A controversial idea to fight invasive species.......

I was thinking about the invasive coqui frogs in hawaii, and how it became an extrem demage to the native wildlife there. I got a idea then. Hawaii like many other isolated islands have no native amphibians. So what if we release the fungus that corses Chytridiomycosis in effected areas there ? It is extremly specialized, and coudn't harm any native species, and selectivily eleminates, or atleast controll the frog population. Similar to how the moth Cactoblastis cactorum in Australia was used to controll the pickely pear infestation.

 

Depending on the species, I know chytrid is not lethal to all amphibians and is actually spread by many species that are carriers. I’m not familiar with the frog but chytrid might not be the best answer.

 

There was a discussion quite a number of years ago by scientists about using chytrid as a biological control agent to erradicate the coqui in Hawaii.

However, the findings of research suggested that the coqui may carry the fungus but is not actually harmed by it nor even sickened.

 

Given the high connectivity of Hawaii to other parts of the world there would be a very high risk of the disease spreading to other areas, where it would do harm.

New Zealand was thinking of introducing a disease against their possums, but this idea was blocked by Australia, because there would be a risk of it spreading to the native population...

 

Actually, the best disease of possums would come from Australia. New Zealand population of possums is isolated for over a century from Austalian diseases, and was presumably imported as healthy to begin with. So importing sick possums from Australia (or just their faeces, or saliva, or whatever, also from related possum species) could introduce a strain of disease which would help rid New Zealand of invasive possums.

I had a similar idea, that one could wipe out mice or rats from oceanic islands by importing diseases of rodents. It may not be necessary to know much about diseases of rodents - just import mainland rats and mice and hope they carry some gem not present in rodents on the island. There is a lot of oceanic islands with invasive rodents to experiment on. Additionally, some islands are scheduled for rodent poisoning, so they could be targeted with disease beforehand.

 

You are definitely an out of the box thinker @Jurek7 , I'll give you that.

I think that it has been pretty much established by now (post over 400 successful rodent erradications from oceanic islands) that poison bait is the way to go when it comes to conservation interventions involving control of invasive rodents on islands.

 

What is so out of the box? Biological control has been used for centuries, with textbook examples like myxomatosis and rabbits in Australia 90 years ago. Even when a disease only lowers population density of invasive species, it is valuable.

New Zealand seems a very good place to try biological control of invasive mammals, because there are very few other mammals which are potential off-target hits - and it is well known what diseases are dangerous/safe for humans and domestic animals, and bats and seals are very unrelated to possums, rodents, hedgehogs, stoats etc.

Poison bait has disadvantages - it is expensive, it is logistically difficult, it is danger to other wildlife and humans. Because of these it cannot be used in the scale of whole New Zealand and on many small islands.

 

Well you just illustrate with your posts that you think outside the box, it was a compliment.

The problem with biological control of invasives using disease is that there is always an outside chance (even if a low one in the case of islands) in our globalized world that pathogens could reach other regions that do have native rodent populations and that have no immunity to a disease and decimate these.

Yes, myxomatosis was successful in Australia but we are now seeing alarming population declines of hares and rabbits in Europe (so much so that the European rabbit is now listed by the IUCN as endangered) mainly due to rabbit hemorrhagic disease but recombinant myxoma viruses are also complicating the picture too and accelerating declines.

This of course has wider ecological implications as it impacts the predators that are largely dependent on rabbits as prey like the critically endangered Iberian lynx.

 

I personally don't agree that New Zealand is ripe for biological control of invasives through introduction of diseases.

While controversial I think 1080 (along with selective combined use of improved trap technology) is the best bet in eliminating invasive mammals from the country.

Granted it is logistically difficult and pricey, however, the NZ government, many conservation groups and much of the public seem willing to embrace these challenges.

There are concerns about collatarel damage to wildlife, people and pets which are understandable but it is biodegradable and soluble.

Furthermore, there is a great deal of research going into developing species specific baits and how to implement actions in a way that does not pose a risk to humans, pets or livestock.

 

In case of New Zealand and oceanic islands, there is no need of 'new' pathogens - existing diseases, which exists among rats in Europe or possums in Australia can be used.

I just learned that myxomatosis was also tried in New Zealand in 1952. If the progress of science of the last 70 years was used for biological pest control, much could be done, I am sure.

Curiously, saving New Zealand animals from invasive pests is a conservation ecology in reverse. Normally biologists try to avoid poisoning, diseases, breaking population connectivity and whatever to protect species on islands. In fighting invasive species, all these are desired things.

 

That's because 1080 has proven to be effective at supressing pests like rats and stoats on large scale landscapes, with only mammals really eating the baits, save for a few very curious kea. There was a recent project in Perth Valley using 1080 on 12,000 hectares of native forest to remove predators and using the landscape and constant monitoring to prevent reinvasion.

Its a pretty cool project and was the precursor to Predator Free South Westland, which is pretty much using the same technique but in 100,000 hectares over both farmland and forest, using rivers and a smart trapping network to prevent reinvasion. Its really just a really unique situation which makes it sort of perfect for this very cool and revolutionary approaches to pest control which I would love to see uses worldwide someday to manage invasive species

The Perth Valley Project - what is it all about? — ZIP
South Westland - Predator Free 2050 Limited

 

Well said and totally agree !

 

I myself also have a potentially controversial idea on how to control at least two of Hawaii's invasive species. Those being the feral pigs and Axis or chital deer, at least on the island of Molokai, Hawaii.

Now in Hawaii, you can hunt both of these animals as a way to control their numbers, but unfortunately, it seems this has given people the incentive to keep these animals in Hawaii. Despite this, hunting will continue to be practiced. But I was thinking that in this case, the humans could use help from another hunter: the dhole (Cuon alpinus).

I chose the dhole because there wouldn't be enough room for tigers in Hawaii (duh) and leopards, while adaptable, are also generalists that don't just stick with medium-sized ungulates, granted those make up most of their diet. They feed on small mammals and birds as well, and that could have a negative impact on native species.

Dholes, on the other hand, are more like specialists, hunting small and medium-sized prey when available, and when it comes to human safety, not a single person has ever been attacked by dholes, so that's a plus.

 

Introducing a fairly large pack-hunting canid to highly populated islands doesn't exactly sound all that safe, regardless of the Dhole's current track record.
Also I don't think I'd quite consider feral pigs and Chital medium, they're a bit more on the large size. Besides you mentioning that the Dhole will take small prey when available, which was your reason for not using leopard.

A further drawback to this idea would be the Dhole's inclusion as an injurious wildlife species by the USFWS, and thus attempting to do anything in regards to this would require a lot of bureaucratic hoops and an almost certain decline.

 

Biological control using actual animal predators is an even more risky business than using pathogens, particularly on islands - if you're not familiar with the story, the rarity at best and extinction at worst of a large number of Partula snail species is directly related to the introduction of the predatory snail Euglandina rosea in an attempt to control introduced Giant Land Snails in Polynesia. They found Partula a much easier meal.

Introducing a predator like Dhole to Molokai would be almost certain to have unexpected negative effects on native species.

 

Currently classical biological control focuses solely on introducing host-specific invertebrates and pathogens to limit spread of invasive plants and animals. That has a clear reason, as alluded by @Maguari , there are plenty of examples where generalist predators (which Dholes also still are) wrecked havoc on native non-target species. Introducing larger carnivores just sounds foolish and would be completely unrealistic as not a single stakeholder on the island would think it is a good idea...

 

The shortcomings of biological control in a nutshell

 

You know how mongoose got to Hawaii, right? And the problems they cause? Dholes would be the exact same situation.