Cambodian legend states that the
Irrawaddy dolphin was once a beautiful
maiden.
When she was going to be forced to marry
a python she decided to throw herself
into the Mekong River, where she was
then transformed into a dolphin.
Irrawaddy dolphins (Orcaella brevirostris) are
found in waters from Australia to
India. Freshwater subpopulations also
occur in countries in Southeast Asia
including: Cambodia, Indonesia, Lao PDR,
Malaysia, Myanmar, Thailand and Viet
Nam. This species is able to occupy
various bodies of water including oceans
(near coasts), rivers and estuaries.
The dolphin gets its name from the
Irrawaddy River, extending from the Bay
of Bengal to New Guinea and the
Philippines.
The Irrawaddy looks similar to the Beluga whale.
However, they are most closely related
to the Killer Whale. These dolphins
have a distinct large rounded head with
a small beak and long flippers. Their
color is a steel gray with typically
paler colored undersides. Adults can
weigh up to 287 pounds (130 kg). Diets
of the Irrawaddy include various
cephalopod,
crustacean, fish and fish egg species.
At approximately eight years of age the Irrawaddy
reaches sexual maturity. Mothers, also
called cows, give birth to a calf every
two to three years. The gestation for
these animals is quite long and lasts
over a year (14 months). After a calf
is born it relies heavily on its mother
for survival for quite some time and is
weaned only after two years. The life
span of these magnificent animals is
approximately 30 years.
Irrawaddy dolphins are most often
observed as a group living species;
comprising of up to ten individuals.
They have complex modes of communication
called
echolocation or biosonar,
using ‘clicks’ and ‘buzzes’ at
frequencies of 60 kilohertz.
Although total range population surveys have not been
carried out, the total estimated
population of Irrawaddy dolphins is 7000
individuals, 90% (or 6300) of which
occur in Bangladesh. Irrawaddy dolphin
populations found in Lao PDR, Malaysia,
Myanmar, Philippines and Thailand are
classified as Critically Endangered
species by the IUCN Red List, while
populations in Bangladesh and India are
classified as Vulnerable.
They are also listed in Appendix I of the Convention on
the International Trade of Endangered
Species of Wild Fauna and Flora (CITES)
since 2004. This listing forbids all
commercial trade.
Unlike other dolphins that occupy deeper oceans,
Irrawaddy dolphins are more susceptible
to human induced threats as they live in
a variety of aquatic habitats and closer
to coastal areas.
The primary threats
to the few remaining Irrawaddy dolphins
are mainly due to:
-
Habitat loss: as a
result of dam building, pollution and
gold mining
-
Bycatch and other fishing
practices including: bottom trawling,
electro-fishing and drowning in gill
nets and crab nets and
-
Trade for the
aquarium/tourism industry.
Despite low population numbers in the wild, Irrawaddy
dolphins can be seen throughout Asia in
shows at dolphinariums and aquariums.
They are popular for this purpose as
they can be easily trained to perform
‘tricks’ and can live in freshwater
tanks. According to a press release
from the World Wide fund for Nature
(WWF) in 2004, it was stated that there
were over 80 established
dolphinariums
in nine Asian countries alone.
All cetaceans, including
the remarkable Irrawaddy dolphin, belong
in the wild. It is up to us to ensure
their survival and welfare!
What you can do?
*
Don’t promote or contribute to captive
dolphinariums and other
marine park facilities that hold
cetaceans. Regular hunting of these
animals occurs to up-stock these
facilities. Not only are individual
animals welfare comprised but the
conservation of wild populations as
well.
*
Know where your food comes from. Try and buy fish that has
been caught using sustainable
fishing methods and avoid products
sourced using practices like bottom
trawling, dynamite fishing and
electro-fishing.
*
As always, spread the word!
What does that mean?
Cetaceans:
Aquatic mammals including dolphins,
porpoises and whales.
Bycatch:
Describes fish and other aquatic life
that has been caught unintentionally
while fishing for other species and is
often attributed to overfishing. The
Organization for Economic Co-operation
and Development (OECD) defines bycatch
as ‘total fishing mortality, excluding
that accounted directly by the retained
catch of target species.’
Cephalopods:
Include the mollusk species, all of
which are marine invertebrates that have
large heads and arms/tentacles. The
name comes from Greek meaning
“head-feet.” Examples of cephalopods
include: squid and octopus species.
Echolocation or Biosonar:
This is a form of communication used by many
animals. This works by animals emitting
calls into the environment and listening
to the echoes of these calls that return
from various objects around them.
Echolocation is used to communicate with
other individuals and for navigation and
foraging. Donald Griffin first
described the term echolocation in 1938,
which discovered and described this
means of communication in bats.
Dolphinarium:
An aquarium for dolphins.
