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Blue whales depend on their memories to find the best feeding sites

Researchers at Oregon State University have discovered that blue whales locate productive feeding sites by relying on their memories instead of depending on environmental cues.

The experts analyzed records of whale migration and ocean conditions in the California Current Ecosystem. They found that blue whales match the timing of their migration to the historical timing of krill production almost perfectly, rather than matching their movement based on the annual availability of krill.

The findings suggest that blue whales rely on their memory to return to sites where prey has been historically abundant. The results also indicate that it may be difficult for the whales to adapt to ecosystem changes that result from climate change.

Study lead Briana Abrahms is a research ecologist with the NOAA Southwest Fisheries Science Center in Monterey, California.

“We know that many species that migrate on land, from caribou in the Arctic to wildebeests in the Serengeti, enhance their survival by carefully adjusting the pace and timing of their migrations to find food as it becomes seasonally available along the way, rather than just migrating to get from point A to point B,” said Abrahms.

She noted that blue whales seem to embrace this same strategy, which is enhanced by their memory.

“These long-lived, highly intelligent animals are making movement decisions based on their expectations of where and when food will be available during their migrations.”

The study was focused on ten years of tagging data that showed the daily movements of 60 individual blue whales. They compared these observations with satellite-based measurements of ocean productivity.

“We think that blue whales have evolved to use historical migration routes and timing that put them in proximity to the most predictably high production feeding areas and then make minor adjustments based on local conditions,” said study co-author Daniel Palacios.

“There are various time scales of events that could change the timing of phytoplankton blooms – and thus the availability of the whales’ preferred prey, krill, including La Nina and El Nino events and the Pacific Decadal Oscillation. But the whales’ strategy of relying on memory and historic timing at least gets them into ‘the Goldilocks zone.’”

Around 2,500 of the world’s 10,000 blue whales can be found off the western coast of the United States. Known as the eastern North Pacific population, the majority of these whales spend the summer and fall in the waters off Santa Barbara and San Francisco, which puts them in danger of ship strikes.

Abrahms explained, “We still have a lot to learn about how large animals navigate in the ocean, how they find good habitat and how they are affected by human activities and environmental changes.”

The study is published in the journal Proceedings of the National Academy of Sciences.

By Chrissy Sexton, Staff Writer

Image Credit: Oregon State University

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