Humpback whales have babies much further south than previously thought

Australia Broadcast Center

20-05-2025

Humpback whales are on the move again.
At this time of year, the whales travel up the eastern and western sides of Australia, treating viewers on the coast to a show.
They're migrating from cold, krill-rich southern waters to spend their winters in the warmer seas north of the continent, which are the whales' breeding grounds.
You may even see mums with newborn humpbacks on the northern route well before they reach the tropics, according to a new study.
The study challenges assumptions about where humpback whales breed, and possibly why they migrate, according to lead author Jane McPhee-Frew.
And observations by citizen scientists played a key role in the findings.
Until now, many researchers believed whales only gave birth to calves in warmer tropical waters.
But the study, published in Frontiers in Marine Science, found records of baby humpbacks in the east as far south as Tasmania and New Zealand.
Humpback whales occur in every ocean around the world, with both northern hemisphere and southern hemisphere populations moving between their respective poles and the tropics.
They were nearly hunted to extinction by the mid-20th century, but their numbers have since rebounded, with tens of thousands now migrating up the Australian coasts.
Each year begin their northward migration from April, and return south between August and November.
Around Australia, humpbacks generally weren't thought to give birth further south than 28 degrees latitude in the east (near the Gold Coast), or 23 degrees in the west (just south of Exmouth).
"Our general concept of humpback whale ecology is that they feed at high latitudes in the poles, breed in the tropics, and they have this migration that's driven between the two needs," Ms McPhee-Frew said.
Ms McPhee-Frew, a PhD candidate at the University of New South Wales, had been surprised to see a very young whale while working as a tour guide in Newcastle in 2023.
"I saw a newborn right at the mouth of Newcastle Harbour," she said.
Her PhD supervisor was also surprised, but Ms McPhee-Frew's colleagues in tourism weren't. They had apparently seen baby humpbacks in colder southern waters.
This prompted Ms McPhee-Frew and fellow ecologists to search for more records of newborn whales south of the tropics.
"We clearly have a gap here," she said.
The researchers compiled records of baby humpback whales from a range of sources: government agencies, migration surveys and citizen science records from places like tourism boat trips.
They found records of more than 200 newly-born whale calves appearing further south than the previously assumed limit.
Some of the neonates were recorded at 43 degrees south, in the waters around Tasmania and New Zealand.
This was as far south as the observations went, so it's possible that humpbacks were giving birth even closer to Antarctica.
This means the whales don't need to breed in warmer waters — although they might prefer to.
The baby whales were born while their mothers were heading north, towards the tropics.
Olaf Meynecke, a whale researcher at Griffith University who wasn't involved in the study, said the results were "not surprising".
Dr Meynecke and his colleagues had seen newly-born humpbacks well south of their traditional breeding grounds in the past decade, all heading north.
"We know that they undertake all important behaviour — feeding, mating and birthing — not only in dedicated areas, but also along their migratory corridor," Dr Meynecke said.
If the humpback whales don't need to breed in the tropics, why are they migrating thousands of kilometres to do it?
"I don't know, but it's exciting," Ms McPhee-Frew said.
It may be that whales born in the tropics are still better off.
Ms McPhee-Frew pointed out a number of "really obvious" benefits to warmer waters: they're better for baby whales with poor temperature regulation, they're calmer, and they have fewer predators such as orcas.
Dr Meynecke says that while humpbacks can give birth in cooler waters, they still migrate north to "ensure faster growth rates" for their calves.
"With an expansion of the population and higher stress on food availability during summer feeding, it may be an advantage to give birth further south," Dr Meynecke said.
But there could also be other factors driving the migration.
"Is it that the female is just driven north through some deep either cultural or genetic instinct?" Ms McPhee-Frew said.
Either way, studying baby whales born in cold waters will help researchers find out. If these calves grow up worse off than their warm-water peers, that will show that there really is a good reason to migrate for breeding, she said.
"What we have now is this really important comparison group."
Dr Meynecke wants to see systematic studies on the mothers and calves who are born mid-migration, to learn more about their true numbers and behaviours.
He said it would be interesting to know the effect of being born during migration on an individual calf.
"Will it return to the same waters where it was born for reproduction?" he asked.
Ms McPhee-Frew, meanwhile, recommended that people keen to see whales book in tours with local responsible operating groups — both for the fun of seeing them, and because their observations may help further research.
There are a number of citizen science projects in many states. If you're planning to do some whale watching this winter, you can help researchers wherever you are along the coast by logging your observations.
If you're interested in drone photography, note there is a blanket rule of keeping drones at least 100m away from marine animals including whales. Each state may have additional rules.
Ms McPhee Frew said photographers should include the distance (and zoom or photography settings) in the caption when posting pictures.
"We encourage people to enjoy these lovely animals, provided they're following the rules that are in place for the whales' protection," she said.