Following the incident, the International Whaling Commission facilitated a review of the evidence and an Independent Scientific Review Panel (ISRP) of five experts was invited to examine that evidence. The ISRP has just published its findings, and concluded that air gun blasts from seismic survey vessels in the area were not to blame, as they in fact took place several days after the incident.
ANALYSIS: Whale Ear Wax Tells of Short, Contaminated Life
However, a vessel using a different type of surveying technique - a high-power 12 kHz, multi-beam echosounder system (MBES) - was, says the report, "moving in a directed manner down the shelf-break the day before the event, to an area approx. 65 km offshore from the first known stranding location. The ISRP deemed this MBES use to be the most plausible and likely behavioral trigger for the animals initially entering the lagoon system."
Most attention has focused on the likely impacts of mid-frequency and low-frequency sound sources, because of their greater propagation through water; it is possible, the ISRP noted, that high-frequency sounds like the MBES also affect some cetaceans more than previously realized but that, under normal circumstances, those cetaceans swim away. It was to the considerable misfortune of those melon-headed whales five years ago that they were in the wrong place at the wrong time, and that when they turned tail and fled, they swam into an inhospitable area from which there was no escape.