Humpback whales are giving birth where we least expected

Humpback whales are famous for their long migrations from icy Antarctic waters to warm tropical seas, where they are known to breed and give birth. But new findings suggest these epic journeys may not be as necessary as once thought – at least when it comes to calving.

It turns out that humpback whales are giving birth much farther south than previously documented, with sightings as far south as Tasmania and New Zealand.

The research team, based at the University of New South Wales, studied sightings, strandings, and surveys to piece together a new picture of where young humpback whales are being born.

The findings challenge old assumptions and point to a need for broader conservation measures along the migration path.

Surprising humpback whale birthplaces

“Hundreds of humpback calves were born well outside the established breeding grounds,” said Dr. Tracey Rogers of the University of New South Wales, senior author of the study.

These calves weren’t just found drifting a bit off course. Some were spotted in areas full of human activity.

“In July 2023, during a whale-watching tour, I encountered a mom and calf at the mouth of Newcastle Harbor – the busiest shipping port in Eastern Australia,” said Jane McPhee-Frew, a Ph.D. candidate at the University of New South Wales.

“The calf was tiny, obviously brand new. What were they doing there? But none of my tourism colleagues seemed surprised.” This encounter sparked a deeper look into calving locations.

Records of humpback whale births

The researchers compiled data from a wide range of sources, including citizen science sightings, government surveys, and whale stranding records dating back to 1991.

The team also utilized data from New Zealand’s Department of Conservation Cook Strait Whale Project and Australian wildlife authorities.

In total, the team identified 209 records involving newborn humpback calves. The records included 11 confirmed births, 41 strandings, and 168 sightings of live calves – at least 169 individuals in all.

For many of these humpback whales, the direction of travel was known, and 118 were continuing their journey north even after giving birth.

Extensive long-distance migrations

“Humpback whale populations undertake extensive long-distance migrations from the Southern Ocean to breeding grounds in the tropics,” said Dr. Adelaide Dedden of Australia’s National Parks and Wildlife Service.

“They rely heavily on body reserves from an enormous amount of Antarctic krill to support the physiological costs of the journey and reproduction.”

One of the southernmost calves was recorded in Port Arthur, Tasmania – 1,500 kilometers farther south than scientists thought humpbacks could calve. Another was found slightly farther north in Kaikoura, New Zealand.

Overlooked behavior of humpback whales

Interestingly, most of these observations are from recent years. About two-thirds occurred in 2023 or 2024.

Still, this behavior may not be new. The researchers believe it may have gone unnoticed before due to the dramatic decrease in whale populations during the era of commercial whaling.

“I think it’s very likely that this pattern has always existed, but the low number of whales obscured it from view,” said McPhee-Frew. “The Eastern Australia humpback population narrowly escaped extinction, but now there are 30, 40, or 50,000 in this population alone.”

“It doesn’t happen overnight, but the recovery of humpback whales, and the return of their full range of behaviors and distribution, just goes to show that with good policies built on good science we can have excellent outcomes.”

Why migrate at all?

If humpbacks can give birth so far south, why do they bother migrating at all? That question remains unanswered.

One theory is that while births can happen anywhere along the migration route, the benefits of tropical calving grounds – warmer waters and lower risks from predators – still outweigh the risks of staying south.

In some areas, like Flinders Bay in Western Australia, the researchers found potential nursery zones. While most calves still seem to be born in the tropics, the new data shows that births outside of these regions are more common than once believed.

The team emphasized that this isn’t just a curiosity – it has real conservation implications. Some of the calves seen outside of the usual zones were injured. That suggests greater vulnerability, especially in areas with heavy human traffic, like shipping lanes.

Protecting calves on the move

As whale numbers rise and sightings increase, the need for broader protection becomes clearer. Researchers are calling for more awareness of calving outside traditional breeding zones. That means rethinking how we define critical whale habitats.

“This study was based on opportunistic observations,” noted McPhee-Frew. “This data is excellent for answering questions like, ‘are there newborn whales here?’ But we can’t stretch the interpretations too far.”

“It might appear that we see more calves the further north we go, or that we have seen more over time. But it could be that there are more people whale-watching in the north, or more cameras and social media sharing in recent years.”

“We can only document what we see,” added Dr. Vanessa Pirotta of Macquarie University. “Perhaps there are things happening in our ocean that we are yet to find out.”

For now, this discovery expands our view of where humpback whales are giving birth. As populations of these gentle giants continue to recover, further research is needed to protect them wherever they go.

The full study was published in the journal Frontiers in Marine Science.

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