The effects of climate change may be a contributing factor in the delayed migration of humpback whales to Cook Islands waters, says a world-renowned whale researcher.
Rarotonga-based whale researcher Nan Hauser says she’s observed 2020’s annual migration to be roughly six weeks late.
This follows a delayed migration last year as well.
Hauser said from mid-June to mid-August – historically known to be the beginning of prime whale watching season - only 16 whales were observed.
Since then, they’ve seen 16 in just one day.
The observed change in migration patterns is indicating a possible change in the whale’s food source due to climate change, Hauser said.
“This information right here shows us that whales could be bio-indicators of climate change,” she said.
One method Hauser and her team are using to investigate the theory is by collecting skin samples of whales, which provide details on their diet.
The humpbacks that travel annually to Cooks Islands waters feed predominately on krill and herring, which are found in the frigid waters of Antarctica.
Down south, they gorge themselves to thicken their blubber. This is a store of water and fat - essentially a battery, she said.
Because these whales then migrate to the warm waters of Oceania to mate and give birth, they won’t eat for a period of six to eight months.
It’s a lengthy fast, and changes in this vital food source could be playing a role in their migratory patterns, said Hauser.
“The theory is they’re staying in Antarctica for longer to build their energy stores. After all, they have to travel up to Rarotonga, over to the Tonga trench, then back down south,” she said.
Mothers need energy to give birth and nurse their young, she said, adding a humpback calf gains at least 45 kilograms a day when being nursed.
While changes in the whale’s migratory patterns and their food source could potentially have adverse effects, Hauser said this year’s visiting Humpbacks appear to be a “well-fed bunch”.
“The good thing is that we are observing whales that look like they’re well-fed. We’re not seeing malnourished whales,” she said.
Hauser and her team of researchers have also observed that some whales may be remaining in Antarctica and not making the trip up to Oceania, and it’s unknown whether this is a new feature of their migration patterns or something they’ve always done.
“I’ve spent 23, 989 hours on the water in the Cook Islands with whales, and in that time I’ve had 4483 whale sightings in the past 23 years,” she said.
“What we’re seeing are profound scientific changes and pattern shifts.”