Fig. 8. Relationship between dive duration and respiration rate for singing and foraging humpbacks. Data for foraging whales are for MnA (gray circles) and MnB (black circles) and data for four singing humpback whales are shown as open symbols (Chu, 1988). Dive duration increased with the number of breaths taken after that dive (MnA, y=5.450–0.409x+0.155x²), r²=0.77, P<0.001; MnB, y=4.085–0.908x+0.207x², r²=0.62, P=0.005). Note that the longest singing dives (20 min) are approximately twice as long as the longest foraging dives (10 min). Also, at dive durations of 10 min, the number of breaths taken is three times higher during foraging.