The size difference in a full-grown typical male Pacific gray whale born in 2020 vs. the year 2000 (dotted line). Image: K.C. Bierlich, OSU Marine Mammal Institute

Why are Animals Shrinking Worldwide?

Mammals, birds, fish, lizards and bugs are downsizing dramatically, a clear sign something’s up

Robert Roy Britt
Aha! Science
Published in
12 min readJun 17, 2024

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Each year, a couple hundred gray whales congregate in shallow waters off the US Pacific Northwest coast to feed. Over the years, scientists have documented an alarming change in the majestic beasts. Adult males born in 2020 will be nearly 5–½ feet shorter (1.65 meters) when fully grown compared to those born 20 years earlier — a 13% size reduction from their past average of around 40 feet.

The stunted growth hints at serious problems with the ocean’s food web and the whale’s long-term survival chances, researchers concluded in a new study published in the journal Global Change Biology.

Scientists don’t know exactly what’s going on. But the potential consequences are clear: Being smaller can reduce the whales’ ability to store energy during tough times, which could hamper reproduction as well as the survival odds of smaller newborns.

“This could be an early warning sign that the abundance of this population is starting to decline, or is not healthy,” said K.C. Bierlich, co-author on the study and an assistant professor of marine science at Oregon State University. “And whales are considered ecosystem sentinels, so if the whale population isn’t doing…

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Robert Roy Britt
Aha! Science

Editor of Aha! and Wise & Well on Medium + the Writer's Guide at writersguide.substack.com. Author of Make Sleep Your Superpower: amazon.com/dp/B0BJBYFQCB