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Several types of dolphins can be found in the ocean waters off Costa
Rica’s shores. While the killer whale (not really a whale), bottlenose
and spotted dolphins are the most common, the rough-tooth and risso
dolphins, pilot whales, pseudo orcas (false killer whales) and
melon-headed whales are also somewhat commonly sighted.
The Killer Whale:
The
killer whale, the largest member of the dolphin family, weighs between
4-8 tons with length of 22 to 30 feet, with the males typically being
larger than females. Killer whales do not migrate like the humpback
whale, but do have seasonal movements related to prey and other
environmental factors.
They live in pods of 5 to 70 individuals and are thus very social animals.
Killer
whales have a wide variety of behavior ranging from transient groups to
residential and offshore pods. Transient groups travel long distances
in unpredictable patterns and smaller numbers feeding on other mammals,
while the resident groups tend to travel in more predictable locations,
eat mostly fish and tend to be more vocal. Transient dolphins have a
distinctly more pointed dorsal fin and are less vocal than the resident
groups. The rarely seen offshore groups travel in large numbers (up to
70) and feed on squid and fish.
Though not technically
endangered, some groups are threatened. The transient killer whales
are considered one of the most polluted animals on earth because PCB’s
tend to collect in their blubber as a result of eating contaminated
fish.
Bottlenose Dolphins:
Bottlenose
dolphins are commonly sighted along both of Costa Rica’s coasts. They
are characterized by their long, beak-like snout. They range in size
from 8.2 feet (2.5m) to more than 12 feet (3.7m) in length and can
weigh as much as 1000 lbs (454kg). Males are typically longer and
heavier as adults, but the females tend to grow more quickly as
juveniles until about 10 years in age.
Their bodies are gray
to gray-green on the back, fading to white or light pink on the belly.
This color design is known as counter-shading and is a form of
camouflage. When viewed from below the surface of the water, the light
color of the belly blends with the bright surface of the sea. When
viewed from above, the dark back blends in with the color of the ocean
and the depths below. Older animals sometimes have spotting along
their sides and bellies.
They have a very well developed and
acute sense of hearing and eyesight, but a limited sense of smell. They
breathe through their blowhole and hold their breath while under
water.
Bottlenose dolphins live in groups called pods and
are very social animals, actually having preferences as to with whom
they hang out. They develop strong social bonds, hunt, feed and play
together. They spend about 33% of their day sleeping. They are active
predators eating a wide variety of fish and crustaceans, averaging a
total daily consumption of 4-5% of their body weight.
Bottlenose
dolphins inhabit temperate and tropical waters throughout the world in
a variety of locations including pelagic zones as well as harbors,
bays, lagoons, gulfs, and estuaries. Dolphins of colder climates
demonstrate a clear tendency toward seasonal migration, which is highly
dependant on food availability. Those in warmer waters like those in
Costa Rica, show less extensive, localized seasonal movements.
Fortunately, bottlenose dolphins are not endangered and some populations are even growing in number.
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