The question is vague but leading. The species would adapt thru moving. The population from the south would stretch southward if the climate got colder. If the climate gets warmer, they would expand to places with a cold climate. They look like they want to conclude doom, but it really depends on the place’s geography and its range of distribution. Some animals have enormous ranges of climates that they are suitable with. The question is leading but vague because you require variation to have selection. The variation that exists will get heavier pressure on selection with less variation since with less variation, they be evolving much lesser and they would have to change their bearing or area to survive. During each glacial cycle, sever climate change happens and animals usually migrate and don’t evolve during the short span of time.