Active Sonar
The US, NATO and British navies are currently testing a submarine detection system that employs new Low Frequency Active Sonar (LFAS). The aim is to deploy it across 80 per cent of the world’s oceans by 2006.
• Humans can tolerate sounds in the air up to 120 decibels, but LFAS reaches 240 decibels.
• At 300 miles from the source the active sonar can still reach 140 decibels.
• Whales are affected by sounds of 110 decibels.
• At 180 decibels a whale’s eardrums can explode.
Effects on whales
For whales and other marine mammals that rely on sound for communication and navigation, active sonar means serious disruption, deafness and ultimately death.
Physiology
Human divers accidentally exposed to LFAS have reported various physiological traumas including lung resonance. This can lead to haemorrhaging, soft tissue damage and death in both humans and marine mammals. Studies subjecting navy divers to LFAS have produced alarming results. After only 12 minutes one of the divers experienced dizziness and drowsiness and had to be hospitalised. He continued to suffer memory problems and seizures and only improved after treatment with antidepressants and seizure medication. There have been mass beachings of various whale species in areas where LFAS has been used, including Greece (1996), Bahamas (2000) and the Canary Islands (2002). Examinations of the dead whales showed extreme auditory trauma.
Communication
A humpback whale’s vocal cycle lasts between ten and 20 minutes and can be repeated for hours at a time. Songs are specific to a region and change slowly over generations. LFAS is known to stop humpback whales singing even when the sonar’s source is hundreds of miles away. The effect on their breeding and social behaviour is unknown.
Breeding
A female humpback whale invests heavily into each calf she rears. Each pregnancy lasts 11–12 months and produces only one calf. A calf is not fully weaned until it is one year old and even after that the female rarely abandons her calf. However, following LFAS tests in Hawaii in 1998, marine scientists and tourists found abandoned and distressed whale and dolphin calves, including those of humpbacks.
Migration
In the spring humpback whales undertake the long migration from their tropical winter breeding waters to their summer feeding grounds in polar regions. The longest confirmed migration of any mammal is made by humpbacks that breed off Colombia and Costa Rica and then travel south to feed in Antarctic waters south of Cape Horn. But these migration patterns are becoming increasingly disrupted as humpbacks and other whales look to avoid LFAS sources.
Diet
Southern Ocean humpbacks mainly eat krill, while those in the northern oceans eat mainly fish – herring, pink salmon, Arctic cod, sardine, mackerel, anchovy and haddock. LFAS’s full effects on species other than whales and dolphins have not been considered. But it is thought that the sonar will alter fish species’ distribution and abundance. Because the whales avoid the sonar they would be forced out of their normal feeding grounds into areas with less prey.
To protest against the use of active sonar join the Whale and Dolphin Conservation Society: www.wdcs.org
This article first appeared in the Ecologist February 2003
