From the Reef: A tale of two whale types
Contributed by Brent Chatterton.
Whales (crustaceans) are divided up into two main groups: those with teeth and those without.
Whales without teeth feed by filtering water containing food through curtains called ‘baleen’ up to 300 individual flattened plates, which hang from the roof of the whale’s mouth in the fashion of vertical blinds.
The inner surface of the plates is fringed with bristles, frayed at the edges like a worn paintbrush, which trap prey such as krill (shrimp-like crustaceans up to 5cm long), plankton or small fish.
These bristles gave these whales their scientific name, Mysticeti, which is Greek for ‘moustache whale’.
Although it is called whalebone, baleen actually consists of material similar to our fingernails.
It was once used rather as plastic is today (and particularly in women’s corsets).
Baleen can reach lengths of 60cm in humpback whales and 3m in right whales.
Baleen whales also have double blowholes.
Sunbathing whales are termed rorquals because of the deeply pleated skin on their throats.
The pleats can expand enormously (the blue whale may triple in bulk!) as the whale takes in large mouthfuls of water before forcing it out again through the baleen.
Rorqual whales recorded from Queensland waters include the humpback, two forms of minke, Bryde’s whale, sei and blue. The last two appear to be very rare.
Baleen whales without the extra pleated throat capacity (such as the right) simply swim along with their mouths open allowing water to flow through the baleen filters.
The other group, the odontocetes, have teeth and actively chase prey such as fish and squid (interestingly, the developing foetus of a baleen whale has tooth buds at early stages).
This group includes the beaked whales, killer whales, pilot whales, dolphins and porpoises and is characterised by a single blow hole.
Generally the larger whales are members of the baleen group, producing their massive bulk from the smallest prey.
Of the toothed whales the sperm whale is the only giant, measuring up to 18m in length.
That’s all for this week – see the reef, love the reef, protect the reef.