First published in the MLA Newsletter, November, 2011
The MLA continues its series of articles on endangered whales and the laws in place to protect them. New whale rules to reduce the risk of entangling endangered whales in vertical lines will go into effect in 2014. The fifth part of this series investigates how right whales’ vision could affect the gear fishermen use.
Before comparing a whale and human eye, it is important to understand the basic parts and functions of the eye. “Think of the eye like a camera,” explained Dr. Jeffery Fasick, assistant professor of biological sciences at Kean University in New Jersey who has researched marine mammal eyes. “You have a lens in front for focusing and a film in the back for recording.” The colors we see are determined by our eye’s sensitivity to certain wavelengths of light. Photoreceptors called cones allow us to see in bright light, while rods help us see in less light. The human eye contains three types of cones: red, blue, and green-sensitive. The combination of these allows us to see one million hues and colors during the day. We only have one type of rod, though, which is why we can only see in black and white at night.
“Whales only have one cone, which is sensitive to green light, so they see in black and white in light and dark,” Fasick said. They have one cone and one rod, both of which are sensitive to light in the blue/green range of the color spectrum. “They match their cones and rods to the color of the water. To them, everything is bright,” explained Fasick. This means that anything that looks blue or green to the human eye is invisible in the water to whales. The one color that whales can see as a dark shape in their bright, watery environment is red. Copepods, the main food source for right whales, are red, allowing whales to see a group of them as a dark mass.
“Sight is the best way to get the most information in a short period of time,” said Fasick. “Their eyes bulge out to focus on the mouth to see copepods go in.”
Dr. Scott Kraus, vice president of research at the New England Aquarium in Boston wanted to know what would happen if fishing gear came in different colors, vertical lines in particular. Kraus wanted to find out if different colors would contrast with the color of the water, allowing whales to see a potential threat. To investigate, Kraus used different colored PVC pipes and placed them in front of whales. This research is still underway, so no conclusions have been made yet. However, Fasick points out that there is very little known about the optics of the eye, so color may not be the only player in the search to understand what whales see.
“We (scientists) know almost nothing about the optics of the eye,” Fasick said. “We know they have a shallow eye cup, which makes us believe a whale’s focal point is only a few meters in the distance. So even if whales can pick out red vertical lines, they would have to be close to them for the gear to be in focus.” Fasick also pointed out that we don’t know how smart right whales are. “What you have is a large, slow moving whale with poor vision. They might see gear as a foreign object, but they don’t know how to react to it,” he said.
In order to learn more about right whales’ eyes, Fasick said researchers need an eye to study. “We had a good eye from a stranded calf, but it still wasn’t great,” he said. There aren’t many right whale strandings and even when there are, the tissues in the eye aren’t fresh, explained Fasick. The best option, according to Fasick, is to study bowhead whale eyes. “[They] are a good source of tissue and are kissing cousins of the right whales,” he said.
In depth studies on other marine mammals’ eyesight have revealed interesting findings. Bottlenose dolphins were found to have acute, focused vision both in and out of water. “Bottlenose dolphins are able to focus straight ahead and to their side,” said Fasick. Eyesight appears to be important to dolphins for locating food, but they also rely on echolocation, something right whales lack.
“We are just starting to embark on the senses,” Fasick said. There is still much to be learned about right whales, but Kraus and Fasick have made great strides towards better understanding what whales see. And if Kraus’ research finds that right whales can see red rope well enough to swim around it, fishermen may start seeing some colorful changes to their gear.Category: Science