Imagination is the genesis of creativity – an original idea with value.
“The path to least resistance leads to crooked rivers & crooked men” [Henry David Thoreau]
I picked up a copy of Peter Ryan’s ‘Guide to SEABIRDS of Southern Africa‘ & was struck by the recurring theme – ‘… high chick mortality due to mouse predation.‘ That tends to get annoying.
Appended nearer the front of the publication are some harrowing pictures of partially devoured [still living] albatross chicks. The images were captured on Tristan da Cunha’s Gough Island – the culprit – Mus musculus or the House Mouse; biting-off as much as they can chew.
Mice were brought to Gough Island [a World Heritage Site today] by 19th century seal-whackers & since then, have evolved into creatures 50% larger & a good deal meaner than their greatest grand-daddies. Preferring a more balanced diet – today’s mouse muscles sitting birds, often 300x heftier; & puts them to the tooth, alive. Some 900 000+ seabirds, including the Atlantic Petrel & the Tristan Albatross, succumb to these supersized ghouls [nearly 2 million strong] each year. The Gough Bunting isn’t faring any better. As a consequence, better late than incompetent, the Tristan Island Council [à la ‘Lord of the Flies‘ if ‘Chief Islander’ is anything to go by], working with the UK’s RSPB, have developed their Gough Island Restoration Programme [mooted for 2019]. The intention is multi-faceted, yet simple – serve the Mus musculus community a poisoned apple & whilst the hunting party’s out & about – eradicate an alien plant for being a touch too rowdy. 2 for the price of 1. The funders will be thrilled…
Since I have the conch I have to ask – why has it taken so long? The standard one-size-fits-all defence either blames the sealers or amorphous funding. I don’t think so…
Academia are described as the uncontested champions of impotent communication, vacillation, & donor-dollar compliance. These luminaries, disconnected from the ‘real’ world, see no personal gain from public participation & focus exclusively on their own research community as a result. Academia is not the crucible of creativity once lauded as vocationally systemic. The cracks are there for all to see.
Gough’s carbon copy plays out, under similar circumstances, some 3800-odd kilometres to the south east.
The Prince Edward Islands Group, including Marion Island, one of two volcanic spits of land (24km x 16km), is a sub-Antarctic archipelago in the Southern Ocean’s ‘Roaring 40s’. It’s also front and centre in the ‘Guide to Seabirds…’ & a haven for supersized mice exploring their own Den of Shadows. Nobody likes them; the mice that is – not the islands.
- In 1803 seal-wackers & penguin-stickers landed on Marion Is. to pursue their trade in oil & gloves. Nearby Prince Edward Island [not to be confused with THE Prince Edward Islands] was too steep a climb to drag a pot; still is. Whilst on Marion, the gentry found signs of earlier habitation and history assumes Cpt. Cook, his mates & others had successfully landed on the island a century or so before.
- In 1947/48 the South African government annexed the archipelago (ie: expropriated w/o compensation); & glued the islands onto that country’s Western Cape province. 2100-odd kilometres of fairly deep ocean still baffles pedestrians intent on hiking from Cape Town to Marion. I assume earlier trekkers suffered the same annoyance; waterproof boots notwithstanding.
- Before the annexation, whackers & stickers, hailing from all geographies, incl. Cape Town, enjoyed free rein; unimpeded by hygiene or a care for tōmorgen. The Southern Elephant Seal was clubbed & blubbed until circa 1930 when populations were considered too low to pay the beach-master his share. The sealers left in a bit of a huff, at a guess.
- After the annexation, meteorologists set up shop – history tells us to establish de facto ownership & to ‘study’ the weather. Punters, on an expenses-paid exchange program, have been rotating out of Cape Town, ever since. The sealers have returned, subsequently, club-less & in white coats; and armed with clip-boards, telemetry & cheap dye, shake & stir the local wildlife, for science. In 1830 Richard Harris [not of Harry Potter fame – although who can be sure?] was the first person to observe [ie: collect] seabirds on Marion. Why none of the others looked up, before Harris did, is proof enough that Harris is indeed a wizard. Other wizards continue to shake a stick at birds today.
