A group of whales is commonly referred to as a pod and a pod usually consists a group of whales that have bonded together either because of biological reasons (i.e. a mother baring offspring and raising her child) or through friendships developed between two or more whales.
In many cases a typical whale pod consists of anywhere from 2 to 30 whales or more.
In some circumstances such as during mating season or in areas where large supplies of food are abundant thousands of whales may gather together to mate and forage separating back to their smaller pod or group once they’ve finished participating in an event.
Also the social behaviors of whales can vary dramatically from species to species and depending on the particular species of whale highly social species may have many pods that contain several hundred whales or more, while lessor social species may have a dozen or less whale in their pod.
In many cases larger pods or often found among the smaller toothed whale species as it helps them protect themselves and one another from predators, and allows them to hunt for food in a more effective manner.
The larger baleen whales tend to prefer small groups or traveling alone.
In fact some of the larger baleen whales are so big they don’t have any fear being attacked, so they can feel confident swimming alone or in small pods.
Whales that live and travel in a pod often hunt together using sophisticated and collaborative hunting methods.
While some adult whales may not have to worry about being attacked by a group sharks or a pod of killer whales their newborn children and young are often easy prey, so it is common to see adult whales (particularly female whales) traveling with their children in order to protect them from predators and threats, and in these cases the larger the pod the better, which helps explain (at least partially) why it is common to see smaller species in larger pods.
As far as parenting goes women are more likely to form pods with their children and other female whales in order to protect themselves and their children, while males are more likely to wander off on their own.
In these cases a small pod will consist of a mother and her child which can extend to larger protective groups if the species is a social one, and depending on the particular species some pods that are formed by a group of whales can last anywhere from a couple of days to a lifetime.