On the west coast of Canada there are two distinct communities of killer whales. These two communities are genetically identical, they are one species. One of the communities are termed the “local Pods”, (a pod is an extended family group). The other community are called the “Transient Pods”.
The local pods eat exclusively fish, occupy a set range of several hundred square miles, and cavort with delight whenever they meet another “local pod”. The “transient pods” eat almost exclusively marine mammals, such as seals, dolphins, and sea lions. The Transient pods do not occupy a set range, but travel extensively, and avoid any contact with the “local pods”. It’s like the nexus of a species split. In ten thousand years, perhaps these will be two closely related but distinct species, with minor adaptations for their different lifestyles.
I watched a documentary which was made on the west coast, it was following a happy little pack of dolphins. According to the people who inhabited that particular stretch of coastline, transient whales had never been seen in their coves and inlets. The dolphins spotted the killer whales, and didn’t really react, figuring them to be fellow fish eaters. The film follows the killer whales getting very close before the dolphins begin to react. Then the s–t really hits the fan, dolphins start leaping out of the water, left, right, over the boat, it was amazing. The documentary ended with the observation of a new behavior the dolphins had adopted. They had begun harassing pods of local killer whales, probably in revenge for the attack from their cousins the transients, however if a transient pod appeared, the dolphins vanished.