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DOLPHINS
Dolphins
are mammals, not fish. They are warm blooded like man and give birth to one baby
called a calf at a time. They are highly sociable animals living in pods with
dolphins from other pods interacting with each other from time to time.
Dolphins
use their powerful tail flukes in an up and down motion to move through the
water. They also use their tails when hunting, hitting a fleeing fish up into
the air with their tail, stunning it, then scooping the fish up when it falls
back into the water. A dolphin slapping its tail on the water in the wild may be
a sign of annoyance, or a warning to other dolphins of danger.
Their
pectoral flippers are used to steer them through the water, and they also use
them to stroke one another, increasing the social bond between them. Dolphin
"friends" may swim along face to face touching flippers. Dolphins that
appear to be closely bonded may swim in synchrony, twisting, turning and
swimming in perfect harmony together.
In
terms of their feeding habits, all dolphins are carnivores.
They eat mostly a variety of fish and squid, but depending on what
part of the ocean they live, some have
a more varied diet including fish, squid, crabs, shrimps, octopus, and lobsters.
A
dolphin's cone-shaped teeth interlock to catch fish. Their teeth are not used to
chew, and they swallow their food whole. Their teeth are interlocking rows of
conical pegs, suitable for holding slippery fish. They eat their fish whole,
headfirst. In the wild an open mouth is a sign of aggression, as is head
nodding. A sign of greater aggression is violent jaw clapping.
Dolphins
and porpoises are not the same animal. They
have different body shapes. Dolphins usually have a large forehead. The easiest
way to tell them apart is to look at their teeth. All dolphin teeth are round.
All porpoise teeth are flat. In
Destin, there is an easier way - porpoises do not live in our waters, so you
know you are looking at a dolphin.
Looking
at a dolphin you would not think it has a nose, but it does. Dolphins breathe
through their blowhole located at the top of their head. Their nostrils are
their blowholes. Over millions of years of evolution, whales and dolphins
nostrils moved to the top of their head. This allows them to breath by surfacing
instead of them sticking their whole head out of the water. A dolphin may empty
and refill its lungs in less than a fifth of a second. As the dolphin breathes
the air leaves the blowhole at speeds of over 100 mph. Complex nerve endings
around the blowhole sense pressure changes so the dolphin knows exactly when the
blowhole is in or nearing the air and can be opened. Water in a dolphin's
blowhole will actually drown it so powerful muscles close the blowhole as it
dives under the water again. If
another dolphin is drowning, other dolphins will come to its aid, supporting it
with their bodies so it's blowhole is above the water allowing it to breathe.
The
dolphin's eyes produce a special slippery secretion that protects the eyes from
foreign objects and water friction. To sleep, a dolphin must shut down only half
of its brain, as it’s breathing is under voluntary control. Dolphins take
short catnaps floating just below the surface, and then slowly rising to
breathe. Often dolphins are very active during nighttime for some this is their
main feeding time.
Dolphin's
ears are barely noticeable marked only by a small hole just behind the eye. In a
bottlenose dolphin the ear is about 5-6 cm. behind the eye and only 2-3 mm in
diameter.
The
dolphin's skin is completely smooth allowing the dolphin to move easily through
the water, and also reduce heat loss. Unlike most mammals, a dolphin's skin is
hairless, thick and lacks glands. It is also kept smooth by constantly being
sloughed off and replaced. A bottlenose dolphin for example, replaces its
outermost layer of skin every two hours. This is nine times the rate of human
skin renewal. A drawback of their smoothness, however, is that their skin is
easily scarred. Their skin may bear rake marks from other dolphins’ teeth
during play or mating. Virtually
all adult dolphins have an array of scars, notches and nicks that they acquired
through interactions with companions, enemies or the environment. Scars on
dolphins are so prevalent, in fact, that researchers often rely on them as a
means of identifying individual animals. Their
smooth skin can also become badly sunburned.
