So far humpback whales, those of them who swim up and down the East Coast of Australia every year on their migratory path from the Antarctic, have ignored every attempt we’ve made to warn them of hazards.
Researchers led by Macquarie University scientists found that humpback whales are not only unfazed by complex sounds designed to alert them to dangerous fishing gear but they have no response at all.
Humpback whales frequently get tangled in nets. The most recent case was humpback calf a few months ago.
The researchers say entanglement in fishing gear is an international problem likely to increase with the growth of fishing and with the recovery of whale populations after the end of whaling in the 1970s.
“We used louder sounds combined with complex tones to see if this would work to deter the whales,” says Vanessa Pirotta, the lead author and a Macquarie PhD student.
A whale alarm was placed in the middle of the what’s known as the humpback highway off the Sydney coast during their 2013 northern migration.
A theodolite, a surveyor’s tool, was used to track whale movements in response to the alert signals. However, the whales didn’t respond. They just continued to dive and surface in the same direction as normal.
Humpback whales also make their own sounds, including complex songs by the males.
“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,” says Pirotta.
The study builds on previous work by the same research group.
“In the previous study we wanted to see if whales would avoid fishing gear when a simple alarm was turned on versus when the alarm was off,” she says.
“Much like your mobile phone or GPS, the idea of a whale alarm is to alert whales of something, in this case the presence of fishing gear, so that they move away from danger.
“Unfortunately the research suggested that simple alarm sounds were also not effective in preventing whale entanglement at least for single unit fishing gear such as lobster or crab pots as we tested.”
The research on warning whales is published in the journal Endangered Species Research.