The menace of stoats

You could say that Selena kept herself warm in the most exotic sleeping bag in New Zealand. Researchers John Dowding and Elaine Mur­phy uncovered her dwelling while working in Fiordland’s Eglinton valley. “When we looked inside,” recalls John, “we found a bowl of feathers from some of the most en­dangered native forest birds in the country, including New Zealand robin, kakariki, kereru, mohua (yellowhead) and kaka.” Selena wasn’t some crazed eco-terrorist; she was a stoat the two biologists were tracking.

Written by       Photographed by Marty Taylor

In a 1997 report to the Department of Conservation (DOC), Elaine identified several endangered species at risk from stoat predation, including the Haast tokoeka (one of the rarer South Island kiwi), North Island brown kiwi, Okarito brown kiwi, orange-fronted parakeet, black stilt, takahe and fairy tern. “Stoats are widely regarded as the most significant predator of a number of New Zealand’s most threatened and endangered native bird species,” she explains. “Stoat control will have to be ongoing if some en­demic species, such as kiwi and kaka, are to survive on the mainland.”

In response to mounting evidence of the stoat threat, the Labour-led government allocated $6.6 million in the 1999 budget to the problem. A group, under Elaine’s lead­ership, was set the task of conducting research on stoats so that they would no longer pose such a danger to indigenous animals.

Stoats belong to the mustelid family (Mustelidae), a group of mostly small carnivorous mammals allied to dogs that includes wolverines, otters, mink, badgers, skunks and—also introduced to New Zealand—ferrets and wea­sels. Of the grim immigrant trio, the most versatile, wide­spread and deadly is the stoat. Stoats infest every terrestrial habitat—including areas above the tree line—and will eat birds, lizards, rats, mice, possums, insects and even koura (freshwater crayfish).

Native birds have been particularly hard hit by rats and stoats: since human settlement, 40 per cent of species have become extinct, and the proportion of those surviving classed as threatened is higher in New Zealand than in any other country.

A keen sense of smell is just one of the attributes that make the stoat--a small cousin to dogs and seals--the formidable hunter it is.
A keen sense of smell is just one of the attributes that make the stoat–a small cousin to dogs and seals–the formidable hunter it is.

Stoats were introduced from Britain in the 1880s in a misguided attempt to control rabbits, and until 1936 they even enjoyed legal protection as a “natural enemy of rab­bits”. Yet they were soon implicated in the decline of native species, although, despite much anecdotal and circumstan­tial evidence, it is only recently that scientists have proven the causal link between stoats and species decline. Even now, the full extent of their influence on indigenous wild­life is poorly understood.

In the austere low-alpine tussock of the Tasman valley, John Dowding is catching and radio-tracking stoats in an attempt to learn more about their habits. His eyes pick up even the smallest of details. He stops abruptly, crouches and points. The grey boulders, pebbles and silt merge and I can’t make out what he’s pointing at. “There, 15 metres ahead—a wrybill.” Crouched statue-still on her eggs, a fe­male dotterel with distinctive right-curving beak is practis­ing the only defences she knows—immobility, silence and camouflage. These work with me but not with stoats. John has found wrybill remains—egg, chick and adult—in and around stoat dens.

Few people appreciate the extent of stoat predation on lesser-known endemic species. “People have largely been unaware of the threat to shorebirds, for instance,” explains John, “but these appear to have suffered at least as much as other birds.” According to The World List of Threatened Birds, published by the Smithsonian Institute, six of New Zealand’s most endangered species are shorebirds. “The New Zealand region currently has 155 species of endemic or native bird. Forty-five are threatened and a further 12 are near-threatened. We have no fewer than five of the world’s rarest shorebirds, with total populations of 150 in­dividuals or less, and predation has been the main agent of this decline.”

We leave the wrybill to her fate and move on to check John’s traps. Peering through a slight gap round one trap door, John confirms there’s a stoat inside. Back at the Hilux, he determines it’s a female, fits a radio collar, records details of the animal’s condition and names her. I’m sur­prised to see she’s almost entirely white. “She’s in her winter coat. White is ideal camouflage in snow.”

