50
MARINE MAMMALS OF THE WORLD
smaller and proportionately more
compact than true blue whales
Blue Whale
adult Pygmy Blue
Whale, 22 m
greyish/mottled body: can
appear pale grey, purple-grey or
blue-grey (all blue whales)
tiny nub-like (variable)
dorsal fin (all blue whales)
adult nominate race, 27 m
darker underbody
(all blue whales)
shorter and more
rounded rostrum
U-shaped,
elongated and
rather broad
rostrum
the largest whale with
massive elongated rear body
deep tailstock
relatively short and
slender tailstock
adult Pygmy Blue Whale,
dorsal view, 22 m
mottling ends, making head
appear dark (all blue whales)
massive shoulder and
splashguard (all blue whales)
adult nominate race,
dorsal view, 27 m
proportionately large flippers with distinct
kink to leading edge (all blue whales)
proportionately elongated
with slender rear body
Tall, columnar blow; massive shoulder/splashguard emerge; in prepararing for deep dive, body rolls, tiny dorsal fin briefly
emerges, and tailstock is strongly arached; flukes occasionally lifted.
built, with narrower heads
and more prominent, less
set-back dorsal fins, stronger
dorsal/ventral contrast,
and very different dive
sequences/behaviour.
Pygmy Blue Whale (brevicauda)
breaks the surface with the rostrum/
splashguard and shoulders; blow dis­
persed by wind.
Blue Whale (nominate) in smooth mid-body roll. Pale/greyish-mottled coloration and diagnostic miniature dorsal fin set well back.
Below: Fluking Blue Whale. Note underside pattern (cf. Fin Whale).
Variation
Age/sex Perhaps estimable
by size. Physical notes
20–33.6 m and 80–150
(exceptionally 190) tons
(the largest whale); ™ slightly
larger than ¢. Newborn
6–7 m and 2.5–4 tons.
Taxonomy Varies in size and
coloration, both individually
and geographically. Status
of the various forms
highly controversial and
information to permit atsea identification lacking.
However, at least Pygmy
Blue Whale B. m. brevicauda,
of S Hemisphere, may merit
specific recognition. Other
forms include B. m. intermedia
(Southern Blue Whale) in
S Hemisphere (north to
22ºS off S America and
6ºS off W Africa, though
winter/breeding range
almost unknown), B. m.
indica (Indian Ocean Blue
Whale) in N Indian Ocean,
and nominate B. m. musculus
(Northern Blue Whale) in
N Hemisphere. B. m. indica
seems morphologically and
genetically close to, or even
the same as, brevicauda (the
name indica has priority).
The N Indian Ocean whales,
however, have a limited
range and seem to undertake
a rather unique migration.
Hybrids: Blue × Fin recorded
in N Atlantic (with fertile
offspring), and possibly Blue
× Humpback in S Pacific.
seas where winters and
breeds. Population Perhaps
fewer than 10,000, of
which c.5,000 in S Indian
Ocean and 710–1,255 in
Antarctic waters, whilst in N
Hemisphere largest numbers
in NE Pacific, where c.3,000
(of which c.2,000 summer
off California); c.400 in NE
Atlantic, off Iceland and in
adjacent waters, and 350+ in
NW Atlantic.
Ecology
Usually encountered alone
or in twos. Migrates in
groups of 2–3, rarely more;
loose aggregations of up
to 50 on feeding grounds,
Distribution & population
Separate populations in N
Pacific, N Atlantic, Indian
and Southern Oceans;
mainly in cold waters
(sometimes near polar
ice) and open ocean, but
also inshore, at edge of
continental shelf, where
feeds and possibly breeds.
Migrates between summer
feeding areas and warmer
Pygmy Blue Whale (brevicauda) is
relatively compact in structure and
length.
Pygmy Blue Whale (brevicauda) has a pale-mottled body and tiny dorsal fin set well back.
51
RORQUALS WITH STREAMLINED BODIES