Are we losing the koala and quoll?
Dr Willa Huston: So tonight I’m to talk to you about whether or not koalas are in fact on the path to extinction. So we all recognise this beautiful creature – it’s an icon of our country. People come here to see the koala, and if there’s anyone notorious or famous in the media you can Google and find a relevant picture of them holding a koala from some trip to Australia. These pictures are from the GO8 that was held in Brisbane recently, and I think you’ll recognise why I chose the other one. And so they’re an icon, they’re worth lots of money for our tourism trade, but they’re also something that we really hold dear to our hearts. They’re very precious to us, and so we need to take care of them, and I’m going to tell you about the dangers they face, and particularly I’m going to tell you about the dangers they face from this really cute looking little guy here. This is chlamydia, and chlamydia is one of the major threats to the koala. So it looks kinda cute, but it doesn’t present that way to the koala, so we’ll talk more about the chlamydia. But before I do that, the thing I always want to do first is acknowledge the team. Science is not an individual game – science is a team sport. In my lab there’s a lot of people who work in the lab, they work had, they work long hours. Chlamydia’s hard to work on. And particularly Amber Lawrence in the middle there did some of the really tricky experiments I’m going to tell you about, but also working on koala is a very big team project. Vets, collaborators who are developing a chlamydia vaccine at the Sunshine Coast, and medicinal chemists all played roles in this project. And these are people from New Zealand, from the USA, from Stanford University, and we’re supported by the Queensland Government for this project. So what is chlamydia? As I said, it looks kind of cute, and in fact in these beautiful microscopy images that you can see, it always looks really cute. We always think it’s green – it’s not really green, but we stain it so it looks green. Chlamydia is a really ancient pathogen, so this tree of life that you’re looking at on this side is a microbiologist’s view of life, so we’ve excluded us from this tree. And what’s that telling you, where the chlamydia are coming off there, that’s about 750 million years ago. So the chlamydia have evolved to live inside our cells and inside the animal they infect’s cells for millions of years, and that makes them really hard to treat, really hard to investigate and really hard to control. On the top, what you’re looking at in the green in chlamydia pneumoniae from a koala. This is a chlamydia pneumonia outbreak in a captive population in lone pine in the 90s. All of that green, that’s the chlamydia, and what it’s doing is it’s overtaking those red host cells. If you know anything about cells, you’ll see that it actually looks bigger even than the host nucleus, so it really overtakes the cells of the organism it infects. And the other pictures are chlamydia, environmental chlamydia infecting amoeba. Chlamydia are actually everywhere – this is not a unique problem to the koala. I’m not saying necessarily that Beyoncé and Jay-z have had chlamydia but they’re an example of humans. So we see chlamydia everywhere, and generally the chlamydia have their own particular hosts that they like to live in. But there’s a couple of exceptions, and they’re the ones we’re going to talk about. Down the bottom here you can see chlamydia pecorum, and it’s a major pathogen in farm animals but also in the koala, and they’re quite different chlamydias. And also chlamydia pneumoniae, also a pathogen of the koala and a whole range of different animals. The reason why chlamydia are so fascinating to work on, but also so challenging, is because they live inside the cells of the organism that they infect, as I mentioned earlier. They do that by having this extracellular spore-like form that’s tough and transmits by contact or faecal-oral route, and then they co-opt that cell and they take it over and replicate a lot inside that cell and then they go back out again to re-infect. Now, how that presents as disease – I’ll tell you about the humans first, because sadly we know a lot more about human chlamydia than koala chlamydia. If you look at that eye, on that side for you, if you look at the eye, what you can see is little white pustules, so the chlamydia are infecting there, and they’re causing an immune response, and the eye is trying to clear that infection, but what it’s doing is it’s actually scarring really severely, and so the eyelid turns over and condenses and those eyelashes rub on that eye, and they rub and rub until the person goes blind, and that’s trachoma. There’s about 5 million blind today from that disease; exactly the same disease happens in koalas in the ocular tissue. The figure below that – this is