Stony corals provide habitat for an eye-popping one-fourth of the ocean's species. They serve as the centerpiece of a rich and diverse ecosystem, which is why their recent behavior has scientists concerned. New research shows that stony corals around the world are hunkering down into survival mode as they prepare for a mass extinction event, according to a new study published in Scientific Reports.

The international research team was composed of scientists from New York, California, Israel, England and Germany. They noticed a suite of behaviors that correspond to a survival response commensurate with how they behaved during the last mass extinction 66 million years ago, according to the new study. "When we finally put all this together and saw the result, for me it was that moment when the hair on the back of your neck stands up," said marine biologist David Gruber, from The City University of New York, to Newsweek. "It was like, Oh my goodness, [the corals] are doing exactly what they did back then."

The researchers had a rich-history of corals to compare with modern species. Coral skeletons leave an indelible, time-stamped fossil record for scientists to examine the conditions that led to their dying. The scientists were able to compare those fossils with the 839 coral species on the red list of threatened species recognized by the International Union for Conservation of Nature, as Newsweek reported. The scientists looked at the traits of corals that survived the last major extinction event. They found that the colorful, wavy corals that attract scuba divers did not last. The ones that did survive are the ones that form small colonies and seek out deep water, which are the same ones showing signs of thriving today, as Newsweek reported.