The dolphins in Western Australia are now part of the growing list of marine animals under threat of extinction due to climate change, suggests a new study.
Climate change is never more real than at the bottom of the ocean. As the temperatures in the waters increase, they can result in the collapse of the marine food chain.
The sudden extreme increases in the temperature may also prevent several creatures to eventually adapt, decreasing their chances for survival.
For the bottlenose dolphins in Shark Bay, it means a trend of declining survival and birth rate that can extend for years.
Marine Heatwave Marked The Beginning
In 2011, a marine heatwave happened in Shark Bay, a UNESCO Heritage Site. During this period, the temperature in the ocean went up by 4 degrees than the annual average.
It eventually destroyed meadows of seagrass that served as habitats and food sources for different marine animals.
The University of Zurich researchers then wanted to find out how it could affect the creatures at the top of the food chain.
To know the answer, they used the data collected in the area for the past 10 years starting in 2007.
They then learned that there's a correlation between the event and the survival rate of the bottlenose dolphins. It fell by 12 percent after the heatwave. The female dolphins were also giving birth to fewer calves.
They also found out that these two trends persisted until 2017, or more than five years since the heatwave.
Making Sense Of The Information
The researchers believed many factors may be causing these two phenomena.
For one, the heatwave might have changed the speed of sexual maturity of these dolphins. Mothers might be neglecting their calves in a desperate move to survive.
More calves might be dying due to the warming ocean temperature. It's also possible it could be a combination of all these.
Either way, the results surprised the researchers.
"Lower survival has persisted post-heatwave, suggesting that habitat loss following extreme weather events may have prolonged, negative impacts on even behaviourally flexible, higher-trophic level predators," said the study now published in Current Biology.
The Glimmer Of Hope
Remarkably, the same study pointed out that certain bottlenose dolphins had a better survival rate than the others. Those who used foraging or hunting tools such as sponges experienced a decline of only 5.9 percent.
It's possible their behavior buffered them somewhat by giving them access to areas that had been less affected by the marine heatwave.
Previous studies also showed that some marine animals could adapt to the water changes brought about by global warming.
Still, the researchers warn extreme changes in the weather can threaten marine mammal populations.
"If we want to conserve these populations, we have to think how the frequency of such events can be kept at a minimum," recommended Michael Krützen, study author, in an email to CNN.