Fig. 2. Time spent at the surface relative to dive duration. (A) Blue whales; (B) fin whales. For clarity, we depict only non-foraging dives and three-lunge foraging dives. The different slopes between non-foraging and foraging dives indicate that lunge-feeding incurred a cost. Dashed lines, open circles, non-foraging dives; bold solid lines, filled circles, three-lunge foraging dives. The thin solid lines indicate the predicted surface time according to different values of the cost of foraging relative to the cost of traveling to and from the prey patch. Note that for three-lunge foraging dives the relative cost of foraging appears to be 3 for both species.