What is the relevance of young animals in AC3

On occasion, I see bear cubs and fawn.

• Do they have a purpose other than adding additional realism to the game?
• Can they be hunted?
  • Are they worth more or less than adults?

Young animals can't be hunted. They are only a sign that larger game is nearby. This means that you can shoot at the baby animals and they will take no damage and will not die. Larger game is show with a white outline surrounding the animal. When you get to a baby that outline is not shown and thus you will not be able to use any attacks on it. There is a video below that shows the outline and the babies without one.