Identifying the Kimberley species that are impacted by cane toads, quantifying that impact, and understanding the way toads spread through the Kimberley landscape.
There are thousands of native species in the Kimberley, and we need to concentrate resources on those species that the cane toad will actually affect. In order to accurately identify those species with accuracy, we need to measure the impact of the toad in the field, before and after toad arrival. We also need to understand toads will move across the Kimberley (a very different landscape to the NT!).Read More
"If you can't measure it, you can't manage it": The starting point of any effort to mitigate cane toad impact is to identify which species are affected, directly and indirectly (i.e. including ecological cascades), and the extent of that impact (i.e. individual vs population level impacts).
- Severe reductions of 3 species of riparian goannas
- Severe impact, including local extinctions, of northern quolls (listed by David Attenborough as one of the top 10 international conservation priorities).
- Population impacts of freshwater crocs in some systems but not in others
- Indirect effects on pignose turtles and Gilbert's dragons.
However, there is still a great deal that we don't know. What other species of goanna are affected? - previous work was based upon river surveys only, so no there was no measurement of terrestrial species. Are there direct/indirect effects on freshwater turtles (which prey on native frogs)?
Do freshwater crocs in the Kimberley suffer individual or freshwater effects? Do cane toads affect the Magnificent Tree Frog, Australia's largest native frog which lives only in the Kimberley? Will the very different nature of the Kimberley landscape (compared with the NT) mean that the nature of can-toad spread and impact is different to previous experience?
Since 2009 we have been conducting faunal surveys at El Questro Wilderness Park in the East Kimberley. To measure toad impact we needed baseline data of the fauna prior to the arrival of cane toads; this was collected over 4 field seasons from 2009-2012.
Cane toads arrived in late 2012; post-arrival data will comprise the 2013-2015 field seasons. The 2013 work was completed in June, and already we are seeing notable impacts of toads upon the goannas, some impact on crocs, and very high potential for impact on the Magnificent Tree Frog
Question 1: What is the spread and impact of toads in the Kimberley?
The Kimberley ARK
A genebank for species that will be affected by cane toads.
When populations crash, they lose important genetic diversity. Even if a species doesn't go extinct straightaway, or recovers in numbers over time, the long-term prospects for populations with low genetic diversity are not good. Thanks to Assisted Reproductive Technologies, we can store sperm and eggs indefinitely - this is an effective (and cheap) way to store genetic diversity, and is known as a Genebank.
The time to start making a genebank is before the population crash happens - we still have the chance to do this for the Kimberley species that will be impacted by toads. Even if the entire Kimberley could be purchased and converted into a national park, it would not stop the decline of many native predators due to toads. Genebanking is the only strategy to effectively prevent genetic collapse in affected species on a wide scale, when the cause of decline (in this case toads – in the future, climate change) cannot be halted.Read More
We know that certain species are going to be seriously affected. That impact may not be species extinctions but it going to be local extinctions and >95% population crashes. The long term consequences of severe population declines are serious, including the loss of genetic diversity - which has important implications for long term population viability. There are many examples of conservation issues involving species which are not extinct but which now have very low genetic diversity, and who are now extremely vulnerable to environmental changes as a result.
An obvious way to store genetic diversity is to freeze down cells that can be used to create new individuals. Suitable cells include sperm and eggs, which can be collected, stored, and reactivated using assisted reproductive technology (ART). Another option is to use stem cells or other somatic (non-reproductive) tissues, and combine ART with cloning to produce viable embryos. Recently, an Australian team was able to use frozen somatic tissues from an extinct species of frog to produce an embryo.
The advantages of this approach are that it doesn't rely , in the short term, on healthy environments and/or populations, and provides conservation options for situations where other techniques, such as protection in national parks, will not address the threat (the spread of chytrid fungus through Australian frog populations is an example of that situation). Also, the basic techniques have been worked out, thanks to applied research in human biomedical science and agricultural science. The running costs are cheap - essentially, a supply of Liquid Nitrogen and a place to store the tissues.
