Breeding of Cetaceans- Dolphins
Breeding of dolphins in captivity is very complex and shape only rarely from success. The most dolphin cubs don't life long.
Cetaceans are mainly social animals, they are not solitary but
spend all of their lifes together in groups of varying numbers
ranging from a family of three to many hundreds. Because the oceans are so bountiful,
the cetacean population was very large. Unfortunately today, the situation
is rather different. Modern methods of hunting have decimated some
species to the point of virtual extinction, as in the case of the Baleen Whales.
Even if all whale hunting was stopped now, it would take over a hundred
years for some members of the mysticeti to significantly increase their
numbers. Once a population drops below a certain figure the chances
of finding a mate are significantly reduced, this is doubly so for Cetaceans
who life in the immensity of the oceans. Cetaceans are slow breeders,
only producing one offspring at a time, usually every other year and
even the shortest lifed do not start breeding until they are about five years old.
In order to reproduce, mammals have to mate. In order to mate, they
have to find a partner who is receptive or can be induced to become so.
This can be quite a problem when they life in an environment in which they
cannot see very far, or their nearest neighbour may be 150 miles away.
One said earlier that cetaceans travel in groups. They do, but a particular
group of Baleen Whales could be spread over an area of several hundred
square miles. The only method of communication between them is sound.
We have discussed the incredible hearing of these creatures before
and now it is perhaps time to go into some aspects of their speech. Cetaceans
produce sounds by passing air through various passageways in the head,
but unlike other animals, for reasons that may now be apparent to you,
do not actually expel air when they are vocalising. The air is only
being transferred from one cavity to another within the head and it is though
that the prominent bulge displayed on the forehead of some species,
acts as a lens concentrating the sound waves into a beam. These
20-Hz low frequency sounds can be heard over hundreds of miles between some of
the mysticeti and are the only means of communication between them.
Some of you may have heard a ballad that was often played on the radio
a few years ago which featured the song of the Humpback Whale. It had
a lovely haunting real whale accompaniment. What in fact you were listening
to was the mating call of this animal. It is a very peculiar fact,
but the song of the Humpback Whale may last as long as 30 minutes
without any repetition of the words at all. During a period of several weeks
the singing, which may last for twenty four hours at a time, is gradually
changed, each whale composing his own special version.
Once having found a suitable mate, the male cetacean puts on a display of diving
and leaping that has to be seen to be believed. Right alongside
the boat, one have seen Pilot Whales leaping as high as 12-15 ft out
of the water during such a display. The object seems to be to make
the biggest splash possible, the sound carrying a great distance underwater as
the impact is in the region of 2 tons. Eventually the female joins
in, the two quite literally making high speed passes at each other. Gradually
they come into physical contact, swimming belly to belly, sometimes
with their flippers around each other, this still being part of the courtship.
The actual method of mating varies from species to species, some couples
remaining stationary in the water in a vertical position whilst others
are horizontal. In some cases they may involve a very close friend
on the other side of the female to keep her pushed against the male.
The reproductive organs of cetaceans are not visible externally,
but for better streamlining are kept within slits in the body;
the male's some distance from the vent, the female's in close proximity. In her
case the two mammaries are also enclosed, and are in the same area.
Coition lasts for about 30 seconds, which may not seem very long, but the cetacean
is a very sexually active animal and may mate a dozen times a day.
It is also interesting to note that this high level of sexuality
is unusual in animals apart from man. One are afraid to say that in the case of
the Common Dolphins they are not too selective in choosing an object
for their sexual gratification. One have seen males chasing males and other
immature dolphins. The male dolphin is able to indulge in this high
level of sexual activity, as he has a muscular erected penis which he can erect
at will.
In the film "Ride a Wild Dolphin" shown by Yorkshire TV there is a lovely
episode, where Maura Mitchell is approached by Donald the Dolphin who
appears to be sexually aroused. One cannot say whether he was attracted
by her femininity or because he wanted to examine the texture of her
wetsuit in the only way he could. However ladies, if you are ever approached
by a friendly dolphin whilst swimming, please remember that they are
classed as Royal Fish and belong to the Crown. Complaints to Buck House
please!
