Summary: Large body size allows air-breathing vertebrates to increase
their oxygen stores and thus prolong underwater foraging
duration (Hochachka and Somero, 1984; Kooyman, 1989).
The largest air-breathing vertebrates are the blue whale
(Balaenoptera musculus) and the fin whale (B. physalus).
Adult blue whales average 24.7m in length and 92671kg in
mass, adult fin whales average 21.2m in length and 52584kg
in mass (Nishiwaki, 1950). Nonetheless, these two whales
spend no more time under water than smaller species diving to
similar depths (Croll et al., 2001).
Oxygen is a limiting factor in air-breathing vertebrates, and
some marine mammals, including the blue whale, glide during
a dive, a behavior that appears to reduce oxygen consumption
(Williams et al., 2000; Davis et al., 2001; Nowacek et al.,
2001). The amount of time that a diver is able to remain under
water relying solely on its oxygen stores is called the
theoretical aerobic dive limit (TADL) and is calculated by
estimating the oxygen stores and diving metabolic rate of a
species, usually on the basis of body mass (Kooyman, 1989;
Boyd, 1997). The TADLs of blue and fin whales are 31.2 and