Let’s save Australian frogs! “It’s not easy being green” - Kermit the frog

Frogs across Australia are disappearing at an alarming rate due to habitat loss, climate change, and pollution. About one-third of our amazing range of frog species are now classed as vulnerable or endangered. But what can we do about it?

Easy! Build a frog pond in your backyard. Whether you have a tiny courtyard or a five-acre garden, we can all find space to build a little bit of frog habitat for our frogs to live and breed in. The more of us who do it, the more their numbers increase, and populations become stable again. Here in the Gympie Region, we are fortunate to still have quite a range of frog species, so you never know who will come calling to make themselves at home. (For more information on our local frog species visit the MRCCC website and investigate their long-running citizen science project: Find a Frog in February). And who doesn’t want Kermit, or one of his cousins, living in their back or front yard?

With thanks to the Qld Government’s Department of Environment and Science, the Australian Museum, the Queensland Frog Society, and Sustainable Gardening Australia, here are some guidelines for building a great frog pond.

Where to put a frog pond

Frog ponds need to be sited where they can get morning sun but be shaded during the middle of the day (aim to have part of your frog pond in the shade at any time). This may mean that you have to provide shade planting when you put in your frog pond.

You also need to consider how close the pond is to a bedroom window (both yours and your neighbour’s) as some frogs call loudly and persistently throughout the night. If you plan to install a water pump you may need to have access to electricity (solar-powered pumps are available). You may also consider a solar-powered light. This will attract insects and become a focal point for feeding frogs—and allow you to watch them at the same time.

Before any digging starts, mark out where the frog pond will go and make sure you are happy with its location and how it fits in with the rest of the garden space (it will be far easier to change your mind now than when it is fully installed).

What to make a pond out of

You can create a frog pond from just about any non-metallic water-holding container. Possibilities include:

A children’s plastic pool
An old plastic water tank
Half a wine barrel
A hole in the ground lined with a plastic or rubber pool liner
Bath tub

Don’t use a metal container, or any other metal objects in your pond, as frogs and tadpoles can be sensitive to the metal impurities that they leach into the water.

Pond size is largely a matter of personal choice, available space, and practicality. Frog ponds should be shallow around the edges gradually deepening to a maximum of 60cm (ponds can be shallower if required). The varying water depth creates a range of water temperatures and allows tadpoles to retreat to cooler water when it is hot, and deeper water when disturbed. So if you’re using something like a bathtub, think about putting some level variations in it with the use of aquatic plants in pots, rocks, logs, or smaller containers.

Building & filling your pond

Dig a hole to fit your chosen container, add sand or gravel to level the base, and check with a spirit level. Ideally, the water should be 30-60cm deep at its deepest point. Add 3-4 centimetres of washed sand or gravel to the bottom to hold the roots of aquatic plants, and place logs, rocks, and pebbles to create a variety of depths and to provide additional shelter, basking sites, and safe places for new frogs to emerge from. This will help your pond accommodate a wider variety of frogs with different preferences and provide anchoring points for plants in pots. If you are using a pond liner, you’ll need a piece big enough to allow at least a 40cm overhang all the way around. Don’t trim it to size until after you’ve filled the pond with water and secure the liner over the wall using large rocks.

Frogs are highly sensitive to the use of chemicals and other pollutants and water quality is critical for a healthy frog pond. Ideally, rainwater should be used. If you are using tap water, let it sit for five to seven days before adding any life (cover it to keep frogs out of it for this length of time) to allow chlorine and other chemicals to dissipate. Grow your frog home – both the pond and the surrounds – without the use of chemical pesticides and fertilisers, and stick to naturally-derived organic fertilisers.

Fit out your frog home

While a frog pond will become the hub of activity for wildlife in your backyard, the pond’s surroundings also make up an important part of the frog’s habitat. The area surrounding one side of the pond needs to provide a sheltered and moist refuge area for young frogs emerging from the pond. The substrate could include moist river gravel and leaf litter for burrowing frogs to hide in. You may also want to build a garden up to one side of the pond to provide a safe mini-wildlife corridor between the pond and other parts of your garden. This will make it easier for insects and other wildlife to use the pond (but beware of the dreaded cane toad – read below).

Frog friendly plants

Thinking about plants for your frogs, you should think about what you plant outside of the pond, as well as the aquatic plants in the pond. A variety of water plants, such as native reeds and rushes, will keep the water oxygenated and provide food and hiding places for tadpoles. Leave the plants in their pots and place in the water at different depths. Floating plants like native duckweed and Azolla will also provide protection, but make sure they cover no more than half of the water’s surface.

Plant a wide range of vegetation around the pond – grasses and sedges are ideal planted densely around the water’s edge as they provide lots of great hiding spots for frogs. Sedges also provide male frogs with higher points to call from.

Don’t forget to make the rest of your backyard frog-friendly too! Try using a variety of native plants to achieve multiple levels of foliage, including a dense understorey of grasses and groundcovers which will provide shelter for frogs and other small animals. Our wonderful staff at the Gympie Landcare Nursery can advise you on what plants to use in and around the pond and throughout the rest of your garden. They will also be able to advise you on what plants not to use, as many non-native species are invasive and damaging to our natural ecosystems.

