‘Lest we forget’

How to entice frogs into your backyard ...

By wildlife writer Justin Harrison

First published in the Permaculture International Journal Issue No. 60 Sept ~ Nov 1996

On a recent trek through Kakadu National Park in Northern Territory, Australia, many wonders caught my imagination. One group of animals, however, astounded me with its diversity and sheer numbers. Frogs! Millions of them in one of the most unspoiled waterways in the world.

Elsewhere in Australia, and around the globe, frogs are losing a battle with pollutants and urban sprawl.

You can help our soggy little friends by providing a safe haven near your home. Why? Read on.

ABOUT FROGS

Frogs, as well as their eggs and tadpoles, have a permeable skin. What this means is that whatever is in the water is in the frog. That's why they're so vulnerable to pollutants and fertilisers (particularly ammonia) in the water supply.

Most frog species lay their eggs in submersed clumps or in floating foam nests. The eggs hatch into tadpoles. The gilled, water breathing tadpoles eat rotting leaf litter and the like, browsing on the bottom of their pond. Frogs, and here's the good news, eat insects! They eat the insects that eat your vegetables.

Isn't that wonderful?

So we have a member of the backyard community that:
• Is an invaluable indicator of the 'health' of your property and watershed.
• Eats insects at ground level or in trees, where the damage happens, a non-toxic control of pests.
Sings lovely songs on balmy evenings.

Now that you're just dying to hop to it (sorry) and create a frog pond and attract these bug munching units to your garden, I'll introduce some of Merinda Voigt's work, excerpts from 'Frog facts II' *. I couldn't put it better myself, so I won't try.

POND CONSTRUCTION

The simplest way is to scoop a hole in the ground (at least I-2m across and 60- 80cm deep), surrounded by a shallow region (say 50cm wide and 30-50cm deep) and again surrounded by a very shallow ring (irregular but at least 50-200cm wide, 10-20cm 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, from pond product suppliers). Don't use building grade polythene, it will deteriorate. Tum the edges up around the perimeter of the liner and anchor them with rocks so 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. Don't let rainwater runoff that may be polluted by a compost heap or other fertilizers or chemicals enter the pond . Cut the surplus liner off above ground level, taking care the overflow is in a suitable position and its height still adjustable by packing a few rocks against the outside of the liner. To keep tadpoles in, lay some nylon fly screen across the overflow, against the inside of the liner 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 useful nitrification bacteria and material for browsing by the tadpoles.

Check with your local council in case there is a water depth restriction and fencing is required. If you make a shallow pond, it can overheat in summer unless you give it extra shade.

LOCATION OF THE POND

An ideal place is part sunny, part shady, but not directly under trees. Give a wide berth to trees that have poisonous leaves (eg. 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 neighbours' houses because frogs can be noisy at times. The taller bog plants should be around the back of the pond. A low garden lamp that is reflected in the water will not only add to your garder’s appearance in the evenings but also attract insects for the frogs. Your compost heap, another good source of insects, should be close to the pond. (Part of the heap can be slightly raised on a wire mesh tray or pallet. Insects and worms that fall through will provide food for the frogs sheltering below.) Other shelters at the edge of the pond should consist of vegetation, a rock pile and planks or fallen logs.

FISH

All pond fish eat tadpoles, but a few species will leave the older tadpoles alone. Do not introduce the predatory 'Mosquito Fish' (Gambusia affinis) or goldfish into the pond. To control mosquito larvae, use the White Cloud Mountain Minnow (Tanichthys albonubes) from pet shops. It will also breed in your pond. However, should the pond be subject to flooding and your 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.

CANE TOADS

Maline toads or cane toads, were introduced into Australia and into many other countries with disastrous results.

If you live in a cane toad area, surround your pond with a 70 cm high wall which they cannot climb but many tree frogs can. Also leave 20mm holes in the bottom of the wall (eg. as gaps between bricks) through which most ground dwelling frogs 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 every day, and remove any cane toad spawn (very long entangled strands which look quite different to most other frog spawn).

THANKS MERINDA

If frogs don't colonise your pond, you may need to transport them in but only from your local area. I recommend speaking to the Herpetological Society in your state before making such a move, as they will give you the advice to do it legally, safely and above all, successfully.

Good luck and I wish many frogs for you all.

'Frogfacts No.2' was produced by the Frog and Tadpole Study Group of New South Wales Inc. The author was Melinda Voigt. The full fact sheet can be obtained by wliting (with a stamped addressed envelope) to:

The FATS Group PO Box A2405,
Sydney Sth 2000, Australia
Low Garden Lamp