The seals settled back into some sort of routine, post their 1930 knock-about; but wait ’till you hear what happened to the birds AFTER the white-coats arrived. Listen to this:
In 1949, fed-up with holes in the oats’ bag, the weathermen brought cats to Marion. The island was infested – yessir indeed – Mus musculus ie: mice. Stuart Little & his descendants had jumped ship centuries before and had occupied the building. 5 cats: a ginger castrate – 1 b&w queen – & 3 kittens warmed their tuchis at Marion’s hearth. Although Ginger’s heart wasn’t in it after the op & what goes on tour, stays on tour, the evidence was overwhelming. The 1949 – (5) became the 1977 – (3405) …
In 1975 an archetypal numpty, in a fit of pique, tore himself away from the wind-sock & ventured outdoors. There he discovered that two tins & a fish wouldn’t satisfy the feral mob, even if the fat-cats inside were carrying on regardless. Mice can be tricky – even for cats – better the burrow-nesting birds. The cats were catching [ie: walking up to] & eating 450 000+ birds per annum. Nobody’d noticed; slap-happy & scrabble at the fire, much more fun. By 1977 the Common Diving Petrel, Grey Petrel and Soft-plumaged Petrel had all but disappeared from Marion [ie: they were locally extirpated – yes – extinct].
In 1977 ‘it was agreed‘, by committee & after years of peer-reviewed debate, that the Marion Island Cat Eradication Programme would be a foot forward for Marion’s remaining resident birds. Rather than get their hands mucky, however, even if their consciences were tainted, the white-coats introduced biological warfare to the island [ie: Feline panleucopenia (FPV)] – an infectious, highly-contagious cat-targeting pathogen which compromised the cats’ immune systems. The seals watched for hakapiks, but this fight wasn’t theirs. By 1982 only 615 cats remained. The Feline Resistance was determined, however, & with one hand on the exit knob, continued to procreate. In 1986 the white-coats rolled-out their Final Plan. Eight ‘2-man teams‘ armed with buck-shot, jack-lit the remaining 800-odd cats & cancelled their membership one-by-one; until the teams got bored that is. One or two Top Cats remained unaccounted for. In 1989, traps tackled these Rambo-cats & in 1991, Marion was declared cat-free; even if, perhaps, idiot-free it wasn’t.
I put my heart & my soul into my work, and have lost my mind in the process. [Vincent van Gogh]
Marion – like many other isolated islands, is a sandpit, without safety rails, for academic chums safeguarding their one-dimensional thesis. The ecological impact, however, falls on the collective & remains largely unacknowledged. No apology has been forthcoming – the cat faux pas an unmitigated disaster. Meanwhile, the mice remained largely forgotten, but in 2003/4 the first photographic evidence of mouse-predation, on albatross chicks, highlighted something more insidious at work on Marion.
Marion Island (29 000 ha), a ‘managed sub-Antarctic ecosystem’, is not only afflicted by barefoot-stereotypes, but continues to labour under various threats including invasive weeds. The parallels with Gough Island (6500 ha) are apparent. In 2006, Angel & Cooper published their review on the impacts of feral mice on Gough Island & in 2011 published a similarly-themed review for Marion. Appended to their review two important nuggets / caveats:
- The first postscript recommended ‘do nothing‘. Wait; leave Marion be until mouse-eradication attempts were successful, elsewhere. ‘Big Problems‘ on Marion … The island’s geography is mountainous. They feared that at a height of 1242m, Mascarin Peak [Marion’s highest point] could prove a jump too far for the AS350s – the helicopter-model popular, then & now, for aerial baiting. In May 2005, the same model aircraft flew to & landed on the peak of Everest [8850m] …
- They also recommended that an invitation be extended to an international expert to research & compile a feasibility study [incl. risks, constraints & costs] for the eradication of Marion’s mice. As expected, funding for this ‘research’ would be sought from the private sector rather than from the government who were, however, handed the report at the time.
The South African government put the team’s recommendations on ice, however, pending the release of a similar study being conducted by the British government for Gough. Birdlife South Africa’s seabird manager, an experienced fieldsman & Angel’s husband, ‘fully supported’ .. the mouse eradication initiative. In April 2015, Birdlife South Africa commissioned Kurahaupo Consulting to conduct the Marion study.
Kurahaupo’s John Parkes, based in Christchurch, New Zealand, published his ‘Eradication of House Mice Mus musculus from Marion Island: a review of feasibility, constraints and risks‘ in 2016. Read more here. The publication is the intellectual property of Birdlife South Africa which, I assume, paid for the study or at least its donors did. Apparently, the publication was peer reviewed by two independent scientists and edited by Birdlife’s Seabird Division. That’s nice. What isn’t too impressive is the fact that none of them could do a basic currency conversion & that’s annoying. Either that or nobody actually read my copy of the report. Yes, it’s an oversight, obviously, but when a project is dependent on external funding – from the ‘real’ world, that is, do the maths…
A$930/ha is not R87 000/ha. At R87 000/ha x 29 000ha [Marion Island] – the aerial baiting component would cost R2 523 000 000 [It’s actually A$930ha x 9.13 (cross) = R8490/ha]
The primary prey of mice, on Marion, is the larva of a flightless moth. The larvae take more than 2 years to mature & are detritivorous ie: they fragment, ingest and excrete leaf litter. 1500 tonnes [estimates] are processed by these larvae annually; a process that facilitates nutrient release and improves microbial decay. Since 1970, whilst everybody was darning socks or making shapes in the clouds, 90% of Marion’s invertebrate biomass disappeared. It’s estimated that mice eat 65g of these larvae / ha daily, predation which indirectly & perhaps more critically, has a detrimental effect on nutrient cycling & therefore, on Marion’s ecosystem as a whole.
