No, polar bear is a common noun, a general word for a type of bear. A common noun is capitalized only when it is the first word in a sentence.
A proper noun is the name of a specific person, place, or thing, such as Polar Bear International (conservation organization) or Polar Bear Drive, Westford, MA.
Yes, "Polar Bears" should be capitalized as it is a proper noun referring to a specific species of bear found in the Arctic region.
Polar bears are solitary creatures; normally the only group of polar bears is a mom and some cubs, a family group. However, when several polar bears do end up together, the collective nouns are an aurora of polar bears or a pack of polar bears. Although pack is one of the collective nouns given, I believe that it's a misnomer since a pack infers a group working together like a pack of dogs, wolves, or coyotes. But even when polar bears are together, they don't work together.
polar bears are related to bears.
They reproduce.
Polar bears do.
POLAR BEARS Polar bears actually grow pretty fast.
Polar bears are mammals.
humans are polar bears
Polar bears are bears
A sleuth or a sloth of bears
There are no polar bears in Antarctica. If there were, they would eat the penguins.
Polar bears are animals of Arctic regions. The only polar bears here are in the NC Zoo.