The Rakali – (Eastern Water Rat)The Rakali – (Eastern Water Rat)

Rodents of the WorldRodents of the World Australian rodentsAustralian rodents

EvolutionEvolution Rakali breedingRakali breeding The Rakali peltThe Rakali pelt The Rakali diet The Rakali diet

HabitatsHabitats Rakali research – Rakali research –

Swan BaySwan Bay

Michelle Smith

Rodents of the WorldRodents of the World Order RodentiaOrder Rodentia

Squirrel, beaver, porcupine, guinea pig, Squirrel, beaver, porcupine, guinea pig, capybara, mice, ratcapybara, mice, rat

Large, gnawing incisorsLarge, gnawing incisors

Strong jaw musclesStrong jaw muscles

Varied diet, including tough Varied diet, including tough woody plant materialwoody plant material

Australian RodentsAustralian Rodents

55% marsupials, 22% rodents, 22% 55% marsupials, 22% rodents, 22% bats, 1% monotremesbats, 1% monotremes

61 rodent species – 6 introduced61 rodent species – 6 introduced

4 self-introduced, 4 self-introduced, including black and including black and brown rats, and brown rats, and house mousehouse mouse

Evolution of the RakaliEvolution of the Rakali 14 genera of native rodents14 genera of native rodents Most are “Old Endemics” - including RakaliMost are “Old Endemics” - including Rakali Rakali in Hydromyinae subfamily – 9 in New Rakali in Hydromyinae subfamily – 9 in New

Guinea, 2 in AustraliaGuinea, 2 in Australia• False Water Rat in False Water Rat in coastal Nth Qldcoastal Nth Qld

• Rakali widespread, Rakali widespread, although patchyalthough patchy

• Aquatic niche – fur Aquatic niche – fur and feet adaptedand feet adapted

Rakali BreedingRakali Breeding Females breed at approx. 5 months age for Females breed at approx. 5 months age for

3 seasons3 seasons Spring / summer breeding in VictoriaSpring / summer breeding in Victoria 1 – 7 in litter, average of 41 – 7 in litter, average of 4 Blind, short-furred and grey/black at birth, Blind, short-furred and grey/black at birth,

with white tail tipwith white tail tip • Eyes open at 14 days, Eyes open at 14 days,

and eat some solids at 3 and eat some solids at 3 weeksweeks

• Weaned at 4 weeksWeaned at 4 weeks

The Rakali PeltThe Rakali Pelt Thermal balance and buoyancyThermal balance and buoyancy Colours vary according to geographyColours vary according to geography All have white tail tipAll have white tail tip Black and orange individuals more Black and orange individuals more

aggressiveaggressive Hunted until 1938Hunted until 1938

The Rakali DietThe Rakali Diet CarnivorousCarnivorous 2 molars per row instead of 3 – required for 2 molars per row instead of 3 – required for

crushing hard-shelled prey itemscrushing hard-shelled prey items Most prey taken in waterMost prey taken in water Fish, molluscs, birds, amphibians, insects,Fish, molluscs, birds, amphibians, insects,

lizards, eggs, spiders, lizards, eggs, spiders, yabbies, turtles, yabbies, turtles, crabs, snails, carrion, crabs, snails, carrion, small mammals, small mammals, crayfish, crustaceans, crayfish, crustaceans, rubbishrubbish Climb trees!Climb trees!

Capturing and Consuming PreyCapturing and Consuming Prey Eyes opened underwater, ears closedEyes opened underwater, ears closed Prey captured and carried in mouthPrey captured and carried in mouth Prey taken to suitable feeding tablesPrey taken to suitable feeding tables Leave behind evidence including crab and Leave behind evidence including crab and

mollusc shells, yabbie remains, fish scales, mollusc shells, yabbie remains, fish scales, bones, feathers etc.bones, feathers etc.

Rakali HabitatRakali HabitatMainly considered freshwater animalMainly considered freshwater animal

Inland rivers and irrigation channelsInland rivers and irrigation channels

Permanent water bodiesPermanent water bodies

Little research or knowledge of coastal Little research or knowledge of coastal habitatshabitats

Rakali Habitats - GeneralRakali Habitats - General Dense vegetation cover or rocksDense vegetation cover or rocks Low banks preferable to flat water edgeLow banks preferable to flat water edge Stable and friable soilStable and friable soil Semi-submerged hollow logsSemi-submerged hollow logs Round burrow entrance in bankRound burrow entrance in bank

Rakali in Coastal ZonesRakali in Coastal Zones In Victoria, Rakali have been located at:In Victoria, Rakali have been located at:

Melbourne (Williamstown, Port Melb, St Kilda, Melbourne (Williamstown, Port Melb, St Kilda, Elwood, Brighton, Black Rock)Elwood, Brighton, Black Rock)

Mornington Peninsula (Sorrento)Mornington Peninsula (Sorrento)Bellarine Peninsula (Clifton Springs, Swan Bay – Bellarine Peninsula (Clifton Springs, Swan Bay –

Queenscliff)Queenscliff)Westernport Bay (French and Phillip islands)Westernport Bay (French and Phillip islands)Wilsons Promontory (Corner Inlet)Wilsons Promontory (Corner Inlet)

Rakali Research at Swan BayRakali Research at Swan Bay Sandy beaches, mudflats, saltmarshSandy beaches, mudflats, saltmarsh Capture – Mark – Recapture Capture – Mark – Recapture Individually ear-taggedIndividually ear-tagged Animals weighed, measuredAnimals weighed, measured Injuries assessed Injuries assessed Released at point of captureReleased at point of capture

Rakali at Swan BayRakali at Swan BayFeeding tables investigatedFeeding tables investigatedPrey items identifiedPrey items identifiedStomach, intestinal and faecal contents Stomach, intestinal and faecal contents

examinedexaminedHabitat variables defined and analysedHabitat variables defined and analysed

Bank characteristicsBank characteristics DistanceDistance Prey abundancePrey abundance Plant speciesPlant species SoilsSoils Veg densityVeg density Disturbance Disturbance Rocks and logsRocks and logs

Rakali at Swan Bay – PopulationsRakali at Swan Bay – Populations156 males and 94 females (20 hectares)156 males and 94 females (20 hectares)Sex ratio of 1.5 males: 1 femaleSex ratio of 1.5 males: 1 female72% were adults72% were adults33% males with injuries33% males with injuriesMale weight – 776g (375g - 975g)Male weight – 776g (375g - 975g)Female weight – 636g (330g – 840g)Female weight – 636g (330g – 840g)

Rakali at Swan Bay - DietRakali at Swan Bay - Diet 50% Rock Crab50% Rock Crab 20% Mottled Shore Crab20% Mottled Shore Crab 20% Surf Crab20% Surf Crab Other components included:Other components included:

Smooth Seaweed CrabSmooth Seaweed Crab PilchardPilchard Silver GullSilver Gull Prickly ToadfishPrickly Toadfish Smooth Pebble CrabSmooth Pebble Crab Shore CrabShore Crab Bridled LeatherjacketBridled Leatherjacket Pheasant ShellPheasant Shell

No luck with gut analysisNo luck with gut analysis

Rakali at Swan Bay - HabitatRakali at Swan Bay - Habitat

Coast Saltbush - (Atriplex cinerea)

Saltmarsh vegetation:

• Shrubby Glasswort, Beaded Glasswort, Austral Seablite, Coast Saltbush, Marsh Saltbush, Southern Sea-heath,

The EndThe End