There are fears a humpback whale and her calf, which have stayed inside a reef at the Rowley Shoals in Western Australia rather than migrate to Antarctica, are starving to death.
It started as an incredible experience when mother and calf humpback whales approached a charter boat moored inside the Rowley Shoals’ Mermaid Reef and apparently frolicked among snorkelers.
It is a sight general manager of the Great Escape Charter Company, Kylie Bartle, had never seen before.
“The most amazing thing that we’ve seen ever were two humpback whales at Mermaid Reef,” Ms Bartle said.
“I don’t think it is usual for humpback whales to come and interact with people and a boat.
“When we were snorkelling around with our guests and that happened, it was amazing,”
But over the course of five trips to the reef through November, it became apparent that something was stopping the whales from leaving the reef and making their usual migration to Antarctica for summer.
“They’re not stuck in there by any means, they can come out any time they want, but we’re just a bit baffled as to why they’re still there and why they want to stay there.”
General manager of Great Escape Charter Company Kylie Bartle
The whales became increasingly interested in approaching the tourist boat and would even follow the vessel some of the way along the large entry passage to the circular reef.
Everyone was saying, ‘Oh wonderful, they’ll follow us out and then head down to Antarctica where they’re supposed to be’,” Ms Bartle said.
“But they don’t, they sort of hesitate at the end; they keep turning around and going back into the lagoon for some unknown reason.”
Orca attack may be responsible
The best theory the tourist operator can come up with is that the mother and calf may have sought refuge from killer whales which are known to feed on humpback calves on other parts of the West Australian coast.
“We have seen orcas out at the Rowley Shoals on a few different occasions over the last 20 years, and that’s one of the predators that will hassle mothers and calves,” Ms Bartle said.
“We’re thinking that maybe that’s why she’s in the lagoon, maybe she swam in there for protection, and that’s the only thing we can think of as to why she doesn’t want to swim out.”
Professor Lars Bejder of Murdoch University agrees some kind of fear response could have produced the unusual situation.
“It is very strange that they are still there; they should be well, well south of Australia now, heading down to the Antarctic region.”
He said being so far north at this time of year was dangerous for the survival of the two whales.
“She only eats in Antarctica and at the same time, as soon as she gives birth to the calf, the calf starts suckling on the mum, so the calf is sucking out all the energy and the fat content of the mum,” Dr Bejder said.
“Every two days, the humpback mum will lose one centimetre in girth, so it really speaks to how much energy that the calves are suckling from the mums.
“And at the same time, the mum’s not able to feed until she’s back in Antarctica.”
The mother whale’s health has been deteriorating according to Ms Bartle.
“We think she’s starting to look a bit thin, and when she rolls over and smashes her pec fin on the water, we can see that the white part of her pec fin is starting to look a little bit sunburnt, it’s looking a bit pink rather than white,” she said.
It seems there is little that can be done for the whales beyond hoping that they will find the courage to leave the reef and head south to feed.
“We were pretty disheartened when we left on our last trip,” Ms Bartle said.
“We were really hoping that she would have followed the boat out, but she didn’t, she chose to go back in.
“So, fingers crossed we have some great news and a great Christmas.”