Presentation on theme: "Different Places Different Diets Different Places Different Diets Feeding habits and diet of the Water-rat Rakali Hydromys chrysogaster in the waters of."— Presentation transcript:
Different Places Different Diets Different Places Different Diets Feeding habits and diet of the Water-rat Rakali Hydromys chrysogaster in the waters of City of Port Phillip Andrew McCutcheon - Earthcare St Kilda Inc
Feeding habits and diet of rakali n They are amphibious hunters of mostly aquatic and marine organisms. They also hunt on land. n Diet consists of larger aquatic insects, crustaceans, molluscs, fish, frogs, birds and even aquatic plants. n They are opportunistic and will quickly adapt to other types of food if there is a shortage of the normal or preferred food source. n They hunt or forage for food by running on waters edge, wading in shallow water or swimming and diving in water to a depth of 2 metres. n Prey is generally taken to a feeding platform such as a rock or log in or beside the water. They will frequently use moored boats for this purpose.
How can we find out what rakali eat? n Direct Observation n Analyse food left on feeding platforms - middens Middens provide a good indication of prey species that exist in a particular habitat area. Middens provide a good indication of prey species that exist in a particular habitat area.
Rakali eating Red Swimmer Crab ctober 04
Rakali resting - Note abundant whiskers
Partially webbed hind-foot
Four Habitat Areas in City of Port Phillip n St Kilda Harbour n Elwood Canal & Point Ormond shore n Albert Park Lake n East shore of Webb Dock & Port Melbourne Foreshore
St Kilda Harbour n Sheltered and exposed marine habitat n Habitat subject to heavy storms battering breakwater n Populations can be reduced or vanish after storms and/or heavy rain producing flows of turbid/ polluted water from the Yarra River and drains n Prey species consist of crabs, European Fanworms, fish and possibly baby penguins. Red Swimmer Crabs are the preferred diet. n Main threats are heavy storms, floods and water pollution impacting on prey.
Inside of breakwater - St Kilda Harbour
Pier and breakwater - St Kilda Harbour
Rakali eating Red Swimmer Crab ctober 04
Floodwater from Yarra after storm - 2 February 05
Turbid water 3 days later - 5 February 05
Rakali midden with small Common Shore Crab - 23 march 05
Rakali midden with small clam and European Fan Worms - 23 March 05
Rakali midden with European Fan Worms - 23 March 05
Rakali feeding on European Fan Worm - 23 March 05
Rakali midden with European Fan Worms - 1 May 05
Midden with Common Shore Crab & Fanworm- 2 October 05
Midden with Common Shore Crabs - 16 October 05
Rakali feeding on Sea lettuce - 16 October 05
Elwood Canal & Point Ormond shore n Freshwater surface drain, tidal canal and exposed marine habitat n Habitat subject to complete inundation and rapid change of water quality (salinity, turbidity) after heavy rain n Populations can be reduced or vanish after storms and/or heavy rain n Prey species not fully known as there are no middens. Fish and aquatic insects are the most likely diet. n Main threats are heavy floods and water pollution
Elwood Canal -High tide
Elwood Canal -Low tide
Elwood Canal -Very low tide
Foreshore north of Pt Ormond
Baby Black Bream
Albert Park Lake n Freshwater Lake with island n Gunn Island appears to be the land based refuge for rakali. n Habitat subject to little change as water level is regulated, and stormwater pollution minimised by pollution control ponds. n Prey species not fully known as there are no middens. Yabbies and aquatic insects are the most likely diet. n Main threats appear to be water pollution impacting on prey
The Point - Albert Park Lake
Pollution control pond - Albert Park Lake
East shore of Webb Dock & Sandridge Beach (Port Melbourne) n Exposed marine habitat n Habitat subject to heavy storms battering rock armor and groynes n Rakali show great variation in diet. Prey species consist of crabs, mussels, European Fanworms, and possibly fish. No single species appears to form a preferred diet. n Main threats appear to be heavy storms.
Webb Dock East Park
Sandridge Beach Groyne
Midden with Mussels - 1 October 05
Midden with small Spider Crab - 1 October 05
Midden with small Red Swimmer Crab - 1 October 05
Why is it important to find out what rakali eat? n To obtain a better understanding as to how they survive in our urban environment, in what are primarily man made habitats. n To determine the diversity of aquatic or marine species that live in our marine or aquatic habitats. n Rakali are good indicators of whether our marine and aquatic ecosystems are in a healthy environmental condition.