The Pobblebonk (or Banjo) Frog, Limnodynastes dumerilii, gets its name from its distinctive “bonk” call. It is a fairly large species, growing to about 85 mm in length. It can be readily identified by the presence of a prominent tibial gland on each hind leg and a metatarsal tubercle on each hind foot. Three subspecies, L. dumerilii dumerilii, L. dumerilii insularis and L. dumerilii variegatus occur within the greater Melbourne area. These can be separated by their distribution and colour patterns. L. dumerilii insularis has a prominent pale vertebral stripe, which is absent in L. dumerilii dumerilii, and L. dumerilii variegatus is a uniform dark colour. The warty appearance of this frog sometimes causes people to mistake it for Cane Toad.
Pobblebonk or Banjo FrogPhotographer: Peter Robertson / Source: Wildlife Profiles Pty. Ltd.
L. dumerilii dumerilii is widespread over the western and northern areas around Melbourne, L. dumerilii insularis is found in the south-eastern areas, and L. dumerilii variegatus is restricted to the Otway Ranges. The frog is found in a variety of habitats. During periods of inactivity, this species burrows into the ground.
The diet consists of small invertebrates. The loud ‘bonk’ call is often heard in the suburbs. Females lay a large white floating raft of eggs in still permanent water such as dams and ponds. Tadpoles grow to a maximum length of 68 mm and take up to 15 months to complete development.
Barker, J., Grigg, G. and Tyler, M. J. 1995. A Field Guide to Australian Frogs. Surrey Beatty & Sons, Sydney.
Cogger, H. 2000. Reptiles and Amphibians of Australia. Reed Books, Sydney.
Hero, J. M., Littlejohn, M. & Marantelli, G. 1991. Frogwatch Field Guide to Victorian Frogs. Department of Conservation and Environment, East Melbourne.
Tyler, M. J. 1992. Encyclopaedia of Australian Animals: Frogs. Angus & Robertson, Sydney.
Hi Phil, Pobblebonks are known as being really slow developers as tadpoles. Some individuals will mature really quickly but others take as long as you are finding in your pond. We keep them here at the Museum and the time it takes for one spawn to all metamorphose can be well over a year. They can be quite robust individuals before their hind legs finally appear. Best of luck.
It's not a good idea (and not legal) to move the frogs to another location. The Pobblebonks have made their own way to your yard and obviously consider it a reasonably good habitat.
White oil is a suffocant rather than a toxin - that is, it suffocates the insects by blocking their spiracles, rather than poisoning them. It is therefore one of the least harmful insecticides and one of the more environmentally friendly. White oil was traditionally made from vegetable oil but modern versions are made from petroleum.
Frogs are very sensitive to insecticides, particularly in the tadpole stage. White oil is not considered biodegradable, and the product's material safety data sheet (MSDS) recommends not using it near waterways, mainly because toxological studies have not been done on aquatic animals.
If you're keen to use white oil, perhaps you could make your own version from vegetable oil - there are a number of simple recipes available on the internet.
The main threat to the tadpoles is the golfish. If the goldfish remain in the pond, you could expect the tadpole numbers to decrease over time.
In captivity they can be feed a range of food such as egg yolk, vegetables, non-citrus fruits and baby food, but the most successful food is boiled lettuce.
Hi Lina, the Department of Environment and Primary Industry states that it is not permissible to keep a wild-caught specimen as a pet, as dictated by the Flora and Fauna Guarantee Act 1988 and the Wildlife Act 1975.
Hi Faye - we checked with our Live Exhibits folk, and they've responded as follows:
Frog ponds have become very popular in recent years and consequently there is a vast amount of information available on the internet. Three good sites are listed below, but there are many more once you start searching.
Pobblebonks (Limnodynastes dumerilii) will burrow into the soil around the pond more so than using the pond itself.
Good resources can be found here, here and here.
Hi Lesley - we checked with our Curator of Herpetology, who has responded as follows:
The Spotted March frog has two call races ..... the northern call race (central/eastern Victoria) has been described as sounding a bit like a machine gun with a series of distinct clicks, while the southern call race sounds like two stones being clicked together. I’m not sure where the change between the two occurs but it could be around Seymour – perhaps the enquirer has both races of Spotted Marsh Frogs in their area. An example of both calls can be heard here
Hi Serge, if you have frogs already coming to your garden, it suggests you may not need a pond. Banjo Frogs and Common Froglets (the two species you most likely have) will live in moist ground or under logs or rocks, or around and under plant pots. A pond will help keep them and possibly attract other species, but for these two it’s not completely necessary.
The type of pond liner will depend on your budget and how long you want it to last. Black plastic liners will do the job, but plastic and fibreglass custom-made ponds will last longer, and concrete or similar material will last a very long time. You can make a usable pond by inserting a plastic tub into the ground, as long as it’s childproof. Unlike other animal groups, frogs don’t seem to mind what the pond is made from. The other important aspect is to put logs and rocks around the pond to give the frogs somewhere to hide that is moist and well sheltered.
