Blue Whales Appear to Use Ocean Temperature Fronts as Feeding Guides

Blue whales may be using subtle patterns in ocean temperature to find the concentrated krill swarms they need to survive, according to research reported by Phys.org from scientists at the Monterey Bay Aquarium Research Institute and collaborators. The study followed two tagged whales and compared their movements and feeding behavior with satellite observations of the ocean. Temporary electronic tags recorded the animals’ movements, activity, feeding habits and nearby marine conditions. Satellite radar altimeters mapped ocean-surface topography and circulation, while infrared sensors identified temperature boundaries known as thermal fronts. These fronts are narrow areas where water temperatures change sharply. The researchers found that the whales repeatedly oriented their movements around such features. A whale would locate a thermal front near the surface, dive deeper to search for krill, and generally travel from the cooler side toward the warmer side while looking for a dense swarm. When prey was found, the whale began feeding intensively. The pattern was observed both during the day and at night. The whales also responded to the thermal fronts when the search did not result in successful feeding, suggesting that the behavior was not simply a reaction to immediately visible prey. According to the study’s interpretation, the animals appear able to detect temperature and follow how it changes across the ocean surface. The researchers said the systematic movements may indicate sophisticated abilities involving memory, comparison and orientation, though the reported findings concern the whales’ behavior and sensory capacity rather than a direct observation of what they perceive. The research was published in Current Biology under the title “High-precision localization of feeding by Earth's largest predator, the blue whale.” The project forms part of the Monterey Bay Aquarium Research Institute’s Blue Whale Observatory, which combines acoustic monitoring, oceanographic measurements, satellite data and biologging to study whales and krill in the Monterey Bay region. Blue whales remain endangered, and collisions with ships are identified as a primary risk. The researchers said a clearer understanding of where and how the animals feed could help resource managers protect them as they travel through waters also used by large vessels.