a woman and this is her reproductive tract, and what we’re doing is we’re looking from the outside with a type of x-ray, sonography, and we’re putting a dye into her uterus. And you can see on one side the dye is flowing out into her peritoneum, and on the other side the dye is not. So that same scarring that you can see in the eye has happened in that tube. Now, for that woman, if that was in both tubes, her only way to get pregnant would be by IVF. The same scarring happens all throughout the urogenital tract of the koalas. In the koalas it’s even worse; it’s a whole body of cysts and scars. It’s very, very painful. And so as I said, similar disease spectrum in the koalas. To diagnose it in the koalas is quite tricky, because their genital tract is very complicated and very internal. And one of the methods that we can look at, and you can see this video yourselves, is sonography from the outside, a very special machine developed for animals, and we see all this scarring and cysts all through their urogenital tract. So what are we doing? So we’re trying – so many researchers are working on this problem. We’re trying to develop better diagnostic techniques, and this is a sedated koala from the wild that we’re testing for chlamydia, so those orange swabs are our test for chlamydia. We take their blood to look at the immune response to the chlamydia, and another group that I’ll mention are working on a vaccine to prevent the chlamydia, but we also need to treat it. So as I said, we have a real problem with chlamydia and koalas, but this problem is really a story about the lives that koalas are leading in Australia right now. Koalas, whilst we all like to think of them as this cute little guy here who’s having a nap, and we all think that’s what the koala does – they just nap. In fact, koalas cover a lot of territory. They’re fussy, they like very particular gum leaves in their environment, so they’ll travel to find the right gum leaves, so that means they’re down on the ground a lot. As we build more roads and we section off their habitat and as we build out into their environments, we put them under stress. They move around a lot, they run out of trees to eat and they get hit by cars and attacked by feral dogs. So the koalas is a whole spectrum of issues that we need to worry about, and of course, the Australia Koala Foundation symbol of saving the trees. But we need to think about the whole system when we talk about koalas, but importantly, and my focus and my contribution, is a drug for koala chlamydia. As I said, it’s a very severe disease. Here is a koala eye, and you can see just how inflamed and damaged that eye is; that koala’s actually blind. If you’re a blind koala in the wild, your survival rates aren’t good. At the top there, this is what we call ‘wet bottom’. This koala has chronic incontinence from those chlamydial cysts all throughout the koala’s urogenital tract. So we need a drug that’s more effective to treat the koala chlamydia. Sorry – I’ll just have another drink. So why is that tricky? We’ve got lots of antibiotics, we all take them throughout our life. Antibiotics for koalas are very, very tricky because the koala lives on gum leaves. The koala will actually eat – here’s some gum leaves – the koala will actually eat about 300-500 grams of these in a day, and the calorific content will be less than two of these. So the koala has to digest these really complicated, not very high calorie content leaves to get the energy it needs, but those are eucalypt leaves – they also have a lot of toxins. So not only does the koala have to digest those leaves to get the appropriate energy, it has to deal with a whole lot of eucalypt oil at a very concentrated dose, [inaudible] and all sorts of toxic molecules. So that means there are two unique features that we have to worry about when we try to make a drug for the koala. The koalas have an amazing way to metabolise drugs, because of those toxins that it’s exposed to in its diet. So most drugs are metabolised much more quickly by koalas than most other animals, and because of the complexity of degrading those leaves, they actually have a two metre long secum with a really complicated microbiome or mix of organisms that degrade those leaves. And we need to preserve that. If we treat them orally with a classic antibiotic, that microbiome can die and then the koala can effectively starve. So we have to treat them with an intramuscular injection of an antibiotic called [name] every day for 45 days to cure the chlamydia. It’s a long treatment regime, it doesn’t always work, but it’s the only mechanism we have. Unfortunately there’s one company that makes that drug. The site coincidentally that that was made at has been shut down. We have a very limited supply of that drug left in Australia – a number of years. We haven’t found an effective alternative yet. So