The last rat seen on Lord Howe Island was sniffed out by a detector dog about 15 months ago not long after a sometimes controversial program to rid the island of an estimated 200,000 of the vermin began.Endangered animals bounce back on rat-free Lord Howe Island, 31 Jan 21
One of the more important ethical discussions in conservation has to be whether the large-scale eradication of non-native predators (or opportunist generalists) from islands where native wildlife has been terribly impacted by their presence can be justified. All across the globe wildlife that has evolved on islands – often in predator-free ecosystems – are being decimated by non-native invasive species. Typically though those species have been accidentally introduced (mice and rats perhaps); deliberately introduced to control rats attracted to crops which (predictably with hindsight) go on to live off the easily captured native animals instead (Javan Mongoose is an obvious case); or were brought to islands as companions or to control ‘pests’ and which have gone on to cause extinctions (cats that have become feral would be a prime example).
In all cases there is a common factor: those non-native animals arrived in the same way – through us.
Does that latter point mean that we have an obligation to correct the problems we’ve caused – perhaps long, long after many native species have already disappeared and where initial declines were perhaps triggered by enormous habitat changes we ourselves made? Or should we learn our lessons and leave them alone rather than risk more accidental disasters? And those ‘pests’/’invasive species’ didn’t ask to be transported across oceans, after all, and are only doing what they evolved to do, taking advantage of the ‘new world’ they found themselves in – behaving, in fact, very much like humans did when they first discovered the same pristine worlds: raiding them and wiping out vast colonies of everything from fish to seabirds and almost every large terrestrial mammal species they encountered?
Besides, in the case of remote islands like Lord Howe if we really want ‘balance’ restored shouldn’t we get people off them too and make sure they take every belonging and trace of their existence with them?
That is never going to happen of course. While so-called ‘vermin eradication programmes’ are expensive and often logistically difficult, they are straightforward compared with moving even one human family somewhere else – and finding somewhere, presumably, where they won’t do any further damage just by being there.
No, dropping a few tons of poison, baiting a few thousand traps, monitoring a few square miles of island for a few years is a far less contentious action. But it’s not contention-free of course. Moral questions arise, including setting up one species as ‘bad’ (the rat) and, for example, the seabird or flightless rail as ‘good’. Whether the lives of individuals of a rare species are inherently worth more than those of a common one. Our acting as ‘God’ in situations where we may have been the ‘Devil’ for many years. And rodenticides, for example, don’t send an animal off into a gentle sleep – anticoagulants work by thinning blood and affecting clotting response (animals bleed out); metal phosphides poisons work by reacting with stomach acid to produce toxic phosphine gas; hypercalcemia poisons work by calcification and mineralization of the animal’s own internal organs.
But do the results justify the means? Numerous studies have demonstrated how quickly native wildlife rebounds once the pressures of invasive species have been lifted, particularly on islands where eradication can be thorough and comprehensive. And is the suffering of, say, Critically Endangered Tristan Albatrosses being eaten alive by introduced mice on Gough Island (or the endangered finches ravaged on the Galapagos Islands by the introduced parasitic fly Philornis downsi) any worse than that of poisoned rodents?
We’re probably heading off into moral equivalence dead-ends here as it’s unlikely the data exists to say with anything like certainty, but most people’s immediate reaction would almost certainly be to kill the mice and protect the rare birds – even though BirdLife states that the Tristan Albatross “qualifies as Critically Endangered owing to a projected extremely rapid population decline over three generations…a consequence of very low adult survival owing to incidental mortality in longline fisheries [our highlighting], compounded by low fledging success caused by predation of chicks by introduced mice“.
Current concerns of morality aside, eradication programmes clearly work as the following article from the Sydney Morning Herald proves. It talks about a surge in the population of the Endangered endemic Lord Howe Woodhen (a flightless rail) and that the breeding success rate of petrels on the island has jumped from 2 or 3 per cent to more than 70 per cent. What the paper doesn’t say is that islanders used to trade those same petrels in huge numbers or that they lost 35% of nesting habitat to urbanisation between1978 and 2002. Again, while the article points out that “Feral animals have already caused the extinction of six bird species including the Lord Howe Island fantail, white-eye, gerygone, starling and thrush, as well as 13 invertebrates and two plant species” what isn’t explained is that those feral species were cats, pigs and goats: all introduced by man in the 19th century.
So who or what is the problem here – mice/rats or men? That’s not a question conservation (or any government) is likely to ask, and in, say, fifty years time, when no-one remembers the hundreds of thousands of rats that died so that a few scarce birds and plants could reclaim the few patches of habitat we allow them, no-one will care anyway.
But by then – if Australia’s Climate Council is to be believed – much of Lord Howe’s endemic flora and fauna may have been destroyed by the climate change already affecting the island’s critically endangered forests, coral reefs, and the local economy that is reliant upon them anyway.
And perhaps the question will have been answered unequivocally: it wasn’t the rats, it was us all along…
The last rat seen on Lord Howe Island was sniffed out by a detector dog about 15 months ago not long after a sometimes controversial program to rid the island of an estimated 200,000 of the vermin began.
The change in the little island since the rats disappeared has been spectacular, says Terry O’Dwyer, a biologist who worked on the program.
Shoots are now covering sections of the island’s forest floor and its famed Kentia palms are heavy with fruit.
Fears that the woodhen might succumb to the baiting program that was carried out between June and July in 2019 caused some islanders to campaign against the effort, and prompted scientists to capture and keep them in captivity as the rats were being exterminated.
“We knew they were going to be all right as soon as we released them,” Dr O’Dwyer said. “They started copulating before they were out of sight.”
In a recent survey 440 of the hens were counted, twice the number of the previous count a year earlier.
Feral animals have already caused the extinction of six bird species including the Lord Howe Island fantail, white-eye, gerygone, starling and thrush, as well as 13 invertebrates and two plant species. Since rats scurried ashore from a shipwreck in 1918, they have caused or contributed to the extinction.
The impact of the eradication has stunned some observers.
“It has blown me away,” tour operator Jack Shick said. “I was a huge supporter of [the eradication] but I am in disbelief at what I am seeing. There are more birds, there are berries on the trees and insects are coming back. We are hearing crickets calling again at night. I remember that sound from when I was a kid.
“The thing that excites me is that there is no one alive on Lord Howe who can tell us what it was like before the rats came, so there is a new discovery around every corner.”
It will take longer to assess the impact on larger animals, but, said Dr O’Dwyer, the breeding success rate of petrels on the island has jumped from 2 or 3 per cent to more than 70 per cent.
Eradication programs of invasive species on islands have become a key tool against the global extinction crisis. The Database of Island Invasive Species Eradications has tracked 2000 programs between 1950 and 2019.
The $15.5 million Lord Howe Island program involved intensive ground and aerial baiting in 2019, supported by ongoing monitoring and ramped-up quarantine measures.
It is expected that the island will be declared rodent free later thus year, two years after the baiting was finished.Nick O’Malley, Endangered animals bounce back on rat-free Lord Howe Island, 31 Jan 21