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Scientists issue warning after observing concerning change in humpback whales: 'The cost of growth'

Researchers are ramping up monitoring efforts.

Humpback whales are shrinking, according to a new study.

Photo Credit: iStock

Scientists discovered something that's both perplexing and worrisome — humpback whales are shrinking.

What's happening?

A study found that humpback whales in the North Pacific are getting smaller. Compared to the mid-1900s, mature whales are now about one to two feet shorter, according to The Maui News

Researchers also discovered an 80% drop in birth rates between 2013 and 2018 and shorter migrations between Alaska and Hawai'i.

Lead author Martin Van Aswegen, a postdoctoral researcher at The Marine Mammal Research Program, said the findings highlight "the cost of being a humpback whale in the North Pacific: the cost of growth." 

In other words, these massive travelers are burning more energy just to survive, leaving less for reproduction and growth.

Scientists haven't pinned down every cause yet, but they believe human activity and changing ocean conditions — from ship noise and vessel traffic to dwindling prey — play a significant role.

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Why are the study's findings concerning?

Along the coast, humpback whales are more than just a sight to marvel at — they're part of daily life. Whale-watching brings steady work for tour operators, boat crews, and local shops from Maui to Alaska. 

When fewer whales show up or skip breeding seasons, it's not just the ocean that feels it — the communities depending on those visits do, too.

Scientists warn that the changes go beyond economics. Humpbacks help keep ocean ecosystems healthy by circulating nutrients through their migrations — so when their numbers and size drop, the entire marine food web feels the effects.

What's being done to protect whales?

Researchers are ramping up monitoring efforts to better understand how these pressures affect humpbacks and to guide smarter marine policies. Efforts to reduce ship noise and restrict high traffic routes near breeding areas are also making a difference in some regions.

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Meanwhile, conservation groups are stepping up with efforts to clean up oceans and protect migration routes — following big wins like California's Marine Life Protection Act and the U.S. plan to boost ocean biodiversity.

Every day choices matter. Eating from sustainable fisheries, using fewer plastics, or supporting ocean protection laws can help whales thrive — and help people keep their connection to the sea.

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