Drone footage of gray whales captured over seven years off the Oregon coast has revealed new details about how the giant marine mammals find and eat food.
The findings, described in two studies published over the summer, include that gray whales rely on different swimming techniques to collect food based on their size and age, and that larger whales are more likely to exhale “bubble blasts” to help them stay underwater.
“Before this study, we thought that any whale used any of those behaviors,” said Clara Bird, the lead author of both studies and a researcher at Oregon State University’s Marine Mammal Institute. “No one really thought that there was a pattern in who used which behavior.”
Bird’s research also found that whales use different eating techniques based on the depth of the water in which they search for meals and the habitat of their prey. Such information could aid future conservation efforts, she said, because it provides insight into the types of habitats that might need to be protected in order to preserve the whales’ access to food.
“While right now we’re not actively trying to protect specific habitats, it’s really important to know that whales of different ages might not be all using the same habitat for future concerns,” Bird said. “It’ll help us manage them moving forward.”
A segment of the gray whale population is listed as endangered under the Endangered Species Act. The entire species once faced a risk of extinction due to commercial hunting. Once common across the Northern Hemisphere, gray whales are now regularly seen only in the North Pacific. Just under 27,000 of them were estimated to be in the area as of 2016, according to a 2020 report from the National Oceanic and Atmospheric Administration.
The whales eat amphipod crustaceans like tiny shrimp and worms, which they consume by sucking up water and sediment from the seafloor, where such creatures live, then using their baleen to filter the food. Gray whales are typically observed alone or in small groups, though large groups may be seen at feeding or breeding grounds.
Bird and her team conducted their research off the coast of Newport. On sailing trips over seven years, the group tracked and recorded individual whales via drones. They identified particular whales using distinguishing markers like scars, spots or tail shape.
The first study resulting from that work, published in the journal Animal Behaviour in July, focused on variations in the whales’ foraging behavior depending on their size and habitat.
The team tracked 78 gray whales during a total of 160 sightings from 2016 to 2022. In the drone footage, they observed that younger, smaller whales often swam sideways or facing forward, opening and closing their mouths in an attempt to find and take in food. Older, bigger whales, meanwhile, tended to dive then stay in place head-down in what the scientists described as a “headstand technique.”
The probability of such headstands increased as a whale got bigger, the study found, while the probability of the forward-swimming tactic decreased. Water depth and the type of habitat — rocky, sandy or coral reef — also played a role in the approach the whales took.
Bird attributes the switch between techniques to the maturity of a whale’s muscles as well as its levels of strength and coordination.
Her team’s second study, published in the journal Ecology and Evolution in August, described how older, bigger whales release air from their blowholes to help them stay underwater when searching for food.
These “bubble blasts” can help a whale sink by decreasing their buoyancy. Bigger whales have a greater need for this, since their larger lungs hold more air and they have more blubber, both of which make them prone to floating.
The finding was based on observations of 75 whales. On average, a bubble blast came 27 seconds after a whale dove for food, and most were observed while the whales were doing headstands. The older and bigger a whale got, the greater the probability of such a blast.
“This sort of pairing of the size with the behavior on the individual level is a really exciting part of this study,” Bird said.
Susan Parks, a biology professor at Syracuse University who has published studies on whales’ eating habits but was not involved in the new research, said that documenting diversity among one whale species helps scientists avoid inaccurate generalizations.
“As we try to do conservation efforts or conserve endangered species, it’s really important to understand that there could be a wide variation in behaviors,” Parks said. “So we can’t just sort of stop at the single observation.”
Parks also highlighted the potential drones have for collecting detailed data on whales.
“There’s so much unknown about their behavior,” she said, adding that the study shows how “using drone footage to essentially spy on what the whales are doing gave them a totally different perspective on the details of how they were making a living.”
