Sonar used by Exxon mobile to map the ocean floor is now being blamed for the demise of approximately 100 melon-headed whales that became stranded in a the shallow Loza Lagoon in Madagascar from May to June 2008.
Although researchers have linked whale and dolphin strandings to high-frequency sonar in the past, suggesting that the underwater noise “scares them away from their feeding grounds, the new findings from the Island denote the first time a marine mammal mass stranding has been closely tied to high-frequency sonar mapping after a panel of 5 scientists ruled out illness, poisons, weather conditions, boat strikes and other “unusual acoustic events.”
According to their report a survey vessel contracted by ExxonMobil Exploration and Production (Northern Madagascar) had been using a high-power 12 kHz multi-beam echosounder system to map the ocean floor about 40 miles offshore just one day before the strandings.
“The 12 kHz sonar emitted by the survey vessel is within the frequency of best hearing sensitivity for melon-headed whales,” wrote the group. “But these sounds at the 120-decibel level would be well above the hearing threshold the melon-heads.”
"Implications go well beyond the hydrocarbon industry, as these sonar systems are widely used aboard military and research vessels for generating more precise bathymetry (underwater mapping)," Howard Rosenbaum, director of the Ocean Giants program for the Wildlife Conservation Society, said in a statement.
"We now hope that these results will be used by industry, regulatory authorities, and others to minimize risks and to better protect marine life, especially marine mammal species that are particularly sensitive to increasing ocean noise from human activities," Rosenbaum said.
Meanwhile, Exxon Mobile spokesperson, Patrick McGinn stated that the oil giant disputes the findings, calling them “unjustified due to the lack of certainty of information and observations recorded during the response efforts in 2008,"