There is some evidence that mice are switching to weevils, given the decline in larvae, which explains why mice are attacking birds – they’ve eaten the moths & who likes weevils?
When the 2011 review called for an ‘international rodent eradication expert‘, what the team should have said was ‘get somebody who had been successful aerial baiting for mice / rats on an island before’ ie: get somebody from New Zealand. New Zealand are the clear leaders in fixing their own alien-invader problems. In fact, they’ve developed, via state-owned Orillion, their own ‘second generation‘ or ‘superwarfarin‘ anticoagulant or Pestoff 20R / 20M. Pestoff is Brodifacoum wrapped in a blue-dyed, palatable cereal.
Brodifacoum is, we’re told, ‘highly lethal to mammals and birds, and extremely lethal to fish. It is a highly cumulative poison, due to its high lipophilicity and extremely slow elimination’.
‘Highly lethal‘ & ‘extremely lethal‘… ie: derivatives of ‘dead as a doornail’.
In toxicology the median lethal dose [LD50] is the dose required to kill half the (sample) population after a specified time. A lower LD50 = increased toxicity.
Brodifacoum LD50 values are as follows:
- rats (oral) 27 mg/kg b.w.
- mice (oral) 40 mg/kg b.w.
- cats (oral) 25 mg/kg — 40 mg/kg b.w.
- dogs (oral) 3.6 — 25 mg/kg b.w.
- LD50 values for birds varies from about 1 mg/kg b.w. — 20 mg/kg b.w.
Brodifacoum is, therefore, classified as ‘extremely toxic‘ for mammals & ‘very toxic‘ for birds. “Brodifacoum is the most potent of the second-generation anticoagulant toxins” [per the product specification]. In fact, Brodifacoum is absorbed in most soils, is insoluble in water & is active for >5 months out in the field. The rate at which Brodifacoum degrades in soil is related to the organic content of the soil… [see larvae (above)]. Brodifacoum is so toxic it’s considered an environmental pollutant.
Mice have been notoriously difficult to eradicate from islands, elsewhere. The Kurahaupo report includes evidence that concludes: (paraphrased) – a more toxic version of Pestoff might be more effective on mice ie: 25% more toxic that is. Is that so? The standard Brodifacoum content is 20 ppm or 20 mg per kg of food (0.002%).
The ‘more effective for mice‘ version is obviously also ‘more effective for birds‘. To mitigate these risks Parkes recommends a trial run. Fair enough… No point being Gung-ho, is there? Birds are exposed to Brodifacoum in two ways – by ingesting the pellets (Primary poisoning) or from scavenging / ingesting mice or birds already poisoned (Secondary poisoning). In the correct doses both activities “deplete the supply of vitamin K1 necessary for the production of blood clotting factor precursors” ie: dead as a doornail.
During the Macquarie Island eradication process [305 tonnes of Pestoff 20R] birds killed by Brodifacoum included Southern Giant Petrel, Northern Giant Petrel, sub-Antarctic Skua and Kelp Gull. All of these species are represented on Marion. Add the Lesser Sheathbill & that’s a fair crack at ‘non-target species’. On a trial run, caged Lesser Sheathbill on Marion refused non-toxic Pestoff 20R baits but ‘avidly ate dead mice’, apparently. Giant Petrels, elsewhere & on similar trials, have been known to refuse both the bait [*non-toxic] & mice [dead / *non-toxic] (*That would be cruel).
To mitigate non-target poisoning, Parkes recommends:
- Timing the drop in such a way that birds at risk are off the island at the time. For some of the species at risk; that’s in winter. Notwithstanding that trump – Brodifacoum is active in the field for >5 months. Birds return in spring…
- Other species, including the Lesser Sheathbill, could be captured & fed tinned food & dead mice until such time the threat of poisoning passed; & then released. Fair enough. Of 6 sheathbills caught some years ago and held in captivity for 4 days [fed tinned pet food & mice] – ‘most lost body mass & one was overly stressed and released‘; and
- Marion could be repopulated from nearby Prince Edward or birds would return naturally… Oki Doki Doc.
