A review panel says that an acoustic stimuli used by a survey vessel was responsible for triggering the 2008 mass stranding of the melon-headed whales in Madagascar.
The mass stranding of about 100 melon-headed whales in 2008 in Madagascar created quite an uproar. With help from the International Fund for Animal Welfare, the NOAA and the International Whaling Commission, a team from the Wildlife Conservation Society (WCS) conducted a review to further investigate the incident.
The review panel concluded that the stranding was triggered by sonar mapping. According to the review report, acoustic stimuli, more specifically, a multi-beam echo-sound system operated by a survey vessel contracted by ExxonMobil Exploration and Production (Northern Madagascar) Limited was responsible for the incident.
"The potential for behavioral responses and indirect injury or mortality from the use of similar MBES [multi-beam echosounder systems] should be considered in future environmental assessments, operational planning and regulatory decisions," the report stated.
European agencies and a scientific community of the United States were able to save the majority of the whales. The ones that died were inspected for signs of predation, diseases and other causes for the stranding. The findings of the review has raised concerns about the impact of noise on marine mammals as these high-frequency mapping sonar systems are used by various stakeholders including the hydrocarbon industry, military, and research vessels used by other industries. This is the first time a marine mammal mass stranding event has been linked to high-frequency mapping sonar systems.
"Mass stranding response is challenging under the best of circumstances. Together with local individuals and the government of Madagascar, we provided the expertise to rescue as many animals as possible and medical care to those that stranded alive," said Katie Moore, Director of Animal Rescue at IFAW. "Equally important was to gather as much data as possible from the animals to address the root cause of the stranding. We are pleased to see the ISRP report and its conclusions, which will hopefully be used in shaping future conservation policies."
A previous study conducted on the same subject by researchers from Duke University found that blue whales often change their diving behavior and avoid feeding areas after they hear the underwater sonar often used during military exercises. This often results in them getting stranded while they try to flee.
"Whales clearly respond in some conditions by modifying diving behavior and temporarily avoiding areas where sounds were produced," lead author Jeremy Goldbogen of Cascadia Research said. "But overall the responses are complex and depend on a number of interacting factors."
