NC Researchers Find Humpback Whales Have Worse Vision Than Expected Despite Big Eyes

Recent tests reveal that humpback whales see much worse than scientists thought. Their sight falls short by about 15 times compared to human eyes, based on findings in the Proceedings of the Royal Society B.

A study of a whale eye from North Carolina showed these sea giants pick up just 3.95 cycles in each degree of visual space. People catch 60 to 100 cycles. At this rate, whales must swim within 45 to 60 meters of an object to spot it.

"This work helps fill a major gap in our understanding of the sensory ecology of large whales [and] how humpbacks experience their world," said Lori Schweikert, assistant professor of biology and marine biology at UNC Wilmington in a news release.

Scientists at Duke University and UNC Wilmington studied a left eye from a young whale that had drifted onto Thorofare Bay's shore. The specimen sat in storage for over a decade before tests began.

Two key issues cause this weak sight. The sclera, the white part, is too thick at the back. This reduces the focal length needed for clear vision. Plus, the eye lacks enough signal-sending cells to process what it sees.

These ocean dwellers have just 180 retinal ganglion cells per square millimeter, while humans pack up to 40,000 in the same space. This stark difference shows why whales struggle to see fine details that humans spot easily.

Computer analysis proves they can detect big shapes like fish schools from far away. Yet they must swim closer to see smaller items, a fact that puts them at risk near fishing gear. This new knowledge might spark better designs for fishing gear that whales can spot more easily.