452
lL. Aroyan et al.
7. Supporting Evidence
7.1 Anatomical Air Volumes
The volume of the lungs and associated air chambers in blue whales provide
a check on the plausibility of the proposed sound production model. Large
whales' lung volumes have been reviewed previously (Lockyer 1981). Adult
blue whales found off California are typically about 21 m long (Gilpatrick
et al. 1995), and would have a lung capacity of about 2,0001. This estimate
is based on extrapolation from other mammals and agrees well with estimates based on nozzle-type flow volume calculations using blow rise times
and nasal passage dimensions combined with percentage estimates of expiration volume. A significant error may still exist in this lung capacity estimate as methods based on thoracic cavity volume are substantially larger.
Following the analysis of Lockyer (1981), we have largely discounted the
thoracic cavity volume estimates.
The capacities of the blue whale laryngeal sac and nasal passages are
somewhat less studied, requiring extrapolation from a combination of
related anatomical measurements. The descriptions of blue whale laryngeal
anatomy available to the authors (Turner 1870; Beauregard and Boulart
1882) are somewhat confusing due to the use of archaic Latin names. The
description of Beauregard and Boulart (1882) describes two animals, one
as a 12-m female B. musculus and another as a 3.6-m male fetus of B.
sibbaldi, though both Latin names are considered to describe blue whales
today (Tomilin 1957; True 1983), despite significant differences in the
appearance of the thyroid cartilage in these two animals. The description of
Turner (1870) is based primarily on a 5.9-m male fetus taken from an animal
that measured 24m on the curve of the back. References are also made to
an earlier description (Maim 1867) that was not available. The larger of the
two blue whale larynxes described by Beauregard and Boulart (1882) had
an incompletely preserved laryngeal sac, thus only the fetus provided a
complete laryngeal sac length. We prefer to infer likely dimensions of the
blue whale laryngeal sac primarily from a 17.75-m female fin whale, B.
physalus, (Purves and Pilleri 1983) having dimensions proportionally consistent with the smaller intact blue whale specimens described. From these
descriptions we infer a 21-m blue whale would have a laryngeal sac length
of 1.35 m, depth of 0.45 m, and width of 0.35 m for a volume of 210 I before
possible pressure expansion.
Although skull measurements for blue whales are relatively well
described (Omura, Ichihara, and Kasuya 1970), the dimensions of the nasal
passages through the skull are not included, and we have not found nasal
passage volumes described for any of the mysticetes. In order to estimate
the volume of the nasal passages, a blue whale skull, Los Angeles County
Museum # 72562, for which a photograph is published (Heyning 1995,
p. 78 foreground) was measured and checked against skull photographs
(Yochem and Leatherwood 1985). Uncertainty remains in the thickness of
lL. Aroyan et al.
7. Supporting Evidence
7.1 Anatomical Air Volumes
The volume of the lungs and associated air chambers in blue whales provide
a check on the plausibility of the proposed sound production model. Large
whales' lung volumes have been reviewed previously (Lockyer 1981). Adult
blue whales found off California are typically about 21 m long (Gilpatrick
et al. 1995), and would have a lung capacity of about 2,0001. This estimate
is based on extrapolation from other mammals and agrees well with estimates based on nozzle-type flow volume calculations using blow rise times
and nasal passage dimensions combined with percentage estimates of expiration volume. A significant error may still exist in this lung capacity estimate as methods based on thoracic cavity volume are substantially larger.
Following the analysis of Lockyer (1981), we have largely discounted the
thoracic cavity volume estimates.
The capacities of the blue whale laryngeal sac and nasal passages are
somewhat less studied, requiring extrapolation from a combination of
related anatomical measurements. The descriptions of blue whale laryngeal
anatomy available to the authors (Turner 1870; Beauregard and Boulart
1882) are somewhat confusing due to the use of archaic Latin names. The
description of Beauregard and Boulart (1882) describes two animals, one
as a 12-m female B. musculus and another as a 3.6-m male fetus of B.
sibbaldi, though both Latin names are considered to describe blue whales
today (Tomilin 1957; True 1983), despite significant differences in the
appearance of the thyroid cartilage in these two animals. The description of
Turner (1870) is based primarily on a 5.9-m male fetus taken from an animal
that measured 24m on the curve of the back. References are also made to
an earlier description (Maim 1867) that was not available. The larger of the
two blue whale larynxes described by Beauregard and Boulart (1882) had
an incompletely preserved laryngeal sac, thus only the fetus provided a
complete laryngeal sac length. We prefer to infer likely dimensions of the
blue whale laryngeal sac primarily from a 17.75-m female fin whale, B.
physalus, (Purves and Pilleri 1983) having dimensions proportionally consistent with the smaller intact blue whale specimens described. From these
descriptions we infer a 21-m blue whale would have a laryngeal sac length
of 1.35 m, depth of 0.45 m, and width of 0.35 m for a volume of 210 I before
possible pressure expansion.
Although skull measurements for blue whales are relatively well
described (Omura, Ichihara, and Kasuya 1970), the dimensions of the nasal
passages through the skull are not included, and we have not found nasal
passage volumes described for any of the mysticetes. In order to estimate
the volume of the nasal passages, a blue whale skull, Los Angeles County
Museum # 72562, for which a photograph is published (Heyning 1995,
p. 78 foreground) was measured and checked against skull photographs
(Yochem and Leatherwood 1985). Uncertainty remains in the thickness of