1. Warm-blooded: Polar bears are warm-blooded animals, meaning that they can generate their own body heat to maintain a relatively constant internal body temperature, even in the freezing Arctic environment.
2. Fur: Polar bears have thick layers of fur that provide insulation and protection from the extreme cold. Their fur consists of two layers: a dense underfur that traps air for warmth and a longer, coarser outer fur that repels water.
3. Lactation: Female polar bears produce milk to feed their cubs. Milk production is a defining characteristic of mammals, as it allows mothers to nourish and nurture their offspring until they can become independent.
4. Live Birth: Polar bears give birth to live young rather than laying eggs. They have a reproductive cycle that includes gestation, birth, and nursing, which is characteristic of mammals.
5. Care for Young: Polar bear mothers exhibit maternal care, nursing their cubs, protecting them, and teaching them necessary survival skills, such as hunting and navigating the icy environment.
6. Hair or Fur: Mammals, including polar bears, have hair or fur that covers their bodies. Hair provides insulation, protection, and assists with thermoregulation, helping polar bears adapt to their cold habitat.
7. Homeothermic (Warm-blooded) Metabolism: Mammals are endothermic, which means they are able to maintain a relatively constant internal body temperature regardless of the temperature of their surroundings. Polar bears use their thick fur, layers of fat, and efficient metabolism to regulate their body temperature.
These specific characteristics, among others, collectively define polar bears as mammals. Mammals are a diverse group of animals with unique adaptations that enable them to thrive in various environments, and polar bears are remarkable examples of mammals adapted to the challenging conditions of the Arctic.