Environment Australia, February 2003
They may not be cute and cuddly but frogs are an important part of Australia's creeks, rivers and wetlands. If frogs start disappearing from the landscape, it is a sure sign that it's time to take better care of their watery homes.
Frogs are cold-blooded animals that belong to a group of animals called amphibians. There are about 4000 frog species worldwide. Australia has 208 frog species, and many of these are endemic - that is, they are found nowhere else in the world.
A frog's skin is permeable, which means that water and other gases can pass through it. As a result, frogs need to keep their skin moist or they could dry out! They do this in different ways - some live near water bodies, in shady vegetation or rock faces, some cover their skin an a slimy substance and some even burrow into the soil.
Many frogs reproduce by laying eggs in a mass of jelly like material in the water. Tadpoles develop from this jelly mass, rapidly grow arms and legs, lose their tails and eventually transform into frogs. Most tadpoles are unable to leave the water until they have developed into frogs.
Others have far stranger ways of reproducing - some glue their eggs to underwater vegetation, while others hatch from the eggs as fully formed frogs. The male Hip-Pocket Frog carries tadpoles round in little pockets on his hips!
Four species of Australian frogs have become extinct, which means they have died out, and the survival of another 27 species is under threat. Two of Australia's threatened frog species are the Southern Corroboree frog and the Baw Baw frog.
Southern Corroboree frog
The nationally endangered Southern Corroboree frog grows to 30 mm in length and has very noticeable black and yellow stripes. It is only found in a very small part of the sub-alpine area of Kosciuszko National Park in New South Wales. Once there were many but it is thought that there are now only about 100 frogs remaining.
The Southern Corroboree Frog uses two different types of habitat during its lifecycle: pools and wet areas in sphagnum bogs, wet tussock grass and wet heath for breeding; and forest, sub-alpine woodland and tall heath next to the breeding areas during other times of the year.
Females only breed once a year, and the tadpoles are slow growing, spending over six months in shallow pools, some of the time beneath a blanket of snow. The young frogs take a further four years before they start breeding, and can live to over eight years in age. Its restricted habitat and special breeding pattern makes this species extremely vulnerable to disturbances such as fire. Climate change, drought and disease are thought to be the main reasons for a decline in numbers.
Baw Baw frog
The nationally endangered Baw Baw frog is found only in an area of 80 square kilometres on the Baw Baw plateau, Victoria.
Like the Corroboree frog, the Baw Baw frog also needs special habitat. It breeds in wet areas in subalpine heathland and forest. It lays its eggs in foam nests in natural cavities in or under dense vegetation, logs, soil or rock. In the non-breeding season, the frogs shelter beneath dense vegetation, roots, logs, rocks and leaf litter near their breeding sites. These sites provide protection from extreme weather conditions.
Baw Baw frogs breed once a year between early October and late December. Unlike most tadpoles, Baw Baw tadpoles do not feed, instead hatching with a yolk sac that feeds them until they turn into frogs. They do not swim either; instead they develop under vegetation and leaf litter where there is little free flowing water.
Once thought to number between 20 000 and 30 000 frogs, now less than 600 remain. The reasons for the decline of the Baw Baw frog are unknown, but could include climate change, pollution, habitat destruction or disease.
Human activities, as well as invasive plants and animals and land clearing play a role, but more complicated factors are also thought to have an impact. Climate change and pollution are also like to be contributing to the decline in frog populations. The deadly Chytrid fungus - an infectious disease contaminating frogs worldwide, is also affecting many vulnerable species.
You can help threatened frogs by:
- Taking care when visiting national parks that you disturb as little as possible;
- Not removing frogs or tadpoles from the wild;
- Not disturbing rocks and logs that could be habitat for frogs;
- Joining a conservation, 'friends' or Bushcare group or by volunteering for Conservation Volunteers Australia;
- Not touching frogs - this can pass on the deadly Chytrid fungus.
Knick knack, paddywack, give a frog a home
Select the right spot
The ideal place for a frog pond is part shady, part sunny area, but not directly under trees. Don't put the pond too close to your house as frogs can be noisy at times! Placing the pond near your compost heap gives frogs access to tasty insects and worms.
Create the right habitat
Plant native shrubs, ground cover and trees around the pond to give frogs hiding spots from predators and shelter from wind. You'll need to plant native shrubs, ground cover and trees of different heights. Vegetation also attracts insects to your garden for frogs to eat. A rock pile or fallen logs work well to keep the area shaded and cool. Plant shrubs and ground cover around the pond to give frogs a comfy resting place, hiding spots from predators and shelter from wind.
Use the right pond
A frog pond should be spoon-shaped with shallow, sloping walls. This allows easy access for the frogs to get in and out of the pond. Styrofoam boxes, children's pools and old laundry tubs can all make good frog ponds. If the sides are steep, build a ramp using sand, gravel, rocks, logs or tree branches. You could also dig your own pond, and line it with plastic to stop the water escaping. The water will need to be free from chemicals, so let tap water stand for a week before putting it in your frog pond.
Add plenty of swamp plants in trays or pots in the shallowest region, and place a few potted aquatic plants and water lilies further down. Cover their soil with sand. The waterweeds will provide habitat for the tadpoles and baby fish to shelter in while they are small and vulnerable to predators. Some types of fish, like Rainbow fish are frog-friendly and also help control mosquitoes. Some people add local stream insects such as backswimmers and damselfly larvae instead. Never place Goldfish or Mosquito Fish in your pond as they are poisonous to frogs or eat their tadpoles.
Be patient! Frogs sometimes take up to two years to begin settling in your garden. If frogs don't move in of their own accord, you might need a permit to introduce them. Check with your state wildlife authority before introducing frogs or tadpoles.
Check out these web sites for more information:
- How to build a frog pond - knick knack, paddywack, give a frog a home
- Threatened species and ecological communities publications
For more information contact:
Environment Australia (the Department of the Environment and Heritage)
Community Information Unit
GPO Box 787
CANBERRA ACT 2601
Telephone: 1800 803 772