After releasing this latest catch, we start searching for stoats John has collared earlier. Pausing every couple of hundred metres, he hoists a tracking antenna above his head and listens as he changes its orientation. With each adjust­ment it emits a different pattern and intensity of clicks, indicating the direction and distance of radio-tagged stoats. The collar affixed to each stoat transmits at its own fre­quency, so tracing a particular animal is a straightforward matter of tuning in to the appropriate wavelength.

Stoats don't make their own dens, but take over those of their prey, often using the fur or feathers of a victim--here a nesting female kaka--to upholster the interior.
Stoats don’t make their own dens, but take over those of their prey, often using the fur or feathers of a victim–here a nesting female kaka–to upholster the interior.

John points to a hole in the ground, obscured by matted tussock and matagouri. He takes a GPS reading, records the time, checks for any evidence of life, collects a few feath­ers and scats (stoat droppings), and moves on. By analysing scats, he gains clues about stoat diet and behaviour.

Stoats can be active at any time of the day or night. Home range varies significantly depending on habitat, sea­son and abundance of food. Ranges often overlap, especially male with female, but most contain an exclusive core area.

Most animals take a substantial time to reinvade an area from which they have been cleared, but not stoats. As John explains: “It was believed that young females stayed close to where they were born and that they stayed there for most of their life. But Elaine and I identified a female juvenile stoat—probably pregnant—that travelled at least 65 kms in four weeks. Which goes to show that clearing stoats from an area is only effective while trapping continues.”

The carnage wreaked by stoats takes place largely in forest and country areas, out of the public eye. It isn’t easy, either, to pin a crime on the accused. “Stoats are extremely nervous, aggressive, secretive and mostly nocturnal,” says John. “Each of these factors makes it difficult to prove a link between stoats and a particular predation event.”

Nonetheless, over the years John and Elaine have com­piled compelling evidence linking stoats with predation. One example concerns northern New Zealand dotterel. Af­ter the disappearance of five adult breeding pairs on Waiaua Spit, near Opotiki, Mark Dobbins, of DOC Opotoki, followed stoat tracks from a dotterel nest to a stoat den. “Marks in the sand showed clear indications that eggs had been rolled and bodies dragged to the den,” says John, and the den was found to contain dotterel remains.

Ranging from beaches to the snow line, stoats are everywhere--even if their low-slung bodies, small size, and inconspicuous colour mean we are generally unaware of them. Those acute eyes and sharp ears--so vital in locating food--also mean they can stay out of the way of humans.
Ranging from beaches to the snow line, stoats are everywhere–even if their low-slung bodies, small size, and inconspicuous colour mean we are generally unaware of them. Those acute eyes and sharp ears–so vital in locating food–also mean they can stay out of the way of humans.

Several days later Shane Morris and David Rush, also from DOC Opotoki, excavated a second den three metres from the first, and an adult stoat ran from the entrance and three young were found inside along with more dot­terel remains. “One female stoat killed at least 11 dotterels within two months. The deaths represented one per cent of the breeding adults of the total population of the northern subspecies.”

Findings in the Tasman valley have confirmed the extent of stoat depredation. “Remains of eggs, chicks and adults of pied oystercatcher, banded dotterel, spur-winged plover, wrybill and black-fronted tern have all been found in dens,” John comments. But research has also produced findings unrelated to predation. Interactions between stoats may be much more common than previously thought. “Males and females are known to interact during the breeding season, but we have found examples of males using a common den site consecutively in spring, and males and females using them consecutively in autumn outside the breeding sea­son.” If further research confirms that stoats regularly come into contact with each other, and also with ferrets, the use of socially communicated sterilisation or bio-con­trol agents may prove effective counters to their devastat­ing behaviour.

