Are polar bears mammals?
Polar bears are mammals. Although polar bears live in the cold Arctic regions, they still have mammalian traits. First of all, polar bears have the basic characteristics of mammals, such as viviparous, hairy, homeothermic, etc. Secondly, polar bears reproduce viviparously, and their cubs are raised through breastfeeding. In addition, polar bears are also adaptable to their body structure, such as their heavy fur and fat layer, which can help them stay warm in extremely cold environments. Therefore, based on these characteristics and adaptations, we can conclude that polar bears are mammals.
Polar bears are one of the mammals. As mammals, polar bears have some basic characteristics, such as they are viviparous, with small cubs at birth that require the care and feeding of a mother bear. Additionally, polar bears' bodies are covered in thick hair, which helps them stay warm in extremely cold environments. 
Like most mammals, polar bears reproduce in viviparity, meaning that their offspring are relatively small at birth. However, polar bear cubs are able to snuggle up to their mother bears soon after birth, which helps them stay warm in cold environments. In addition to these basic mammalian characteristics, polar bears are also physically structurally adaptable, which can help them survive in extremely cold environments. For example, their heavy fur and fat layer provide great warmth, while their strong bones and muscles help them walk and hunt on ice. Therefore, based on these characteristics and adaptations, we can conclude that polar bears are mammals. 