Scientists attempting to communicate warnings to humpback whales have been left stumped again, with new research showing the giant mammals completely ignore alarm sounds that are supposed to alert them to fishing gear.
The research was conducted in Australia's 'humpback highway' off Sydney's coast by a team from Macquarie University.
During their migration, humpback whales are at serious risk of entangling with fishing gear. Researchers are searching for a way to safely alert the whales of the dangers.
In the study, published today, scientists investigated whales' reactions to two different complex alarm sounds and their effectiveness.
The researchers compared whether the mammals changed their diving behaviour, their travel direction or their travelling speed when exposed to the sounds.
They found no detectable response to either alarm.
"The lack of measurable response suggests that these new types of tones are not likely to be effective in alarms intended to reduce entanglements for the northward migrating humpback whales," said Vanessa Pirotta, lead author and Maquarie PhD student.
"While we haven't yet cracked the whale code in terms of warning sounds, we are still learning a lot about the types of alerts that these animals will and won't react to."
It was unclear whether the animals were detecting the tones, only that it made no change to their behaviour.
The study was launched with the hopes of finding a solution to reducing whale entanglement in fishing gear.
Last October, a young humpback whale calf became trapped in more than 150m of rope off New South Wales' coast during its southern migration.
Rescuers were forced to attach buoys to the rope to slow the whale down, before cutting through the rope with knives on hooks.