Wetland Fauna
Wetland ecosystems contain species that have evolved in a wet environment. Adaptations to an aquatic life are often obvious: fins on fish, webbed feet on frogs and ducks, and waterproof feathers or fur on darters and platypus. Other adaptations are less conspicuous, such as: gills on mayfly larvae and tadpoles (gills disappear as the tadpoles change into adults); salt glands on the tongues of crocodiles that remove excess salt in brackish conditions; and the cloacal bursa of the Fitzroy River turtle that enables this turtle to take up oxygen while submerged (hence the colloquial name of ‘bum-breather’).
The degree that fauna are dependant on the wetland environment ranges from those with complete dependence (yabbies and freshwater fish), to those that exist in other habitats but need wetlands for some significant resource (for example, although they are terrestrial, grey and ornamental snakes hunt in wetlands where they feed on frogs).
Some animal species are so reliant on wetlands that evidence of their occurrence — such as with crustacean exoskeletons or crayfish burrows — can confirm the presence of a wetland.
A list of wetland indicator species is provided for use in determining whether an area is a wetland.
Wetland invertebrates
Certain insect groups, crustaceans and molluscs make up the majority of wetland macro-invertebrates (those that are easily seen).
Insects
Many insects spend at least part of their lives living in or on water. They are a diverse group, with at least 119 insect families recognised as having an aquatic life-stage. Some commonly-known aquatic insects include back swimmers and water-boatman (Hemiptera), water beetles (Coleoptera), mosquito larvae (Diptera), caddis-fly larvae (Trichoptera) and dragonfly larvae (Odonata).
Aquatic insects are important components of wetland ecosystems. They are food for many other animals, including fish, platypus and birds. They are also important for their role in cycling nutrients and carbon through wetland systems. Aquatic insects and other invertebrates have different sensitivities to pollution and for that reason are popular indicators for wetland assessment.
Crustaceans
Crabs are found in saline wetlands of the coasts, but they also occur in freshwater systems (for example, Holthuisana spp.). Freshwater crayfish (Cherax — yabbies, Euastacus— spiny crayfish, and Tenuibranchiurus— swamp crayfish) are more typical in non-estuarine areas. They occur in habitats up to 1000m above sea level.including coastal swamps in wallum to rocky streams in rainforest., Other freshwater crustaceans include atyid shrimps (for example, Caridina spp.) and palemonid prawns (for example, Macrobrachium spp.).
Molluscs
Like crustaceans, shellfish tend to be associated with estuarine or marine environments, but they are also present in inland wetlands and isolated waterbodies (for example, mound springs). Freshwater mussels (for example, Velesunio spp.) occur in streams and were a widely used and important food item for Aborigines, while the endangered Boggomoss snail Adclarkia dawsonensis is restricted to just a few known localities along the Dawson River.
Links
Queensland river assessment manual
Vertebrates
Fish
Fish spend their whole lives in water, and consequently all freshwater and estuarine fish species in Queensland are considered wetland indicators. A fish community can comprise residents (for example, rainbowfish and grunters) as well as migrants, that move upstream and downstream to breed in response to seasons or flood events (for example, Australian bass and silver perch). Not only are bony fish present in wetlands, but a few sharks, sawfish and rays also live in both fresh and brackish conditions.
Frogs
Few frog species spend their entire lives in water. Totally aquatic taxa include the probably extinct gastric brooding frogs (Rheobatrachus spp.). A few species exist independent of wetlands (for example, microhylid species). Most frogs need some form of waterbody into which eggs are laid and tadpoles develop. However, not all waterbodies are wetlands. For example, some burrowing frogs (Cyclorana spp.) are capable of spawning in temporary puddles in grasslands or in wheel ruts.
Frogs living in permanent wetland conditions usually breed in the wet summer months. Those in the arid inland areas with ephemeral wetlands are usually burrowing frogs that lie underground, surfacing to feed and reproduce only after a rain or flood event. Breeding lasts only as long as there is water, so egg laying and tadpole development is relatively rapid.
Reptiles
Unlike frogs, members of one group of wetland-dependent reptiles — crocodiles and freshwater turtles — spend nearly all their time feeding and interacting in the water, coming out on land to lay their eggs in holes in the ground or in nests of vegetation. Other reptiles, such as eastern water dragon, Mertens’ water monitor and Macleay’s water snake, rely on wetlands primarily as a source of food (in the form of crayfish, crabs, fish and frogs) and for a safe haven to hide when disturbed.
Birds
By far the most noticeable fauna of any wetland, birds often present the quintessential images of this habitat — for example, large flocks of magpie geese grubbing for bulbs in a sedgeland or the chaotic nature of heronries when egrets, ibis and cormorants squabble over nest sites in melaleuca swamp wetlands. However, there are many birds just as dependent on wetlands for food, shelter and breeding resources that are rarely seen. Birds such as crakes, rails, kingfishers and reed-warblers are often hidden within dense reed-beds or mangrove-lined channels.
Within wetlands, birds often have great fluctuations in numbers. It is common for wetland birds to migrate (for example, waders breed in the Northern Hemisphere and return in the summer months) and many birds are often opportunistic (for example, during drought conditions aggregations of ducks on the few permanent waterholes). Many international migratory birds return to the same feeding areas from year to year and consequently these species, and the areas they inhabit, are recognised as being important by several international agreements such as JAMBA, CAMBA and ROKAMBA.
Mammals
Although the smallest of the wetland-dependent vertebrate groups, mammals contain what is probably the most iconic of species — the platypus. Breeding and resting by day in riverbank burrows, the platypus relies on freshwater streams and lakes for its food (aquatic invertebrates), which it collects during at twilight and during the night . Swamp rats, water-rats and false water-rats have similar temporal patterns of habitat use, but unlike the platypus they do all their foraging among the vegetation in various fresh and estuarine wetlands.
The only truly aquatic mammals that visit wetlands regularly are two rare dolphin species (Australian snubfin and Indo-Pacific hump-backed dolphins) that sometimes forage in estuaries, lower freshwater sections of rivers and mangrove swamps.
For specific information on wetland species and sightings please go to Wildlife Online.
Links
Status of Freshwater and Estuarine Elasmobranchs in Northern Australia
Fish movement and migration
The Convention on the Conservation of Migratory Species of Wild Animals
(also known as CMS or Bonn Convention) (1979)
The Federal Government’s Environmental Protection and Biodiversity Conservation Act (1998)
References
Last updated: 7 May 2008
