FrogFacts No. 2, December 1992, ISSN 1037-0617

Keeping Frogs in Your Garden

by Merinda Voigt

Summary:
This leaflet shows you how to establish or modify a garden pond for many of those local frog species that spawn in still or slowly moving water. The pond must be be free of predatory fish and polluting chemicals. It must also have gently sloping sides for the frog to emerge and vegetation shelter around the pond

Important

1. Frog numbers of some species are declining alarmingly with several formerly common species one possibly facing extinction. If you can provide a frog refuge in your garden, please do so.
   
   
2. Please don't introduce frogs that don't occur naturally in your area. They may hybridise with local varieties of the same specie or crowd other species out of upset the local balance in other ways - remember the cane toad! Never bring in frogs from more than 50 km away.

Advantages to you

1. A water garden with flowering marsh plants and water lilies is a very attractive focal point. These plants are generally also resistant to pests and diseases and require little maintenance.
   
   
2. The ability to observe the life cycle of frogs throughout the seasons provides added interests to your gardening.
   
   
3. Frogs help to control insects pests.

Location of Pond
An ideal place is part sunny, part shady, but not directly under trees. Give a wide berth to trees that have poisonous leaves (e.g. Oleander, Bleeding Heart, Pines ...). To get the most enjoyment from your pond, locate it so that it's visible from the house but in the back garden, a bit away from your own house and your  neighbour's houses because frogs cam be noisy at times. The taller bog plants should be around the back of the pond. A low garden lamp that reflected in the water will not only add to your garden's appearance in the evening but also attract insects for the frogs. Your compost heap, another source of insects, should be close to the pond. (Part of the heap can be slightly raised on a wire mesh tray or a pallet. Insects and worms that fall through will provide food fro the frogs sheltering below.) Other shelters at the edge of the ponds should consist of vegetation, a rock plie and planks or fallen logs.

Pond Construction
The simplest way is to scoop a hole in the ground ( at least 1-2 m across and 60- 80 cm deep), surrounded by shallow region (say 50 cm wide and 30-50 cm deep) and again surrounded by very shallow ring (irregular but a least 50 - 200 cm wide, 10-20 cm deep). Between the three regions is gently sloping ground, never vertical or steep sloping walls. Remove any sharp objects and spread a thin layer of sand. Over the sand place a sheet of flexible black PVC liner (UV resistant and heavy-duty, approximately Aust. $ 18/m² from pond product suppliers). Don't use building grade polythene, it would deteriorate. Turn the edges up around the perimeter of the liner and anchor them with rocks so that the outer region is level. Add plenty of swamp plants in trays or pots in the shallowest region, put a few potted aquatic plants and water lilies further down. Cover their soil with sand. Fill with tap water and let it stand for at least a week before introducing animals. This will ensure that any chlorine or chloramine in the tap water dissipates. Cut the surplus liner off above ground level, taking care the overflow is in a suitable position and its height still adjustable. To keep tadpoles in, lay some nylon flyscreen against the overflow and keep it in position with rocks. Place a layer of pebbles or gravel between the upturned rim and the potted bog plants, to extend a few centimetres above the water level. In time, you should also allow a thin layer of dead leaves to accumulate in the pond. This provides a larger surface area for browsing by the tadpoles.

The addition of a circulating pump (perhaps at a later stage) gives you these advantages:

1. The  pump allows you to construct a creek bed leading up to the pool. The creek is fed by the pump outlet hose which is easily hidden in a rock fall. Line the creak with black plastic, glued together to the supplier's instructions. Cover this with rounded pebbles and in other places with gravel. Have small pools of varying depth in the creek, provide some overhanging vegetation and a small sand beach. This habitat, although very small, may be suitable fro some stream-side frogs.
   
   
2. As the pump will need a pre-filter, it will also improve the water clarity. (Suspended algae, however, are more easily controlled by reducing the sunlight through more water lily cover and by filter surface is large enough so that small tadpoles don't get sucked against it.
   
   
3. You can remove water for gardening purposes from the rock fall, without scooping tadpoles out. The pump is also useful if the pond ever has to be drained. [partial water changes, as with fish tanks, may be necessary after long dry spells -see later.]
   
   
4. Flowing water is pleasant and allows easier maintenance of water quality. It is better oxygenated and less likely to stagnate, it reduce overheating of the top water layer and is not as attractive to mosquitos.

A small submersible pump in the pond should be sufficient. Its power supply must be installed according to safety regulations.

FISH
All pond fish eat tadpoles, but a few species will leave the older tadpole alone. Do not introduce the predatory "Mosquito fish (Gambusia affinis or G. holbrooki) or goldfish into the pond. To control mosquito larvae, use the White Cloud Mountains Minnow (Tanichthys albonubes) from pet shops.
It will also bred in your pond. However, should the pond be subject to flooding and you fish could end up in the environment, introduce only local native fish from your own watershed region. Select very small species but avoid bottom feeders. Cautiously recommended are:

FLY-specked Hardyhead (Craterocephalus stercusmuscarum), eastern Australia;
Australian Smelt (Retropinna semoni), coastal south-eastern Australia, southern Queensland -transport with care;
Pacific Blue-eye (Pseudomugil signifer), coastal eastern Australia;
and local Rainbow Fishes with preference to species swimming near the surface.

These fish will still eat newly hatched tadpoles. It si best to collect the spawn and keep the young tadpoles in a separates container until they are 15 mm long.

Other Predators
Cats and small children are discouraged by the surrounding bog area. Large birds that eat your frogs and tadpoles may be warded off by your dog or by a suspended profile of a flying hawk. (The later unfortunately also puts off songbirds that are attracted to the pond as their bird bath.) Tortoises should not be put into a small frog pond.

