How do blue whales find food? They check the weather.

How do blue whales find food? They check the weather.

Bigger than even the largest dinosaurs, blue whales (Balaenoptera musculus) are mysterious and elusive–surviving mainly on tiny crustaceans called krill and leaving many unanswered questions about their ecology and biology. They can be found around the globe, with the exception of the Arctic Ocean. Their movements are governed by two main events: when they have to breed and when they have to eat their favorite crustaceans. In the eastern Pacific Ocean, these whales spend their winters off the coast of Mexico and Central America, and then can travel up to 30 miles per day on their migration north towards California in the summer.

Besides their extraordinary size and speed, the blue Whale also makes some very unique sounds . However, the creature’s unique sounds may be revealing one of their greatest secrets. in the journal Ecology Letters, a team of researchers used a directional hydrophones in MBARI’s underwater observatory (kind of an underwater scientific podcast studio that records the sounds of the Pacific) to listen for blue whale vocalizations. These sounds were used to track blue whale movements and to learn that they respond to wind changes to forage for food.

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” The blue whale provides us with such phenomenally useful and clear information for understanding their behavior,” John Ryan (MBARI )) tells Popular Science .. “I feel like the Blue Whale is working with us to understand them by putting sound in the ocean that is so powerful for research that can help protect and understand them .”

[Related: World’s largest shipping company reroutes ships to protect world’s largest animals. ]

During the spring and summer, upwelling occurs in the Pacific Ocean off California’s central coast. This weather phenomenon occurs when wind pushes the water’s top layer further out into the sea while the water below rises to its surface. The cooler, nutrient rich water rises with tiny phytoplankton, which jumpstarts the food web in Monterey Bay. According to the study, blue whales will seek out cooler water when there is an upwelling event. They use the winds and upwelling to guide them. When the upwelling ceases, the whales move offshore to get closer to shipping lanes. They rely on the wind to find food.

The team used directional hydrophones to determine the direction of the sounds. “The accelerometer, which measures water velocity and particle motion, is beyond the hydrophone. Ryan says that we can now go beyond saying “That was a Blue Whale” to “That was a Blue Whale, and the sound originated from over there.”

To help corroborate that it was actually a blue whale making noise, researchers from Stanford University placed temporary suction cup trackers on the whales. The team then matched the recordings with the location of the whales using GPS. The research team established confidence in the acoustic methods and examined two years worth of acoustic monitoring of the blue whale population.

[Related: Biologists vastly underestimated how much whales eat and poop. ]

Previous research had already found that swarms of anchovies and krill (called forage species) reacted to coastal upwelling by swarming the plumes. The team used these insights to combine krill movement data and the acoustic tracks from blue whales foraging. “When coastal upwelling was strong, anchovies & krill formed dense clusters within upwelling plumes. Ryan says that blue whales can track these dynamic plumes where there are abundant food resources.

The research has shown that blue whales are able to recognize when the wind is changing their habitat, and then locate areas where upwelling aggregates of krill. It is crucial that these 165 ton animals find dense groups of krill to survive, since they can eat up to 2 million metric tons of krill per year. To maximize their snack time, the whales closely monitor the upwelling process.

Blue whales are still considered endangered, and their proximity to shipping lanes and vessel strikes remains a threat to their recovery. A 2019 study shows that blue whales are particularly vulnerable to ship strikes, since they do not perform any lateral movements to get out of the way, but instead dive down not realizing that how deep ships sink into the water. This research will help scientists track blue whales and their food and aid in conservation efforts like speed restrictions for vessels.

” The surprise was how much time they spent off-shore in habitat that is translated via shipping lanes. This represents a primary threat for their survival and recovery, as an endangered species,” Ryan states. “We must spread this technology to other areas, as we have it in one area .”

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