Paradise regained: Predator-free Enderby Island

by Sally Blundell / 19 March, 2017
ArticleGalleryModule - Wildlife on Enderby Island

Predator-free Enderby Island, about 460km south of Invercargill, illustrates the ecosystem rebirth aspired to in the Government’s vision of a pest-free New Zealand.

Watchful on a nest of tussock, a southern royal albatross presides over Enderby Island’s wind-blasted coastline. A male mate hovers nearby, its 3.5m-wingspan beating against a howling westerly that threatens to topple Conservation Minister Maggie Barry and her small entourage from a boardwalk on this most northern of the subantarctic Auckland Islands.

Below, on the path down to a scattering of small Department of Conservation huts, a young family of yellow-eyed penguins shelters within the tangled branches of southern rata. Bellbirds sing. Pipits and tomtits skitter through the scrub. A sole falcon sweeps in for a look. Further down, a harem of New Zealand or Hooker’s sea lions, one of the world’s rarest sea-lion species, shows mild interest in the intruders. Pups lunge at pesky skua and giant petrels; young sub-adult males (“Sams”) scrap and scuffle. A sea elephant, slumped on the sand, opens a single bloodshot eye.

More than 460km south of Invercargill, straddling the Roaring Forties and Furious Fifties, the Auckland Islands, now recognised as a United Nations World Heritage Site, are one of six subantarctic island groups in the Pacific sector of the Southern Ocean. Since 2001, Enderby Island has been predator-free, rid of a history of pigs, cattle and rabbits. Human visitors – DoC workers, scientists, media, visiting politicians courtesy of the New Zealand navy – are a rare and, for now at least, unthreatening phenomenon.

But the Auckland Islands’ native wildlife has taken a battering. In the 1800s, the Government released pigs and goats to cater for the high number of sailing ships – eight between 1864 and 1907 with the loss of almost 100 lives – that foundered on its coastline (at least one 19th-century chart put the islands 56km south of their true position). Remarkably, three survivors of the Grafton, wrecked in Carnley Harbour, in 1864, managed to sail on a makeshift boat to Stewart Island.

Conservation Minister Maggie Barry.

Early visitors

In the early 1840s, a group of Ngati Mutunga and Moriori slaves came south from the Chatham Islands. That same decade, American, French and British Antarctic expeditions called on the Auckland Islands for rest, repairs and replenishment. In 1850, the British-based Southern Whale Fishery Company launched a whaling station and farming operation, called Hardwicke, in Port Ross on Auckland Island. The settlement failed: the acidic soil and lack of sun made growing vegetables difficult; sheep escaped; whale numbers had already been depleted. The colonisers left, as did the Maori settlers, but each left a legacy of cleared forest, introduced species and stowaways, including rabbits, mice, rats and stoats.

Disease has also taken its toll. The Auckland Islands are the main breeding site for the critically endangered New Zealand sea lion, Phocarctos hookeri. But between 1998 and 2009, its population went into free fall through a still not entirely understood combination of fishing-related mortality, nutritional stress and Klebsiella pneumonia, a bacterial disease that causes fatal meningitis in young pups. With only about 11,800 in existence, the New Zealand sea lion holds a place alongside the Asiatic lion, the red wolf and the black rhinoceros on the endangered column in the Red List of the International Union for Conservation of Nature. It is a threatened species under our own Marine Mammals Protection Act, “nationally critical”, according to our threat-classification system.

Now, the natural environment is staging a comeback. Grass once nibbled to a bowling-green stubble by the distinctive silver-grey Enderby rabbits – removed in 1992 by DoC and the Rare Breeds Conservation Society – is now ankle high, supporting a healthy regrowth of sedge, tussock and Dr Seuss-like megaherbs adapted to the constant wind, the peaty soil and the almost continual cloud cover.

This year, DoC is celebrating a 14% increase in sea lion pup numbers, from 1727 in 2016 to 1965. Populations of yellow-eyed penguins, considered to be the world’s most-endangered pen-
guin, appear to be doing better than their mainland cousins and some 60 pairs of southern royal albatrosses – one of six of the world’s 24 albatross species that lay eggs here and nowhere else – continue to breed each year on Enderby Island.

As Barry says, it is a victory, a sign of what New Zealand could look like once the aspirational goal of ridding the country of possums, stoats and rats by 2050 – or the more immediate target of removing all introduced predators from offshore island nature reserves by 2025 – kicks in.

“To see what belongs here and what has been adapted through millions of years to belong here is incredibly impressive and I think we need to keep those links or we run the risk of losing them. It shows me we are capable of doing this, and that if you give nature the chance, it will regenerate, and it doesn’t take very long. DoC is internationally renowned as being very good at killing small mammalian predators – I want to see first-hand what New Zealand will look like when predators are gone. I know New Zealand can achieve this vision.”

