How to save a species...
From problems to solutions. When rodents took over the South Georgia Island, they had a devastating effect on the number native rare birds. Izzie Clarke and Katie Haylor were joined by Dickie Hall from the South Georgia Heritage Trust who was a key member of an ambitious and successful project to save them…
Izzie - Dickie what are we actually listening to here?
Dickie - That's the call of the South Georgia pintailed duck which is a tiny, very cute and endemic duck. It's in South Georgia it's found nowhere else in the world.
Izzie - Oh my goodness. What's the problem then, why do we need to have a project at the South Georgia Island to save these?
Dickie - Well a couple of hundred years ago rodents were introduced to South Georgia and basically rats and mice on South Georgia are devastating to the terrestrial environment
Izzie - How big a problem is that and how did they all come over?
Dickie - Well we probably have Captain Cook to thank for the introduction of rodents to South Georgia. He went there a couple of hundred years ago, or 1775, and he didn't spend long in South Georgia but when he came back to the UK he published his notes about South Georgia, and in them he mentioned the fur seals and it was not long after he mentioned this that the first sealers arrived in South Georgia and with them they brought the rodents.
Izzie - What's so bad about them?
Dickie - On South Georgia in particular, the rats were devastating to the environment. It's an environment that's never had any kind of land predator, and when rats were introduced to an environment, they basically run wild. There is nothing to hold them back. There's nothing to stop them. None of the animals in South Georgia have a defense against them. So all of these little tiny birds that are ground nesting and burrow nesting, they have no way of protecting their chicks and their eggs and the rats just feast on them and destroy the populations.
Izzie - So how can you go about solving that problem? That sounds like a pretty big undertaking.
Dickie - Well eradications in general are very difficult. Island eradications especially on the scale of South Georgia are incredibly challenging and the only way to do it is to remove 100 percent of the rodents from the island. If you remove 95 percent you've failed they will breed back up in numbers within a few years and just start all over again.
Izzie - How can you get rid of these rats and mice?
Dickie - Well we used an aerial baiting operation, so we used three helicopters over the course of three baiting seasons to go to South Georgia and we covered the whole of the island with rodenticide, so a bait that would target the rodents and kill them.
Katie - I've got a question. How do you make sure that you're just getting the rodents and nothing else? Is that quite challenging to make it that specific?
Dickie - It is very challenging. The manufacturers of the bait develop the bait so that it is palatable and attractive to rodents, and as unpalatable and as little attractant as possible to any other species.
Kaite - Ah okay. What actually is it?
Dickie - The bait that we use, the toxin is called brodifacoum, and it's basically a cereal based pellet. So it uses cereal grains munched up with a tiny amount of this toxin added to the grain and that pellet is enough to kill an individual rodent.
Izzie - But you said you've got to make sure you get rid of every single rodent so how can you check that that has happened?
Dickie - Well after the three baiting phases we returned to South Georgia and we had a season where we spent six months searching the island using passive monitoring devices and active monitoring devices, and the active side of that was that we have three rodent detector dogs brought in from New Zealand, and we covered the whole of South Georgia searching for any evidence of rodents. And thankfully in May of 2018 we were able to announce to the world that South Georgia for the first time in 200 years was finally free of rodents.
Izzie - Have you seen results from that eradication?
Dickie - Yeah. When we returned to South Georgia just last year we were seeing absolutely stunning results. So every single place that we visited, we were seeing the endemic birds, so the South Georgia pipet, which is a tiny little songbird. And the South Georgia pintail, which was the little duck that we heard earlier. Everywhere we went we were finding these birds which had been completely unheard of before the eradication took place. Now they've returned to South Georgia en masse and we're seeing literally flocks of hundreds and hundreds of pintail ducks and many thousands of the pipets.
Izzie - And have other people or other organisations picked up on this technique of eradication and using that to try and save other species?
Dickie - Yeah it's been widely used around the world. The New Zealanders and the Australians really pioneered it. Since we've done the work on South Georgia, I've now moved on to work with the RSPB and they're conducting another eradication project this time on Gough Island which is a little mid-Atlantic island which has been invaded by mice about 200 years ago, and they're having a similar effect on Gough Island as the rats did on South Georgia.
Izzie - And so would you say eradication is the best way forward?
Dickie - Yeah. There's not really any alternative when an environment is invaded by rodents. It doesn't have a way to recover so you just have to remove the problem. They're not meant to be there, if it wasn't for human activity they never would have reached many of these places. So they just have to be removed.
Izzie - But could prevention ever happen, is there any steps to avoid this situation from happening in the first place?
Dickie - Yeah. There are not many pristine environments left but where they do exist biosecurity is key. It is much easier and much cheaper to prevent an organism reaching a pristine environment than it is to try and remove them after the event.