[Chapter Break]

Leave the Tasman valley and drive south into Fiordland National Park to join Des Smith, a PhD student from Otago University, as he marks a new stoat trap line in the Special Takahe Area of the Murchison Mountains, the only place where takahe—an estimated 130 adults—still roam naturally. Trapping was confined to the lower, more accessible valleys of the national park until Smith’s work suggested this was not sufficient. “During three-and-a-half months of fieldwork for my Masters,” he explains, “I didn’t observe any stoats moving between the valley floors where the trapping was being done and alpine areas where the takahe live, yet there are definitely stoats up in the takahe area.”

Flying up razorback ridges, our helicopter pilot spots a break in the cloud. He pushes the chopper’s nose over a windward lip and catches a much-appreciated updraft. Sud­denly we break through the cloud and touch down among sun-drenched snow tussock in a place with a distinctly other-worldly feel to it.

Ferrets. Longer than stoats, they weigh three times as much, and have been farmed for their pelts.
Two other mustelid species similar to stoats were also liberated here to help combat rabbits. Ferrets have light-coloured underfur with longer, dark-tipped guard hairs and bushy tail. Longer than stoats, they weigh three times as much, and have been farmed for their pelts.

After the drone of the departing helicopter has faded down Ettrick Burn, we glimpse a rock wren, one of New Zealand’s few native alpine birds. Its short, gawky bursts of flight show how defenceless it would be against a quick and determined stoat. “As part of the takahe recovery plan, we will be monitoring the impact of stoat control on other threatened birds like mohua and kiwi, and we will also keep an eye out for vulnerable species like the rock wren, blue duck and kaka,” says Des.

From past observation, it appears probable that stoats at­tack takahe only when their preferred prey is scarce. “The takahe population would be wiped out very quickly during a stoat plague year if every stoat attacked every takahe it encountered.” Killing smaller birds, such as rock wrens and mohua, is easy for a stoat, but taking on a three-kilogram takahe is a different proposition. However, takahe, like kiwi, are notoriously poor parents, often leaving vulner­able chicks to fend for themselves. A captive breeding programme, similar to Operation Nest Egg (a central part of the Kiwi Recovery Programme, joint initiative of DOC, the Royal Forest and Bird Protection Society and the Bank of New Zealand), sees takahe chicks through their first year and then liberated in the Murchison Mountains. The number of birds killed by stoats annually is not high, but, because of the low reproductive rate of takahe, population models predict extinction if nothing is done to save them. With stoat control, takahe appear to have a good chance.

From the top of the Murchison Mountains you can look across Lake Te Anau to the glacially gouged Clinton, Arthur and Eglinton valleys. Every three to five years the beech forests in these valleys experience a seed boom, or masting. In “intermast” years, hardly any seed is produced. Beech employ this cunning strategy either to swamp or to starve seed-eaters, thus ensuring that some of their seed survives. Through New Zealand’s evolutionary history, mast years have been times of plenty, when the animals of the forest have thrived and bred in great numbers. Vari­ations in the birth and death rates of kakariki, kaka and mohua are closely related to the masting cycle. Mice—and sometimes rats—also proliferate in a mast year, and a short time later stoat numbers erupt in response. Unfortunately, mouse-feasting stoats retain their taste for birds.

If the infant ferrets above were stoats, they would be impregnated about now. However, both ferrets and weasels reproduce normally, eschewing the infant mating and delayed implantation practised by stoats.
If the infant ferrets above were stoats, they would be impregnated about now. However, both ferrets and weasels reproduce normally, eschewing the infant mating and delayed implantation practised by stoats.
Weasels are shorter than stoats, weigh only a third as much, and have shorter tails.
Weasels are shorter than stoats, weigh only a third as much, and have shorter tails.

Until recently the Eglinton valley was one of the last strongholds of mohua. Once found throughout the South Island, the little yellow-headed birds have disappeared from more than 75 per cent of their range and are now restricted to just a few small pockets of beech forest. Two features of mohua breeding make them especially vulnerable to preda­tion—their hole-nesting habit and their breeding timetable. According to DOC’s Peter Dilks, “Mohua nest in knotholes so they are unable to see approaching predators, and when one finds them, they’re cornered.” Stoats and rats eat mohua eggs, chicks and incubating females. The birds begin to breed in November and may not finish until March, when stoat numbers are at their highest.

