Humpback Male whales compete with each other for females and also just with each other. Fighting pods are usually some of the last whales to appear towards the end of a whale season in Australia.
Fighting pods can be two whales, three, four or more usually large whales and they can be seen pushing and shoving each other around and butting heads. Pods of up to forty males in a competition or fighting pod have been observed in some parts of the world.
The action can get rough and unfortunately I have not been able to get photos of the really big guys steaming along but on this page are a few of just one fighting pod I witnessed.
This pod was comprised of 4 whales, they huffed and puffed and they are usually traveling fairly fast as they push each other around so spouts are frequent and the water can go white as they roll, push and shove.
They are probably seeing which whale is the fittest and the largest and therefore making themselves a superior male to mate with female Humpbacks in the area.
A male Humpback Whale can sustain injuries from this competition the barnacles under their mouths slice them open as they butt heads and push and shove each other.