that’s where my research comes in. We set out to use some of our human research on a drug compound to develop a koala drug. In order to do that, we had to establish koala chlamydial islet from clinical koalas, and here, again, in the red and green, the green is the chlamydia over time, growing in cells at different time points, and there is an ocular islet and urogenital clinical islets from diseased koalas. So we established a mechanism to grow these islets and look at them. Then we took a drug that had come out of our human research, or a lead compound, and we tested it against these islets. And what you can see now is at different times when we add different doses the green inclusion disappears. We call it an inclusion. The green sack of chlamydia disappears from the cell, and we can statistically graph that over time. So our human compound looks like it works in cell models to kill the koala. That was on two islets. We then got a whole collection of clinical islets from Port Macquarie – the PMS, from southeast Queensland and from Lone Pine from a captive animal, and we looked at ocular islets and urogenital islets and dosed them over time with our drug. Now this is log scales – these graphs are actually for every drop, you’re actually seeing one in 100 to one in 1000 to one in 10,000 drops, so this is actually more substantial than it looks because it’s log scale. And so our drug works really well to quite well on a whole range of clinical koala islets. So this is the first time this many islets have been tested with any drug, in fact. And then we went to the real innovation: we needed to prove that this worked in koala cells. All the work around the world on koala chlamydia has been done using a mouse cell model. So in conjunction with a whole consortium of people, we isolated koala cells from animals that were having to be euthanised due to disease. One of them was a dog attack and one of them had chlamydia. This is Bilbo and Natalie. This is picture of Bilbo and you can actually see some evidence of the clinical conjunctival scarring around his eye. We isolated the cells from these animals, from their conjunctiva, from their uterine tract, and for – in a world first, we were able to grow those cells in the lab. This is the cells from Natalie, not Natalia – Natalie’s uterus – over time. We were able to grow these cells, take them out, look at the toxicity of our compound, the impact of our compound on the ability of the cells to grow, and in a world first, infect those cells with chlamydia from koalas and test our drug against it. And a stylised representation of our data – we did see some toxicity in terms of the uterine cytotoxicity assay there of our compound, and we think we need to work on that. We saw no impact on the proliferation, and we didn’t see any toxicity on the conjunctival epithelial cells, and these were done in triplicate in different tissue islets for the same two animals. In conjunction to that, animals that were being vaccinated for the koala vaccine, which was many, many more – we were able to take additional blood cells from those animals and in a much larger sample size of animals, we didn’t see any toxicity on blood cells. So we’re getting there with the development of this drug. It looks like it’s not toxic, or at least very low levels of toxicity that will need improvement, and it’s quite effective in reducing the burden of koala in the cells, so it is quite an effective antibiotic, in both a lab model but also importantly in real koala tissue. And the final punch line is that we were able to re-infect that koala tissue – that primary, lab-cultured koala tissue with chlamydia and prove in the dark grey there that our compound was able to reduce the infection. So it works in koalas grown in their natural cells.
So that was very exciting, but we recognise that we need to do further medicinal chemistry – so further drug development to make this into a drug that we can actually do clinical trials with infected, diseased koalas. This is a series of experiments that we did on conjunction with those medicinal chemists that I mentioned at the start. So what I’m going to tell you about, if you look at this molecule in the middle, that complicated sort of two-ring structure on the side, that’s the mechanism of activity – that’s the kind of unique chemistry that this particular molecule targets. In the middle is the specificity – how it knows where to bind – and on the end, the chemists just kind of hand wave over that – it’s kind of a protective group. So what we wanted to do was keep that specificity and improve the chemistry and the pharmacokinetics, or the way that it stays in the tissue or gets to the tissue by working on those two end groups. And just to reassure you that the specificity is real, by modifying any of those three internal sites, we basically completely drop out the activity – so it is very specific, the activity. And so by doing a series of experiments, and this molecule over here is actually based on the HIV protease inhibitor that’s already in clinical use for humans, and so we took that motif that’s already been in lots and lots of safety trials for humans and changed our molecule. And it did drop the efficacy – it dropped the activity a little bit, but it’s probably reduced the toxicity and that’s what we’re testing right now. So it’s a balance between decreasing the toxicity but keeping enough activity. Unfortunately some other attempts to improve the tissue penetration by modifying the other end, the [inaudible], which I won’t try and say the full chemical names for, was not as effective. But what our next phase now is to take another medicinal chemistry series of products, test their ability to inhibit, and then text their efficacy and their toxicity, both in the lab model but then back to the koala tissue model by working with our valuable koala collaborators as well. And we think that it’s really a matter of another year of medicinal chemistry approaches before we can actually be going into the animal model. And it’s that urgent as well, so not only is it that the project is at that point, because it’s actually that urgent because it appears that we have a 2-3 year window left of that current drug, unless we come up with a new manufacture site, which hasn’t been easy to do – it’s a very difficult drug to formulate. And so this may now be the solution to koala chlamydia. So I think it’s possible, I think we need it, I think it may become more and more pressing if we keep putting pressure on the koala habitat, the koala environment, if we have another drought, if there’s other external pressures on those koalas, we will need a lot of the drug. So I think it’s a real priority. I don’t think we can rule out the vaccine. And that’s my collaborator’s work, and I think we do need a vaccine, but koalas don’t come into the sexual health clinic for a check-up, even though we ask them. This is how we vaccinate koalas in the wild. It’s not easy – it takes an amazing crew of people to do it. I haven’t been on this field trip before. So we will always need the antibiotic because we will never vaccinate all the koalas in the wild, so those ones that come sick with the chlamydia, we will always need a new drug. So I think we should be thinking about lots of aspects for caring for the koala. So is the koala on the path to extinction? I think if we don’t address all of the factors in the environment to help look after our koala population, I think it is, and I think it’ll be a shame if we’re the generation that’s responsible for that. So I think there’s lots of things you can do. I think that you can think about your local environment – is there lots of housing development going out into new habitats? Do we need to do that? Can we live in smaller environments to protect our environment? Are there other ways that you can act sustainably in your local environment? But if you think you’d like to support the koala drug problem as well, and our drug development activities, then I’d like you to think about clicking on the Giving at UTS website and our project, which is A New Way To Save Koalas. And any donations go directly to the project – there’s no off the top cut for that, and it’s tax deductible, so if you feel that’s an option for you, that would be wonderful as well. But even by being here and being interested, you’ve done a lot for protecting our amazing, iconic wildlife. Thank you.
[Applause]
Dr Jonathan Webb: Good evening everyone. So this is the northern quoll. I think it’s a beautiful animal – it’s probably not as well-known as the koala, but the northern quoll, as the name suggests, is found in northern Australia. And this species once covered one third of the top end of northern Australia. They were really common and they were widely distributed in savannah habitats. When I first went to the Northern Territory back in ’96 with my wife, we had the pleasure of camping at Kakadu National Park, and it was a fantastic place to go because it was teeming with wildlife, so we set up camp and this is what we heard.
[Animal noises]
Barking owls, which are a really typical sound of the top end.
[Animal noises]
And then we heard rustling outside the tent. So we’d just gotten off to sleep, this great rustling noise, so we went out to see what that noise was, and of course, it’s a northern quoll that had raided our esky and was eating our chicken. And that was a really common occurrence back in the 1990s. I mean, quolls were everywhere. People in Darwin thought they were a pest because they got in their chicken coops and so on, and if you went to Kakadu back in the late 1990s, you would have seen quolls on the roads and bouncing around campsites. So it was a fantastic place to go and do biology.
