marine mammals - o'mara's science...
TRANSCRIPT
Marine Mammals
Phylogeny of Marine Mammals
Four groups of marine mammals are separate evolutionary lines – each entering the marine environment independently
Whales share a common ancestor with even-toed ungulates (cattle)
Sirenians share a common ancestor with the Proboscidea (elephants)
Otters are a separate evolutionary line from the walruses, seals and sea lions – all of which share a common ancestor with other carnivores
Whales
Sirenians
Sea
Otters
Pinnipeds
Marine mammals,
birds,and reptiles are
all classified in the
Phylum Chordata,
Subphylum Vertebrata.
Know the Class and
Order associated with
each of the groups of
marine mammals.
Order Cetacea – The Whales
The Whales Group of mammals which includes whales, dolphins,
and porpoises
Natural selection forces have produced convergent evolution for the cetaceans – stream-lined body form
Cetaceans’ front flippers have the same bone structure found in other mammals
Cetaceans have reduced pelvic girdle
1. lost hind limbs as adults
2. hind limbs are present in the embryonic stage
Natural selection on different marine organisms has produced an
efficient, streamlined body form with counter shading in three
separate evolutionary lines. This is called convergent evolution.
Fetus of a white-sided
dolphin. Two pairs of
limbs are present at
this stage of
development. The
limbs will disappear
before birth.
The Whales No external ears – holes are plugged with wax
(in some)
Flukes are horizontal on tail (contrast this with the vertical upper and lower caudal fins in fish)
Blow holes – nose migrated to the top of the head
Blow spouts - water condensation in the lungs, sea water, and mucous; exhale when surfacing then inhale
Cetaceans can fill a lung volume 3000X larger than a human in one half of the time
The Whales
All Cetaceans have a blubber layer
1. increases buoyancy
2. provides insulation against cold water
Very little body hair, produce milk, nurse their young
Mostly marine (approximately 90 species of marine mammals), 5 species of freshwater dolphins
Whale diversity: Baleen and toothed whales
Great whales can be identified from a distance by their blowing
pattern their surface outline at the start of a dive, and how they
dive (portion of their body visible at the end of the dive (fin or
fluke)).
Baleen Whales
Baleen whales have fibrous plates on the upper jaws
1. baleen is made of keratin (protein)
2. there are different types of baleen plates
3. large surface area, strain small planktonic organisms out of the
sea water
4. tongue is used to scrape the plankton off of the baleen plates
Baleen whales are the largest organisms which have ever
lived
Baleen Whales
Among the baleen whales, the females are
much larger than the males
1. females – 110 feet in length
2. males - 80 feet in length
3. weight - 90 to 100 tons (remember that 1 ton
= 2000 lbs)
Bale
en W
hale
sHumpback
Bowhead
Gray
Fin
Blue
MinkeRight
Sei
Baleen Whales Feeding StylesGulping feeding style - huge gulps of water,
accordion pleats on the abdomen (Blue Whale)
Skimming feeding style - leave the mouth open, water moves through the baleen as the whale swims (looks like it is smiling!) - Right Whale
Bottom feeder - stir up sediment on the bottom, filter out the benthic organisms – creates “feeding pits” on the ocean bottom – Gray Whale
Humpback Whales make “bubble curtains” analogous to a net – small plankton will not pass through the bubble curtain – whales take turns feeding in the enclosed area
Comparison of the diet composition of several great whale species.
Comparison of baleen plate filtering mechanisms in great whales.
Toothed Whales
Includes dolphins, porpoises, killer whales
(Orcas), sperm whales
In contrast to the herbivorous baleen
whales, the toothed whales are carnivorous
(have teeth)
70-80 species of toothed whales
Largest toothed whale is the Sperm Whale
Tooth
ed W
hale
s
Sperm Whale
Killer Whale
Dolphins &
Porpoises
Sperm Whale Factoids
Eat giant squid
Can dive 3000 meters and stay submerged
for up to 90 minutes
“Moby Dick” was a sperm whale, based
upon a real rouge Sperm Whale which
ranged off of the Massachusetts coast in
1830's and 1840's which attacked whalers
Sperm Whale Factoids
sperm whales have a substance called
“spermaceti” in their heads which was used for
lamp oil
ambergris - sticky material found in the gut of
sperm whales derived from squid beaks and other
undigested proteins; ambergris is used in the
manufacture of VERY expensive perfume (Older
French scents such as Joy, White Shoulders, etc.)
