For the third year in a row, California beaches have been inundated by a surge of starving and ill sea lion pups. So far, scientists have rescued over 250 stranded sea lions—and the reason for the crisis is stumping marine biologists.
Already, rescuers have taken in more sick sea lion pups than during an unprecedented “mortality event” in 2013, Kurtis Alexander reports for the San Francisco Chronicle. And as in 2013, scientists are unclear about what is causing large numbers of seven- to nine-month-old pups to end up on Southern California shores, showing signs of severe emaciation, dehydration and hypothermia.
“This is the third year that we’ve seen these mass die-offs, but this is the worst so far,” veterinarian Shawn Johnson told Alexander. “If this continues, there will be some long-term effects on the sea lion population.” Johnson and his team at the Marine Mammal Center in Sausalito have found piles of the pups at their facility in Sausalito, California. He notes that since the pups are too young to be weaned, they are too small and weak to feed themselves by diving for fish.
Are California sea lion pups starving because warm El Niño waters are making food more scarce for their mothers? Or could the crisis point to another undersea issue? Marine biologists aren’t sure, but Justin Viezbicke of the National Oceanic and Atmospheric Administration tells the Chronicle that it could have to do with the sea lion population reaching capacity at around 300,000. He notes that sea lions provide valuable insights into the environment, acting as a bellwether for problems that could eventually effect humans.
While scientists struggle to understand what’s causing sea lion pups to get stranded and sick at such an alarming rate, another team of biologists has learned a surprising fact about deep-diving marine mammals. New research shows that, despite their ability to dive to astonishing depths, animals like seals and bottlenose dolphins have a high frequency of irregular heartbeat, or arrhythmia. It looks like even marine mammals get exhausted when they hold their breath underwater—and those insights could eventually be used to help protect and improve performance in human athletes.