The diving behavior of blue and fin whales: is dive duration shorter than expected based on oxygen stores?

Many diving seabirds and marine mammals have been found to regularly exceed their theoretical aerobic dive limit (TADL). No animals have been found to dive for durations that are consistently shorter than their TADL. We attac hed time-depth recorders to 7 blue whales and 15 fin whales (family Balaeno pteridae). The diving behavior of both species was similar, and we distingu ished between foraging and traveling dives. Foraging dives in both species were deeper, longer in duration and distinguished by a series of vertical e xcursions where lunge feeding presumably occurred. Foraging blue whales lun ged 2.4 (+/-1.13) times per dive, with a maximum of six times and average v ertical excursion of 30.2(+/- 10.04) m. Foraging fin whales lunged 1.7 (+/- 0.88) times per dive, with a maximum of eight times and average vertical ex cursion of 21.2 (+/-4.35) m. The maximum rate of ascent of lunges was highe r than the maximum rate of descent in both species, indicating that feeding lunges occurred on ascent. Foraging dives were deeper and longer than non- feeding dives in both species. On average, blue whales dived to 140.0 (+/- 46.01) m and 7.8 (+/- 1.89) min when foraging, and 67.6 (+/- 51.46) m and 4 .9 (+/-2.53) min when not foraging. Fin whales dived to 97.9 (+/- 32.59)m a nd 6.3 (+/-1.53) min when foraging and to 59.3 (+/- 29.67)m and 4.2 (+/-1.6 7) min when not foraging. The longest dives recorded for both species, 14.7 min for blue whales and 16.9 min for fin whales, were considerably shorter than the TADL of 31.2 and 28.6 min, respectively. An allometric comparison of seven families diving to an average depth of 80-150 m showed a signific ant relationship between body mass and dive duration once Balaenopteridae w hales, with a mean dive duration of 6.8 min, were excluded from the analysi s. Thus, the short dive durations of blue whales and fin whales cannot be e xplained by the shallow distribution of their prey. We propose instead that short duration diving in large whales results from either: (1) dispersal b ehavior of prey; or (2) a high energetic cost of foraging. (C) 2001 Elsevie r Science Inc. All rights reserved.