Toothed Whales
Orca’s striking black and white pattern - counter shading; common to many marine organisms (light on the bottom, dark on the top)
1. eat seals, penguins, large fish
2. will tip over ice flows to get at the seals on the ice
3. travel in pods (small social groups of related members)
4. mate for life
Porpoises have blunter faces than dolphins (extended noses)
Spinner dolphin (Stenella Longirostris)
in the eastern Pacific photographed
alongside a ship.
Dolphins
Highly social
Live in pods
Ride bow waves from boats and whales –allows them to swim fast with very little effort.
Dolphins use echolocation to find prey…similar to the mechanism used in bats.
Pacific white-sided dolphin (Lagenorhynchus obliguidens) cruises
in the bow wake of a research vessel.
Echolocation in dolphins uses a series of clicks created by pushing
air through the melon and internal passages.
Naval SONAR research in
the Hawaiian islands has
negatively affected the
ability of whales in the area
to hunt and navigate. Whale
strandings in areas of
SONAR research have
increased. Calls for a
moratorium on SONAR
testing in areas where
whales and dolphins feed,
breed, and migrate have
increased.
Dolphin
Beluga
Humpback
Day 2
Cetacean Social Interactions Toothed whales are very social and form
social groups
Killer Whales (Orcas) and Sperm Whales form tight pods ( 10 to 40 individuals)
Among Orcas, pods are usually 10 or fewer individuals
a. dominant male
b. mature females
c. calves
d. subordinate males
Cetacean Social Interactions
Sperm whales – pod sizes very in accordance
with the season
a. harem pods
b. nursery pods
c. bulls/schools of mature males
d. schools of calves and juveniles
e. bachelor pods - schools of immature males
Sperm whales will surround an injured pod
member to protect it
Spying behavior in Orcas (a), Sperm Whales surrounding an
injured pod member (b), and bottlenose dolphins carrying a stunned
pod member to the surface so that it can breathe.
Cetacean Social Interactions
Most whales mate belly to belly…this behavior serves other social functions in addition to mating.
Humpback whales have long intricate mating songs (10-15 minutes in length).
Whales songs appear to be socially transmitted; dialects of the songs are specific to regions of the world’s oceans.
Mating behavior in Gray
Whales (a) and Humpback
Whales (b). Mating pair
(a) belly to belly and
supported with the
assistance of a third whale.
Humpbacks actually
surface belly to belly, roll,
and slap flukes as part of
the courtship rituals
leading to mating.
Humpback Whale Songs
For 10 years, Humpback songs off of the eastern Australian coast were consistent.
Two new males appeared from the western Australian coast with a different song pattern.
Within three years, the entire 2000 male population had incorporated themes from common to the western dialect.
This suggests that Humpback Whale song patterns are learned behavior!
Whale Reproduction
whale gestation takes 11-12 months, sperm
whales - 16 month gestation
born tail first to prevent the calf from
breathing in water
once the calf is born, swims to the surface
to breathe
Commerson’s dolphin (Cephalorhynchus commersoni) giving
birth in captivity.
Whales feed in colder polar regions during the summer and migrate to
warmer tropical areas to give birth during the winter. Note that because the
seasons are reversed, northern and southern hemisphere whales never meet.
Whale Reproduction
Birth weight/size in whale calves is relatively large compared to the parent in the mammal world, grow very rapidly
Blue Whale calves gain 200 lbs/day for the first 17 months.
Whale milk is extremely rich, 16-40% fat.
Calves nurse for 4-8 months depending upon the species, calves may also nurse from related females.
Can drink the equivalent of 400 glasses of milk a day
Whale Reproduction
Sperm Whale and Gray Whale mothers are
extremely defensive of their calves.
Whales have very low reproductive rates; this
makes it difficult to replace members removed
from the population at rates exceeding natural
mortality – such as hunting
Mature females reproduce every 1 to 4 years,
baleen whales every 2 years, dolphins every 3-4
years.
