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Illustration:
Les Gallagher ©ImagDOP
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Pilot
Whale
Globicephala macrorhynchus & G.
melaena
The name Pilot Whale is used for two species that are very similar and not
easily distinguishable at sea, where the species occur simultaneously. In
the case of the Azores the animals that are usually seen belong to the species
Globicephala macrorhynchus (Tropical Pilot Whale) but it's possible
that the second species, the Long Finned Pilot Whale (Globicephala melaena)
also visit our waters from time to time. The most conspicuous external characteristic
to distinguish between the two species is the length of the pectoral fins,
that is much longer in the case of the Long Finned Pilot whale. Nonetheless,
this characteristic can only be used by experienced observers and in very
special conditions, e.g. when the water is very clear and the animals come
close to the boat , or when they spyhop with the pectorals clear of water.
The males of these species have an average length between 5 - 6 m (16.4 -
19.7 ft) and weight 3 tons and the females measures from 5 - 5.5 m (16.4 -
18 ft), but important populational variations may occur in different areas.
The almost flat forehead and the wider and curved dorsal fin help to distinguish
these species from the similarly dark False Killer Whales.
The species are very gregarious, and can sometimes form groups with hundreds
of individuals, but normally travel are seen in smaller numbers. They associate
with other species, e.g. Bottlenose Dolphins. The social structure of the
groups is very complex, but it appears that there is no sexual or age segregation.
Both species prey essentially on squid, and dive at great depths (at least 600 m - 1970 ft) where the echolocation must play an important role to find the food, due to the complete darkness of these depths.
While very similar in their appearance, the two species have different distributions that overlap only in few areas. In colder waters is more likely that we would find the Long Finned Pilot Whales, while the Tropical Pilot Whale prefers warmer waters.
This difference in temperature
preference will be reflected on the reproduction, since most of the births
of Long Finned Pilot Whales occur between the Spring and the Summer and there
seems to be no peak of births in the Tropical Pilot Whales, that occur throughout
the year. The gestation in both species varies between 15 and 16 months and
the calves measure between 1.4 and 1.7 m (4.6 - 5.6 ft) at birth. The calves
are waned when they are about two years old.