Final answer:
Grizzly bears enter hibernation based on environmental cues rather than at random times, entering a deep sleep rather than true hibernation. Feeding bears can alter their natural behaviors and climate change significantly impacts polar bears due to their reliance on sea ice for hunting.
Step-by-step explanation:
The timing of hibernation for grizzly bears is regulated and influenced by environmental cues. This regulation is evident from the fact that grizzly bears do not enter hibernation at random times but typically do so at the end of winter, providing evidence of a physiological response to environmental changes. Unlike small animals that enter true hibernation and experience significant drops in body temperature and metabolic rates, bears enter a state of deep sleep where their body processes do not slow down appreciably, and they can be easily awakened. This indicates that their winter sleep is less intense compared to true hibernators like ground squirrels.
Environmental factors, such as temperature and food availability, likely act as cues for grizzly bears to begin their hibernation cycle. Furthermore, human interference, such as feeding bears, can alter bear behavior, leading to increased human-bear conflicts. Lastly, climate change, particularly the melting of sea ice, poses a significant threat to polar bears, who heavily depend on sea ice for hunting seals, unlike their grizzly and black bear counterparts who have more varied diets and hunting grounds.