The Rakali – (Eastern Water Rat)

1. Michelle Smith The Rakali – (Eastern Water Rat) Rodents of the World Australian rodents Evolution Rakali breeding The Rakali pelt The Rakali diet Habitats Rakali research – Swan Bay

2. Rodents of the World • Order Rodentia • Squirrel, beaver, porcupine, guinea pig, capybara, mice, rat • Large, gnawing incisors • Strong jaw muscles • Varied diet, including tough woody plant material

3. Australian Rodents • 55% marsupials, 22% rodents, 22% bats, 1% monotremes • 61 rodent species – 6 introduced • 4 self-introduced, including black and brown rats, and house mouse

4. Evolution of the Rakali • 14 genera of native rodents • Most are “Old Endemics” - including Rakali • Rakali in Hydromyinae subfamily – 9 in New Guinea, 2 in Australia • False Water Rat in coastal Nth Qld • Rakali widespread, although patchy • Aquatic niche – fur and feet adapted

5. Rakali Breeding • Females breed at approx. 5 months age for 3 seasons • Spring / summer breeding in Victoria • 1 – 7 in litter, average of 4 • Blind, short-furred and grey/black at birth, with white tail tip • Eyes open at 14 days, and eat some solids at 3 weeks • Weaned at 4 weeks

6. The Rakali Pelt • Thermal balance and buoyancy • Colours vary according to geography • All have white tail tip • Black and orange individuals more aggressive • Hunted until 1938

7. The Rakali Diet • Carnivorous • 2 molars per row instead of 3 – required for crushing hard-shelled prey items • Most prey taken in water • Fish, molluscs, birds, amphibians, insects, lizards, eggs, spiders, yabbies, turtles, crabs, snails, carrion, small mammals, crayfish, crustaceans, rubbish • Climb trees!

8. Capturing and Consuming Prey • Eyes opened underwater, ears closed • Prey captured and carried in mouth • Prey taken to suitable feeding tables • Leave behind evidence including crab and mollusc shells, yabbie remains, fish scales, bones, feathers etc.

9. Rakali Habitat • Mainly considered freshwater animal • Inland rivers and irrigation channels • Permanent water bodies • Little research or knowledge of coastal habitats

10. Rakali Habitats - General • Dense vegetation cover or rocks • Low banks preferable to flat water edge • Stable and friable soil • Semi-submerged hollow logs • Round burrow entrance in bank

11. Rakali in Coastal Zones • In Victoria, Rakali have been located at: • Melbourne (Williamstown, Port Melb, St Kilda, Elwood, Brighton, Black Rock) • Mornington Peninsula (Sorrento) • Bellarine Peninsula (Clifton Springs, Swan Bay – Queenscliff) • Westernport Bay (French and Phillip islands) • Wilsons Promontory (Corner Inlet)

12. Rakali Research at Swan Bay • Sandy beaches, mudflats, saltmarsh • Capture – Mark – Recapture • Individually ear-tagged • Animals weighed, measured • Injuries assessed • Released at point of capture

13. Rakali at Swan Bay • Feeding tables investigated • Prey items identified • Stomach, intestinal and faecal contents examined • Habitat variables defined and analysed • Bank characteristics • Distance • Prey abundance • Plant species • Soils • Veg density • Disturbance • Rocks and logs

14. Rakali at Swan Bay – Populations • 156 males and 94 females (20 hectares) • Sex ratio of 1.5 males: 1 female • 72% were adults • 33% males with injuries • Male weight – 776g (375g - 975g) • Female weight – 636g (330g – 840g)

15. Rakali at Swan Bay - Diet • 50% Rock Crab • 20% Mottled Shore Crab • 20% Surf Crab • Other components included: • Smooth Seaweed Crab • Pilchard • Silver Gull • Prickly Toadfish • Smooth Pebble Crab • Shore Crab • Bridled Leatherjacket • Pheasant Shell • No luck with gut analysis

16. Rakali at Swan Bay - Habitat Coast Saltbush - (Atriplex cinerea) • Saltmarsh vegetation: • Shrubby Glasswort, Beaded Glasswort, Austral Seablite, Coast Saltbush, Marsh Saltbush, Southern Sea-heath,

17. The End