. Responses such as shorter blow intervals would suggest that theseanimals are disturbed, as might more rapid swimming, leading to increased energy expenditure;and might lead to the development of a lactic acid deficit. Cetaceans have finely balanced energybudgets and this type of behaviour could lead to loss of general or reproductive fitness ifprolonged. Humpback whales subjected to explosions showed no obvious response, but localentanglement rates, and thus mortality, increased (Todd et al. 1996).Table 5.2.1. Possible impacts of noise on cetaceans (after Simmonds and Dolman, 1999)PhysicalNon AuditoryDamage to body tissueInduction of the “bends”AuditoryGross damage to earsPermanent hearing threshold shiftTemporary hearing threshold shiftPerceptualMasking of communication with conspecificsMasking of other biologically important noisesInterference with ability to acoustically interpret environmentAdaptive shifting of vocalisations (with efficiency and energetic consequences)BehaviouralGross interruption of normal behaviour (i.e. behaviour acutely changed for a period oftime)Behaviour modified (i.e. behaviour continues but is less effective/efficient)Displacement from area (short or long term)Chronic/StressDecreased viability of individual55