What do we need in order to construct a Kimberley Ark? If we are going to use ART, then we need to have specific techniques that work for each species being genebanked. The details of collecting and storing tissues vary between different species, and these are yet to be worked out for many of the Kimberley species. We also need a map of the genetic diversity for each species; this is essential for preserving the full pattern of genetic diversity for each species, as we need to know which animals, and from what locations, to collect tissues from. There will be a lot of field work to collect animals, a facility for storing tissues, and, down the track: the technology for bringing stored material back to life. Whilst this last component is vital - after all, the Ark will not be much use without it - it doesn't need to be solved in order to get genebank started. We can safely assume that future advances in biomedical technology will solve any technical issues. The most urgent first step is to start banking down tissues before populations undergo a crash from cane-toad impact, i.e. whilst the genetic diversity is still there to preserve.
Question 2: How are the vulnerable Kimberley populations structured?
Question 3: How can we collect tissues from these species for a gene bank?
Question 4: How can we cryopreserve those tissues?
Question 5: Can we establish the Gene Bank before it's too late?
Making sure the Kimberley ecosystem keeps working.
The impact of cane toads on native species in the Kimberley goes beyond population numbers or genes. Reduced numbers of individuals in a population can alter social interactions and breeding patterns. Reduced numbers of predators can result in changes in the abundance of their prey species, changes that cascade through the rest of the ecosystem.
For the Kimberley ecosystem to function, certain species need to be present and their numbers must be above threshold levels. By monitoring ecosystem function, we can identify when key interactions are under threat and take appropriate action to minimise harmful effects on the rest of the Kimberley ecosystem.Read More
Wilderness areas such as the Kimberley are important because they show us how biological systems work in the absence of human interference. Ecosystems are networks of species that interact with each other - the pattern of those interactions give the ecosystem its particular identity, and allow it to function. Cane toads won't affect all of the ecological interactions within the species, but they will affect some. It is important that we identify which aspects of the Kimberly ecological network are vulnerable to cane toad impact.
The ecological interactions that will be affected by cane toads involve those species that will be directly affected by toads. The changes in ecological function can be;
- A result of species population numbers becoming so low that key aspects of its population ecology and behaviour are changed. These are 'within species' effects. For example, social species may not be able to find other members of their species to associate with, or encounter rates with potential mates may become very low.
- A consequence of changed predation, where a predator species becomes rare and its prey species then become more common. These are 'between species' effects. The changed abundance of those prey species can then have flow on consequences for the any species they feed on, or other predators, competitors, etc. Because of the interconnected network feature of ecosystems, these flow-on effects can be extensive and difficult to predict - in ecology, they are referred to as 'ecological cascades'.
How can we tell if these affects are occurring? To detect the first kind of effect upon ecological function - the 'within species' changes - then we need first to know what sort of population ecology is actually normal for that species. What sort of social interactions does it have? What sort of population densities are required for basic processes such as breeding? For many of the species likely to be impacted by cane toads, we have very little information for these questions.
To detect the second kind of effect requires us to be monitoring, not just the species likely to be impacted by toads (see Aim 1), but the predators, competitors, and prey of those species; and their predators, competitors, and prey, and so on.
Once a change in ecological function has been detected, then suitable action can be taken. For 'within species' effects, it may be necessary to create a sanctuary where the species can be maintained at high population densities, sufficient for the species to exhibit a normal level of population ecology. For 'between species' effects, being able to identify keystone species (i.e. a species that has a high importance to the ecological network, so that a change in its abundance has flow-on consequences to lots of other species in the system) allows management efforts to be focused on that species.
Question 6: What important behaviour & ecology is under threat?
Question 7: Can the Kimberley species eventually adapt to toads?
Question 8: What ecological cascades are caused by cane toad impact?
Question 9: Can the predator guilds continue to function?