Dolphins are appealing intelligent sea creatures well known for their love of play and friendliness to humans Despite their appearance , dolphins are not fish but mammals ; air breathing, warm blooded animals whose young feed on their mother’s milk

1. BIOLOGY OF DOLPHINS
Vinod Kumar
FRM -2021-20-03

2. INTRODUCTION
• Dolphins are appealing intelligent sea creatures well known
for their love of play and friendliness to humans
• Despite their appearance , dolphins are not fish but mammals
; air breathing, warm blooded animals whose young feed on
their mother’s milk

3. TAXONOMY
• Kingdom : Animalia
• Phylum : Chordata
• Class : Mammalia
• Order : Cetartiodactyla
• Family : Delphinidae
• Genus : Delphinus
• Species : Delphinus delphis

4. HABITAT
• Found in seas and ocean waters expect the
coldest polar waters.
• Many dolphins live in shallow coastal
waters while others inhabit the open
oceans.
• They can be found in ports, bays, gulfs and
estuaries and frequently in the shallow
waters of the continental shelves
Bottle nose dolphin (Taken
from WWF)

5. DISTRIBUTION
• Dolphins have a worldwide distribution
• The Atlantic, Pacific and Indian Oceans and their seas host a large
number of dolphin species since they prefer tropical, subtropical and warm
waters.
• Also, some species are distributed over large areas while others may
inhabit a small region. Other species are particularly endemic to a zone,
and some may have different populations scattered over an extensive
range

7. EXTERNAL MORPHOLOGY

9. ADAPTATIONS
• Swimming ability
• Echolocation
• Group hunting
• Blow hole - Respiration
• Blubber - Insulation
• Countershading
• Keen eyesight
• Large brain

12. BEHAVIOR
 Social grouping
• Dolphins are highly social
animals, often living in pods of up
to a dozen individuals, though
pod sizes and structures vary
greatly between species and
locations. In places with a high
abundance of food, pods can
merge temporarily, forming
a superpod.
A large pod of dolphin in Kaikoura, New
Zealand

13.  Foraging
• Foraging methods, habitat use patterns, and
spatial dispersion are diverse in dolphins, and
tend to be influenced by habitat type, prey type
and accessibility.
• Dolphins forage both in groups and individually,
and display different and innvotive foraging
techniques : sponging, snacking, kerplunking etc.
Sponging

14.  Sleep state
• Dolphins shown to engage in
unihemispheric slow wave sleep
(USWS) during which one half of the
brain goes into a sleep state, while
the other maintains visual and
auditory awareness of the
environment and allows the animal to
resurface for respiration.
Sleeping dolphin in captivity: a tail
kick reflex keeps the dolphin's
blowhole above the water

15. PHYSIOLOGY
• Physiology is the science that studies the functions of living beings.
• In the case of dolphins, it is interesting to know how they perform their
physical and chemical functions in their changing environments.

16.  Diet
• Many dolphins eat only fish, although some
also eat small numbers of cephalopods,
crustaceans, small rays and sharks.
• They generally consume about 5% of their
body weight daily.
• Most fish in their stomachs were bottom
dwellers (Sciaenids ) but some were found to
be Mugilids and Clupeids and pelagic
(Carangidae ) .

17.  Cognition
• Dolphin cognition is relatively sophisticated among nonhuman animals.
• Ddolphin cognition refers to how dolphins think, know, remember.
Physical cognition : Understanding
the physical world.
Social cognition : Understanding the
social world.
Symbolic cognition : Understanding
representaton.

18.  Thermoregulation
• Dolphin, being a mammal, is warm-blooded. It requires a constant body
temperature .
• Its metabolism is higher than that of land mammals of similar size, it
generates a great deal of heat.
• The heat production must be regulated to keep the animal from over-
heating.

19.  It can“thermo-regulate”, or control its body temperature in the
following ways
• (1) Blubber insulates the body against temperature changes.
• (2) The dorsal fin and flukes release excess heat from the body.
• (3) During dives, blood circulation is reduced at the outer portions of the
body and concentrated into the animal’s core organs and tissues.
• (4) Body heat is conserved by transferring it from one blood vessel to
another during circulation instead of being released to the environment.

