Transcript cetacean behaviour - Mater Academy Lakes High School

WHAT IS A MARINE
MAMMAL?
•Member of Class: MAMMALIA
•All possess major adaptations that allow
them to live in the water (to a greater or lesser
extent)
•Some marine mammals live entirely in the
marine environment, others may come on land
for part of their lives
•However, all marine mammals derive all (or
most) of their food from the marine
environment
POLAR BEAR
Ursus maritimus
SEA OTTER
Enhydra lutris
SIRENIANS
- Manatees and dugongs
PINNIPEDS
- Seals, sealions and walruses
CETACEANS
Whales, dolphins and porpoises
PINNIPEDIA
(Seals)
CARNIVORA
CANIDAE (Dogs)
FELIDAE (Cats)
PAENUNGULATA
SIRENIA
PROBOSCIDAE (Elephants)
HYDRACOIDEA (Hyraxes)
PERISSODACTYLA (Odd-toed ungulates)
UNGULATA
ARTIODACTYLA (Even-toed ungulates)
CETACEA (Whales and dolphins)
CRETACEOUS
65
PALAEOCENE
55
EOCENE
OLIGOCENE
39
Whales, dolphins and porpoises are
all members of the mammalian order
CETACEA
There are currently 84 (±)
recognised species in the order.
Order: CETACEA
Sub-Order:
MYSTICETI
The Baleen or
“filter-feeding”
Whales
10 or 13 species
•The Baleen
whales all possess
hundreds of plates
of baleen instead
of teeth.
•Baleen is made of
keratin and hangs
from the upper
jaw.
•The fringed
baleen plates trap
engulfed prey and
filter out water.
Order: CETACEA
Sub-Order:
ODONTOCETI
The Toothed
Whales
69 to 73 species recognised
The sub-order
ODONTOCETI is split
into ten families:
Order
Sub Orders
Archaeoceti
Sperm whales
Physeteridae
Pygmy sperm whales
Kogiidae
Beaked whales
Ziphioidea
Indian river dolphins
Platanistoidea
Amazon river dolphin
Iniidae
Yangtze river dolphin
Lipotidae
CETACEA
Mysticeti
Odontoceti
Franciscana dolphin
Pontoporiidae
Beluga & Narwhal
Monodontidae
Dolphins
Delphinidae
Porpoises
Phocoenidae
Cetaceans have adapted to a
wide range of aquatic habitats
RIVERS, LAKES, LAGOONS AND ESTUARIES:
eg River, Irrawaddy and humpback dolphins
INTERTIDAL (mudflats and mangroves):
eg bottlenose & humpback dolphins
SUBLITTORAL (continental shelf)
– c. 45 miles from coast <200m deep
BATHYAL ZONE (continental slope)
to 3,500’ (1,100m): eg beaked whales
ABYSSAL ZONE
– flat and low productivity av. 13,000’ (4,000m):
eg sperm whale and beaked whale
Cetaceans have adapted to a
wide range of aquatic habitats
• TEMPERATURE:
40oC – humpback dolphins in the Arabian Gulf
-1.9oC – cetaceans in Antarctic
• DEPTH:
<5m – river dolphins
2,000m – sperm whales
200 x atmospheric pressure
TEMPERATURE ADAPTATIONS
COLD TEMPERATURES
• Insulating blubber layer
• Counter-current system reduced heat
loss through flukes and fins
as blood flows from body gives heat to cooler, parallel blood
vessel entering body
HOT TEMPERATURES
• Vasodilation (blushing)
• Increased blood vessels in skin
SWIMMING ADAPTATIONS
•
•
•
•
•
•
•
Closable blowhole on top of head
Fore limbs → flippers
No hind limbs (or minute vestiges)
No zygapophyses → back bone flexible
Cartilaginous flukes
Thick cornea & thick eye mucus
Hydrodynamic (reduced drag)
HYDRODYNAMIC
•
•
•
•
•
•
Low Surface Area: Volume ratio
No hair (facial bristles on some young)
Skin replaced every 2 hours (keeps smooth surface)
Genitals and gonads internal
Blubber smoothes contours (tapered shape)
Shape indicates speed:
– Spinner dolphin: long beak (concorde)
– Risso’s dolphin: blunt head (jumbo jet)
– Sperm whale: square head (submarine)
BOUYANCY CONTROL
•
•
•
•
•
•
Buoyant blubber layer
Flippers act as hydroplanes (produce lift)
Porous bones
Fat filled bones (eg mysticeti vertebrae)
Dense bones (eg rib cages)
Spermaceti organ –
Waxy spermaceti changes density with
temperature - adjustable buoyancy
DIVING ADAPTATIONS
• High level of myoglobin (O2 storage)
