Marine Mammals
Order Cetacea
Tamisha Michalewicz
Order Cetacea
• Two suborders
– Mysticeti (Baleen Whales)
– Odontoceti (Toothed Whales)
• One extinct suborder
– Archaeoceti (Ancient Whales)
Archaeoceti
www.seaworld.org/.../KillerWhale/sciclasskw.html
• Live, Breed, Rest, and carry out all of their life
functions in the water
Cont.
• Inhabit all of the world’s oceans
– As well as, some freshwater lakes, rivers,
brackish waters of estuaries and coastal
marshes
Mysticeti
• Most of the largest Cetaceans
– i.e. Blue Whales (Balaenoptera musculus) which are the
largest animal in history
• Exceeding 100 feet and weigh as much as 160 tons
– Smallest is the pygmy right whale (Caperea marginata)
• Measure up to 23 feet
– More examples: humpback whale (Megaptera
novaeangliae), fin whale (Balaenoptera physalus), and
southern right whale (Eubalaena australis)
www.nefsc.noaa.gov/.../beached_blue_whalebb.jpg
Humpback Whale – Megaptera
novaeangliae
cas.bellarmine.edu/tietjen/RootWeb/Chiroptera.jpg
Fin Whale - Balaenoptera
physalus
www.exzooberance.com/virtual%20zoo/they%20swi
Odontoceti
• Largest and most
diverse group
– i.e. the sperm whale is
the largest
• Reaching about 60 feet
– The largest living
predator of warm-
blooded animals is the
killer whale Sperm Whale – Physeteridae
animals.nationalgeographic.com/staticfiles/NG...
– More examples:
Dolphins and
porpoises
Bottle Nose Dolphin – Tursiops trucatus
www.naturescornermagazine.com/NaturesBlog/ima...
Harbor Porpoise - Phocoena phocoena
animals.nationalgeographic.com/staticfiles/NG
Taxonomic History
• Hippopotamids are closest living relatives
– Followed by ruminants
• i.e. cows
– Followed by Artiodactyls
www.redmills.ie/images/ruminants.jpg
cas.bellarmine.edu/.../RootWeb/Artiodactyla.jpg
www.cbc.ca/gfx/photos/hippo_cp_5128012.jpg
How do Cetaceans reduce drag for
fast swimming?
• Fusiform body
– Tapered at both ends
• Paddle-shaped front limbs
• No external digits or claws
• Tail flattened laterally and bearing horizontal
flukes at the tip
• Vestigial ear pinnae
• Hairless body
• Thick subcutaneous blubber layer filled with fat
and oil
Cont.
• Addition of compressed vertebrae
• Shortening of the neck
• Lack of sweat glands
• Internal reproductive organs
• Three chambered stomach
• Telescoped skull bones
• External nares on top of head
– Odontoceti have one blow hole upload.wikimedia.org/.../300px-Cetacea.jpg
– Mysticeti have two blow holes
Coping with Cold Climates
• Small cetaceans
– Have high metabolic rates
– Flippers and flukes have a
countercurrent heat
exchange system
• Heat from arterial blood
warms venous blood as it
returns to the heart
• Large cetaceans
– Small surface to volume
ration
www.cresli.org/.../2003_WW/breacher_fluke.jpg • Lose little heat to the
surrounding environment
• Both are insulated by
thick blubber layer
Physiological Adaptations for Deep
Diving
• Rapid exchange in lungs
– Enhanced by double capillary layer in the
intraalveolar septae
– Humans use 4% of Oxygen inhaled, Cetacea
use 12%
– Twice the number of erythrocytes and
myglobin molecules in their blood
• Allows for efficient capture and transport of
oxygen
Cont.
• Alter blood distribution
– Rate of flow slows down (Undergo bradycardia)
• Heart rate slows by as much as 80 beats per minute
– Eliminated at non-critical organs via shunts
• i.e. digestive tract
– Reserved for critical tissues
• i.e. heart and brain
• High tolerance to Carbon Dioxide and lactic acid
build up in tissue
Physiological Problems with Deep
Diving
• Increased pressure with increased depth
• At high pressure gases go into solution
more quickly
• Air breathing organisms have a problem
with Nitrogen gas absorption into blood
– Causes decompression sickness
• i.e. Bends or Caisson’s Disease
Physiological Solutions to Deep
Diving
• Structural Adaptations
– Lungs are small
• The total amount you take in
= the total amount you let
out
– Dead air spaces are large
• i.e. trachea and nasal cavity
– Trachea is large and
supported by cartilaginous
rings
– Bronchioles are small but
braced by muscles and
cartilaginous rings down to
alveoli Sperm Whale – Physeteridae
– Ribs are free from sternum www.nwf.org/nationalwildlife/article.cfm
Cont.
• Mechanism
– Total exhalation before diving
gimp-savvy.com.