Food for your new frogs

A healthy garden with lots of plants will have a good range of insects – frogs’ favourite foods! Placing a small solar light near your pond will also attract flying insects like moths. Tadpoles will happily feed on the decaying vegetation and some water plants and algae, so a well-designed pond should sustain them without any help from you.

If you build it, they will come

Once your pond is all setup, don’t worry about finding frogs for it. Frogs will find your new pond all by themselves.

Oh no – mosquitos!

If you are building a frog pond, you will also be providing a breeding site for mosquitoes. While frogs and dragonflies (another critter loving the pond!), will feed on mosquitoes you can also add native fish such as blue eyes to your frog pond to prey on mosquito larvae (these fish may also eat some of your frog eggs and smaller tadpoles). Never add exotic fish to your pond, such as mosquito fish or goldfish as you risk these getting out and adding to our invasive species list.

Another option is to install a pump which will improve water flow and water aeration, and also deter mosquitoes as they prefer laying their eggs in shallow, still water. Some aquatic plants like water lilies prefer still water so installing a water pump may affect your choice of plants for your pond.

Microbats are also effective mosquito predators and you may consider installing a few microbat boxes in a tree near your frog pond. These are also available from the Gympie Landcare nursery.

Oh no – cane toads!

Given that cane toads are sadly enough the most common (and extremely unwanted) wildlife in our region, keep an eye on your pond to make sure they don’t take it over. There are some ways to manage them in regard to your frog pond:

Firstly, consider building a raised frog pond with overhanging vegetation. Frogs will be able to access it, but it will certainly prove difficult for the cane toad. While they are good scramblers, they can only “hop” to the height of about 50cm.

Secondly, keep an eye out for their eggs and tadpoles in the pond. Unlike native frog eggs, which look like floating clumps of white foam, toad eggs are small black dots suspended in long clear jelly ‘shoelaces’ (a female can lay up to 35 000 eggs a year!). Remove the ‘shoelace’ from the pond by running a stick through the water and catching it up, then simply leave it on the side of the garden to dry out. Toad tadpoles can be distinguished from native tadpoles by their behaviour and colour. Toad tadpoles swim in a swarm, whereas native tadpoles do not keep such close company. Toad tadpoles are black all over, but native tadpoles are always lighter underneath than on top. Cane toad tadpoles can be removed by netting and then placed in a waterproof container and frozen.

Thirdly: you can deter toads by surrounding your pond with a dense border of plants such as lomandras or erecting a 50 cm mesh fence around your pond area.

Fourthly: keep toad numbers down. It is not their fault we brought them into our ecosystem, so it is important to kill them in the most humane way possible. The recommended way to kill cane toads is to catch them (making sure you wear gloves and avoid the poison gland on their back), then place them in a container with air holes and cool them down in a refrigerator until they become completely dormant. Then place the toad in the freezer for several days. There is some evidence that a cane toad can still feel pain after it has been in a refrigerator for an hour. Therefore a toad should be cooled down for as long as possible before being placed in a freezer to minimise the likelihood of it feeling any pain when it is frozen. The dead toad can be disposed of by burying them or putting it in your wheelie bin (on the day it will be emptied).

Pond maintenance

The pH of the water should be checked regularly to ensure it is as close to neutral as possible. pH measuring kits are available from pet shops.

Aquatic plants should be thinned out to ensure they do not cover more than a quarter of the pond surface.

Algal blooms can also occur in frog ponds. These blooms occur when the nutrient level in the water is too high. Blooms in an isolated pond should eventually die off as the algae consume the nutrients. If the algae persist, it should be removed along with any nutrient source (e.g. decaying leaves). Excess dead leaves and old uneaten food should be removed as part of the general maintenance of the pond. Care should also be taken to avoid nutrient runoff from the surrounding lawns and gardens.

Disease

Frogs are affected by Chytrid fungus. The best way of controlling the spread of this fungus is to treat your frog pond as a quarantine area by not bringing in any material that could be infected. Frog ponds should only be populated by frogs that have moved into the pond by themselves. Never take a frog from another area and introduce it to your backyard from a pond or farm dam. Not only is this illegal, but it can also spread diseases among frogs.

Handling frogs

Avoid handling frogs. Frogs have sensitive skin and can readily absorb chemicals from anything they come into contact with, including your hands. Your frog pond should give you many opportunities to observe frogs closely without having to handle them.

Other points to consider

It is important to ensure your frog pond doesn’t pose a safety hazard for young children. If this is a concern, ponds can be fenced or covered with mesh. Ponds can also be kept shallow with gently sloping, non-slip beds.

Always supervise children around your frog pond.

Check for any underground pipes or cables before you start digging.

Keep cats inside at night. Cats will eat frogs and other small wildlife if left to roam, making your frog pond a dangerous place to be.

Make sure you include only native plants and fish. Exotic species can escape and become pests in local waterways, impacting native wildlife, and some fish species, such as mosquito fish, will actually eat tadpoles.

Further information

https://environment.des.qld.gov.au/wildlife/animals/living-with/frogs/ponds

https://mrccc.org.au/wp-content/uploads/2020/01/FFF-Frog-Finders-guide-lr-1.pdf: MRCCC’s “Find a Frog” project, a long-standing Gympie-based citizen science project

https://australian.museum/learn/animals/frogs/

https://www.sgaonline.org.au/frog-ponds/