Hi Bruce, the residue in the wine barrel should not be a problem for the frogs. Any active compounds will have evaporated long ago and others will be diluted by the water. It would be safest to rinse it once or twice before use. Make sure that if you use other material to waterproof or re-waterproof the barrel, you'll need to give it an opportunity to off-gas and shoud rinse it well once again.
Fifty centimetres may be a bit high for some frogs, particularly the smaller ground-dwelling species, but if the habitat is desirable they will find a way in, particularly if foliage is draped over the sides. Frogs are accustomed to water being at or below ground level, but many will climb short distances and some common species, such as Peron's Tree Frogs, are regularly found high on tree trunks. If you need the barrel to remain intact for aesthetic purposes, the frogs will adapt if they find the habitat appealing enough.
Hi Will, the Department of Sustainability and Environment doesn’t recommend relocating animals for a number of reasons (http://www.dse.vic.gov.au/plants-and-animals/native-plants-and-animals/problem-wildlife), and in some cases it is illegal to do so. The only way to keep them out would be to build a fence around the pond or to drain the pond. If your concern is the noise they make but you still want a pond, you could drain the current one, fill it in, and construct another pond further away from the house.
Having said that, many people build ponds in their backyard specifically to attract frogs, and many wait long periods before they are finally blessed with their presence.
We forwarded your question to the Museum's Live Exhibits team and they provided the following information:
Banjo Frogs will eat Marsh Frogs unless they are well fed themselves. But if you keep the food up to the Banjos, this shouldn't be a problem. Coco peat is best for burrowing species such as Banjo Frogs, but fine gravel will work just as well and is easier to clean. Soil is not particularly good as the acidity is wrong and soil tends to turn 'sour' over time with constant watering and accumulation of wastes. Frogs tend to stop eating when they are full so you are unlikely to overfeed them, but they are easily underfed. An adult frog will take 8-12 medium-sized crickets per week, and they are best fed three times a week or so. That is 2-4 crickets per feed, and this should only take a minute or two.
Hi Lorna, the incubation period for Banjo Frog eggs can be as little as four days, but they can remain as tadpoles for up to 15 months. Both time periods depend greatly on the ambient temperature at the time.
As for keeping the frogs you don't need a licence to keep pobblebonks for private purposes, provided they have come from a lawful source. It is not legal to take them from the wild. If they came from the wild then ideally release them back where they came from. We feed our pobblebonks three times a week and one of those feeds we dig them up and make sure they eat. Otherwise, we dust the crickets etc in vitamins and leave them on the surface overnight.
We forwarded your questions to Museum Victoria’s animal keepers, who responded with the following:
Pobblebonks are common in certain situations throughout their range – the subspecies you have in Rutherglen is the Eastern Banjo Frog (Limnodynastes dumerilii dumerilii). These situations include gardens, where the soil is often moist and a range of plant species attract a range of invertebrate species. So your garden is more attractive to frogs than a paddock across the road, and if you relocate the frog it will most likely return at the first opportunity. Females lay their eggs in ponds and dams, but do not make a nest as such. Pobblebonks will bury themselves underground during periods of inactivity, or even just during the day. Once uncovered, they will rebury themselves as soon as possible.
Snakes can be attracted to frogs, but generally only if frogs are present in large numbers. They are usually more attracted to water bodies, for the water itself rather than the frogs. There will probably be snakes in the area anyway, and a few Pobblebonks will not make your garden any more or less attractive.
Hi Wendi,Pobblebonk spawn can be gently picked up by cupping both hands underneath and lifting it up. Alternatively you can use a small net to do the same. Transfer it to a bucket or container and then gently tip it into the new pond. Pobblebonk eggs are generally safe to leave in with White Clouds as the tadpoles will quickly grow too big for them to eat. Even if they do eat some they are unlikely to eat them all.
Hi Ross. Good question! We contacted our Live Exhibits department and they provided us with the following information:
The fish in the pond is the most likely reason that no tadpoles are surviving. Pobblebonk tadpoles are generally really hardy and will survive in just about anything so we believe they are being eaten.
Ideally in an outside pond you need varying water depths. Shallow areas where the tadpoles have access to good sunlight and higher temperatures, as well as deeper sections to get away from threats and to retreat to if it is excessively warm. Water depth should be 45 – 60 cm with some shallower areas.
The frogs in the foam box will have to be fed on frozen lettuce, bok choy or spinach leaves and will take quite a lot of work. We would suggest that if you really want to encourage frogs to breed in the pond then removing the fish or swapping to some frog-friendlier types would be the best solution. Species such as Murray River Rainbows or White Clouds are a good choice.
Any froglets that emerge must be left to disperse naturally. It is illegal to translocate frogs as you may be spreading things such as chytrid fungus. It can also affect the genetic integrity of frog populations.
Hi Kim, there are several possible reasons your frogs are not making noise.
Firstly, they may be juveniles or may all be females. In this case they either won't be calling yet or won't be calling at all. Secondly, the conditions may not be right for calling, particularly if the substrate is too dry or the wrong type.