A Snares crested penguin. Photo/Getty Images

Not signed and sealed

But the paradise regained on Enderby Island is a precarious triumph. The rapid decline in sea-lion numbers – pup survival dropped from an 80% chance of reaching a year old before 1994 to about 40% since, with a clear impact on breeder numbers – is slowing. But still, of the 348 pups born on Enderby Island this breeding season (most are born on tiny Dundas Island), 62 have died.

Pup fatalities are nothing new. They topple off cliffs, fall into deep holes once laced with webs of tree roots (DoC workers have installed sloping ramps so pups can extract themselves from the boggy ponds) and are squashed by 400kg bull sea lions. Researchers are now looking at options for vaccines and/or antibiotics for Klebsiella pneumonia, believed to be responsible, at least in recent years, for about 60% of deaths in very young pups.

Survival rates for adult sea lions are harder to measure. In the ocean they are prey to great white sharks – many bare the scars of close encounters. There are also signs of nutritional stress, thought to be the result of changing water temperatures and climate, or the depletion of squid, hoki and red cod through commercial fishing and trawling.

“So it is not just the decline in pup survival,” says Niwa marine scientist Jim Roberts. “We’ve also seen a number of years when the breeding rate has been very poor – a strong indicator of nutritional stress. But disentangling climate and fisheries effects is extremely challenging. We know food availability has been an issue over long periods and we have an idea what they like to eat, but we need to know what kind of mortality is caused by food and what changes the availability of those species.”

Although a marine-mammal sanctuary and marine reserve protect a 12-nautical-mile area around the Auckland Islands, sea lions can travel hundreds of kilometres offshore, where they are at risk from capture and drowning in the trawl nets of squid and southern blue whiting fishing boats – about 15 years ago, commercial trawlers were estimated to be catching as many as 100 sea lions a year.

Since sea-lion excluder devices (Sleds), a kind of escape hatch fitted to trawling equipment, became standard in the Auckland Islands squid fishery in 2004/05, the numbers caught have fallen below the annual fishing-related mortality limit, currently set at 68, although post-Sled survival is difficult to gauge – the water is too deep and dark for meaningful video evidence and laboratory necropsies of incidentally caught sea lions have not been able to distinguish Sled-related injuries from onboard handling of frozen carcasses. Submitters to the draft threat management plan for New Zealand sea lions developed by DoC and the Ministry for Primary Industries (MPI) have called for closer scrutiny of the fishing industry and the long-term effects of Sleds.

Simon Childerhouse, senior research scientist at Blue Planet Marine, which does sea-lion monitoring for DoC on the Auckland Islands, was sceptical of the devices to start with. “When they were initially rolled out, they weren’t particularly effective, and there were concerns about whether they were doing what they were supposed to be doing. Sea-lion  survivability after escaping the net suggested they were getting extensive injuries – it turns out what looked like extensive bruising was tissue damage from freezing.”

Over the past five to 10 years, Sled use has been monitored and refined. “That doesn’t mean they are foolproof – there are still animals dying in there – but they are exceptions rather than the general rule.”

He says ongoing monitoring is important to minimise fishing’s effects on the sea lions, “and we are probably doing that as well as we can without closing the fishery”. And commercial fishing, he says, is far from the only threat.

Further research into the effect of disease and hookworm parasites on pup populations and the viability of food sources will also help what appears to be a tentative improvement in sea-lion survival.

“The population is still 30% lower than the peak in 1998, so there is nothing to celebrate, but the annual decline has ended and that is a positive step. So, at a worst interpretation they are stable, and at best they are increasing.”

Although seabird by-catch numbers have decreased, MPI data cites an estimated 16,200 potential annual seabird fatalities, mostly from trawl fisheries, but also from bottom-longline, surface-longline and set-net methods (there are also fatalities related to non-commercial fisheries). This figure is an extrapolation of observed fatalities, which, the report states, “may under-represent the total number of fishing-related seabird mortalities”; a 15-year study of surface-longline fisheries, for example, found only half of seabirds caught when lines were set were retrieved during line hauling.

A black-browed albatross. Photo/Getty Images

Uneven kill rate

The impact of fisheries on seabirds is not spread evenly. Niwa seabird ecologist David Thompson says some species are barely affected and any losses have to be balanced with population numbers. “If commercial fishing takes 10 of a particular species, it might not have any effect on the population; for other species, 10 could have a direct effect on the breeding population.” The nesting southern royal albatross on Enderby Island is far less likely to be caught by trawling or longline fishing than other species, such as the white-capped albatross, also resident in the Auckland Islands, Salvin’s albatross, the southern and northern Buller’s albatross, the flesh-footed shearwater and the black petrel.

“About 1-2 birds are being killed each year by commercial fishing operations so although that’s bad for the birds, the impact on the population isn’t that high.”

