Browse Island Mouse Eradication.

Brails is an island that was essentially decimated and then to a point where we lost all the seabirds with guano harvesting. Guano is accumulated bird poo that is used as a fertilizer for agriculture. This became a really valuable commodity across the world in the late 1800s. Sailing ships and steamers taking huge volumes of accumulated guano and at that time they bought mice they bought cats and of course there's people living on the island eating seabirds you know subsistence kind of living very very tough environment and nested in all that we lost the seabirds. The presence of cats at least through to the 1950s and the presence of mice through to now means that when birds do try and re-establish there's just enough of a pressure that it prevents them from doing that. Just had a mouse quickly dart across the field of view here and just see if we can get back onto it. These birds are significantly disturbed by mice they just abandon their nest and they unfortunately fail. That's why all the bait is here with us it's one go it's not like try and trap over years and years and years it's get rid of the entire population and then allow the system to bounce back. If we fail it will mean that seabird recovery we would expect would be continue to be inhibited on that island. Browse Island is a is a link in the chain of the northwest that maintains this population of the seabirds that was taken out didn't return for many many years but they've just started to come back which has been amazing to see which makes the timing of this critical in that they're just trying to re-establish and we're going to remove probably the key threat. Our mission is for the successful eradication of mice Made it we're here so we've only got a pretty quick little window now we've only got about half an hour to get out basically drop the party off and then come back in and do a bit of a recce for tide and entry points and put a safe track and then uh yeah straight out tomorrow morning. It's a good height to come in on good amount of water keep bringing gear over. Really great outcome just to get a few more transfers and a bit more gear on the island than we expected once that tide comes in tomorrow we'll get the bait on we'll get the drone here and yeah that's when things will really fire up and we'll get stuck into the operation properly. Browse is also a really important green sea turtle breeding area so highly likely we'll see a few come up to nest might even get a few hatchlings if we're lucky. It goes above the five star system man it's better than any five star hotel in the world. A team just working together we all need each other to make a difference. If you love delivering meaningful conservation outcomes in beautiful areas and with great people then working for Parks and Wildlife I mean how could it get any better than this. Rodents generally on islands are recognized as one of the most significant threats to biodiversity globally. We know that Browse Island was once thriving with seabirds we know it was an probably an incredible place. So this is the first time that an eradication has been attempted for house mice anywhere in the world that's using drones. It's a pretty ambitious project it's especially ambitious when you think about how remote we are. We're hundreds of kilometres in the Indian Ocean there's a fringing reef that you have to navigate to get to the shore and then you have to navigate a shore break to get onto the land. What we'd love to see here is the island to return to that incredibly beautiful state. It's really exciting to be involved in leading the charge and really it's all about conservation outcomes. If we can learn something here and be successful here and pass that on to others to then also implement these management strategies then yeah that would be fantastic. These islands are really important for seabirds they'll lay their eggs out here raise their young and then after all of their breeding's done then they head back out to sea. So they're very important sites and if we can't protect them during their breeding then that's a real problem for their seabird populations. When I'm flying when I go to arm the drone I'll be yelling out arm when the drone is down and to stand I'll yell out safe that's when the bait loaders can go and load the bait. Already pretty sweaty but that's all right any work you do on this island it's pretty brutal. You've got to be real precise get a nice even spread one little square meter then the mice can just hang out in that area and they might have enough food within that area and then start breeding again. Systematically cover the whole island it's similar as a lawnmower pattern like mowing the lawn going back and forth back and forth and then we'll go all the way around the coastline as well. You can send a drone out to cover an entire island in the space of a morning out in a remote place like this that could be the difference of getting the job done and not getting the job done. Mice will emerge from there from where they've been living from underground from their holes go out and forage as usual find the bait maybe take it home with them maybe have a little nibble. A critical point of this poison is that you only have to eat a very very small amount of it in to consume the lethal dose. Mid-morning on the first day and we're yeah we're already a third of the way through the bait. We're going to set up our bait availability monitoring transects now. We run transects to look at how many individual pellets are actually being eaten or taken so we go out and measure that each day and that tells us how much consumption is actually happening and it's really important that we know that because we need to have bait available for three or four nights ideally if the bait disappears earlier than that then that's potentially an issue. We still want there to be quite a lot of bait available because that means there's a higher chance of a mouse encountering a piece of bait. You could probably achieve eradication with just one drop but the best way to do it is to drop bait at least twice. That might be because the bait was mopped up before they had an opportunity to eat it or because maybe there are individuals that were not yet out and about that were too too small. We're also doing measures of the amount of bait that falls on the ground from the drone so that we have a real measure of density of bait on the ground that we can correlate with the information that comes from all of the digital outputs associated with the drones. As long as we have enough bait available distributed evenly across the island then we're giving ourselves the best chance for success. This is the only bit of infrastructure here so we're just trying to make sure there's no holes that the drone couldn't get to. As part of the program to eradicate the mice here there's a bunch of different