Humpback numbers have dropped in Hawai‘i and Alaska

For years, the news about humpbacks was positive. Rebounding from near decimation after landing on the endangered species list in 1973, more and more whales came to Maui each winter from their feeding grounds in Southeast Alaska to breed and give birth. The Northern Pacific humpbacks were “de-listed” in 2016. Ironically, that’s the year things got weird.

The past few whale seasons have been… different. Reports of fewer whales and shorter visits in Alaska and Hawai‘i have persisted and led to a special meeting on O‘ahu this fall, where some 30 leading humpback whale researchers convened to discuss the situation.

Their findings sound a lot like the old rock anthem: “There’s something happening here. What it is ain’t exactly clear.”

Marc Lammers, Research Coordinator at the Hawaiian Islands Humpback Whale National Marine Sanctuary, who helped organize the gathering, picks his words carefully when discussing the situation. “We don’t have evidence of actual numbers of whales that are coming here and what’s different,” he explains. “We have a pretty good sense that they’re lower, and not just a trivial amount, but I wouldn’t go beyond that.”

Many scientists at the meeting had startling reports from the most recent 2017-2018 research season.

Since 2001, Adam Frankel, a scientist with the Hawaiian Marine Mammal Consortium, has compiled humpback data each winter along the Big Island’s Kohala Coast. “For the first nine years, whale numbers increased,” he says. “But by 2012, the trend was starting to curve down. Our numbers from this year are basically the same as what we had in 2002-2003.”

Frankel quickly adds: “Now those are the numbers of whales that we saw in our little part of one island, that doesn’t translate into saying the whole Hawai‘i whale population is down to what it was in 2003.”

Frankel is finalizing a paper on the subject that suggests a strong correlation between whale numbers and the Pacific Decadal Oscillation, a long-term climate pattern that alternately cools or heats surface waters in the Northern Pacific. In recent years, the PDO switched from a colder temperature to a warmer one.

“In our model, there was a very strong relationship between a cool PDO and an increase in the number of whales we see in Hawai‘i,” Frankel explains. “With a warmer PDO, we’ve seen reduced numbers of whales off Hawai‘i Island.’

Marc Lammers has been studying humpback acoustics in Maui waters for the past 20 years. “If you looked at the amount of song chorusing [singing by male humpbacks] that took place between 2015 and 2018, we saw a drop of 50 percent in acoustic energy.”

But, he emphasizes, “We’re talking about decibel levels; we can’t extrapolate that to a specific reduction in the number of whales. Maybe fewer whales are singing and are spending their time doing something else, or they are going to places where we are not recording.

“So we have to be real careful about overstating what we know.”

Researchers have seen an 80% drop in mother-calf pairs off Maui since 2014

Biologist Rachel Cartwright, founder of the Keiki Kohola project has been studying humpback mothers and calves on Maui since 1999 and keeping track of their numbers since 2008. Each year she and her students compile numbers by doing whale counts “at exactly the same times of the season along the same routes,” criss-crossing the waters between Mala Wharf and Thousand Peaks. “We compared our sightings from the winter of 2013-2014 with 2017-2018 and that’s where we’ve seen an 80-percent drop in sightings of mother and calf pairs,” Cartwright says. “From 2014 on, we’ve seen no drop in adult numbers.”

Cartwright is concerned about the fates of mother-calf pairs they did count. “Last season we saw 34 calves in 30 days of field work. Yet, only three calves were sighted in Southeast Alaska. So we don’t know where the Maui moms are going. Are they going back to Alaska, but their calves aren’t making it? Or, are they going other places?”

This year, Cartwright adds, “We’re going to build a very comprehensive ‘fluke catalogue’ (whales can be identified by the distinctive markings on their tails, or flukes) and then we’ll distribute that to Alaskan, Canadian, and Californian researchers and whale watchers to see how many of those moms they sight with or without those calves.”

In the meantime, Cartwright worries about the impact of tourism on the mother-calf pairs. “If the numbers stay low this year, we’re concerned that those moms and calves around Maui will be the focus of a lot more attention from whale watchers, kayakers, and paddle boarders. It’s a fragile time for them.”

The report from Alaska’s humpback feeding grounds was equally bleak. National Park Service biologist Christine Gabriele has spent summers monitoring whales through photo identification in the Glacier Bay region since 1991. She says the population increased “fairly steadily” until 2013, when it topped out at 239 individual whales. Since then, the numbers have decreased. “In 2018 we had 100 whales, that’s a drop of 59 percent,” she says. “That’s about the same number of whales we had in 1999. The same whales – with a long pattern of coming back each year – are not coming back anymore,” she adds. “Comparing notes with other Southeast Alaska researchers, I know my whales didn’t just move 20 miles down the road. If the whales moved, they’ve gone somewhere that researchers aren’t studying.”

The calf situation is even more concerning, Gabriele says. In Glacier Bay, the long-time average used to be about nine calves for every 100 whales. From 2014-2017 that number went to about three. “This year it got to zero. We saw one calf early in the season that was missing by mid-summer. It’s very unlikely it was weaned by then, so we presume it died.”

Gabriele surmises that the Glacier Bay change has to do with food sources. “I think it’s going to take some really strong cooperation with different disciplines – like oceanography and fisheries – to get to the bottom of it.”

She called the scientists’ gathering “pretty powerful. The Hawai‘i and Alaska data seemed to be telling the same story regardless of what method the researchers were using to do the study. We identified several research questions and we’ll form working groups to get the right people together to do the work.  I think that was the important outcome.”

Still, the question remains: Where are Maui’s missing humpbacks?

“We don’t know,” says Adam Frankel. “There are many possibilities. It could be that they are not coming as far as Hawai‘i; it could be that they’re spending less time here; it could be that fewer animals are migrating to Hawai‘i. It’s rarely just one thing. But this season we will count again. Everyone’s hoping that the numbers tick up.”

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Photo 1 courtesy Wikimedia Commons

Photo 2 courtesy J. Moore – HIHWNMS/ NOAA Permit # 15240