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Warning signals that deter minke whales from wind farm construction sites are being tested in Iceland. It’s the first time such acoustic deterrent devices, or ADDs, have been used for this purpose.

The deterrents, a series of amplified electronic pulses projected into the water, were originally developed to stop seals from stealing farmed fish.

This trial will see if they might also help ward off whales during noisy pile-driving activity in the North Sea. Each ADD is tuned to emit a noise that, while being a nuisance to whales, is not harmful.

Whales use sound to navigate, communicate and find food. “So if a lot of anthropogenic noise is emitted into the ocean, they can experience temporary or permanent hearing loss,” says from the Carbon Trust, which managed the 40-day��study in Iceland. “That’s what we are trying to avoid through this trial.”

Danny Groves from the charity Whale and Dolphin Conservation agrees. “Noise pollution threatens whales because it interrupts their normal behaviour and can drive them away from important breeding and feeding areas,” he says. “Excessive noise levels underwater can also cause injury and, in some cases, death.”

Minke whales are��thought to be abundant in many areas earmarked for��wind farm development.

Prolonged din

New wind farms are becoming ever larger in size. And because it can take many hours to erect each turbine,��the sound emitted during the construction of an entire wind farm can be prolonged.

“You use steel cylinders as foundations, which��are��piled into the ground in a similar way to hammering a nail into a piece of wood,” says Reeve. “They use large hydraulic hammers that essentially push the turbine into the ground.”

The current method of reducing the impact of construction noise on minke whales in the UK involves both human observers and acoustic monitoring. If any whales are seen or heard during construction, all pile-driving stops until they have left.

But this passive approach has drawbacks. Firstly, an observer has to wait for the whale to surface, says Reeve. “Another problem is that not all marine mammals communicate in a similar way and, like us, may also choose not to communicate at all at a particular time,” she says.

The hope is that the active deterrent being tested will discourage minke whales from even entering a construction zone while work is under way.

Turn tail

Olly Boisseau, senior scientist on board Song of the Whale, the research vessel that carried out the Icelandic tests, says whales can respond subtly to ADDs.

“We are looking for an evasive response, where the whales turn away from the sound,” he says. “Perhaps they will increase their swim speed or the amount of time between successive surfacing.”

The team also wants to see how far and fast the whales travel from the deterrent, and how quickly they return once construction has finished.��“We would not want to see a marine mammal deterred indefinitely. We would certainly want to see them return,” says Reeve.

Simon Stephenson, an acoustics expert from environmental consultancy RPS, was also in Iceland to take part in the study. His aim was to determine which type and level of deterrent sound minke whales respond to most effectively.��“The idea is that we might be able to use less powerful devices for animals in a small area, or more than one device or a more powerful device for a larger area,” he says.

The Carbon Trust says analysis of the trial will take place over the next few months, with results expected early next year.

Read more: Drowning in sound? The sad case of the baby beluga whales