Animal noises]
Sadly, around 2000, 2001, there was a new kid on the block – the cane toads. The cane toads moved in from Queensland, they invaded the Northern Territory, and they not only sounded different to native frogs, but they tasted different to. And they had these massive toxin glands on their shoulders that had very different chemicals that are found in native frogs. And native predators, like goannas, snakes and freshwater crocodiles, had no immunity to toad toxins, so when these predators attacked or bit a cane toad, they got a lethal dose of toxin, and we saw massive population declines of predators as toads invaded the Northern Territory. Unfortunately one of the animals that was most heavily impacted by cane toads was the northern quoll. Quolls are really interesting because they’re short-lived animals. Females only live two or three years. Males only live about one year if they’re lucky. They, in the mating season they run around trying to mate with as many females as they can, they travel huge distances in a night – six or seven kilometres – and not surprisingly they get really run down during the mating season and then they keel over and die. So you end up with a population composed mostly of females, and when the toads invaded, these females saw the toads as a great food source, they attacked and they died, and the young were left defenceless in the den, and the populations collapsed. Luckily the Northern Territory Parks and Wildlife saw this collapse happening – they were monitoring populations in Kakadu, so they trans-located 64 quolls from Kakadu to two offshore islands off [name] – Astell Island and Pobassoo Island, and established an insurance population off the coast to insure that the species didn’t go extinct. After they did this, populations kept collapsing on the mainland, quolls became very rare, and n 2005 the Federal Government declared the species as federally endangered, and they’re now listed as critically endangered in the Northern Territory. Cane toads are amazing dispersal machines. The toads at the invasion front are travelling at a rate of about 60 kilometres a year, which is incredible for a big frog to hop that far in one wet season. The toads are now poised to invade the Kimberly – they’ve already invaded places in the Kimberly like [name] station, and we’ve already seen quoll populations decimated in those areas, and eventually the toads will invade the last two strongholds of the northern quoll: the Kimberly populations in the central and western Kimberly, and the Pilbara. And if the models of toad distribution are correct, then in the next 20 years, the toads are going to make their way through the Kimberly, and eventually they’ll invade the Pilbara region. There’s not much we can do to stop the spread of cane toads; we know they’re going to invade the Kimberly pretty soon, but we might be able to do something to protect quoll populations and stop them going extinct. The major problem if you’re a quoll and you encounter a cane toad is the toads at the invasion front are these really big toads that have got there first – they’re amazing dispersal machines, so the first toads that quolls encounter are these large toads that have lots of toxin, and these are killer toads. The quolls don’t have a chance. When they bite or mouth one of these toads, they get a lethal dose of toxin and they die. They don’t get a chance to learn. However, after toads invade, they breed, and there’s lots of little toads, and I’d been working on some smaller marsupials that are really just miniature quolls – things like planigales and dunnarts. And I was interested to see if these animals could learn to cope with cane toads, and what I discovered was dunnarts and planigales, when they see little toads they grab them, they think they’re good to eat, they start chewing on them and then they feel sick, so they discard the toads and they never touch them again. So this is what happens when a planigale that’s eaten a toad encounters another toad.
[Long pause]
There’s no way he’s going to eat that toad. And this is called condition taste aversion. And any of you out there that have had food poisoning will know exactly how this works. I guarantee you that if you get sick tonight, and you spend the night throwing up and I put the food that made you ill in front of you in the morning, you’ll push it away and go ‘There’s no way I can eat that.’ And condition taste aversion is a really powerful form of learning. It was discovered in the 1970s and when it was first discovered, people didn’t believe that it could work, because it only requires one bout of poisoning for you to remember not to eat that food and to develop a long-term aversion, and this is quite different to classical conditioning where you need multiple trials to learn, so it’s quite a different form of learning. So I did some research about condition taste aversion and discovered that way back in the 1970s, conservation biologists had discovered condition taste aversion and they used it as a tool to train predators not to eat certain foods. And one of the classic trials was on coyotes that were eating sheep in America, and what the researchers did, which was really smart, was they fed the coyotes a bait laced with a nausea-inducing chemical, so they gave the coyotes some lamb with a nausea-inducing chemical. The coyotes ate it, they threw up, they then put the coyotes in a pen with the lambs. The coyotes chased the lambs because they thought they were good to eat, and when they got close the coyotes gagged and left the lambs alone. And there’s this classic video of the lambs chasing the coyotes around the pen.
