For millions of years, narwhals have lived year-round in the high Arctic waters. It’s not an easy environment to live in, but sea ice has helped keep them protected from disturbances. But recent declines in polar sea ice (fed by climate change) are making the region more accessible to human shipping and natural resource exploration.

In particular, one activity expected to cause disturbance to narwhals (and pretty much every other creature in the Arctic) is drilling for fossil fuels. If we do decide to drill for fossil fuels in the Arctic, it could be catastrophic to the animals living there — but even before that happens, narwhals could have a great deal to suffer.

In this drone image, researchers in the water watch as a narwhal swims away with a physiological monitoring tag (yellow instrument attached with suction cups on the back), which will record heart rate, breathing rate, swimming stroking frequency, and depth for 1-3 days. Image credits: Eva Garde, Greenland Institute of Natural Science.

People don’t just randomly drill for oil; first you need to figure out where the oil is. The most common way of doing this is through a seismic survey, where you basically simulate seismic waves (with specialized equipment or explosives) and see how the underground responds to them. The problem with this approach is that seismic waves are basically acoustic or sound waves — and these waves can have a negative impact on the ecosystem, particularly marine ecosystems.

The reaction of narwhals to the loud noise of this type of survey is very disruptive, researchers report in a new study. It sends the animals into a frenzy as they try to escape the noise, costing them a lot of energy and altering their circulation of blood and oxygen.

“They’re swimming as hard as they can to get away, and yet their heart rate is not increasing—we think because of a fear response. This affects how much blood and oxygen can circulate, and that’s going to be problematic,” said Terrie Williams, a professor of ecology and evolutionary biology at UC Santa Cruz who led the new study.

A pod of narwhals in Scoresby Sound, East Greenland, where the study took place. Image credits: C. Egevang.

Previously, Williams and colleagues looked at how narwhals react when they get entangled in nets set by indigenous hunters and subsequently released. It was a similar response, but the disturbance lasts much longer in the case of seismic noise.

“When they escape from the nets, their heart rate comes back up to a more normal rate within three or four dives, but with the seismic ship moving through and the sound bouncing around, the escape response occurred over a longer period,” she said.

All the narwhal parameters suggest they got very spooked. When they try to escape the sounds, they swim faster and less efficiently than normally, and paradoxically, their heart rate drops significantly. Their breathing at the surface (narwhals are mammals and therefore can’t breathe underwater) increases by 50% after such an event.

A large male narwhal raises his tusk as he catches his breath before diving in Scoresby Sound. This study recorded the first breathing rates for diving narwhals during quiet periods and in the presence of a seismic ship moving through the fjord. Image credits: Terrie Williams.

In the wild, this type of event can be very costly. It’s not just that the narwhals got spooked — they spent time and energy running away instead of looking for food or performing other activities. This means they’ll need to catch up and will be under more stress and the difficulties can add up.

It’s not just seismic surveys, either. Noise from human sailing and sonar has increasingly been linked found to damage whales, particularly beaked whales. But this could be affecting other creatures that are harder to study as well.

Williams and colleagues have been working on this for years, developing instruments that monitor the physiology of marine mammals. The instruments are attached with suction cups to the narwhals and then fall off after 1-3 days, floating to the surface, where they are recovered by researchers.

“Most of the potential impacts on the animals take place underwater, so it’s really difficult to study,” Williams said. “We are fortunate to have this technology to show what’s happening at depth where these animals live in order to understand how their biology may be disrupted.”

The Arctic area is particularly at risk from climate change, and creatures that rely on the polar ice are particularly threatened. Any additional stressor could be a tipping point that sends species towards extinction.

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