The
life cycle of dolphins is similar to that of other cetaceans. As mammals,
dolphins bear live young and the mothers nurse them on milk and provide care. Dolphins
carry their young inside their womb and gestation is about 12 months for a
bottlenose. At birth a bottlenose dolphin calf is about 90-130 cm. long and will
grow to approx. 4 meters. A
dolphin calf is born tail-first with eyes open, senses alert and enough muscular
coordination to follow its mother immediately. At birth, the mother helps her
calf to the surface to get its first breath. It
will suckle from its mother for about 1½ to 2 years or even as long as 4 years.
The baby will stay with its mother for between 3-8 years, during which
time it learns all about feeding techniques, social interaction and group
foraging. There is some
variation in the age at which sexual maturity is reached, the reproduction rate,
and the life expectancy among the different species of dolphins. Most species
tend to bear one calf every other year or so during their reproductively active
years and are believed to have an average life expectancy of 30-40 years. Females
are likely to stay within the family pod with their mother and sisters, though
males will leave and form associations with other males.
Dolphins
are characteristically very social creatures and often depend on social
interaction for the purposes of hunting prey, defense, and reproduction. They
have defined home ranges, an area in which they will roam and feed. Though
dolphins live in small groups called pods, these pods can be quite fluid and
dolphins can be seen interacting with dolphins from other pods from time to
time. Many dolphin groups appear
to have rigid hierarchies of power with a few individuals considered dominant.
Large groups are often mixed in terms of age and sex, but smaller groups are
generally one of three types: 1) a nuclear group, comprised of a single adult
male and female; 2) a nursery group, consisting of a number of females and
young; and 3) a bachelor group comprised of adult and younger males. Regardless
of the type, all groups of dolphins seem to have well-developed skills in
cooperating and working together as a team whether it be for the purpose of
finding food, mates or caring for their young.
Dolphins’
main predators are sharks and unfortunately man, through direct killing for
food, netting, pollution, and fishing. Dolphins spend a large part of their day
looking for food or actually feeding. They may either hunt alone or together as
a pod. They use their echolocation (sonar system) to locate fish by sending out
a stream of pulses and clicks.
Dolphins
communicate with each other by whistling or body language. When a baby is first
born, some dolphin research suggests a mother dolphin will whistle to it
constantly, imprinting her sound on the baby so it will recognize her, and the
baby learns to develop its own signature whistle. It is thought that each
dolphin has its own individual signature whistle, just like a name.
A dolphin's sound probably originated in its nasal passages. These nasal
passages are located on the top of the head. Dolphins can make sounds to see
what lies ahead. This sense is called echolocations.
Echolocation is a process where a dolphin emits a steady series of
split-second "clicks" through its blowhole. The dolphins' sound waves
hit an object and the echo bounces back. The
"clicks" are pulses of ultrasonic sound (sounds repeated as rapidly as
800 times/second) produced in a dolphin's nasal passages and focused in a large,
lens-shaped organ in the forehead known as the melon.
The melon concentrates the sound pulses into a directional beam. When the
outgoing sound waves or "clicks" bounce off objects in their path, a
portion of the signal is reflected back to the dolphin. The bony lower jaw of
the dolphin receives the incoming sound waves and transmits them to the inner
ear where they are converted into nerve impulses and then transmitted to the
brain. Echolocation sounds are called sprays. Sprays are so strong they can stun
a whale. Dolphins don't "point" their melon at any other sea life
except their enemies. Using this amazing skill, a dolphin can create an acoustic
picture of its surroundings and can determine the size, shape, direction of
movement, and distance of objects in the water. This permits dolphins to hunt
prey over a greater range than the limits of visibility allow.
Even
though dolphins are warm-blooded and their internal temperature is about 98
degrees, they need to conserve their body heat in colder water. Just like a
whale, the dolphin's body is surrounded by a thick layer of fat (called blubber)
just under the skin that helps keep the dolphin warm.