Cane Toads
If you live in a cane toad area, surround your pond by a 70 cm high wall which they cannot climb but many tree frogs can. Also leave 20 mm  holes in the bottom of the wall (e.g. as gaps between bricks) through which most ground dwelling fit, but not adult cane toads. Remove any juvenile toads found in the pond. If you can't build a wall, inspect the pond every few days, in hot weather very day, and remove any cane toad spawn (very long and entangled gelatinous strands which look quite different to most other Australian frog spawn).

Tap Water
Tap water contains sufficient chloramine or chlorine to kill tadpoles. The water is safe after has stood in the open for a week.
Subsequent topping up should be done in one of three ways:

1. If you add or change no more then 5% of the water volume, no chemical treatment is necessary. It is then easiest to permanently connect the water supply to a small ball valve at the surface level (e.g. to a self-fill horse drinking bowl with the bowl's drain plug removed: approx. Aust. $ 55 from rural supply shops). Be careful not exceed the 5% figure.
   
   
2. When changing or adding up to 30% of the water volume, the new water must fist be conditioned in a mixing bin into which 10mg/l (1 level teaspoon per 600 litres) of sodium thiosulfate has been added. Sodium thiosulfate can be obtained from chemist (typically Aust. $ 5.55/100g) or more economically from pharmaceutical suppliers.
   
   
3. Alternatively, trickle tap water slowly through a thick layer of activated carbon (from pet shops).
   A vertical length of plastic drainage pipe, flyscreen at the bottom and partly filled with the granules,
   will do the job. The carbon should be changed every two months or to supplier's directions.

Periodic partial water changes are beneficial in removing accumulated nutrients, toxins and acid or alkaline substances. Don't change more than 30% of the water on the same day, to allow tadpoles time to adjust to the new water.

Pollution
Frogs and tadpoles have permeable skins and are particular susceptible to pesticides and herbicides. Tadpoles are also effected by fertilisers and manure, especially by its ammonia component. Keep these substances well away from the pond and don't let rainwater runoff or
compost heap runoff enter the pond.

Transporting Frogs, Tadpoles and Spawn
If frogs don't colonise your pond by themselves, you will need to introduce them from your local area. The legality of collecting frogs is undergoing changes and also varies from state to state. Non-commercial collecting in small quantities of still common species is often permitted, but it is best to check fist. In any case, don't collect from protected area such as National Parks.

1. Frogs are best transported in a lightly inflated strong plastic bag about twice the size of an A4 sheet of paper and few drops of water in it. Protect the bag from collapsing and from heat and keep dark. If the frogs must remain in the bag for longer than a day, rinse them in the bag with water to remove a build up of poisonous secretions and of wastes products. Do not mix species during transport, nor large and small frogs and Not crowd frogs. They are not immune to each other's skin secretions. One very large frog per bag, or up to four small ones, is enough. Because their skin are sensitive, handle frogs only when there is  a need to and only with wet hands. Wash your hands afterwards: their skin secretions could irritate your mouth or eyes.
   
   
2. Tadpoles are transported in bags or jars with plenty of water and some detritus from where they occurred. Acclimatise them to your pond water gradually, taking at least half a day. Keep them out of the sunshine during transport and acclimatisation. Newly hatched tadpoles (larvae) tend to withstand transport better than older ones or than spawn.
   
   
3. Spawn is transported like tadpoles, but fill the container nearly to the top to avoid sloshing and cushion (e.g.on a pillow) to minimise jarring. If you have fish in the pond, then keep spawn with its original water in a large bucket (or a polystyrene broccoli box, which has a larger surface area) and add some of the water, some water plants and leaf litter from your pond. When the larvae start to feed by grazing on submerged objects, you can feed them with very small quantities of powdered fish food, wholemeal bread, rabbit food pellets and/or boiled lettuce. If there is the slightest indication that the added food is becoming putrid then too much food is being given. Release some tadpoles into the pond (again gradually) when they are 15 mm long including tail, and release the rest when they are a bit bigger.

Providing The Metamorphs With A Head Start
Newly metamorphosed forgets suffer losses from drying out. In dry conditions use your lawn sprinkler in the vicinity. Also, place fruit scraps on the top of the heap to attract fruit flies (if there is no problem with orchards) and cover this loosely with a sheet of plywood or similar.

Converting A Goldfish Pond
Remove the goldfish, drain and dry the pond to remove their spawn and fry. Arrange fro sloping side at surface level and ensure there are plenty of plants and moist sites around at least part of the pond. Fill, and when the water is matured, add White Cloud Mountains Minnows. Add tadpoles.

Further Reading

Cogger, H.G. (1992): Reptiles and Amphibians of Australia. 4th ed.Reed Books, Sydney.
Hero, J-M.,  Littlejohn, M. and Marantelli, G. (1991): Frogwatch Fieldguide to Victorian Frogs.
                DOCE, Melborne.
Robinson, M. (1998): A Field Guide to Frogs of Australia. Australian Museum/Reed Books, Sydney.
Voigt, M. (1992): Establishing Frog Habitats on Your Property. FrogFacts No. 3. FATS-Group,
                Sydney.
White, A.W. (1990b). Frogs. In "Care and Handling of Australian Native Animals", S. Hand (ed).
                Surry Beatty and Sons, Chipping Norton. pp 17-42.
Mattison, C. (1993): Keeping and breeding Amphibians. Blandford, London.

Reviewed by
Harald Ehmann (FATS Group)
Niall Johnston (Water Board, Science and Environment)
Martyn Robinson (Australian Museum)
Lothar Voigt (Australian Herpetological Society)