MARS2014 Lecture Notes - Lecture 7: Dwarf Sperm Whale, Weaning, Indo-Pacific
Unit 7: Marine mammals in Australia
▪ How many species of marine mammals are there, and what are the three
orders?
• 57 species
• Order Carnivora, sub-order Pinnipedia (seals)
• Order Cetacea (whales and dolphins)
• Order Sirena (dugongs)
▪ How have they adapted to move?
• Streamlining of body
• Buoyancy unsung integument and blubber
• Propulsive force: axial body and tail
• Steering: fore flippers/hydrofoils
• Whales/humpbacks can use huge pectoral fin to control amount of
lift
▪ How do they thermoregulate?
• Large body to maintain heat
• Counter-current exchange systems, where heat circulation is
redirected back to the centre of the body
• Mainly insulation
• Some mammals can increase their metabolic rate (e.g. Sea otters,
seals)
▪ How do they dive and respire?
• Have efficient respiratory exchange – can exchange >80% of the air
in their lungs with each breath
• Often will exhale and close off airways before diving, so can take
oxygen down in their blood or myoglobin
• Have a high blood volume, with extra and expanded blood vessels,
each cell has high haemoglobin and muscles have high myoglobin
▪ What are the three families of the sub-order Pinnipedia?
• Octariidae (14 species)
• Phocidae (18 species)
• Odobenidae (1 species – walrus)
▪ What are the characteristics of the sub-order Pinnipedia?
• Tied to land or ice to breed
• United by obvious anatomical and physiological features
o Fusiform body
o Flippers
o Insulation (fur, blubber, both)
▪ What are the characteristics of the family Otariidae?
• Eared seals
• Cold water species
▪ What are four of the types of Otariids?
• Australian fur seal
• NZ fur seal
• Australian sea lion
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• Antarctic fur seal
▪ What are the characteristics of the Australian sea lion?
• The only endangered Pinniped in Australia
• Lives around islands and mainland in SA and WA
• Total approximately 14,700
• Endangered and in need of special protection
• Asynchronous breeding cycle
o 5-7 months breeding
o 17-18 months non-breeding
o Unlike most seals, which have a 12-month cycle
▪ Why are Australian sea lions endangered?
• Harested i the past ad the populatios hae’t reoered
• Due to their long complicated breeding cycle
• Have small breeding colonies
• Females always return to the same site
• Have a low reproductive rate
o Few breeding at one time, long dependency phase, very
energy-consuming for females
• Have high mortality
o Pup at weaning: disease, nutritional stress, attacks by males
o Adults: fisheries by-catch
• Exposure to human activities
o Gill nets, lobster pots, entanglement in lines, poaching,
pollution, disease
▪ What are four of the types of Phocids (true seals)?
• Weddell seal
• Leopard seal
• Crab eater seal
• Elephant seal
▪ What are the characteristics of the Southern Elephant seal?
• Lives in Southern Hemisphere
• Swim long distances (1000s of km)
• Move far offshore and dive very deep
• Aggressive and territorial
• Have harems of females
▪ What are the characteristics of the Weddell seal?
• Very southerly distributed (smallest and most southerly distributed
of all seals)
• Do’t oe far offshore
• Have elaborate courtship rituals
• Live on ice
• Spend time under the ice and maintain breathing holes
• Use their teeth to scrape at the ice, which may compromise feeding
ability
▪ What are the characteristics of the crab eater seal?
• The most numerous seals in the world
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• Have a circumpolar distribution, broader than the Weddell, around
Antarctica
• Feed on krill
• Use teeth as a sieve in feeding
▪ In the order Cetacea, what are the characteristics of the whales?
• Inhabit polar to tropical regions
• Some reside year round at a single latitude, others are migratory
▪ What are the sub-orders of Cetacea?
• Mysticete (have plates on their jaw)
• Odontocete (have teeth)
▪ What is the external anatomy of the whales?
• Streamlined for swimming
• Have horizontal flukes
• Hindlimbs are lost
• Have pectoral fins and flippers
• Must have a dorsal fin
• Have dorsal nares/nostrils – blowholes
• No external genitalia or mammary glands
• Have no hair
• Have no pinna/ears
▪ What is telescoping?
• Where maxilla and pre-maxilla bones elongate backwards, putting
nostrils on top of head
▪ What are the kinds of odontocetes?
• Amazon River dolphin
• Baiji and franciscana
• Narwhal and beluga
• Porpoises
• Oceanic Dolphins
• Ganges and Indus River Dolphins
• Beaked and bottle nose whales
• Sperm whale
• Pygmy sperm whale
▪ What are the kinds of Mysticetes?
• Right and bowhead whale
• Pygmy right whale
• Rorquals
• Grey whale
▪ What are the differences between Odontocetes and Mysticetes?
• Size
• Anatomy of nares
• Dentition and feeding ecology
• Echolocation
• Migration
• Social organisation
• Life histories
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Document Summary
Live on ice ability: what are the characteristics of the crab eater seal, the most numerous seals in the world, have a circumpolar distribution, broader than the weddell, around. Antarctica: feed on krill, use teeth as a sieve in feeding. Long pre-reproductive period, 1-20 years: 1 offspring a season, although some species will have twins, gestation for 10-17 months, slow population increase 2-10%/yr. Little studied in australia, found in waters off all slopes: whaling until 70s, what are the characteristics of the beaked whales, 6 genera, mesoplodon, ziphus, tasmacetus, hyperodon, beradius. Large, up to 4m, social pods: coastal and oceanic waters. Inshore bottle nose dolphins: up to 2. 6 metres, belly is light grey, shallow inshore water, australian humpbacked dolphin. Long-lived (>70 years: slow growth, slow reproduction, the female matures in 13-17 years, has one calf at a time, 15 months gestation period, 3-7 years between calves.