[Laughter]
Now, field trials with coyotes weren’t successful, so the technique got forgotten – everyone forgot about condition taste aversion, but I read this research and thought well, perhaps we can use this tool to train quolls not to eat cane toads. So I had a meeting with Deon Wedd and Damien Staniock at the territory wildlife park, and they had a captive colony of quolls that was an insurance population, and I talked to them about this project that I wanted to get off the ground, and I basically said to them ‘Can I come and make your quolls sick?’ And the carers at that meeting said ‘No’. Which wasn’t surprising – the carers didn’t think the quolls could learn to avoid eating cane toads, so I had to wait about a year before some new quoll carers came on board. Deon rang me up and said ‘Do you want to give that project a go?’ And I said ‘Yeah, I’d love to give it a go.’ So my honours student Stephanie O’Donnell and I went back to the wildlife park and we trialled this technique using condition taste aversion. So what we did was we had a vet standing by, because we weren’t sure what size toad we could feed a quoll without killing it, and we gave them a small dead toad paired with a nausea-inducing chemical called [name] that’s been tested on livestock and mammals – it’s really safe to use – and lo and behold, the quolls ate the toad, they got mildly sick, but what happened next was really exciting: these toad-smart quolls refused to eat cane toads. So this is one of the quolls from that study that Stephanie O’Donnell, my honours student, did, and you can see the quoll’s really interested in eating that cane toad, because it’s giving out all the signals that quolls normally associate with something good to eat. The toad’s jumping around, it looks good to eat, but you can see the quoll’s really using its sense of smell to identify whether that’s palatable food or not, and you can see the quoll’s not eating that cane toad, which was really amazing for us, because we’ve witnessed quolls eating toads, you know, with disastrous results, and here’s a quoll that’s just getting frustrated and taking it out on our camera equipment.
[Laughter]
So we’re really excited about the prospect of using this technique to train quolls not to eat cane toads, so the next step in the project was we fitted quolls with radio collars so that we could locate them daily, and Stephanie enlisted a large team of volunteers and she released toad-trained and controlled quolls in areas near Darwin, and she monitored their survival, and what she found was really exciting: you can see here we’ve got toad-smart quolls with males and females, and toad-naïve quolls, and the take-home message is our toad-smart quolls had much higher survival than our toad-naïve quolls, and you can see that males were more stupid than females.
[Laughter]
And that’s not really surprising. So that research really was the impetus to the research that we’re currently doing, so that was proof of concept that perhaps this technique could work – maybe we could help save the quolls. So what we’re doing now with this collaborative project is we’re aiming to try and reintroduce toad-smart quolls to Kakadu to see if we can help those populations to recover in areas where quolls are locally extinct, and the second project is much more ambitious, and it’s largely being done by one of my PhD students, Naomi Walters, with the Australian Wildlife Conservancy, and Naomi is going to attempt to try and prevent quoll extinctions from occurring by putting out toad aversion sausages ahead of the toad invasion front, which I’ll come to a bit later in the talk. So the first project has been up and running for quite some time now, and the aim was really to see if we could bring quolls back to areas where they’re locally extinct, so this work was done up in Kakadu National Park up in northern Australia. If you haven’t been to Kakadu yet, I think you should put it on your bucket list. It’s a great part of the world. It’s just a fantastic place to work. So what we did was we reintroduced toad-smart quolls to an area near Ubirr, near East Alligator River in 2009 and 2010, and this is what the study site looks like – it’s on the edge of the Arnhem Land escarpment. It’s savannah woodland interspersed with rock outcrops – it’s a beautiful part of the world. And it has a fantastic art site called Ubirr, which – and this is the view that you get looking out from the Ubirr escarpment onto the East Alligator floodplain. It’s just a magnificent part of Australia, there’s some fantastic Aboriginal art, and I think the nice thing about working in this part of Kakadu is the Aboriginal people are still very much engaged in managing the land and they’re still doing traditional rock art and traditional ways of hunting and so forth. And there’s some really amazing art – does anyone know what that beast is? I’ll give you a hint: it’s got stripes. Yeah, it’s a thylacine – it’s a Tasmanian tiger. So Tasmanian tiger’s were present in the top end of northern Australia roughly 5 or 6000 years ago before the dingoes invaded. So what we do to monitor quolls is we put out these cage traps with a bait of peanut butter, honey and oats – I have no idea why that bait works and why it’s used by mammal biologists, but that’s the bait that everyone uses, and we catch lots of really amazing animals like short-eared rock wallabies, you can see in the left here, and rock rats on the right, and we also catch quolls, which is our target animal, and I’ve put this slide up, not because we were sponsored by Qantas – it would have been nice to be sponsored by Qantas but they lost Tim’s luggage. But they did give him a shirt that he got to wear for the week.