• Blood diverted to essential organs
• Retae mirabila: extra circulatory system
→ greater blood volume
• High anaerobic tolerance in tissues
• Blood storage in spleen – released in
dives
• Reduced blood viscosity
• Bradycardia (25% in bottlenose
dolphins) and decreased metabolic rate
DIVING ADAPTATIONS
• Brain and heart most vulnerable to lack of
oxygen
• Cetacean brains operate at O2 concentrations
where a human would be unconscious
• High levels of anaerobic respiration in brain at
end of dive
• Heart activity decreases (& O2 demand)
• Blood flow fluctuates (high/none) to
periodically flush out anaerobic by-products
• High levels of anaerobic respiration
AVOIDING THE BENDS
• ‘The Bends’ are caused by dissolved
nitrogen being absorbed into the blood
stream under high pressure.
• When pressure decreased the
dissolved nitrogen come out of
solution as tiny bubbles.
• These bubbles can block blood
capillaries – causes pain, paralysis etc.
AVOIDING THE BENDS
• Rib cage collapsible & lungs can compress.
• Air squeezed out of lungs and thorax into
windpipe.
• Windpipe thickened, does not absorb air
(or dissolved nitrogen).
• Rapid transfer of nitrogen from blood into
lungs
• Some absorption of nitrogen in mucus
• Reduced circulation of blood to muscles –
less risk or capillary block
OSMOREGULATORY
ADAPTATIONS
• High in take of salt
• Saline surroundings (high OP) absorbs
water from cetaceans
• Specialised globular kidney (reniculi)
looks like bunch of grapes
•
•
•
•
High surface area for filtration
Water produced by fat metabolism
Seawater desalinated by kidney
Very concentrated urine
SLEEP
• Voluntary breathing – must be conscious
to open blow hole.
• A few species sleep as such:
– Right whales (very buoyant)
– Sperm whales (float – do not have to breathe
for hours at a time)
• Duplication of brain function – part of brain
can sleep while another part awake.
HEARING
• Odontocete vocalisations produced in
windpipe
• Focussed by fatty melon (acts like a lens)
• In water sound would reach dolphin ears
simultaneously – would not be able to pinpoint direction.
• Sound received through lower jaw.
• Two halves of lower jaw separated by
insulating tissue.
• Sound travels through jaw and vibrations
passed to inner ear.
MIGRATIONS
• Many large whale species migrate from
polar region (to feed) to tropics (to
breed)
• Accumulation of stored fat before start
• Vast distances – up to 50% weight loss
• High speed: blue and fin whales
17kmph for 3,700 km.
Why?
MIGRATIONS
• Breed in warm waters as weather calmer for
calves.
• Calves loose heat easily as have a high
surface area: volume ratio
BUT – half of humpbacks, belugas, bowheads,
orcas and narwhals never migrate (always
polar)
• Escape predators (killer whales) – although
in tropics other predators (sharks)
• Possible behavioural relic from when
breeding and mating grounds closer unlikely
REPRODUCTION
• Seawater is a spermicide – water tight
valves
• Prehensile penises
• Some polygynous (eg orca, dominant male)
• Almost all cetaceans promiscuous
(multimate polygynandry)
• Male competition
-aggression (eg humpback - fin slapping)
-vocalisations (eg humpback song – territories)
-sperm competition (on average testes 25x larger
than expected - dusky dolphins testes relatively
100x larger than humans)
REPRODUCTION
• Most species sexually mature after 5-6 years
• However, may be denied mating by more
dominant animals for several years
• Always single calves are born
• Some species have calving seasons, some
species give birth year round
• Usually 2-3 year calving interval
• Low reproductive rate
REPRODUCTION
• Calves are born in water and pushed to
surface.