And the fishing industry, he says, “is generally receptive to the idea that something needs to be done to avoid the amount of by-catch it returns.” Many fishers are adopting mitigation techniques – including heavier or dyed bait, night setting, line jigglers, streamers and other bird-scaring devices – to deter birds from getting caught in the steel warps attached to nets. The fishing industry also contributes about $2 million a year through levies to the Conservation Services Programme to fund research on new mitigation measures and for observers to monitor the fishing vessels.

Although only a proportion of boats carry observers, those that do must report and record any by-catch. If there is no observer, says Thompson, no one knows what bird deaths a boat might clock up, but “most New Zealand fishing folk don’t like to be killing seabirds – they are not keen on doing it and it is not good for their image”. A recent MPI discussion paper agrees – it is not in the interest of the fishing industry, it says, to catch seabirds: “As a result, over a number of years there has been heavy investment in developing ways to avoid this. A number of voluntary measures and systems of education and monitoring have been developed across a wide range of fisheries, which have complemented regulated measures.”

Barry says she is working closely with MPI, which has “been putting money into research on minimising bird by-catch. The fishing industry has been co-operative, paying for videos and getting people on to inspect. There are odd people who don’t see the point, but penalties have been increased so it is a multifaceted approach.”

Although Enderby Island yellow-eyed penguins appear to be doing better than those on the main Auckland Island, where feral pigs leave a grim legacy of “feather bombs”, they are shy and nervous of intruders. If they encounter activity on the beach, they will abort a foraging trip, so endangering their health and that of their chicks.

This has important implications for ecotourism. Already seven companies hold concessions to bring about 1000 visitors each year to the Auckland Islands, contributing a vital $400 per person to DoC for the upkeep of tracks and boardwalks and spreading the word on these unique environments. Tour groups are strictly guided and go through full quarantine measures, but the viability of increasing visitor numbers is still up for discussion.

Barry believes there is room for more visitors and higher financial contributions from non-New Zealanders at least. “We are looking at the impact of recreational tourism and ways to charge tourists and visitors without ruining Kiwis’ experiences,” she says. “I will be going back and asking officials to look at increasing the charges on the boats that come through. Most are bringing international visitors and I would like them to pay more for the infrastructure and for the projects we need to do to preserve our taonga species. But more New Zealanders should be able to come here and have another layer of concessions – I don’t have a problem with foreigners paying extra.”

Allan Munn, head of DoC’s southern South Island conservancy, is not so sure. Boosting public education and support is “a big part of the equation” in arguing for more visitors, but the benefits are not clear-cut. “What’s our role – to drive demand? Or are we in the business of managing demand? I think the latter.

“We are providing an opportunity and it will always be a limited opportunity and a managed one. There are situations on the mainland where it is important we have that revenue stream, but the situation here, if you are walking on a boardwalk or going through some quarantine process or getting staff to manage tour permits, it is very much user pays.”

Sir Paul Reeves mistakenly shot a black-browed albatross during target practice on a navy ship when he was Governor-General. Photo/Alexander Turnbull Library: EP/1988/2417/19-F

Out, damned pig

Island by island, predator by predator, pests are being eradicated. Enderby is now one of more than 100 offshore islands rescued from, or never threatened by, invader species. In 2001, the last rat was removed from nearby Campbell Island through a multi-agency force responsible for 120 tonnes of cereal bait containing anticoagulant toxin Brodifacoum. Last year, the Million Dollar Mouse campaign, led by the Morgan Foundation and supported by WWF-New Zealand, Island Conservation and DoC, took to the estimated population of 200,000 mice on tiny Antipodes Island with three helicopters, 30 tonnes of fuel, a temporary hangar and 65 tonnes of bait at a cost of about $4 million. Next year, dog handlers and monitoring tools will return to the island in the hope of declaring it pest-free.

Barry gave the green light during the subantarctic islands visit to eradicating the estimated 1000 pigs from Auckland Island.  “We can do it,” says Munn. “We know how to shoot and trap things and we are improving that all the time.” The challenge, he says, is to keep abreast of new ways to monitor and trap predators – satellite communication, computers, heat-seeking technologies – and to keep an eye on the end goal.

“We need to get ourselves into a position that the day we catch our first pig, we have an eye on the day we catch the last one. Doing the job efficiently, achieving your objective in two years rather than four or five, can save many millions of dollars. But killing 98% of pigs is kind of easy. Getting the last 2% is hard, but unless you get that last 2%, you have wasted your time. It is really easy to keep people enthusiastic when they are catching a pig a week, but when they are stooging around the island for a week looking for a hoof mark, that is a different matter.”

The Auckland Island pig eradication will require a network of tracks and perhaps a temporary hangar for helicopters used for shooting and transporting gear around the island.  “You can get excited when you are looking on an A4 map on your desk, but 50,000ha is a big hunk of dirt.”

A hunk of dirt that, as with Enderby and Campbell islands, holds the promise of a renewed, if still fragile, natural ecosystem.

This article was first published in the March 18, 2017 issue of the New Zealand Listener. Follow the Listener on Twitter, Facebook and sign up to the weekly newsletter.

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