- Competition for resources: Killer whales and porpoises are both top predators that compete for the same food sources, such as fish and seals. By killing porpoises, killer whales can reduce the competition for these resources.
- Play and socialization: Killer whales are highly intelligent and social animals. They may engage in hunting and killing other animals as part of their play or social behaviour.
- Hunting practice: Killer whales may use porpoises as practice targets for their hunting skills. This allows them to hone their skills and become more effective predators.
- Teaching behaviour: Older killer whales may teach younger killer whales how to hunt by allowing them to practice on smaller animals, such as porpoises.
- Communication: Killer whales may kill porpoises as a way to communicate with other killer whales. For example, a killer whale may kill a porpoise and bring it back to its pod as a gift or as a way to show its dominance.
- Retaliation: In some cases, killer whales may kill porpoises in retaliation for past interactions. For example, if a pod of porpoises has been harassing a pod of killer whales, the killer whales may retaliate by killing some of the porpoises.
