Marine mammals Flashcards
Marine mammals belong to which category of mammals
Eutherian mammals
Cetacea
Whales, dolphins and porpoises
2 suborders:
Mysticeti - Baleen whales
(including family: Balenopteridae = Rorquals - Largest animals ever to live)
Odontoceti - Toothed whales (including dolphins and porpoises)
Canivora - Suborder: Pinnepedia
Divided into 2 families
Phocidae (True seals)
Otariidae (Fur seals and sea lions)
Phocidae (true seals)
More solitary
Mate in water, birth on ice
Less sexually dimorphic or females larger
Very short lactation, concentrated milk
Uncommon on Australian coast unless vagrant/ debilitated immature animals
Clumsy on land
Otariidae (sea lions and fur seals)
Less highly adapted to diving
Common on southern Australian coast
Visible ear pinnae
Quadrupedal ambulation, agile on land
Use forelimbs for propulsion in water
Breed on land -sexually dimorphic
Australian sealions have 18 mth breeding cycle.
Australian Sea lions
Endangered
Endemic
Reduced range
Slow recovery from hunting
- high pup mortality (DR 40%)
- Fisheries interactions
- Direct-fish farms and cray pots
- Competition-cray fisheries
- Predation
- shark fishing by-catch
High female site fidelity and asynchronous breeding
- Limited recolonization
- Limited genetic diversity at mtDNA
Australian pup mortality causes
Crushing and hookworm
- Larvae via milk - eggs hatch to produce larvae in soil
Diving adaptations of Australian Sea lion
Increased blood volume with enlarged venous sinuses
Increased Haematocrit
Increased Myoglobin
Collapsible trachea and lungs, absence of paranasal sinuses,
Ablation of middle ear cavity
Dive with empty respiratory tract
Dive response in seals/ sea lions
Peripheral vasoconstriction - preferential circulation to vital organs
Apnoea
Reduced metabolic rate
Anaesthesia problems with seals/sea lions
Tracheal collapse-weight, lack of support
Proximity to water
Apnoea
Hyperthermia
Lack of peripheral circulation
Predominantly with Phocids rather than Otariids
Thermoregulation: Phocid (seals) vs Otariid (sealions)
Phocid:
- Blubber
Otariid:
- Insulating fur
Both:
- Peripheral vasculature
- Behaviour
- Low surface area/kg
Order: Sirenia
Dugongs and Manatees
Dugongs
Hind-gut digestion
Grinding teeth which migrate rostrally
Males have 2 tusks
Dense boned, generally slow but capable of speed
Dugong threats
Vulnerable to silting, motor vessels, fishnets
Bio-concentrations of dioxins and heavy metals - significance unknown
Very slow to breed (maximum population growth under ideal conditions 5%)
Dugong management
International management required as dugongs travel long distances over shallow, protected parts of the continental shelf.