The relationship between high stoat numbers and mohua mortality is not straightforward. During a stoat eruption in the summer of 1990–91, 60 per cent of nests were lost and 60 per cent of female birds were killed, mostly by stoats. To reduce stoat numbers a low-intensity trapping programme was begun in 1997; then, during the summer of 1999–2000, 27 pairs of banded mohua were intensively monitored, 66 per cent of which produced fledglings. The trapping pro­gramme appeared to protect breeding mohua from stoat predation. However, during two consecutive beech masts in the summers of 1999–2000 and 2000–01, numbers of rats sky-rocketed and the Eglinton valley mohua were wiped out. The evidence suggests that rats, not stoats, were the culprits. Further work is under way to see if stoat control allows rat numbers to escalate.

Kaka mortality, on the other hand, seems to be directly linked to stoat numbers. In areas without stoat control, kaka nesting success rates are usually below 38 per cent, while success doubled in the Eglinton valley after trapping had commenced.

Largely because of their keeping properties, eggs have been the traditional bait in stoat traps. However a range of more attractive baits, incorporating such delicacies as salted and freeze-dried rabbit, are under development.
Largely because of their keeping properties, eggs have been the traditional bait in stoat traps. However a range of more attractive baits, incorporating such delicacies as salted and freeze-dried rabbit, are under development.

In the Arthur valley, where there is no stoat control, DOC has been investigating the impact of stoats on whio (blue duck). In the 2001–02 breeding season, six female whio were monitored and nine nesting attempts observed. Five nests were destroyed before incubation could begin, and stoats were recorded killing one of the incubating fe­males. The only nest to go undetected by stoats was located among boulders in the middle of a fast-flowing river. With­in three days of fledging, however, one of the five ducklings, along with the mother, was killed by a stoat, and the other ducklings didn’t last much longer. Two other females in the valley were found covered in blood and with stoat-inflicted lacerations and puncture injuries to the head and neck, and were lucky to survive. Overall, two females were killed and no chicks survived beyond fledging.

In 2003, the International Union for the Conservation of Nature and Natural Resources (IUCN) raised the risk sta­tus of blue duck from vulnerable to endangered.

The stoat problem isn’t confined to Fiordland. Through the Kiwi Recovery Programme, DOC has put a mammoth effort into saving the rowi (or Okarito brown kiwi)—one of the most endangered kiwi species—between Okarito and the Waiho River, in Westland National Park. The 11,000 ha rowi sanctuary occupies a corridor between the sea and the Southern Alps, and is clad in dense lowland rimu for­est. Project leader Jo Crofton recalls the summer of 2002: “Things went nuts. The juvenile stoats started showing up in mid-November, and by Christmas Day we had only two radio-tagged chicks left. I went out on Boxing Day to check on one of them, and its signal was coming from under the ground. [Stoats store dead prey underground.] By early Jan­uary, all 14 monitored chicks were dead.” A couple of weeks later, the last two chicks in the sanctuary were recovered and evacuated to Motuara Island, a bird sanctuary in the Marlborough Sounds.

Trained dogs--such as this pair owned by Scott Theobold of Trounson Kauri Park--are also being used to sniff out stoats, especially the breeding females which are particularly difficult to trap.
Trained dogs–such as this pair owned by Scott Theobold of Trounson Kauri Park–are also being used to sniff out stoats, especially the breeding females which are particularly difficult to trap.

Sid Marsh, an experienced kiwi fieldworker who de­scribes himself as a “frontline kiwi-grunt”, has been work­ing with kiwi on and off for the past 12 years, including with the Okarito project. He thinks that most conservation people underrate the intelligence and adaptability of stoats. “They’re like scaled-down arboreal tigers that work below ground, in cavities, on the forest floor, and right up to the top of the canopy. I’ve watched one moving at high speed over the top of a tawa canopy in kokako country in the Coromandel Range. It moved along horizontal branches 10–15 metres up and jumped from leaf spray to leaf spray.

