All creatures great, small and vanishing
We can’t see them, and they give us the heebie jeebies. But some of our most invisible endangered species are indicators of the health of our natural environment.
‘‘That should have been fabulous, but actually it was heartbreaking.’’
Kath Walker on discovering a new, but threatened, species
Bats get a bad rap. Associated with eccentricity or absent-mindedness: ‘‘bats in the belfry’’ or ‘‘batty’’. Linked to nocturnal behaviour and dark, often cold places such as caves and mines. A mystical connection to bloodsucking Count Dracula, or hokioi, a bird which foretells death. And blamed for the spread of disease, such as rabies and more recently Covid-19.
But their reputation is undeserved. They are vital, not only to the environment, but to humans. Without pollinating and seed-dispersing bats, plants would fail to provide food and cover for species at the bottom of the food chain, causing entire ecosystems to deteriorate.
Once common in forests throughout New Zealand, bat range became restricted by felling, and colonies were attacked by introduced predators, rats, stoats and cats.
There are two species of bats in New Zealand: the long-tailed bat and the lesser short-tailed bat, and they are its only land mammals.
There were once two species of shorttailed bat, but the greater short-tailed is probably extinct. The lesser short-tailed is found only at a few scattered sites.
‘‘The short-tail bats are important pollinators and seed dispersers,’’ says Colin O’Donnell, principal science adviser for the Department of Conservation (DOC). ‘‘They eat nectar and certain flowers and pollinate them.
‘‘They eat lots of insects, as well. It’s well-known, from overseas studies, bats can control insect numbers, to a degree. Long-tailed bats, which feed on the edges of forests, are good consumers of insect pests.
‘‘They love grass scrub beetles [and] purini moths, which are two big agricultural pests. So, if we could recover their numbers then they would be free insecticides.’’
The chestnut-furred long-tailed bat is classed as ‘‘nationally critical’’, and the short-tailed subspecies range from ‘‘nationally vulnerable’’ to ‘‘recovering’’.
But the mousy-grey short-tailed bat is especially precious as the only remaining species within its family.
O’Donnell is New Zealand’s bat man – and yes, he’s heard that joke many times before.
He’s worked with the mammals here and internationally for more than 25 years. Each summer he pitches a tent in the beech forests of Fiordland’s Eglinton Valley, one of the only South Island sites with both species.
‘‘When I first came down here, I thought: ‘I’m going to find the Bat Cave, and we can protect it from the predators, study the bats and monitor them nicely’.
‘‘And the first thing I discovered was that they didn’t use caves at all. They live in cavities in trees, and quite often they are 25-30 metres up, which makes them really challenging to find and study.’’
It also makes them vulnerable to introduced predators. ‘‘The first 10 years, it was a bit depressing, because each year, the numbers were declining. We determined predators, like stoats and rats, were killing the bats.
‘‘Because bats live in tree hollows, when a predator runs up the trunk and pops its head in, there’s no escape for the animals inside.’’
By 2000, numbers were getting close to extinction. ‘‘After that, DOC started doing more extensive predator control. And over the last 15 years or so, we’ve been monitoring a steady increase in numbers. A depressing project became quite an exciting one.’’
Catching bats to study them isn’t easy. Because they use echolocation, conventional nets for trapping birds are useless.
A harp trap – a frame supporting two rows of fine thread, and a catching bag at the base – captures them without damaging their delicate wings.
O’Donnell also uses a high-frequency speaker, emitting bat calls, to lure the animals, which are deeply social. Once caught in the plastic liner, the bats cuddle together until they are handled by researchers.
Before first light, O’Donnell’s team measures, weighs and gives the creatures a health check. They are fitted with metal bands, and if they are the correct size, minuscule tracking devices.
It is crucial to keep them warm and release them before day breaks – otherwise they must be tucked into cloth bags and hung in an airing cupboard in a bedroom back at the Knobs Flat base. Of course, it’s known as ‘‘the Bat Cave’’.
The bats don’t hibernate in winter, but survive by dropping their temperature, slowing heartbeats, and sleeping for up to 10 days to conserve energy. ‘‘It’s barely alive, but it is very alive,’’ O’Donnell says.
‘‘When it snows here, it can be minus 13 for two weeks in the mornings. And they’ll just curl up and go to sleep.’’
O’Donnell is beguiled by the flying mammals. ‘‘There’s lots of things that fascinate me. They only have one baby a year, really slow breeders, but they live for a really long time.
‘‘Our oldest long-tailed bat here is at least 25 years old. That’s remarkable for such a tiny animal.
‘‘And they’re essentially a huge kite with a little body in the middle. They can fly a long way, really fast, for their size.’’
But there is one mystery he cannot solve. ‘‘The really irritating thing is they move to a new tree cavity virtually every day. And for the life of me, I can’t figure out why they do that.
‘‘Each colony has got maybe 180-200 different trees, and they cycle around, moving daily to the next one.’’
B efore humans arrived, the mossy forest floor was once alive with frogs. Now, only four of seven native species survive. Hochstetter’s frog/pepeketua, of which there are believed to be about 100,000, live in isolated fragments around Waitakere and Hunua Ranges, Dome Valley, Coromandel Peninsula, Great Barrier Island, Sanctuary Mountain Maungatautari, and the East Cape. They prefer streams but can survive on land.
