That is essentially their entire point: "By contrast, many species in the Southern Hemisphere would have been preparing to hibernate for the winter as oppo

That is essentially their entire point: "By contrast, many species in the Southern Hemisphere would have been preparing to hibernate for the winter as opposed to gearing up for their reproduction cycles. That may have contributed to the survival of those species—particularly mammals, certain amphibians, birds, and crocodiles—who were more likely to be sheltering in burrows or caves at the time of impact."