Photo: Unsplash
Humpback whales have surprisingly poor eyesight, it turns out. By examining the way whale’s vision works, scientists were able to learn more about how the massive cetaceans see the world – and possibly why they often run afoul of boats and fishing equipment.
The discovery was made by a group of scientists from the University of North Carolina Wilmington and Duke University, and outlined in a study published in Proceedings of the Royal Society B. During the study, they dissected the left eye of a whale, which had been collected from an animal that had perished after being stranded in Thorofare Bay, North Carolina. The UNCW Marine Mammal Stranding program collected the sample.
While the eye itself was quite large, which would normally indicate a long focal distance, the researchers found the distance between the retina and lens was much shorter than expected. What’s more, the eye had a low density of retinal ganglion cells – the cells that transmit visual information to the brain. Based on anatomical and perceptual models, the scientists estimated that the whales can see large, simple shapes from a distance, but can only see fine details from close range – around three to four whale lengths away.
Normally, this would not be a problem for whales, according to University of North Carolina Wilmington assistant professor of biology and marine biology Lori Schweikert. “That visual acuity, however, is often suited to what they need to survive in their natural environment,” she told the BBC. “For humpback whales, they may only need to resolve large silhouettes, such as that of a large school of prey or another whale swimming by.”
However, the presence of boats and other man-made objects complicates the matter. They are likely unable to see something as small as a fishing net until they are too close to maneuver away. As we see all too often, this can spell disaster – leading to entanglements and boat strikes. Hopefully though, this new knowledge can help to find ways to protect them in the future.