– Diving pressure forces collapse of lungs
• Forces air into dead air spaces, including nasal passages
– Dead air spaces devoid of vascular tissue
– Nitrogen is six times more soluble in oils then in water
• Blubber is highly vascular and serves as Nitrogen reservoir
• Oil also present in nasal sinus and may absorb nitrogen there
as well
Mating
• Usually have one mating season per year
• Gestation is about 10 to 17 months
• Females give birth to a single calf every
one to six years
• Calves are born tail first and must swim
from the moment of birth
• Mysticetes nurse for about six months
• Odontocetes nurse for over two years
Social behavior
• Highly sociable within their respective
species; often forming pods
– Pods often collaborate in hunting, playing,
traveling, and taking care of young
– Usually remain in pods throughout their life
– Pods are beneficial because hunting is easier
in a group; also pods decrease predation
Communication
• Flukes or Flippers
– Slap the surface
• Breaching
– Leaping from the waters
surface
– Helps them to attain an
elevation of several yards
• Spy-hopping
– Raise head out of water to
investigate objects or
potential prey
Cont.
• Emit various sounds from their head’s
– Sperm whales have simple clicks
– Humpback whales have complex “songs”
– These sounds and echolocation help them
navigate, investigate their surroundings, and
hunt
Echolocation in Mammals
• Four orders of mammals use echolocation
– Order Cetacea (Whales, Dolphins)
– Order Soricomorphia (Shrews)
– Order Carnivora (Pinnepeds)
– Order Chiroptera (Bats)
northern short-tailed shrew-Blarina brevicauda
clackhi.nclack.k12.or.us/.../cute%20sea%20lion
cas.bellarmine.edu/tietjen/RootWeb/Chiroptera.jpg
Echolocation in Cetacean
• Important means of navigation
• Very well developed in Odontocetes
• Very Rapid
– Size, shape, and distance of the object can be determined
• Anatomy of nasal regions
– Ducts and diverticula
– Nasal plugs
– Air cycled back and forth
• All are used to siphon air to create different sounds
• Hearing the return echo
– Mandible
• Small thin bone, that allows the animal to hear through the lower jaw in
front
Food
• Mysticetes
– Filter feeders
• Use their baleen to strain plankton and other tiny
organisms
• Odontocetes
– Feed on fish, squid, and crustaceans
• Larger species eat aquatic birds and mammals
(which include other cetaceans)
Prey debilitation by Odontoceti
• Spermaceti organ
– “Shocks” prey so they can eat
Ecosystem Roles
• Vital roles as consumers
• Host a range of internal
parasites
– Cestodes in their intestines
(Tetrabothrium and
Diplogonoporus)
– Plerocercoids in their blubber
(Phyllobothrium and
Monorygma)
– Trematodes in their stomachs,
livers, intestines, and sinuses
(Bolbosoma)
• Host a range of external
parasites
– Cookie-cutter sharks (Isistius
brasiliensis)
Cont.
• Cetaceans are mutualists with animals that feed
on ectoparasites
• Birds have a commensal relationships with
cetaceans
– Seagulls often follow schools of dolphins and
consume small fish stirred up by the feeding
cetaceans
– Pilotfish (Naucrates ductor) sometimes accompany
killer whales and eat scraps from their kills
Economical Importance for Humans
• Disadvantage
– Impact commercial
fisheries due to competition
for fish
• Advantage
– Hunted for meat, oil, and
blubber in 19th century
• Oil is used for lighting and
heating
– Important for
entertainment and tourist Killer Whale – Orcinus orca
industries www.destination360.com
Human Impact on Cetaceans:
Negative
• Commercial whaling in the 19th
and 20th century decreased the
populations of mysticeti
• Many small odontocetes
threatened by commercial fishing
operations
– Become entangled in nets and
drown, or killed by explosives
www.chinadaily.com.cn/world/2006-10/18/xin_46
– They are killed on purpose
because fishermen see them as
competition
• Use of military sonar in the ocean
and increase in ocean noise
threatens cetaceans
• All cetaceans face the threats of
pollution and global climate
change
www.wwf.org.ph/_content/bycatch.jpg
Human Impact on Cetaceans:
Positive
• Commercial whaling was banned in 1986
• Captive breeding programs help critically
endangered odontocetes
www.onevoice-ear.org/.../dolphins_jobs.jpg members.greenpeace.org/.../source/action_129.jpg
References
• De Maddalena, Alessandro. June 2004. Giants of the Deep. World and 1, 19:6
• Ellis, E. and A. Poor. 2006. “Cetacea” (on-line), Animal Diversity Web. September 30,
2007 http://animaldiversity.ummz.umich.edu/site/accounts/information/Cetacea.html
• Werth, Alexander J. June 2006. Mandibular and Dental Variation and the Evolution of
Suction Feeding in Odontoceti. Journal of Mammalogy. 87:3, 579-588