Earthquakes rattle ocean life, leaving hungry sperm whales hunting for food, study says
A 7.8-magnitude earthquake struck the coast of New Zealand in 2016 when 12 faults ruptured at once, Science Magazine reported. It was the most powerful quake to rattle the island nation in over 150 years.
The aftermath wasn’t just structural damage — marine life suffered too, according to a new study.
Sperm whales’ feeding habits were disrupted for at least a year after the earthquake, in part because their prey’s location and behavior had changed, researchers at the University of Otago said in a report released Jan. 17. The university highlighted their research — “the first to examine the impact of a large earthquake on a population of marine mammals” — in a news release Wednesday.
“We really didn’t know what to expect, as there is so little known about how marine animals react to earthquakes,” lead author on the study Dr. Marta Guerra told the university news service.
According to their research, titled “Changes in habitat use by a deep-diving predator in response to a coastal earthquake,” earthquakes and aftershocks are noisy events under water.
Given that whales use sound to communicate, hunt for prey and navigate ocean waters, those disturbances can cause hearing damage and disorientation, researchers said.
They can also lead to “behavioral modifications.”
Researchers monitoring sperm whales near Kaikōura, where the 2016 earthquake hit, saw such changes firsthand from data they collected on the behavior of 54 sperm whales between January 2014 and January 2018, according to the university.
Sperm whales are among Kaikōura’s most “famous residents,” the New Zealand Herald reported.
They help drive tourism — which the town relies on to propel its economy, according to the university. But after the earthquake, Guerra said the area where they typically saw sperm whales feeding “was quiet as a desert.”
That area is known as the Kaikōura canyon.
After the earthquake, the canyon experienced an underwater mudslide known as canyon flushing — in which “high energy currents” flushed “850 tons of sediment from the underwater canyon into the ocean,” the university said.
Researchers said the event had a direct impact on whales’ ability to forage for food.
They pointed to how long the sperm whales were staying at the surface in the year following the earthquake — about a 25 percent increase.
According to the university, that could mean “they needed to spend more effort searching for prey, either by diving deeper or for longer times.”
Researchers attributed it to two factors: prey displaced from the canyon during the mudslide and disorientation for the whales.
“Sediment deposition and erosion may have required sperm whales to ‘re-familiarise’ with a modified habitat, increasing the effort to navigate and locate prey whose location may have changed,” the university said.
Sperm whales are at the top of the food chain. But canyon flushing likely caused animals that fed on the since-eroded seabed to dissipate.
“This would have indirectly affected the prey of sperm whales (deep-water fish and squid), becoming scarce and making it harder for the whales to find food,” Guerra said.
According to the study, the whale’s behavior had returned to normal by the summers of 2017 and 2018.
Guerra told the university their results highlighted something important about marine wildlife.
“Deep-sea systems are so out of sight that we rarely consider the consequences of them being disturbed, whether by natural or human impacts,” she said.