• Stay with mothers for six months to 10
years or more
• Lactation via retractable nipples
• Milk has very high fat content (40% only 4% in cow milk)
• Calves may suckle for several years
even after weaning (- bonding)
• Females go through menapause
LONGEVITY
• Harbour porpoise – 15 years
• Bottlenose dolphin – 50 years
• Killer whale – 90+ years
• But only 20-25 years in captivity
• Blue whales - 100+ years
• Bowhead whales – 218 years +
Long life cycles and low reproductive
rate means that the recovery of
depleted populations is slow
West African manatee
Similar to W. Indian manatee but:
blunter snout
more protruding eyes
more slender body
West Indian manatee
Dugong
Tusks
Cetacean-like tail
No nails on flippers
Totally marine
Amazonian
Manatee
<3m long
White patches
Totally freshwater
SIRENIAN ADAPTATIONS
All sirenians are totally aquatic
- like cetaceans but unlike otters & pinnipeds
Herbivorous
- unique amongst marine mammals
Various adaptations to aquatic
environment
AQUATIC ADAPTATIONS
•
•
•
•
•
•
No pelvic limbs
Reduced/paddle-like pectoral fins
Fusiform (streamlined/spindle-shaped) body
Very large - reduced heat loss
Thick impermeable skin - reduced water loss
Lobular kidney - improved water extraction/salt
excretion
• Nostrils on top of muzzle
• Thick heavy bones (pachyosteosclerotic) – ballast
• Lungs dorsal with two horizontal diaphragms –
buoyancy control
MANTEE ECOLOGY
• Nutritionally poor diet
• Metabolic rate 20-30 % lower than expected
• Primarily plant diet
-some times eat fish captured in nets & tunicates
• Predation low: crocodiles/alligators and
sharks
• Most mortality:
cold
red tides
boat collision
by-catch
Pinniped = pinna (wing) + ped (foot)
Comprise 25% of the 115 marine
mammal species
More than 50 million pinnipeds
worldwide
Order: PINNIPEDIA
Family:
OTARRIDAE
Eared seals
Fur seals (9 species)
Sealions (5 species)
Otarrids all have certain characteristics
in common
Visible
external ears
Hinged hind flippers
Used fore flippers like
wings – flying through
the water
= mobility on land
Order: PINNIPEDIA
Family:
OBENIDAE
Walruses
1 species
Order: PINNIPEDIA
Family:
PHOCIDAE
True seals
Northern seals (Phocinae) 10 species
Southern seals (Monachinae) 9 species
Phocids also have certain
characteristics in common
No external ears
Use hind flippers for
propulsion (side to side)
Fore flippers used to direct
Hind flippers not hinged
= less mobility on land
Although they feed in the sea all seals
give birth on land
They “haul up” onto beaches to breed
Seal pups are very vulnerable so they grow
and are weaned quickly
Seal milk is 30-60% fat (vs 4% in cow milk)
Pups gain weight & a thick blubber layer quickly
AQUATIC ADAPTATIONS
• Webbed toes and fore limbs have
developed into paddle-like pectoral fins
• Fusiform (streamlined/spindle-shaped)
body
• Thick blubber layer - reduced heat loss
• Insulating hair layer (especially in fur
seals)
• Flippers enervated with blood vessels –
radiate heat when on land to avoid
overheating
AQUATIC
ADAPTATIONS
• Counter current
system to
prevent heat loss
via limbs in water
• Nostrils on top of
muzzle
• Sensory
vibrissae
(whiskers) help to
detect movement
in water
• Reflecting layer
or TEPETUM in
eye- allows low
light vision
DIVING ADAPTATIONS
• Can store large amount of oxygen in
blood and tissues
• Can withstand high concentrations of
lactic acid (product of anaerobic respiration)
• Can reduce their heart rate
(BRADYCARDIA) and metabolic rate –
reduces rate oxygen is used up
• Lungs collapse when they dive – no
absorption of nitrogen under pressure –
no “BENDS”