Sea Sabres Scuba Diving club, Southern
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BRYDE'S WHALE
(Balaenoptera edeni)
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FAST FACTS |
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Order: Mysteceti (baleen whales) |
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Family: Balaenopteridae (rorquals) |
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Length: 45 feet |
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Weight: 14 tons |
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Longevity: Up to 72 years |
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Gestation: 12 months |
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Calf Size: length 4 m, weight ? kg |
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Sightings: Bryde's whales live in all oceans, in the
tropics and sub-tropics |
Appearance
Bryde's
whales named after Norwegian whaler
Johan Bryde, occur
in tropical and sub-tropical latitudes in the Indian Ocean and can be seen
anywhere along the south-eastern Cape coast. But as with most baleen whales,
the best sites are capes or promontories, such as Robberg. This is especially
so during autumn and early winter, when shoals of small fish are plentiful inshore
and are easily spotted by the diving gannets associated with them. When seen at
sea, Bryde's whales are difficult to tell apart from some other rorquals, such
as minke and sei whales. But, they are most likely to be confused with minke
whales, because both have prominent dorsal fins. Minke and Bryde's whales can
also be distinguished by their feeding patterns. Minke whales swim rapidly at
the surface, on the perimeter of fish shoals, taking fish on the outside of the
shoal. In contrast, Bryde's whales can be seen lunging up through shoals,
sometimes exposing the whole head with the mouth massively distended and
scattering any penguins and gannets in the way. The upper body of Bryde's
whales is dark grey and often has a 'blotched' appearance. In relation to the
body, the dorsal fin of Bryde's whales is large and upright, making them look
more like huge dolphins than whales. 3 parallel longitudinal ridges on head -
falcate dorsal fin - slender grey-chocolate, sometimes mottled, body -
back and tail strongly arched on diving - flukes rarely appear - inquisitive -
may breach vertically thin not clearly visible blow (3 m)
Behaviour & Feeding
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Little is known of the biology of Bryde's
whales. Off the south-eastern Cape coast there appear to be two populations or
stocks. One is seemingly 'resident' (non-migratory) in inshore, shallow waters,
where shoals of small fish are likely to be abundant. The second appears to be
an offshore stock, possibly undertaking seasonal migrations and occurring here
only in spring and summer. Although Bryde's whales from elsewhere are known to
feed on small crustaceans (euphausiids) and small shoaling fish, the inshore
'resident' stock apparently feed exclusively on small shoaling fish, mostly
pilchards, anchovies and maasbanker. Bryde's whales are usually seen singly,
although small groups may form during feeding. They are not particularly fast
swimmers, attaining speeds similar to humpback and minke whales, but they can
move rapidly when disturbed. Equally, they are not deep divers, usually
spending no more than about two minutes underwater, although dives as long as
four minutes have been recorded.
Reproduction
In
the North Pacific, Bryde’s whales have a definite breeding season and though
very little is known of their reproductive cycle in this area, the 'resident'
stock presumably mates and gives birth here. After a gestation period of about
one year, females give birth to a single calf of about 4 m, that is suckled
during the following year, before she once again falls pregnant.
Threats
None known. Whaling for this species was generally only
on a small scale and no populations are known to have suffered serious
depletion.
Conservation Status: Insufficiently known - although it is suspected that this
species may be Endangered, Vulnerable or Rare, there is insufficient
information available to place it any of these categories.
Subspecies
Possibly two (offshore and inshore), and maybe a third, dwarf subspecies around
the Solomon Islands.
Recent
genetic analyses conducted on this species by Dr. Andy Dizon, has revealed that
the Bryde's whale is not a single species, but in fact two, a 'regular' and a
'pygmy' form. The pygmy averaging one to two meters shorter in length.
Remarkably, DNA sequencing of the two species has proven them to be more
distantly related to each other than either one is to the Sei whale. To make
matters more complicated, the regular Bryde's whale appears to consist of two
types, an 'inshore' and an 'offshore' form, which differ is distribution, movement
and ecology.
Bryde's whales were
not recognized as a separate species until 1878, and confusion reined long
after that. As a result of several decades of misidentification, catch
statistics for this species are greatly confused and it is impossible to know
how many of each form of these whales were actually killed and indeed how many
are left today.
Good Additional Reading:
http://www.pbs.org/odyssey/odyssey/20030203_log_transcript.html
Hawaiian Stock:http://www.nmfs.noaa.gov/prot_res/PR2/Stock_Assessment_Program/Cetaceans/Bryde's_Whale_(Hawaii)/PO00brydeswhale_hawaii.pdf
Posted March 5, 2003
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