It might be difficult to determine the exact cause of the issue but you could try the following things. Use cocopeat as a substrate if you're not doing so already, or swap the substrate for fresh substrate, whatever you're using. Add more moisture to the enclosure, at least temporarily, to encourage them to think it's raining. Add live food or a variety of crickets/cockroaches/flies to stimulate activity.
Good luck with your frogs and we hope this helps.
We love receiving comments, but can’t always respond.
Hi Emma - the Pobblebonk isn't deadly (except to the small invertebrates that form its diet), however we certainly don't reccommend licking it! You can find out more about this interesting species from the following links:
To hear the frog call, the “bonk”, and another unusual photo, see: http://museumvictoria.com.au/bioinformatics/frog/images/dumelive3.htm
Try also: http://frogs.org.au/frogs/species/Limnodynastes/dumerili/
Hope this helps!
Hi Maddie, I don’t think you need to be worried about having 3,900 frogs all calling from your backyard. The number of tadpoles that actually make it through to becoming frogs is very tiny – many will die before maturing. Within your pond ecosystem the tadpoles feed on the algae and plant matter and are quite low on the food chain. This means they can exist in quite large numbers before competing for food. Frogs on the other hand are predators and need other animals in which to feed upon. Other animals such as bugs tend to be harder to come by than algae so they cannot exist in such large numbers.
I think you will be lucky to have a big population of frogs calling from your yard – with pobblebonks it often tends to only be a few individuals calling from a single pond each season.
Great questions about your frogs. The first question about how goldfish affect frogs and eggs is – yes they do enjoy eating eggs and tadpoles so you need to be careful when you introduce these fish into a pond system. If you wanted to be good to the frogs you could try some local fish such as Southern Pygmy Perch that are not interested in feeding on the young tadpoles and they are local to the Melbourne region. The second question about them jumping into your pond – chlorine does not go all that well with frogs but if you can get them out quickly enough they may be fine. If they are pobblebonk frogs, or other frogs with claws rather than pads on their fingers that will really struggle to climb out of a pond – adding a ramp for them to climb onto and out of the water is a great solution to help. If they do however have pads on the end of their toes they are tree frogs and should be able to use these pads to climb up the wall – although a ramp to escape would also help. Best of luck
Hi Diane tadpoles have some great survival strategies to help them live in adverse conditions – even in a laundry tub. You should find that some of them will grow quite quickly and all four legs will pop out and they will metamorphose into frogs at a rapid rate – other tadpoles may stay as tadpoles for more than 12 months. This is a strategy to divide the emergence of the young between two years to increase the chance of some surviving to reproduce. If they are burrowing frogs, such as Pobblebonks they may find it hard to climb out of a laundry tub – the best thing you can do is provide a platform and branch for them to climb out of the water and onto land when they become frogs. As to what they eat – tadpoles will feed on algae and other things they can scrape of the plants and walls of the pond. Here at the museum we freeze pieces of lettuce that we then add to the tadpoles enclosures so they can feed. Here are links to the Live Exhibits blog that shows photos of Pobblebonk egg masses (which sit above the water) and Pobblebonk tadpoles just before they leave the water to become frogs.
Great weather for frogs!
Pobbles Grow Up
Hi Chris, if you have Pobblebonk tadpoles / frogs it is good to remove your frogs as they metamorphose and transfer them to an enclosure that they can burrow underground and rest. Your frog has a very different diet to the tadpoles – they eat insects and any other small animals they can fit into their mouths. I would recommend that you either collect some invertebrates from your school grounds – such as crickets, cockroaches, grasshoppers etc or you can purchase crickets from lots of pet shops. Newly emerged frogs tend to have quite small stomachs so small meals (i.e. 1 – 2 food items) every one to two days.
Hi Darren, it is important to remember that keeping wildlife is illegal and they should be returned to the wild. Saying that – to keep them happy and healthy I can give you a few pointers.
Hi Emerald, thanks for your enquiry. The Live Exhibits team recommend placing the frog back in the garden bed not far from where you found it. Dig a small hole and let it burrow down.
Hi there. We would expect that a Pobblebonk may live up to 10 years. Some species of Australian frogs have been known to live to 20. Despite what our human emotions cause us to think, a lone Pobblebonk would not be sad. Pobblebonks are not social animals, and don’t relish the company of other frogs - so being alone should not affect its lifespan. The calling is to attract females (which do not call), so he may be having silent success without anyone knowing. (If a frothy egg-mass appears in the water, he is definitely having success). A second call would be that of a rival male. We can’t speak for that particular Pobblebonk, but if I was calling for a mate, the less competition the better!
Hi there, Yianni. For your information, The Department of Sustainability and the Environment states that it is not permissible to keep a wild-caught specimen as a pet, as dictated by the Flora and Fauna Guarantee Act 1988 and the Wildlife Act 1975. Ideally, you should leave tadpoles where you find them, as translocation of individual animals can disrupt local gene pools, and contribute to the spread of disease.
Furthermore, instances of albinoism in frogs are extremely rare, even in controlled environments, as described in scholarly journals TRSSA and the Journal of Heredity. Hope this helps!
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