A powerful earthquake in 2016 affected sperm whales’ ability to hunt for food for at least a year, a recent study has found.
A group of scientists from the University of Otago in New Zealand who had been studying sperm whales off the coast of Kaikōura noticed a change in how the marine mammals behaved after a magnitude 7.8 earthquake struck the southern island of New Zealand in November of 2016.
In the immediate aftermath of the quake, the whales had seemingly disappeared — researchers say it took six days before they spotted their first whale. They believe that the whales swam away due to the loud sounds — comparable to explosions — produced by the earthquake. Exposure to these loud noises can be highly dangerous as it can lead to injuries and hearing damage.
The earthquake also caused around 900 million tons of mud, sediment, and invertebrates from an underwater canyon to be flushed out into the ocean, a phenomenon known as “canyon flushing.”
This phenomenon caused the animals such as squid and deepwater fish — who preyed on the invertebrates — to flee or seek food elsewhere. Since the whales preyed on squid and deepwater fish, they, too, had to make some adjustments in order to find food.
The team of scientists, led by Dr. Marta Guerra of the University of Otago’s Department of Marine Science, observed that the whales spent 25% more time on the surface in between dives. This was an indication that they were trying to gather more oxygen for a deeper dive underwater.
Since the earthquake caused underwater landslides and the displacement of sediment, the whales became disoriented, which contributed to the slowing down of their hunting process.
The ecosystem began showing signs of recovery about ten months after the quake, when invertebrates started reappearing in the head of the canyon. The whales’ behavior eventually returned to normal a few months later.
The research team carried out their study of the behavior of 54 sperm whales over a four-year period from January of 2014 to January 2018. Thanks to the earthquake, their study also became one of the first to examine the impact of earthquakes on marine mammals.
The findings of their study were later published in the journal Deep Sea Research Part 1: Oceanographic Research Papers in January of 2020.