(ORDO NEWS) — Scientists have studied the chemical composition of whalebone to trace changes in the diet of these animals. It turned out that periodic fluctuations in the temperature of the water surface in the equatorial Pacific Ocean can seriously affect the diet and survival of whales.
The baleen are horny plates attached to the upper palate of baleen whales that serve to weed out plankton. Scientists from the University of New South Wales (Australia) have found that changes in the chemical composition of the whalebone can tell about the history of nutrition of these animals.
In addition, baleen has made it possible to assess the impact of climate cycles on the life of whales and to predict how mammals will react to future climate change.
Because of their gigantic size, baleen whales need a huge amount of food. This makes them vulnerable to environmental changes that can affect food availability.
Such changes include fluctuations in the temperature of the surface layer of water in the equatorial part of the Pacific Ocean – a change in the phases of El Niño and La Niña. During El Niño, the area of warm near-surface waters shifts to the east, the trade winds weaken, and the rise of deep waters to the surface slows down. La Niña is the opposite.
Because whales are difficult to study in a lab, the researchers focused on analyzing the baleen. Over the course of a whale’s life, the mouth plates in its mouth accumulate stable isotopes – chemical clues that allow us to understand what the animal ate and where it was.
The scientists analyzed samples of whalebone kept in museum collections. The mustache belonged to humpback and southern right whales washed up on the shores of the Pacific and Indian oceans.
It has previously been known that changes in whalebone chemistry reflect changes in whale physiology. However, now scientists have shown its connection with environmental factors.
It turned out that the composition of stable isotopes depends on the phase of the ocean, since the nutrition of whales is associated with climate-conditioned availability of resources.
Humpback whales spend the winter months in warm tropical waters before returning to South Antarctic waters during the summer.
During migration, they are away from their usual food sources and must rely on their body stores and the swarms of Antarctic krill they encounter along the way.
As it turned out, humpback whales migrating along the east coast of Australia were starving during the La Niña phase.
This is probably due to the fact that krill prefer cold water, and during La Niña, the waters off the coast of Australia warm up, reducing their population. As a result, the whales are left without their main source of food.
Due to global climate change, the La Niña phase is projected to become more frequent and intense, which means that whales will face additional difficulties in migrating. Therefore, scientists hope to use the results of their work to create models that will accurately predict the behavior of humpback whales.
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