“On a separate occasion I was manning a kokako mist-net rig, with a speaker emitting tape-recorded kokako song. As I sat absolutely still, I heard a movement close by and was surprised to see a stoat stalking the speaker. With kokako near, I moved, and this scared off the stoat. They’re preda­tors without peer.”

Near Blackball, on the West Coast, I was sitting once with a friend in his garden, surrounded by primal rimu and kahikatea forest. We were chatting beneath the towering trees, and listening to tui and bellbirds, while his delighted daughter chased giant dragonflies. In mid-phrase, my friend suddenly jumped to his feet, sprinted into the house and fetched his gun in feuding-hillbilly fashion. Then: Crack! Crack! Two shots and two misses. Annoyed, he muttered, “I’ve been trying to shoot that bastard for weeks. They’re bloody hard to kill.” A stoat, of course.

Elaine Murphy agrees. “They have very few chinks in their armour and they’re incredibly adaptable.” However, as she goes on to explain, the news isn’t all bad. “We’ve made some promising progress on a toxin that is fairly predator specific, but we still have a few hoops to jump through. The trouble with PTF [Predator Toxin Formula­tion] is that although it works well in a lab situation, it’s not so good when delivered in a bait. Connvation, an Auckland company, have come up with some ‘secret herbs and spices’ to make it work better, but more non-target testing needs to be undertaken, especially with birds.”

Landcare Research and DOC have tested a host of sub­stances in pursuit of a bait that will reliably entice stoats into traps and bait stations. As regularly replacing baits can be a lot of work, long-term attractiveness is another desir­able quality.

Fresh dead lab rat, ground freeze-dried rat and synthe­sised rat-odour molecules have all been added to PVC pel­lets. The freeze-dried rat proved more attractive than the fresh, and although the odours alone were less potent than either, they still showed potential.

Ian Domigan of Lincoln University has developed two new traps--Hammer and Thumper (seen here)--which meet new humane killing standards that require animals to be rendered irreversibly unconscious within no more than three minutes.
Ian Domigan of Lincoln University has developed two new traps–Hammer and Thumper (seen here)–which meet new humane killing standards that require animals to be rendered irreversibly unconscious within no more than three minutes.

Rabbit and sparrow have also been found to be palat­able, the former more so than the latter. Freeze-drying or salting to maximise durability marginally reduced the attractiveness of rabbit meat. Stoats spent quite a while chewing salted rabbit—the most durable bait—but ingested relatively little, which suggested it would be suitable for a trap but less so as a carrier of poison.

Rabbit meat has also proven effective combined with wax and tallow, with gelatine, wax and bran, and with a dairy-product matrix. With polymer it was less toothsome. Freeze-dried mouse has met with some success, but after the first bite, a stoat’s appetite wanes. Softening carcases by injecting them with gelatine improves their palatability.

A French fragrance manufacturer has developed three synthetic lures using frozen samples shipped from New Zealand—rabbit meat, rat musk and rabbit aroma. Most devastating is rabbit meat, but there is still work to be done in integrating it into a suitable carrier. Dried pet foods, it appears, hold no appeal for stoats.

Improvements are also being made to traps. New models promise the swift dispatch of all captives—no escapes, no prolonged suffering.

[Chapter Break]

The reproductive biology of stoats is unusual, and, with time, we may be able to find some way to exploit its idiosyncrasies. As Janine Duck­worth, a reproductive biologist at Landcare Research, Lin­coln, told me: “Female stoats are almost always pregnant. Males mate with the mother of a litter soon after she has given birth, then turn to the females in the litter. New­born females are normally receptive even before their eyes open. It’s a great survival mechanism for a solitary animal.” Stoats do not pair bond, and there is a rapid turnover in the population (most die in their first year), so it is unlikely that males mate with their own young.

