Simple acoustic recording equipment could track whales near the Irish coast and ultimately help protect them from stranding, writes Claire O'Connell
LAST FRIDAY a 20-metre long fin whale died after he became beached on a sandbank at Courtmacsherry in west Cork. And while the story had a sad ending, it was a national reminder that majestic cetaceans – whales and dolphins – glide through the waters near Ireland’s coast.
Much of what we know about the distribution of large marine mammals in Irish waters comes from visual sightings from boats or aircraft, or, more distressingly, from strandings. Around 24 cetacean species have been recorded in Irish waters to date, according to the Irish Whale and Dolphin Group.
But using our eyes may not be the best way to find some species, according to whale expert Dr Rebecca Dunlop, a post-doctoral researcher at the University of Queensland, Australia.
She and Belfast-based marine biologist Dr Adam Mellor used underwater microphone recordings to detect sperm whales off the north Co Antrim coast, and they believe that simple acoustic technology could have immense value in tracking the animals and developing conservation strategies.
Sperm whales spend much time under the water, making them difficult to spot, explains Dunlop.
“They have incredibly long dives, up to 40 minutes. And when they are at the surface they are resting, so they are pretty hard to see,” she says. “So if you are flying over on a plane the chances are small that the whales are at the surface and that you actually see them.”
Listening for whale vocalisations with a hydrophone is often a better bet, she notes.
“When sperm whales go for a dive they are foraging around, so they send out these clicks, and when the clicks return they can tell what they are looking at. Then they lock on to a fish or a squid and the clicks get faster and faster as they get closer and the whale hopefully grabs it,” she explains. “And sperm whales are so loud that even if you are tens of kilometres away you will still hear faint clicks.”
On a visit home to her native Belfast, Dunlop and and her friend Mellor, a scientific officer at the Agri-Food and Biosciences Institute, decided to carry out an experiment.
They travelled on a fisheries patrol vessel and dropped the hydrophone into the water at sites between Ballycastle, Co Antrim, and the Inishowen Peninsula. And to their surprise, they hit the jackpot straight away, hearing the distinctive handclap-like clicks of a sperm whale.
"We were pretty amazed. Although I thought we were going to get the odd dolphin off the Antrim coast, I didn't expect that we would hear sperm whales even as we lowered down the hydrophone," says Dunlop of their findings, which are published in the current Proceedings of the Royal Irish Academy.
The duo didn’t see any sperm whales, but recorded one or two animals, thought to be young bachelor males, in relatively shallow waters.
“Sperm whale clicks are very distinctive, so when you hear a sperm whale click you automatically know it. No other click sounds like it,” says Dunlop, who reckons that such simple recordings could provide important and accessible data about whale populations. “It’s such a cheap way to do it and it’s so easy.”
Mellor wants to build on the initial findings with further spot surveys off the coast, noting that acoustic technology is being used more frequently now and can be used to identify other species too.
“There’s a huge gap of knowledge,” he says. “And we want to get a better understanding of what species visit, how often they visit and the density and the importance of those populations.”
He is also exploring funding options to leave acoustic recording devices in situ that can monitor and transmit information back to scientists on land.
“[The system] can operate around the clock, 365 days a year,” he says.
Surveying is particularly important against the backdrops of environmental change and the development of marine resources, and more generally could help avoid strandings like that seen last week, says Mellor.
“There’s certainly concern that the number of marine mammal strandings is up, so a better understanding of what’s there around the coast should allow us to identify if there are patterns with strandings, and try to understand better how to conserve these environments.”