“Now that we’re out of La Niña, the number of calls we detect may decline, which could mean a period where the whales may not be as productive,” Truong said.

Hunting is one of the key causes for whales low numbers. While some populations have bounced back, including the humpback, others have struggled.

Macquarie University marine scientist Dr Vanessa Pirotta said whales were difficult animals to study, with insufficient data for certain species, like the pygmy blue whale or sperm whale, compared to the humpback whale. The former have less reliable migratory patterns and tend to swim further offshore than humpback whales.

While hunting no longer poses a threat to whales, climate change and human-led activities did. As oceans warm, the availability of food sources including krill could decline.

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“Commercial shipping and looking for oil and gas can be detrimental to the whales when they are present,” Troung said. “Managing those activities, particularly over the more active migration years, can help reduce the impact on these animals as they swim past.”

Troung added that while these impacts and their influence on animals might not be well-known, they could make habitats less livable for marine animals.

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