In Cook Strait, fewer than 200 Stephens Island frogs cling to a 600sqm patch of bare land, and nearby 19,000 Maud Island frogs survive.
All four species evolved from one ancient genus. They are small, do not croak, and hatch as tiny froglets, rather than free-swimming tadpoles.
The smallest of the endemic species is the 2-3cm-long Archey’s frog, now limited to Waikato, and is one of the world’s rarest and most endangered amphibians.
Auckland Zoo manages a breeding programme and assists DOC with annual surveys in Whareorino Forest, near Te Kuiti.
Richard Gibson is head of animal care and conservation. He says all four endemic species are threatened, and the threats are loss or disturbance of habitat, introduced predators, and now climate change, which affects the humidity of the forest.
Amphibians are known as ‘‘indicator species’’, because they are extremely sensitive to changes in the environment and give insight into how an ecosystem is functioning.
Globally, populations have declined at an unprecedented rate. About one-third are threatened with extinction.
‘‘People often ask, if we were to lose Archey’s frogs, the other frogs, why does it matter?’’ Gibson says.
‘‘Everything has a place in an ecosystem. Archey’s frogs are prey items, and they’re also predators of smaller prey, invertebrates is what they eat. So they play an important part in a food web.’’
P owelliphanta augusta, or the Mt Augustus snail, snatched international headlines when it was first discovered in the mid2000s. It became a symbol of the battle to protect nature from industrial extraction.
The molluscs were taken from Mt Augustus into captivity before their habitat was mined for coal. For the last 17 years, they’ve been cared for in DOC fridges in Hokitika.
DOC science adviser Kath Walker discovered the snails. ‘‘It was a bit sad, because finding a new species is actually pretty neat. That in 2004, you could find something as interesting, and as beautiful [and] get to name it. That should have been fabulous, but actually it was heartbreaking.’’
Over millions of years, the snails had evolved and slowly climbed their way up steep slopes to a tiny slice of the Stockton Plateau, high above the West Coast.
‘‘It’s a strange, remarkable place,’’ Walker says. ‘‘It gets a heap of rain, six metres a year. It’s like a little Japanese bonsai garden, everything’s hiding from the wind and growing low to the ground. It’s a really harsh place to live. And yet the snails have managed to conquer it.’’
After almost two decades away, can they reconquer it and return home?
The site changed hands when stateowned Solid Energy collapsed in 2015, and is now mined by a Bathurst Resources and Talley’s joint venture.
‘‘We have finished mining the ridge line just in the last year. And it has now been progressively rehabilitated,’’ says Stockton’s community and environment manager Barry Walker.
‘‘It’s a long, involved and committed process. This is really the exciting end of the project. We made sure the surface was stable, then brought in vegetation from other areas of the mine, a bit like laying a lawn.
‘‘The vegetation is deemed acceptable for the release of snails, juvenile snails and the eggs. And that’s exactly what’s been happening over the last few years: a snail release programme.’’
He says the mine and its employees are committed to returning the site to nature.
‘‘The snails are the butt of jokes. That you would spend so much time and money and effort for a snail,’’ he says.
‘‘But it’s much more than that. It’s a native species of New Zealand that we committed to look after.
‘‘It’s a real myth to think that miners drive a big digger and dig a big hole and spray and walk away. They care for this environment. They choose to live here because this is a beautiful place. And this is what they can do to ensure that it remains a beautiful place that they can be proud of.’’
Kath Walker is not so optimistic. Just over 3913 of the northern subspecies were returned to the mine, in an area unfamiliar to them. Subsequent monitoring has shown no consistent evidence of a stable, or increasing, population.
‘‘They were surviving. I guess our concern has always been that it’s a longerterm thing.
‘‘Mt Augustus was a cloud capture and, every 100 metres in altitude that you gained, even more rain would fall. [Because] the top of the mountain was gone, these snails were [placed] some hundreds of metres below.’’
Hot, dry summers, which are increasing in frequency, put the released snails in jeopardy, as they are prone to drying out.
‘‘It’s going to be a 30 or 50-year drought, that could wipe out the whole population,’’ Kath Walker says. ‘‘Because of that uncertainty, we kept about 1500 of the snails, including the 25 from the southern end, in captivity as an insurance policy.’’
Forest & Bird chief executive Kevin Hague believes the snails can never return to the home they once had. ‘‘I acknowledge there are some people who are putting a lot of effort into trying to recreate a habitat.
‘‘But it’s the very existence of minerals close to the surface, that unusual geology, that also means that the biodiversity associated with that place is also particularly special. You dig it up? The biodiversity is severely compromised, you may have lost it forever. In the case of those snails we probably have.’’
There is another problem. The snails eat through a $60,000 annual DOC budget. So who will pay for the rehabilitation?
‘‘Well, it’s our job, isn’t it?’’ says Kath Walker. ‘‘We, as a country, gained from the mining of the coal, it was a stateowned enterprise.
‘‘We dislodged a whole species by doing this mining, and it’s up to us to provide the funds to make this happen. It’s going to be hard. But we haven’t even tried because we haven’t had the money to do the large-scale reconstruction of the environment that it needs.
‘‘Time has moved on and the world’s forgotten, and we still haven’t got a pathway to try and fix it.
‘‘I have invested so much of my life and I want to try and get us through this next bit of it, because it is achievable. We’ve just got to do it.’’