[Laughter]
What we do when we’re working on our mammals is we microchip every animal that we catch, so every animal’s got a little microchip similar to what you put in your cat or your dog on the scruff of the neck, and because we wanted to know if each generation of quolls would learn to avoid eating cane toads, we took tissue samples from all the toad-smart females that we re-introduced, and also from any offspring that we caught. And our geneticist, Peter Spencer at Murdoch University, was then able to use the tissues and the DNA to work out who the mums and dads were of all the animals in this population. And this is just showing how we release the animals – we just let them go in a crevice after we’ve finished processing them. Okay. So when we started this work, there was only one female left in this population, so it wasn’t a terribly healthy population. We knew from the work Mary Oakwood did on this population that it used to have roughly 30 females. When toads came through, it crashed down to two or three, and it was on a path to extinction. We then introduced our 22 toad-trained females. Six of these females survived long term and reproduced, and not surprisingly, the population increased, which was exactly what we were hoping for. And I guess the really exciting thing for us was that we saw recruitment of juveniles – the green bars on that graph – into the population. And so we’re really excited about these results. When Peter Spencer looked at the genotypes of all the animals in the population, he found that roughly two thirds of the animals in this population were direct descendants of those toad-trained females. And that was really exciting for us, because it means that each generation of quolls learns how to avoid eating cane toads. And that’s really important if we want to use toad sausages ahead of the toad invasion front, because it means we only have to do it once, because thereafter the quolls will learn to avoid eating cane toads. How do juvenile quolls learn not to eat cane toads? That was the question we were really interested in. We had no idea how they’d learn that toads were not good to eat. My PhD student Tegan Cremona put radio collars on quolls as they were leaving mum’s dens, and she radio tracked them to try and find out what they were doing. And what Tegan did that was really innovative was she put remote cameras near the dens of quolls that had left home, and also their mother’s den, to see if there was any ongoing interactions between mothers and offspring. So the traditional wisdom about quolls that everyone told us was that quolls are solitary – there’s no capacity for social learning. But what Tegan found was really exciting: by putting these cameras out, she saw lots of wildlife like the rock wallaby. These are rock ring-tailed possums that live in family groups – amazing animals. What Tegan found that was these quolls that had left home came back to their mothers dens. So just like humans that have left home, the quolls come back and raid their parents’ pantries and go foraging with mum. And so what we think’s happening is we know that toad-smart mothers, when they encounter toads, they sniff and reject them as you saw on that video. Juveniles are clinging on mum’s back when she’s out foraging – they’re probably watching mum sniff and reject toads on a nightly basis. Any of you that have got kids will know that if you want your kids to eat healthy food, you have to eat that food because your kids will copy what you do, right? So if I want my kids to eat fruit, I have to eat lots of fruit. So we think that quolls probably learn what to eat by watching what mum eats. Now, if mum doesn’t eat something, the quolls are probably not going to eat it either. So we know quolls can learn to avoid eating toads. Unfortunately they’re still not really common in this area where we reintroduced them, and we think the reason for this is that the country’s burnt too frequently, and this burning every year in Kakadu that’s been occurring opens up the habitat and it really allows predators like dingoes and feral cats to prey on quolls and that’s exactly what we’ve found. When Tegan was tracking her juvenile quolls, she discovered that dingoes were the major predator, and feral cats were also a major predator. So in a nutshell we think we could probably bring quolls back, but we’re going to have to manage the country a lot better than we have been if we want to do this. So what we found was toad-smart females survived and reproduced in this population. We know that each generation can learn not to eat cane toads, so what we’re hopeful of is that we should be able to bring quolls back to areas where they’re locally extinct by reintroducing these toad-smart quolls that we’ve trained not to eat toads, but if we’re going to do that we really need to manage fire, because that’s the biggest problem we’ve got right now in northern Australia. Okay, so I’m going to change track now and I’m going to take you over to the central Kimberly to Mornington Wildlife Sanctuary where Naomi is currently working, and the aim of Naomi’s project is to see if we can actually prevent some of these population declines from occurring. So this is Sir John Gorge at Mornington – it’s a beautiful part of the world. It’s one of the, I guess, the most pristine landscapes that I’ve been to. It’s just magical at this time of the day. And the good thing