Distributing Tadpoles

Last edited: June 3rd, 2009

If you have set up a frog pond properly that is well used by the frogs, you will soon find yourself with more tadpoles than you can handle. Many species of frogs breed in large numbers to compensate for the high mortality of their larvae. In other words, it is a natural process for a certain number of tadpoles not to survive to metamorphosis. However, many more tadpoles could survive if they were distributed over more sites of permanent water, such as new frog ponds or those which haven't attracted any amorous adult users.

On the one hand, tadpole distribution can allow more tadpoles to survive and it can be used to reintroduce species to areas where they once were. On the other hand, distributing tadpoles is an excellent way to quickly spread diseases that can wipe out as many frogs as what were saved in the first place, if not more.

In January, 2003, three batches of awful looking tadpoles from three households in the suburb of Redlynch, Cairns were turned into us for evaluation. They were off colour, sluggish, not eating well, and some had bent tails. They were dropping like flies, so to speak, and we had them virus tested by the School of Virology and Immunology at James Cook University. The researcher found a virus using sequencing but he was unable to identify the virus. We have dubbed this problem the "Redlynch" virus until we can get more work done it. From what we've seen since and the rate of spread that is occuring with this aquatic pathogen, it is obvious that there are two very effective ways that this problem can be carried from place to place: the first is moving tadpoles around and the second is people who do surveying in the field and do not use disinfection procedures.

The presence of an aquatic virus that kills nearly all the tadpoles in a body of water and causes the few survivors to be deformed is VERY SERIOUS stuff! It will have a serious impact on our frog populations and all tadpoles should be viewed with suspicion, especially since this pathogen does not make its presence known until the later stages of tadpole development. Everything seems fine until the back legs are at least halfway grown and then all heck breaks loose!

Viruses have a long dormancy period - up to two years but some are much longer. Psitticine Beak and Feather Disease and Feline Immunodeficiency Virus (both rampant in Australia) have dormancies up to five years - so tadpoles and frogs in your garden can be carrying a virus without showing any symptoms. When tadpoles and frogs that have been exposed become stressed, which is the case at metamorphosis or during the dry season/drought, then the virus is triggered and spreads to other frogs. As soon as those sick frogs go to water, they can spread their pathogens into the water where all the tadpoles can pick it up.

There was also a disease outbreak which started in July 2002 and covered a large part of Queensland. We are still trying to get the exact fungal species identified (our top two shortlisted pathogens are a species of Fusarium or a species of Mucor - both drought tolerant fungal groups) but it can have an affect on tadpoles. The only real symptom is that the tadpoles appear fine but they are not eating and just get thinner and thinner with no other symptoms. The aquarium product Rapid White-spot Remedy is effective on this problem and cures it after one to three applications. (Follow the directions on the bottle except use half the dose on tadpoles the first time to make sure it is not too strong for the species of tadpole you have.)

Aside from the problem of spreading disease, regulations in QLD changed during 2004 making it illegal to relocate tadpoles without a rescue permit.

We recognise that rescuing and distributing tadpoles is a tool that can assist the restoration of frog populations on a local level, but we are also extremely concerned about the spread of disease, especially a pathogen as devastating as the "Redlynch" virus. We would like to find a sensible, middle ground to a complex problem. Until we hear otherwise from the researchers, we are making the following suggestions concerning the movement of tadpoles anywhere, not just where there are regulations. These suggestions are subject to change based on new findings on the spread of disease in FNQ.

1. Do not move tadpoles outside of your own water catchment and suburb. This includes tourists who are visiting Far North Queensland for holidays - do NOT collect tadpoles here to bring home with you. The most serious amphibian diseases we know of so far are aquatic so keeping to your own catchment might help prevent an aquatic pathogen from spreading throughout a new catchment. If you do not know what area makes up your local catchment, contact your local council or Integrated Catchment Management community group.
2. Do not move tadpoles at all if you have had any incidences of tadpoles with problems (such as bent tails, multiple limbs instead of one, lumps or growths) or tadpoles dying off in moderate or large numbers in your pond. There are a few reasons why tadpoles would die off in numbers and one of them is disease but bad husdandry or toxins can also cause deaths. Another time when large dieoffs would occur is at metamorphosis and, if this is seen, the dead tads/morphs should be frozen or preserved by a vet for testing later. If you have tadpoles with the problems listed above, please contact us. We will ask you to turn in all the remaining tadpoles so that we can raise them under optimal conditions and document what problems they are having.
3. Do not move tadpoles or metamorphs to any site where rare frogs currently live. For example, in the Cairns area, that would mean to avoid Stony Creek (in Barron Gorge National Park), Crystal Cascades and the stream that crosses under the top end of Toogood Road to name three. If you are unsure about a location being a rare frog site, contact us or the frog monitoring staff at the Atherton office of QPWS (phone 4091-4262).
4. You should not move tadpoles unless you confidently know what species they are. Each species should go to the right habitat and the right enclosure. If you have more than one species breeding in your pond, how do you know which species the individual tadpoles are? Is it a species that needs to be fished out of the tank/pond it has been put in or will it be able to get out of the water without falling back in and drowning? Is it a burrowing species that needs pliable soil to burrow into or a tree frog that needs lots of surrounding vegetation? Are the tadpoles being moved to outside their known range (such as Striped Marsh frogs being moved any further north than Cairns)?
5. If you need to disburse tadpoles, please do so only to others in your own suburb. Put up a notice at the corner shop for other frog pond owners to contact you. It will be best for those receiving your tadpoles to raise them in aquariums and NOT release them directly into your pond. Tell the recipients to let you know if there are any die-offs or deformities so that you can stop giving any more away.
6. If you can't find any other frog pond owners in your suburb to take some tadpoles, you can set up a fish tank or two and raise some tadpoles yourself so that more will survive.
7. If you're not sure about any of this, please contact us to discuss it before you distribute any tadpoles to the wild or to anyone else!