actions that need to take place. Some of them are compliance, some of them are monitoring that informs the science, some of them are just direct action that's kind of in the mix and then we're really also focused on what we would call the biodiversity assets here so particularly the seabirds, the other birds that are present so we're counting all of those and getting a good understanding of what's here because this is a fantastic opportunity while we're on the island and then there's some stretch goals going on as well because we're on the island and we've got these opportunities there's people been doing turtle monitoring and there's been litter patrols and things like that that are you know gathering up the marine litter and also improving the the management outcomes for the reserve as well. It's really special to come and work in places like this to come out here and implement management actions that will have a meaningful benefit. It just really resonated with us as something really meaningful and impactful through Monash University and the partnership they'd linked up with DBCA for this project and then we've got the experts coming in essentially as contractors with the drone delivery and it wouldn't happen if we didn't have the funding and the support to deliver these types of actions. I'm doing research on the bridal terns so doing some tracking work looking at where they're foraging away from Browse Island and so the reason that we've chosen bridal terns is because they were one of the first seabird species to come back here and start breeding. They nest down on the ground usually pick an area that's got a little bit of cover. We've done one year of tracking already so last year in 2024 I put 10 trackers out on bridal terns on Browse Island. Almost immediately it showed us how connected all of these island systems are in the region. Before we started this work we didn't know oh maybe the birds are just using one island and they're staying fairly locally but straight away we had movement where bridal terns left Browse Island went down to Adele Island. Lots of connectivity with the lassopedes and then it's also shown that over the wet season these birds are migrating up into Indonesia so they're traveling really long distances which is showing that well they're potentially going to be exposed to threats away from the breeding ground as well or on other islands so we can use these movements to potentially suggest future sites for restoration and conservation work. Yeah it's probably fair to say that the people that do these sorts of gigs are mostly obsessive biologists and on this trip there's a fair number of obsessive birders and so that means that yeah whenever something interesting flies over it's called on the radio and and people down tools and have a quick look at it. There's a bit of friendly banter going on on the island in terms of who's found what. Favourite bird for the trip would be yellow wagtail. It's a songbird they breed in China and just to think that a bird that weighs 10-15 grams was in China a month ago. Today we had three on the island and they flew off through the day heading south to the Kimberley Coast. All right back into it. You're gonna get pretty soupy again. This island has been a tough place for a lot of people. We had blueberries and strawberries this morning. At least you're not shipwrecked huh? Be thankful for that. Stop it. This morning first day after bait drop one of the key questions we have is what take-up looks like. You want a balance, you want them to like the stuff and eat it but you also want it to still be available to those who don't get to it first. Still a little bit. A little bit but still. Really just a trace. Looks like it's been taken. It's rounded off. We don't put down bits of bait that are half length and so yeah this thing looks a bit short so it'll be scored as a 75 which means the mice have had a nibble but that's pretty much bang on. It's like we're almost at the end of the transect and that's the second one with a bit of bait missing. It's kind of what you'd expect if things are going really well. It's good to see that the mice are eating some of the bait but at the same time it's good to see that there's still some bait left on the transect. Yeah it's another classic bit where it's been moved a short distance in the dense cover. That one's a 50. Yeah that's the first one that we've had where half of the piece is missing. They don't like to just sit out wide in the open and eat a meal. They get it and they take it back to some sort of structure. Probably a surprise that it's eaten 50% but it might be that you know two or three mice have found this through the night and all had a little nibble so they only need to eat about 10% for it to be effective. Looking good. Should be the last one and we'll be away after this. Safe. That was it. Yeah. All right. Nice. Good work guys. You may take it off. First application down. One more to go. You do your first drop and the idea is you hopefully catch most of the population then. Just in case there are a few individuals that you missed you want to come out again. Hopefully that gets the last couple of mice that might be remaining. We're really hopeful that this will be successful. We've targeted the hottest and driest time of year when food resources should be at their lowest but ecology is really dynamic and it doesn't always work that way. We know that cockroaches also consume the bait so if there was a massive population of cockroaches at the moment on the island for unknown reasons and if they were consuming all of the bait and that wasn't available for the mice then that's another example of how yeah that the operation could fail in achieving its outcome. My dream would be to come back to Browse Island in say a decade's time and just see that cloud of birds over it. That would be amazing. Typically it's 12 to 24 months before you formally declare success. It depends a little bit on the size of the island and what tools you have to monitor but also what access you have and this island's really remote so it means that we're not going to be here every other month checking. It might be that you know over the next year we have two or three opportunities to get back to have a look and monitor to see if we can detect any mice and we're obviously hoping for zeros. And in the context of a lot of negative stories about the state of nature and our capacity to do something about it, islands like this are demonstrations that we can, that actually there can be huge wins in conservation. Island restoration projects around the world have demonstrated that that's possible and we need to recognize that and focus on that. Amongst a lot of doom and gloom there are a lot of very inspirational stories that are very true, very real and in the next 10-20 years our hope and our expectation is that Browse will be one of those stories.