SYDNEY, March 22 (Xinhua) -- Australian marine scientists have discovered a surprising way to monitor the eating habits of some toothless whale species in the process, shedding light on how the aquatic mammals are adapting to climate change.
The researchers from the University of New South Wales (UNSW) said the jawlines of humpback and southern right whales contain a lifetime's worth of biochemical information chronicling their feeding patterns.
The findings, published in Frontiers in Marine Science and revealed to the public on Tuesday, are based on analysis of the whales' baleen, which are long and slender bristle-like structures in their upper jaws that are used to filter enormous amounts of krill from the ocean.
"As the baleen grows, biochemical signals from their food are trapped," said UNSW marine ecologist Professor Tracey Rogers. "Like the information on the pages in a book, they don't change with time.
"These signals allow us to reconstruct the behaviour of the whales through time - what they ate, and the general area they were at the time."
Using baleen samples from museum archives and whale standings and previously published data, they discovered that humpbacks migrating along Australia's east coast showed signs of poorer feeding opportunities during climate upheavals.
"We found that the same conditions - the La Niña events - that bring us these devastating floods are also not good for the humpbacks that migrate along the east coast of Australia," Rogers said.
Antarctic krill need sea ice to thrive, but following La Niña phases there is less ice where the whales feed, meaning fewer krill to sustain the huge animals through their migration months.
Humpbacks usually spend their winter months in warm tropical waters to breed before travelling back to southern Antarctic waters during summer to feed.
Amid this migration to the tropics, they are away from reliable food sources and must depend on their body's reserves to survive.
"They fast for the long periods when they leave their productive feeding grounds to breed," Rogers said. "That's why they're extremely susceptible to changes in ocean-atmospheric cycles."
Previous research found links between increased whale standings on the Australian coast following La Niña years, which the researchers said can be attributed to less feeding success.
"Our colleagues have shown humpbacks are leaner - a sign they're experiencing poor feeding conditions - and have a higher chance of stranding in the years following La Niña events," Rogers said.
"With La Niña events predicted to increase in intensity and frequency, it unfortunately means these whales may continue to have more of these poorer feeding prospects, and we could see more standings."
The study did, however, find some positive outcomes such as humpbacks off Australia's west coast showing increased feeding success during La Niña periods.
The researchers also noted that the whales off the east coast of Australia were developing alternative feeding strategies in more temperate waters.
"East coast humpbacks have shown signs of adapting to different feeding strategies in other known productive regions on their migration route … something that future research could look at," said UNSW doctoral candidate Adelaide Dedden.
Meanwhile, the researchers hope to use their findings to develop models that could help predict future whale behaviour and calculate when they are most likely to be at risk due to the environment. ■