Natasha Coad of DOC with an image of the contents of a stoat den--mother, five kits and young kiwi--sniffed out by Scott Theobald's dogs.
Natasha Coad of DOC with an image of the contents of a stoat den–mother, five kits and young kiwi–sniffed out by Scott Theobald’s dogs.

Embryos develop to about 250 cells, then remain at that size until the following spring, when they become implant­ed in the uterus and complete their development over the next six weeks. Since females are such proficient procrea­tors, it takes only a single mother to infest a new territory­ which might be an entire island. And as stoats are capable of covering great distances quickly—particularly evident when young disperse to find their own territories—they can over­run a vast area in short order.

“When we started our work, we didn’t know what con­trolled pregnancy so we didn’t know how we could disrupt it,” Janine tells me. It is now evident, however, that levels of progesterone—one of the hormones essential for preg­nancy—rise considerably when embryos are implanted in October–November. “So if we can disrupt progesterone, we can probably disrupt pregnancy.” Another possible target is the embryo itself. Using the animal’s own immune sys­tem, it may be possible to attack the embryo while it is in the uterus. “The work that we are doing tricks the immune system into thinking a protein that is really important for normal pregnancy is a foreign target. This immuno-con­traceptive approach may result in effective stoat control—if the problem of delivery to the stoats can be sorted out.”

Stoats’ long skinny shape, agility and electric speed are great assets to a predator, but there is a downside: their fast-twitch muscle fibres need regular refuelling. Winter and early spring are the most energy-sapping time of the year for stoats. Males must eat a quarter of their body weight every day, while lactating females need to devour half to three-quarters of their body weight daily. Once a female starts feeding weaned young, she has to work even harder. Stoats unable to catch sufficient prey starve within 24 hours.

Stoats' teeth are small and sharp, and prey are typically despatched by a bite to the back of the neck. The heads and bodies are narrow, to allow small burrows and holes to be infiltrated effectively.
Stoats’ teeth are small and sharp, and prey are typically despatched by a bite to the back of the neck. The heads and bodies are narrow, to allow small burrows and holes to be infiltrated effectively.

Since bushman Richard Henry’s abortive attempt in the closing years of the 19th century to relocate endangered flightless birds to Resolution Island, in Dusky Sound, ma­rooning threatened species has become New Zealand’s bread-and-butter method of averting extinction. In the 20th century, translocation steadily grew in popularity, and by 1994 over 392 translocations of 50 species (42 birds, five reptiles and three invertebrates) had taken place.

The most suitable locations are islands out of the swim­ming range of stoats, but such refuges are in short supply. Murray Willans, from DOC Te Anau, suggests closer islands may still be useful. “A swim of a few hundred me­tres is possible but it still poses a substantial barrier. After eradicating predators from such an island, we expect reinva­sions but we also expect the rate to be very low. It’s a rare stoat that chooses to swim more than a few hundred metres for its next meal. At present we don’t know how rare so we are trying to figure that out. One thing we are pretty con­fident of is that the speed of re-infestation on the mainland is much greater.” The Te Anau conservancy is undertaking its most ambitious inshore-island clearance—on Secretary Island, in Doubtful Sound.

Here, Mike Elliot examines the remains of a bird killed by stoats in the Tasman valley, close to a site where the highly endangered black stilt occurs. Ground dwelling birds are not the only ones at risk since stoats are nimble climbers.
Here, Mike Elliot examines the remains of a bird killed by stoats in the Tasman valley, close to a site where the highly endangered black stilt occurs. Ground dwelling birds are not the only ones at risk since stoats are nimble climbers.

Despite their obvious value as refuges, islands are no panacea in the war on stoats. They offer only a fraction of the range of mainland habitats. There are, for example, no high dry islands, so geckos, skinks and weta from arid valleys and ranges are unlikely to adapt to island life. As a partial response to this problem, an attempt was made in the mid-1990s to provide safe havens on the mainland. Known as mainland islands, there are now six of these dot­ted around the country.

Natasha Coad is a ranger in one of them—Trounson Kauri Park, near Dargaville. “We’re trying to restore the ecosystem by controlling pests,” she explains. “Traps ring the outer margin of the park with the intention of develop­ing a protective boundary, a little like an island.”

