The most distinctive feature of a Sperm whale is its very large, rectangular head, which can be as
long as one third of the total body length. Despite the unusual size, the head of a Sperm whale looks quite narrow
when seen from above.
As it often happens for cetaceans, the name "Sperm whale" comes from the acute scientific sense of observation of
whalers. The head of a Sperm whale does in fact contain huge amounts of an oily, withish substance called
Spermaceti, which whalers mistook by sperm. Later scientific investigation made it clear that both
male and female Sperm Whales have Spermaceti in their head.
The function of spermaceti is still matter of debate among researchers, but it seems this very fine oil plays a role
in buoyancy control (while diving) and in focusing echolocation waves.
A second very distinctive feature of this species is the asymmetric positioning of the blowhole, which is well
displaced forward and on the left, making it easy to recognise the blow of a Sperm Whale especially when
right in front or behind the animal, as it really sprays at an angle of about 45° forward and on the left.
The Sperm Whale lacks of a true dorsal fin, having instead a series of "knuckles" on its back,
the first of which is taller than the others.
Among mammals, Sperm Whales are the undiscussed masters of diving. They regularly reach depths of
1000-2000m while hunting, and it seems that even depths of more than 3000 metres are not beyond their phenomenal
abilities. As a result of Sperm whales regularly being recorded hunting deeper and deeper, it now seems quite clear
that their depth limit must be dictated more by the amount of oxygen they can take with them while diving rather than
by the amazingly high pressures they must stand.
Most noticeably, the Sperm whale can dive for longer than 2 hours on a single breath!
When back from a deep dive, Sperm whales spend 10 to 40 min at surface, which allows them to re-oxygenate their body.
It is indeed the condition most Sperm whales are seen by Whale Watchers, when the animal is foating almost motionless
while catching its breath, showing only about 10% of its body.
Before diving again, the Sperm whale arches its back and dives alomost vertically, rasing its flukes well above the
surface to gain a big push from gravity force.
Male Sperm whales are bigger than females, which is common feature among Odontoceti (toothed whales).
Females also have smaller heads. In both sexes the skin is very wrinkled over the middle part of the body, making it
Sperm Whales have teeth in their lower jaw only, in numbers of 36 to 50, which can be up to
25cm (10in) long. Despite their large teeth, Sperm whales are believed to feed mostly by suction.
Indeed, it has been observed at least in one case that a naturally injured animal, lacking its lower jaw,
is still able to feed efficiently.
The Sperm Whale's migratory routes and habits depend on both sex and age.
In the Southern Emisphere's summer, mature males move to Antarctica to feed. In most cases, they can be seen during
their journey in groups of one or two individuals, while females and young prefer to stay in warmer waters, forming
the so-called social groups. Mature males then join the social groups in winter, during the breeding season.
In most places where Sperm whales are known to live, it is not uncommon to be able to observe year-round quite
large groups of immature males sticking together, the group size decreasing as the youngsters grow and reach maturity.
Sperm whales also inhabit the Northern Hemisphere, with no noticeable habit differences to their "downunder" brothers
and sisters. Their summer migrations to rich feeding grounds, in this case, reach the high latitudes of Arctic waters.
While the above migration patterns are observed in both hemispheres, some Sperm whale populations are year-round
During the time of whaling, the Sperm Whale was among the most hunted cetacean species.
Luckily, it appears to be still quite abundant, even if the data collected are still insufficient to assess the real
health state of most populations.
Sadly, after decades of whaling, the average size of Sperm Whales has now decreased, and
the selective hunting of the largest mature males has afforded a male/female unbalanced ratio,
which may prevent (on a larger time scale than the one we can now take into account) the normal growth of this species.