Dolphins
are fast swimmers. When a speeding boat passes the bottlenose dolphin, it will
start to race out in front. They will take off hitting the water and keep going.
Bottlenose dolphins typically swim at 3 to 7 miles per hour. They can go over 20
miles per hour when they work hard. The body shape of a dolphin helps it swim
fast. A dolphin's body is shaped like a tube that is pointed at both ends. This streamlining
helps the water flow over the dolphin's body as it swims.
Their smooth skin also increases dolphins' swimming speed by reducing
their drag in the water. Coastal species that feed on slow moving prey rarely exceed
speeds of 10 mph, and oceanic species that feed on fast-moving fish generally
attain speeds of 15 mph, although bursts of speed up to 25 mph have been
recorded. The way that dolphins are able to achieve such high speeds is by
leaping from the water in a series of dives and spending as little time as
possible under the water. This is known as "running". Dolphins can
attain greater speeds by riding the bow wave of a fast-moving vessel than they
are able to on their own.
Bottlenose
dolphins are shallow divers and typically don't go deeper than 150 feet.
Dolphins navigate by following the hills and mountains of the ocean floor, by
tracking the sun, by sensing currents, and by tasting the water along the
journey.
As anyone who has had the
opportunity to watch dolphins perform in a show can attest, dolphins have an
impressive ability to learn and imitate behaviors, often for what appears the
sheer pleasure of doing so. We
all love to see dolphins and for many people the only way in the past to do this
was by visiting an aquarium. However, aquariums varied in their care and housing
of the dolphins in the past, and some may have been quite substandard.
Tragically, in the past, many of these dolphins were mostly
violently
captured from the wild, taken away from their families and forced to live in
small barren tanks. Records show that at least 2700 bottlenose dolphins have
been taken into captivity worldwide. Statistics (from Dolphin Project Europe)
say that 53% of captive dolphins that survived the violent capture died within
90 days and that half of all captured dolphins died within their first two years
of captivity. Those that did survive longer lasted an average of only 5 years.
Every seven years, half of all dolphins in captivity used to die from capture
shock, pneumonia, intestinal disease, ulcers, chlorine poisoning, and other
stress-related illnesses.
Dolphin’s
impressive ability to learn and imitate behaviors coupled with their large brain
size has led to numerous studies of dolphin intelligence. Dolphins' brains are
about the size of our own. Size alone, however, is not always a reliable
indicator of intelligence. Another characteristic used to determine the level of
intelligence is the amount of folding in the cerebral
cortex, the portion of the mammalian brain associated with thinking and
reasoning. A cerebral cortex, which is more deeply folded, has a greater surface
area available for thinking. Some species of dolphins have brains that are more
deeply folded than human brains, although the cortex itself is not as thick. The
level of folding in dolphin brains again suggests that they have a level of
intelligence comparable to ours.
When
discussing the intelligence of dolphins, or other species for that matter, it is
important to realize that the environment in which they live is often very
different from our own. We must be careful not to place our standards of
intelligence on other species, or assume that they "think" the same
way we do. Dolphins may require completely different types of mental abilities
for survival in their watery home. Sound and light, for instance, travel very
differently in water than they do in air. The speed of sound in water is roughly
four times greater than it is in air. In addition, sound waves are able to bend
around corners and pass through objects and can be detected at any time of the
day or night. On the other hand, water is much worse for vision as vision
depends on the presence of light, and the sea is generally dark and shadowy
except for regions near the surface. Although dolphins are believed to have
fairly good eyesight, their visibility is often limited by their dark and murky
environment. Not surprisingly, dolphins and whales have come up with an
efficient way to combat this problem. They tend to rely chiefly on their sense
of hearing to understand the world around them, much as humans rely on a
combination of sight, sound and smell.
The dolphins we will see today are wild animals. They swim freely without boundaries. Food other than
live fish or squid can make the animals very sick or even cause death.
Please, for the safety of the dolphins, do not throw food or anything
else to the dolphins.
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