The gestation period of cetaceans varies between 10 and 16
months. This is quite a short time for what can be a very large
animal and the foetus has to develop very rapidly. It also has to be
remembered that the new born baby is being born into a very hostile
environment and has to be completely formed and ready to swim alongside
his mother immediately. The trauma of being born is quite a shock to
all warm blooded animals and this must be doubly so for the cetacean,
who after emerging from the warm birth canal, finds that he is in
very cold surroundings and cannot breathe.
Cetacean births are usually breach presented to enable
the baby to stay inside the mother for as long as possible until
the process is completed. In some cases, upon separation, the
mother is assisted by other females who have been in attendance
during the birth, one or more of which will help to bring the
newborn baby to the surface and start it breathing. When this is
achieved and the mother is sufficiently recovered, she takes over
and starts suckling her offspring. The baby at the time of birth
is about a quarter to a third of its mother's length.
Cetacean milk is some of the richest in the animal world, comprising
up to 40% fat content. The mother feeds her offspring by erecting a
nipple from within the mammary fold and injecting the milk under
high pressure into the baby's mouth, enabling it to receive large
quantities in between coming up to the surface to breathe.
This control is affected through several peculiar properties of their skin.
First of all the top layer is not dead, whereas skin of us humans is. When you
vacuum the carpet and then empty the bag, you find a quantity of grey
dust. I am sorry to tell you but most of that is dead human skin.
Compared with cetaceans, we humans seem to have rather a bad case of dandruff!
In comparison their skin is alive, they have control over it and are
able to "shiver" off the stagnant boundary layer that would otherwise slow
them down. It is also slightly porous, the first two layers absorbing
water and then expelling it, further lessening boundary layer drag
and helping them to travel through water with less effort. Another factor
affecting speed is shape. One of the first things yo notice about these
creatures, apart from those that have fins, are that there are no projections
or bumps. In fact it is quite hard to tell the sexes apart, as all
the reproductive and mammary organs are kept within slits
on the underside of the body. The design of the nuclear submarine is a good
example of man copying one of nature's forms.
Cetaceans are the largest animals that have ever lifed on earth. Why
is this so? They life in an environment that is gravity free for all
practical purposes. This was one of the reasons that the Dinosaurs
and their kind never grew any larger. They could so easily get
bogged down owing to their enormous weight. Circularity problems were another
factor when sleeping on a particular part of the body, as the weight would
compress the blood vessels in that part, thus cutting off it's blood supply. To
avoid this, even today, most large land animals either catnap or
sleep standing up. Cetaceans having solved the gravity problem were free
to solve the next, which was that of heat loss.
The Bay of Gibraltar seems to be a favourite place for nursery schools
of Common Dolphin and on one occasion one witnessed the birth of a dolphin
in the wild. It is a very common sight to see baby dolphins accompanied
by their mothers who always stay very close to them, rising to
the surface a few inches away from each other when coming up to breathe. From all
observations in the Bay of Gibraltar, there does not seem to be
a set season for giving birth because young of only a few days
old are present throughout the year.
Lactation lasts for about 12 months, after which the weaning process is
started. In the case of the Odontoceti, the mother bites off the
head of small fish and offers the carcass to the young animal. This technique
is used in Dolphinaria to induce newly captured dolphins to feed,
as they will generally not take dead fish but do have a childhood memory
that such food was offered to them by their mothers. About five
years later, a new generation of dolphins are starting to breed.
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Actual programs for adopt Dolphin or Whale
Would you like to adopt a whale or dolphin? Following are one or more dolphin and whale
adoption programs. Most provide a certificate, photo, chart, and quarterly newsletter.
Check out the following web sites and contact the organizations if there is one for more
information about the programs.
»The Whale and Dolphin Adoption Project«
»Delivery UK wide; The Adopt a Dolphin pack«
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