* Larger sharks: Great white sharks, blue sharks, and mako sharks have been known to prey on harbor porpoises.
* Killer whales: Killer whales, being apex predators, are capable of hunting and killing porpoises, though this is not a common occurrence.
* Other marine mammals: Occasionally, other large marine mammals like seals or larger dolphins might prey on young or injured porpoises.
It's important to note that human activities are a major threat to harbor porpoises, even more so than natural predators. These threats include:
* Bycatch: Getting caught accidentally in fishing nets.
* Pollution: Pollution from chemicals, plastic, and noise can harm and kill porpoises.
* Habitat loss: Coastal development and pollution can degrade their habitat and make it difficult for them to survive.
Therefore, while natural predators exist, human activities pose a much greater threat to the survival of harbor porpoises.