section_path: Adaptation/Climate impact
section_name: Climate impact
paragraph_text: Climate impact
  
  Past studies proposed that changes in dire wolf body size correlated with climate fluctuations. A later study compared dire wolf craniodental morphology from four La Brea pits, each representing four different time periods. The results are evidence of a change in dire wolf size, dental wear and breakage, skull shape, and snout shape across time. Dire wolf body size had decreased between the start of the Last Glacial Maximum and near its ending at the warm Allerød oscillation. Evidence of food stress (food scarcity leading to lower nutrient intake) is seen in smaller body size, skulls with a larger cranial base, and shorter snout (shape neoteny and size neoteny), and more tooth breakage and wear. Dire wolves dated 17,900 YBP showed all of these features, which indicates food stress. Dire wolves dated 28,000 YBP also showed to a degree many of these features but were the largest wolves studied, and it was proposed that these wolves were also suffering from food stress and that wolves earlier than this date were even bigger in size. Nutrient stress is likely to lead to stronger bite forces to more fully consume carcasses and to crack bones, and with changes to skull shape to improve mechanical advantage. North American climate records reveal cyclic fluctuations during the glacial period that included rapid warming followed by gradual cooling, called Dansgaard–Oeschger events. These cycles would have caused increased temperature and aridity, and at La Brea would have caused ecological stress and therefore food stress. A similar trend was found with the gray wolf, which in the Santa Barbara basin was originally massive, robust, and possibly convergent evolution with the dire wolf, but was replaced by more gracile forms by the start of the Holocene.