20.  Swimming
• Dolphins are among the world‘s most efficient swimmers.
• Their fusiform body shape allows water to flow contiuosly from the body to
the tail region.
• Additionally, the curvature of the pectoral flippers, dorsal fin, and tail flukes,
cutaneous ridges, skin folds and subdermal mechanical properties of the
skin, are morphological features that reduce drag and can also lift.

21.  Diving
• Diving cetaceans must balance metabolic demands associated with
limited oxygen while supporting energy loss as they move.
• During breath hold diving, dolphins maximize the use of oxygen
stores by decreasing their heart rate and constricting peripheral
vascular vessels.
• With this favor the most oxygen- dependent tissues by reducing
blood flow to visceral organs, skin, muscles.

22.  Reproduction
• Dolphin reproduction or dolphin mating is the complex process and they
produce a new calf every 3 to 5 years.
• The reproduction of dolphins is sexual and the fertilization is internal.
 Sexual maturity
• Female : 5 to 13 years
• Male : 8 to 10 years

23. CONTD.
 Ovulation
• Female dolphins generally ovulate 2-7 times per year with a cycle length of
30 days.
• They are seasonally polyestrous and estrous occurs from spring to fall.
 Mating
• Dolphins are polygamous, which means they have more than one mate.
• Having more than one possible mate makes dolphins sexual selection
highly competitive and violent.

24. .
 Mating ( contd...)
• Sexual selection is the process of
selecting a mate to produce
offspring .
• Male dolphins begin the mating
courtship with vocalizations and
intricate swimming patterns.
• Male dolphins also try to win a
female‘s attention by gift giving
objects.
• They will also fight other male
dolphins in the area, which includes

25. Gestation
• Approximately 12 months
Birthing season
• Dependent on geographial location.
• Births may occur in all seasons, but typically peaks occur during spring,
early summer and fall
Nursing period
• Nursing / lactation period are difficult to determine in the wild but appear to
be a primary source of nutrition for calves for an average of 18-24 months

26. LIFE CYCLE OF DOLPHINS

28. THREATS
Entanglement in fishing gear
Climate change
Toxic contamination
 Habitat degradation
 Ship strikes
 Oil and gas contamination

29. IUCN RED LIST
Hector's Dolphin
Cephalorhynchus hectori (<EN>)
Irrawaddy dolphin
Orcaella brevirostris(<EN>)

30. Ganges River Dolphin
Platanista gangetica( < EN>)
Common Bottlenose Dolphin
Tursiops truncatus ( <CR>)

31. CONSERVATION
• Whale and Dolphin
Conservation (WDC), formerly Whale
and Dolphin Conservation Society in
the UK
• U.S. Dolphin Protection Consumer
Information Act (DPCIA)
• The Marine Mammal Protection Act
(MMPA)
• IUCN - Species Survival Commission
(SSC)
• The Convention on International
Trade in Endangered Species of Wild
Fauna and Flora (CITES)

32. Project Dolphin: Why is it important to save
a declining river species?
New Delhi : Prime Minister Narendra modi
announced the government’s plan to launch a
Project Dolphin. The proposed project is aimed at
saving both river and marine dolphins

34. CONCLUSION
• Dolphins are known to be incredibly social creatures with close family ties
and established communities.
• Relationships between dolphins and humans are fascinating, and they
can occur both in the wild and in captivity.
• Many species of dolphins are facing the threat of extinction.
• So we must take necessary measures to conserve dolphins and
associated ecosystem.

35. REFERENCE
• Tyack, P. (1986). Population biology, social behavior and
communication in whales and dolphins. Trends in ecology &
evolution, 1(6), 144-150.
• Richard, B. (2000) . Aquatic life of world.( Vol 3) . Marshall cavendish
corporation.
• John, H. S. (2009). A derivative of encyclopedia of ocean science (2 nd
ed). Elsevier publications.

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