A whale researcher says climate change could be responsible for humpback whales becoming exhausted during their annual migration to warmer waters.

Janelle Braithwaite examined historical whaling data and says climate change may be depleting the Antarctic food sources whales rely on to store energy for their long journey to breeding grounds off WA’s northern coast.

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 “If the ice declines in the area that these forage in, then that will reduce krill and that will reduce how much food they have,” Ms Braithwaite said.

Researchers say the whale population is declining.

“Whales live this feast and fast lifestyle.

“Over the summer they’re feasting up on krill down in the Southern Ocean but once they leave, they’re pretty much fasting during their migration journey.

“It’s a bit like a car, if there’s not enough petrol at the petrol station, then you’re setting off with three quarters of a tank and you might not be able to make it.

“If these whales run out of petrol before they get back to the Southern Ocean, then there’s no safety net, they will die from exhaustion.”

Mining, boating and fishing also affecting whales

The research was done as part of Ms Braithwaite’s PhD at the University of Western Australia.

She also said there were other factors making the process of migration more difficult for whales.

“Mining activities, boating activities and even fishing activities have the potential to make it a much less calm environment for whales so they end up using more energy,” she said.

“If mining activity has caused more boat activity in these areas then instead of resting, these whales are going to be moving around using more energy then maybe they would have if human activities hadn’t been there.”

Ms Braithwaite said the issues were causing a decline in the whale population and female humpback whales were especially vulnerable.

“They’re having to feed a calf as well,” she said.

“She’s using more of her own energy stores because she’s going faster and having to give more milk to the calf as they’re burning more energy as well.

“If she’s using more of her energy stores then she might only be able to afford to have a calf maybe once every three years or once every four years.”

Ms Braithwaite’s studies were commissioned by the UWA’s Oceans Institute.