In areas without stoat control, kiwi-chick survival sits at around five per cent. At Trounson the figure hovers around 38 per cent. “Our best year we had 86 per cent chick sur­vival,” says Natasha. “We didn’t do anything different that year. It seems that some years you just get stoats that have a taste for kiwi.” A sustainable recruitment of chicks into the population requires a survival rate of at least 20 per cent. “We’re pretty close to capacity at Trounson, because we’re finding juvenile kiwi beginning to disperse.”

A promising initiative that has come out of Trounson is the training of dogs to track and locate predators. Lead trainer Scott Theobald is an advocate of the canine control of stoats. “Before I had the dogs I only caught three lactat­ing females out of more than 300 stoats. It’s relatively easy to catch the juveniles after they leave their mother’s care because they’re young and dumb. The males are also easy to catch, but what we really want are the females in their dens with their kits.”

While stoats predation stops many chicks even making it to hatching, the carcases of adult birds often bear the marks of stoat teeth.
While stoats predation stops many chicks even making it to hatching, the carcases of adult birds often bear the marks of stoat teeth.

Mick, Scott’s first stoat dog, discovered a den with five kits and a mangled kiwi chick. “Its important we catch these stoats that have eaten kiwi because young stoats brought up on kiwi will probably develop a taste for it and pass it on to the next generation of stoats.”

The dogs have four main roles: to locate stoats, to aid the investigation of sightings on supposedly stoat-free islands, to help ascertain islands are stoat-free, and to aid the set­ting-up of trap lines. Scott and his dog(s) are often rushed out to islands such as Great Barrier after members of the public report stoat sightings. Their contribution has ena­bled Murray Willans in Fiordland to declare islands free of predators, and Des Smith in the Murchison Mountains Special Takahe Area to identify the best places to set up stoat trap lines.

[Chapter Break]

Natasha Coad believes she has a re­sponsibility to educate the public about the impact of stoats. Following a talk she gave at Kaipara College, all the students wanted her to answer a single question: “What can we do?”

“If you can feel something for a species,” she explained, “if you can feel something for what is around you, then that is a start. If you have pets, get them de-sexed so you aren’t contributing to the numbers of unwanted predators. Con­trol your pets, especially if you take them hunting or live close to bush or natural habitats like beach dunes or bush. Stoats are everywhere, so you can volunteer to trap with your local council.”

Eden McLean, 11, is the youngest volunteer I’ve come across. I met him at Kuaotunu, on the Coromandel Pe­ninsula, where he shyly extends his hand, welcomes me to Project Kiwi and introduces me to his dad, Victor, project manager Sharon Macredie and kiwi monitor Nick Gilling­ham.

Nick releases his kiwi dog, Bruce, and we follow his busy nose down one of the peninsula’s many ridges. At the base of an immature kauri Bruce becomes very excited. Nick gets a good foothold and pulls a sleep-grumpy kiwi from his burrow and proudly declares: “This is one of the ones we saved last year. Four years ago Project Kiwi constructed a predator-proof enclosure to help chicks through the vulnerable stage until they reach a kilogram in weight. If a stoat comes across a young kiwi it will just nail it, whether it is hungry or not.” Cradling the young kiwi, he beams. “This one would have died without the enclosure. He was held until he was big enough to kick off any stoat attack.” Now weighing in at 1.8 kg, he should be able to give a good account of himself.

Water is no great deterrent  to a stoat, and it will swim a kilometre or two to reach an island or peninsula.
Water is no great deterrent to a stoat, and it will swim a kilometre or two to reach an island or peninsula.

