Â鶹ÒùÔº

Queensland sites offer play and rest for migrating humpbacks

A new study has compared how migrating humpback whales use two stopover sites along the Queensland coast, finding that one was more social in nature and the other was used primarily by mothers and calves.

While both Hervey and Moreton bays offered ideal resting places, Moreton Bay demonstrated more of a utilitarian role as a stopover compared to the multi-faceted use observed in Hervey Bay.

Dr. Raphael Mayaud conducted his Ph.D. study as part of the Griffith University team that initially identified Moreton Bay as an important stopover for humpback whale mothers and calves on their southward migratory journey in a 2023 study.

For the new study, now in PLOS One, the Southern Ocean Persistent Organic Pollutants Program researcher and his team wanted to further clarify its role within the broader migratory network.

"Given the potential significance of this finding in terms of how it could impact the conservation status of the bay, it's important that we understand the functional roles of stopovers because they give us a holistic perspective of population dynamics and connectivity," Dr. Mayaud said.

"Because Hervey Bay has been extensively studied and well-documented as a stopover for the past couple of decades, it serves as an appropriate benchmark for us to compare Moreton Bay with."

The results of systematic whale surveys conducted in both areas at staggered periods during the 2021 whale season showed Hervey Bay supported a more heterogeneous mix of demographic groups, while Moreton Bay had a significantly greater number of calf-groups.

Whales in both bays exhibited similar resting behaviors, but social interactions among juveniles were unique to Hervey Bay.

Throughout the surveys, the team looked at the overall population structures, behaviors and distribution patterns at both bays.

Dr. Mayaud said spending time on the water during the surveys provided contrasting observations and made it clear that each of the sites provided its own unique offerings for humpback whale groups.

"Hervey Bay felt like a playground, where the whales were socially interacting with one another, and were genuinely curious about the research vessel, whereas Moreton Bay seemed more like a much-needed pit-stop," he said.

"And this was reflected within our results. We found Hervey Bay had a more equal proportion of pod groupings while Moreton Bay was heavily dominated by calf-groups.

"These surveys provided valuable insights into the functional role of Moreton Bay for humpback whales within the broader migratory network, which can help inform targeted conservation efforts."

Dr. Mayaud said more research was needed to help distinguish whether Moreton Bay was a facultative stopover (i.e., one mother-calf pair only used it based on their current energy needs) rather than a socially learned stopover such as Hervey Bay, where a core subgroup of humpback whales repeatedly returned year after year.