Sperm Whale
Physeter macrocephalus
By: Poul Vendel
The look:
The sperm whale is relatively short and robust, but is the largest of the
toothed whales. The Sperm whale is unmistakable with its massive, square head
which make up about one third of the animal's total body (and contains the
spermaceti organ, a waxy substance different from oils of baleen whales which
probably plays a role in diving and focusing sound) and tiny lower jaw. They
have short, wide pectoral fins, a low hump in place of a dorsal fin, a dark body
with wrinkly skin and a single blowhole located on the left side at the tip of
the sout which produces a characteristic forward and angled blow.
A drawing of Sperm Whale
The size:
A Sperm whale grows between 15 and 18 metres in length and 20-50 tons in
weight.
Breeding:
Female Sperm whales are known to form large breeding schools of between
dozens and hundreds (which may include immature males), and they generally
inhabit warmer waters than males. Males form bachelor groups which contain
around 20 sexually mature males of about the same age and size. Males become
sexually mature at about 10 to 12 years, but it's not until they reach their
early twenties that they are able to compete for harems. Males will mix with
females, but only for a short period while they search for mates during the
winter breeding season. The gestation period is long, about 15 months, with the
female giving birth to a 4 metre long calf in around March. Calves are sucked
for 2 to 3 years and females calve every three to six years.
The location in Africa:
Sperm whales are generally deep water animals (deeper than 300 m) and rarely
travel over the continental shelf. They are not generally seen from shore, but
can sometimes be seen from the "Gates" at Port St. Johns. Sperm whales
migrate northwards into the South Atlantic and Indian oceans in autumn and
return in Spring. Females and small males appear off the Cape West and
KwaZulu-Natual coasts in February (with numbers peaking in April) and males peak
a month or two later.
Interesting facts:
Sperm whales seem to have a bad disposition, and there are many accounts of
them ramming ships with their heads and striking them with their tails and even
attempting to bite with their teeth. Many towing-boats were capsized by irate
sperm whales during the early times of whaling. Herman Melville's book Moby Dick
is based around a giant white sperm whale. Sperm whales have between 18 and 30
large conical teeth in the lower jaw and feed mostly on squid, but will eat
midwater fish, octopus, skates and sometimes sharks. They consume between 150
and 300 kg of food per day (3 to 4 percent of their body weight), including
giant squid which have been known to measure nearly 19.5 metres in length and
weigh over 180 kg. They sometimes remain motionless at the surface, but they are
excellent divers, routinely diving 800 metres, with adults males diving to more
than 3 000 metres. This means that in tropical water the whale will dive from
the sunlit surface that may be 25 degrees C to just above freezing, total
darkness and extreme pressure. Dives are known to last over 2 hours. Sperm
whales communicate by means of clicks that can be heard from up to 10 km away
underwater. The oil or spermaceti that's found in the whale's head may be used
to focus these sounds. Research has shown that the clicks probably communicate
complex behavioural information and coded identification.
Human impacts:
Human impacts in African waters are unknown.
Status:
Insufficiently known.
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