Whale Life History Facts
Age at maturity – averages 20 years (9
years for female sperm whales, 20 years for
male sperm whales)
Whale life span: 20 to 40 years on average;
may live to 80 years in the larger baleen
whales
1. Right, bowhead, blue, fin, and humpback whales remain endangered even
though there is an international whaling ban.
2. Seals and sea birds which competed with the great whales for food have all
increased in population size as a result of the demise of the great whales.
Whale Strandings
Occurs more often among the toothed whales –
may relate to the social nature of toothed whales
1. injury to a pod member
2. navigational error
3. food
4. toxins
5. parasites
6. percentage returned to the water is very low, they may
re-strand themselves
Whale Strandings
sperm whales, pilot whales, orcas,
bottlenose dolphins, false killer whales are
the most commonly stranded toothed
whales
20-30 strandings on the GA coast annually,
most frequently bottlenose dolphins or
pigmy killer whales
Order Pinnipedia – Sea
Lions, True Seals,
Walrus
Order Pinnipedia
Streamlined bodies with flippers
Excellent swimmers
Unlike Cetaceans, must come onshore to rest and mate
Restricted to cold water habitats
Layers of blubber – for buoyancy and insulation as in Cetaceans
Predaceous – feed on fish and large swimming invertebrates (nekton)
Pinnipeds
True Seals Sea Lions Walrus
True Seals
Largest group of pinnipeds
Hind flippers can not move forward
Swim by undulating their entire body
No external ears
Harbor seals, elephant seals (largest – males 20 ft), monk seals (Hawaii, Mediterranean – all endangered)
Seals have been hunted traditionally for meat, oil, fur – hunting has been limited to a few native Inuit tribes, seal populations are recovering
Weddell Seal
Leopard Seal
Munk Seals
Elephant Seal
Tru
e S
eals
Sea Lions Can be distinguished from seals by the presence of
external ears
Can turn their rear flippers forward, use front flippers for locomotion (in contrast to seals)
Includes fur seals and the California Sea Lion
Sea lions are killed in fishing nets; killed/shot by fisherman who believe that they are competing with the sea lion for commercial fish.
Sea lions practice harem breeding. Large males are territorial and protect a group of reproductively mature cows.
Steller’s Sea Lion
California
Sea Lion
Northern
Fur SealSea
Lio
ns
&
Eare
d S
eals
Walrus
Only one species of walrus, found in
the Arctic Ocean
No external ears
Tusks appear to be largely used for
mating displays/territorial defense
Benthic feeders
Walrus (Odobenus rosmarus) relaxes on Artic ice.
Order Carnivora – Sea Otters
Sea Otters
spend their entire life in the water (except in the event of severe storm)
no blubber, fur which traps air
eat sea urchins, abalone, mussels, crabs
hold babies on their bellies
live in kelp forests, wrap themselves in fronds of kelp which prevents them from being carried away by currents
Sea Otters
Abalone fishers protest the protection of the sea
otters.
Important relationship between the sea otters, the
sea urchins, and the kelp (keystone predator).
1. Sea otters decline, feeding on sea urchins decline, sea
urchin populations explode.
2. As the sea urchin numbers increase, destruction of the
kelp forests increases.
3. Abalone need the kelp forests to survive.
Order Sirenia – Manatees
and Dugongs
Manatees and Dugongs
Four species (all endangered)
Dugong in East Africa, Western
Pacific Islands and Manatee in
Amazon basin, West Africa, and
the Southeastern United States.
Spend entire life in the water
Herbivorous: graze on Manatee
Grass (Syringodium)
Manatees and Dugongs
Blubber layer present, very wrinkled skin, few
hairs present on face
Extremely slow moving
Nose on top of head at anterior, blow air out when
it surfaces (you can hear it if you are close
enough).
Can reach 15 feet in length, 1300 lbs.
Sirenians produce one calf every three years.
Manatees and Dugongs
The majority of manatee deaths in the US:
boating accidents, especially in Florida as
coastal development increases.
Order Sirenia,
“Sea Cows”
Manatee
Dugong