Humpback whales may be struggling to breed as climate crisis depletes food
Scientists say decline in calves born in past 15 years due to diminishing herring stocks in warming north Atlantic
Last modified on Wed 27 Jan 2021 11.31 GMTHumpback whales could be struggling to breed due to rapid environmental change in the ocean caused by the climate crisis, astudysuggests.Scientists have confirmed a significant decline in the number of calves born to female humpbacks over the past 15 years in the Gulf of St Lawrence, Canada, an important summer feeding ground for migrating whales. They said the climate crisis has led to rapid sea temperature and sea level rise in this area of the north Atlantic, with knock-on effects for the ecosystem that include decreasing numbers of herring, a vital food source for humpback whales.
Researchers from the University of St Andrews sea mammal research unit took samples from the blubber of female humpbacks, to test whether they were pregnant and, by identifying markers on individuals, they determined whether the whales returned with calves.
They related the probability of finding cow-calf pairs to favourable environmental conditions the previous year, measured by herring stock. They found that 39% of the pregnancies were unsuccessful and the annual calving rate dropped significantly from 2004 to 2018. headtopics.com
In a paper published in Global Change Biology, Joanna Kershaw, a researcher of marine mammals from St Andrews and lead author of the study, said: “Together, these data suggest that the declines in reproductive success could be, at least in part, the result of females being unable to accumulate the energy reserves necessary to maintain pregnancy and/or meet the energetic demands of lactation in years of poorer prey availability rather than solely an inability to become pregnant.”Read more: The Guardian »
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