Every animal has to balance the cost of foraging, with the benefit of what they get out of it. They have to make sure the effort is worth the reward! For predators, this means how much energy they expend in the hunt, vs. how much energy they are getting out of the prey the capture. Harbor porpoises generally feed on a lot of small fish, but have a very high metabolism. So they need to eat a lot, and that takes time. In this paper we discuss why this seemingly not effecient strategy is actually pretty effecient and why. For harbor porpoises this strategy is energetically pretty cheap, if not time consuming!

Paper is freely available here: https://www.science.org/doi/full/10.1126/sciadv.adj7132