Kurahaupo introduces us to their ‘Three Obligate Rules‘ – white-coat-speak for the ‘Three Obvious Rules‘. These are the three commandments for island success.
- “Can all mice be placed at risk?” – ie: are we sure we can drop enough super-toxin, close-enough to every mouse, to make this a clean kill?
- “Can the target population be killed quickly enough?” – ie: not applicable to schemes reliant on aerial-baiting the entire island in a single one-hit session. All dead = no breeding.
- “Can reinvasions be prevented?” – Not if those pesky scientists have anything to do with it. I must admit I enjoyed the following titbit from Parkes’ report. Here it is – “...what would the environmental inspectors do if a mouse or rat jumped out [newly arrived cargo & containers] and disappeared down the grating?” What indeed…
The report reviews territory size, highlights suspected hidey-holes & scrutinises breeding activity. The weather also plays a part on Marion as might be suspected for a sub-Antarctic archipelago. To comply with Obligate Rules 1 & 2, w.r.t Marion’s size, it’s volcanic terrain & ice-covered peak; a clean kill requires the coordinated distribution of an effective super-toxin over the entirety of the island. As we’ve seen, the super-toxin’s in the bag & we know the island’s a fixture; – ultimately the outcome is influenced by the distribution in the field.
Accurate & even spreading, at the desired application rate, can be completed in one of two ways:
- 6 boatloads of hand-sowers [volunteers with bags] walking grids – destroying fragile flora & slipping on ice; or
- 4 or more helicopters with high-load capacity, a fertiliser hopper & a GPS to cover the predetermined terrain with the precision expected of a trained pilot.
Prudence favours the air. Notwithstanding, helicopters are bockety in wind, rain and snow. Marion’s extremes include all three; particularly in early winter. Per Obligate Rule no. 1 – juvenile mice, semi-dependent on mom & dad, might not be ‘placed at risk‘ whilst confined to the communal nest. That won’t do. To circumvent this annoyance, the efficacy of the bait-drop is determined by the breeding season. Ideally ‘place at risk‘ would be post the breeding season ie: in winter. Winter’s weather is mercurial in temperament, however – too choppy for the heli squad. Late summer [March] has a more reliable window but then there are the birds… This & much of everything else needs revisiting.
The errors notwithstanding, the Kurahaupo report makes for compelling reading in bits & bobs. Was it necessary? No – & this is my challenge to Birdlife South Africa.
The idea that an international [ie: non-South African] expert carries more weight than one or more of many equally talented, locally-located men & women, is symptomatic of a top-down strategy that is universally irrelevant; relies on flawed risk-allocation; is both inward-facing & self-indulgent; and irrefutable evidence of a puritanical head-set that can only be described as totalitarian. Why go there? Where is the creativity?
It’s impossible to argue against the overwhelming benefits of eradicating mice for the benefit of seabirds, Marion Island included. Clearly a super-toxic WMD [weapon of mass destruction] is the one-hit wonder that has been successful on islands elsewhere. Any one of many second-generation anti-coagulants are effective, even on mice. Those products are readily sourced locally. Distributing defined swaths of bait is simple technology and a common skill set; easily replicated locally. Cape Town boasts the world’s most dynamic industrial-use charter company (w.r.t AS350s). Brodifacoum, an environmental pollutant, kills slowly; is active in the field for months / insoluble in water & because of those properties & others, is ingested in quantities greater than required for a lethal dose. The realities of secondary poisoning cannot be dismissed; mitigation notwithstanding.
Why we insist on an unrelated party to regurgitate / rehash a rendition of the stock-standard strategy, is irritating to say the least. What really irks me is the lack of innovation. It would be a sad day if we succumbed to the temptation of replicable / valueless work. That is undeniably the path of least resistance – & insults the local donor dollar – unless, of course, the Marion project resides in Cambridge – & the ‘international’ stipulation is a funding pre-requisite. That would make sense, perhaps, but then say so. Even so, we can make the argument, well-enough, here; in South Africa. It’s in the name: Bird – Life – South – Africa. That’s not too much to ask, surely?
A final word on Marion. It’s clear mice are substituting their primary prey (equally in need of help btw.) with other food, including the island’s charismatic fauna. In truth, the mice are the unintended consequence of an inattention to detail. Restoring Marion, if our interpretation of pre-landing glory is correct & not imagined is, therefore, a value judgement – do we need to be there?