about Mornington is there’s still lots of wildlife that you can see, so as a biologist it’s one of my favourite places to go and visit. This is a water monitor, and these are brolgas that I saw dancing when I was out there last time, so just a fantastic part of the world to work in. This is Naomi. So Naomi is in the first year of her PhD. Naomi’s attempting to train wild quolls not to eat cane toads, and she’s doing that by putting out toad sausages at baited and controlled site and the aim is to see if she can keep quolls in the system at those baited sites. Now, if that project works, we’re then going to upscale and do helicopter delivery of bates over bigger areas, but we’ve got to start small and just see if the technique will work. Lots of people ask me how we make toad sausages – well, it’s just a lot of hard work. You get your dead cane toads, you chop off their legs; the legs are non-toxic. You can then put the legs through a blender and make a really nice sausage that is apparently quite palatable, so if you were desperate you could probably put it on the barbecue. Once we’ve made the sausage, we put it out under a camera and the reason for doing this is we need to know whether quolls will eat the baits, and also whether there’s non-target species that might also eat the baits, so we need to know that. Here’s a photo from one of Naomi’s cameras – you can see a quoll inspecting a toad sausage, and the really nice thing about using the cameras is you can actually identify individual quolls from their spot patterns. So you can look at these photos and you can work out exactly which quoll has eaten a sausage, and by doing this we’re hoping to see whether the quolls that eat sausages are the ones that survive after the toads invade. So far Naomi’s trials have been really promising. She’s found that 50 per cent of quolls at her study sites have eaten the toad sausages. We know from trials we’ve done in the lab that quolls that eat sausages get sick – we’re hoping they’ll avoid eating cane toads when they come through. Naomi’s deploying baits this coming wet season, around November. She doesn’t have much time – I just talked to Naomi today, and unfortunately the toads have moved further than we thought this wet season, and they’re only 20 kilometres from her study site, so she’s literally got a couple of months to try and protect this population before the toads invade. We’re really strapped for staff – we have been well funded by various granting agencies, but we don’t have enough money to employ a research assistant, and Naomi’s doing this work on her own with volunteers, and we could really use your support if you want to help prevent quoll extinctions and you feel like supporting this research, grab one of the fliers on your way out. Any support would be really welcome to help us trial this technique in the Kimberly. Just to finish, I took my family back to Kakadu this year – these are my kids and my wife – dragged the family up there 20 years after I first went there with my wife, and we went camping and we heard the barking owls at night when we were in our tents. We heard rustling in the leaf litter – we went out there to look and we didn’t see any quolls. My kids wanted to see what the rustling noises were, and so I took them out and we got our torches out and they were cane toads. We didn’t see any small mammals, and the sad thing is that small mammals, not just quolls, are declining all over the top end. We’ve now got a third extinction event going on. Small mammals are disappearing from pristine areas like Kakadu National Park at an alarming rate, and this is a tragedy. And we think that too-frequent burning of the landscape, loss of Aboriginal management with fire and introduced predators are really knocking our small mammals around. So feral cats are probably playing a really big role in this recent decline, but it’s also possible that disease is involved. This is really saddening for me to see mammals that were once common in Kakadu 20 years ago disappearing before our eyes, and I think it’d be really sad if the only small mammals our kids see are at the territory wildlife park or zoos. This would be a tragic loss. So I think just to sum up, we really need to look after our country better for future generations. Thanks for listening.
[Applause]
9 June 2016
43:01
koala, quoll, extinction, disease
Two UTS scientists explain how they are working to help protect and save some of Australia’s most iconic and loved animals from the threat of extinction.
About the speakers
Dr Willa Huston
Dr Huston is a molecular microbiologist with a strong interest in chlamydial diseases in both koalas and women. Dr Huston is working to better understand the “bacterial pathogenic factors” of chlamydia, so new drugs can be developed to treat this devastating disease. Better treatment will hopefully prevent complications.
Dr Jonathan Webb
Dr Webb is a wildlife ecologist who is leading a national joint project using novel approaches to prevent and reverse quoll population declines. hHs team uses conditioned taste aversion to train quolls not to eat cane toads. If successful, these strategies could help secure the future of one of our most iconic marsupial predators.
UTS Science in Focus is a free public lecture series showcasing the latest research from prominent UTS scientists and researchers.
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