Despite the best efforts of the group, the stoats at Kuao­tunu came out on top last year. “Our best year we had 86 per cent survival, and on average we have 50 per cent, but last year we had our worst year ever, with only 20 per cent,” says Sharon. The generally high survival rate is due mainly to a communal effort involving everyone from fundrais­ers to worm-diggers. Sharon is constantly introducing new names: “Lance’s idea, Grant’s energy and leadership, Helen’s business savvy.” Local schools get a mention too, as do particular students, the Whitianga Hotel, local tour guides, farmers, committee members and many more. Then there are the financial supporters, DOC, the New Zealand Lotteries Commission, The Warehouse—the list goes on.

Victor McLean, Project Kiwi’s head trapper, explains one of the advantages of Kuaotunu. “We follow DOC’s specifications for best practice, but being a community group we are flexible enough to try new things. Like the predator-proof enclosure. If those guys down in Okarito had an enclosure like ours, they may have been able to col­lect all their chicks and throw them in there until they were strong enough to survive a stoat attack.” Victor also uses stoat dogs. On a map of the Kuaotunu peninsula is a cluster of blue dots indicating where his latest, Cassie, has smelled stoats. “Dogs are great because you will inevitably have a couple of stoats in an area that are trap-shy, and with the dogs’ help I can adapt my trapping until we catch them.”

Sharon reckons Project Kiwi saves 40–50 kiwi chicks each season. “Our average survival rate means the popula­tion will be expanding, and we estimate there are 300 kiwi here.” The statistics roll easily off her tongue, but the real joy comes when she relates how it feels to nudge a 1000 g kiwi out of its enclosure knowing it stands a fighting chance against stoats. “It usually takes four to six months. You give them a little push and away they go. That’s pretty cool.”

[Chapter Break]

Something of a contrast to the earth-bound kiwi is that master of gliding fl ight, the royal albatross. But as Lyndon Perrimen, head ranger at the Taiaroa Head albatross colony in Otago, emphasises, the greatest threat to albatrosses while ashore is stoat attack. “The chicks are most vulnerable at a few weeks old, when they’ve grown to a size where they can no longer sit beneath the breast of their parent. A stoat will snatch a chick, kill it, then drag it away.”

DOC sets traps inside the reserve, and increased trap­ping by neighbouring tourist operations such as Penguin Place and the Yellow-eyed Penguin Trust (sponsored by Mainland Products Ltd) is helping to control stoat numbers in the area, and no chicks have been lost to stoats in the past five years.

During a recent wine-blurred conversation in Ohakune, a friend and I decided to settle an argument about the need for a stoat-control programme in New Zealand by visiting Tiritiri Matangi, a predator-free island sanctuary in the Hauraki Gulf just a short boat ride from central Auckland. We agreed that Tiri would provide a good illustration of what our local bush had lost. Sitting at anchor by the DOC jetty, the bay and the land behind forming a natural amphi­theatre, we waited for the dawn chorus.

Other animals hold little fear for stoats either, and they regularly prey on creatures many times larger than themselves. Unless we can outsmart these doughty invaders, much of our wildlife will face no brighter future than this hapless rabbit.
Other animals hold little fear for stoats either, and they regularly prey on creatures many times larger than themselves. Unless we can outsmart these doughty invaders, much of our wildlife will face no brighter future than this hapless rabbit.

At first light, it began. Kokako led the choir. For 30 minutes, beautiful birdsong filled the bay. After breakfast we landed and walked up Wattle Track. Within minutes we saw red-crowned parakeets, tui, bellbirds, saddlebacks, pukeko and takahe. My friend could hardly contain his excitement and amazement at how much more wildlife there was than in any bush he had been in before. A little further in we saw whiteheads, North Island robins, stitchbirds and, to my delight, my first kokako.

From the people and places I have visited, it is obvious there is no simple solution to the stoat problem. Science alone is unlikely to deliver a silver bullet. An integrated ap­proach is required, with input from government, scientists, the commercial sector, communities and individual volun­teers. Responsibility lies with all New Zealanders. A mod­est financial contribution or a simple investment of time, multiplied a thousandfold, could make all the difference.

The important question is not “Can we control stoats?” We can. What we need to ask is “How important is our natural heritage to us, and how large an investment, as a nation, as communities and as individuals, are we prepared to make to safeguard it?”

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