Category Archives: Field Notes

Pigeon Spotting

Years ago, I was at an ecology conference where scientists were sharing the results of a study on our native pigeon or kererū. They’d been tracking the long-term decline of kererū in native forests; some of the birds they’d been monitoring had been killed by predators during the study; others had been poached by hunters. Their conclusion was that kererū were in trouble.

Kererū, kūkū, or kūkupa are known to scientists as *Hemiphaga novaezelandiae*, the “New Zealand half-eater”, for the way they gobble up fruit and poo out the undigested seeds.

Kererū, kūkū, or kūkupa are known to scientists as Hemiphaga novaezelandiae, the “New Zealand half-eater”, for the way they gobble up fruit and poo out the undigested seeds. Photo: CC-BY-SA, Angrysunbird/Flickr

Someone in the audience stood up: a local. How could these scientists say that kererū were in decline, he asked. Why, just the other day he’d seen a flock of twenty five!

To the local, the evidence of his own eyes counted for more than years of research by scientists. But our own observations can be misleading. We tend to remember the day we saw twenty five kererū, and forget all the days we saw none at all. Also, our memories don’t stretch back very far. A few generations ago, flocks of dozens or even hundreds of kererū were not uncommon; today they’re very rare.

It matters if kererū are less common than they used to be. Our native pigeons play a vital role in the forest’s ecology: they’re the only bird species left with a big enough mouth to swallow the fruit of native trees like karaka, tawa, and matai. These trees have evolved to have their fruit eaten by birds, and the seeds passed out the other end some distance away. Now that larger birds like moa are extinct, we rely on kererū to help native forest regenerate.

The 2015 Great Kererū Count results, reflecting the distribution of observers as much as pigeons. From: greatkererucount.nz

The 2015 Great Kererū Count results, reflecting the distribution of observers as much as pigeons. From: greatkererucount.nz

One way to find out where kererū are – and aren’t – is the Great Kererū Count, a citizen science project that enlists members of the public to look for kererū locally and note down whether they’re regularly seen there. It runs September 16th to 25th. To take part, you just need to make an observation for 5 to 30 minutes, which could be in your backyard or walking in the park. You note down how many kererū you see, or if you saw none (equally important data) and enter the results at the Great Kereru Count site. You can add what the birds were doing or eating, and how common is is to see kererū in your area. You can even download an app to help count kererū on the go, or join up with the Great Kererū Count project at NatureWatch NZ.

Enlisting thousands of volunteers means kererū numbers are no longer just one person’s opinion. Last year there were over 8,700 observations, and over 19,000 kererū counted. It’s not the absolute numbers that matter, but the trends over time. As the data accumulate over the years, ecologists will be able to build up a picture of regional trends in kererū population: where numbers are healthy, and where the birds are in trouble. Most participants are in cities, so observers from out in the country are especially valuable. Looking at the map from last year, there are very few observations between Kai Iwi and Hawera, so I’ve been asking people around Whanganui to consider volunteering for half an hour and keeping their eyes peeled for kererū.

(This post appeared in the Whanganui Chronicle, 10 September 2016)

Slowly Saving the Longfin Eel

New Zealand has two species of native freshwater eel, longfins and shortfins. Longfins are found nowhere else. They live further inland than shortfins, and get older and bigger: over a century old, for ones that are 2 m long and as thick as your leg. They’re down to about 20% of their former numbers, and the population has been declining for decades from overfishing, pollution, and forest clearance. If it drops any more, DOC will have to declare them an endangered species.

800px-NZ_eelEvery longfin eel in NZ is a virgin. At the end of their lives, some time between 30 and 100 years old, they head out to sea, spawn in the ocean near Tonga, and die. The tiny fry make their way back to NZ and work their way up rivers as elvers, where they settle down and slowly grow bigger. So every eel we catch is one that has yet to breed.

And yet, amazingly, there’s a commercial export industry in longfin eels. It’s perfectly legal to catch tonnes of them every year, and export them alive to countries who long ago wiped out their own eel stocks but still think eels are a delicacy.

The Parliamentary Commissioner for the Environment prepared an excellent and very readable report on the longfin eel in 2013, looking at numbers, threats, and the commercial fishery. She concluded:

“It is critical that we stop fishing longfin eels. It is not just fishing that is a problem, but stopping it is the only action that has immediate potential to reverse the decline of this extraordinary creature.”

The commercial eel industry employs maybe 100 people, mostly part-time eel fishers, and is worth only $0.5 million a year: a tiny fraction of our exports. Quite a bit of taxpayer money is spent propping up this industry though. Apart from the PCE report, the Ministry for Primary Industries (MPI) assembled a panel of international experts to comment on the longfin monitoring, ran workshops, consulted, and has now prepared a discussion document on the South Island quota, which it will have to administer, collect data on, make regular reports, monitor… It seems like a lot of effort so that 30 full-time eel processors can keep making private profits off a public resource.

One of the recommendations was that the MPI set up a separate quota for the South Island longfin stocks (they’d been lumped in with shortfins) so the fishery could be at least monitored and controlled. The MPI are setting the quotas for different regions in the South Island right now, and are inviting public submissions, deadline Monday 11th, 5pm – although submissions opened on June 13, fisheries biologists were apparently only told a week or two ago, and the word’s hardly gotten out. There’s a Forest and Bird blog post with some advice on making a submission (it’s quick and easy, just write a clear, concise email stating your interest in this and your opinions and suggestions). Here’s mine.


TO: FMSubmissions@mpi.govt.nz

I am writing this submission on discussion paper 2016/15, Review of Management Controls for the South Island Longfin and Shortfin Eel Fisheries (LFE 11–16 & SFE 11–16) in 2016, to comment specifically on the South Island longfin eel fishery.

I am a biologist, and Curator of Natural History at the Whanganui Regional Museum. Whanganui has a deep connection with tuna and their harvest, and local iwi have resolved to improve the health of the river so stocks can recover; in my job I talk to the community about freshwater health and the biology of our native fishes. And of course as a South Islander, and a New Zealander, I’m a stakeholder in the health of South Island freshwater ecosystems, including longfins.

The independent panel commissioned by MPI in 2015 concluded that, although longfin numbers had probably dropped 80% from its original level, the decline may have slowed or “perhaps even slightly reversed” in the last five years. I am concerned that MPI has represented this as evidence that longfin eel stocks in the South Island are now recovering and can continue to support a commercial eel harvest.

There could be numerous explanations for the small uptick that is being used to claim longfin stocks are now recovering. Given longfins take well over a decade to reach a commercial catch weight, any real population increases would have to have begun at the height of mass dairy conversion and degradation in water quality we are observing in the South Island. Conversely, impacts being made today on breeding success and the recruitment of elvers into waterways will not affect the commercial eel harvest for over a decade. So it is unlikely that variations in catch per unit effort now, in isolation, are actually giving us good information on longfin population trends.

The independent experts commissioned by MPI found numerous problems with measures currently being used to assess eel numbers, and recommended that an integrated, long-term monitoring process begin, using a wide range of techniques and assessing all potential threats to longfins. Even adjusted for unit effort, catch rates represent the behaviour of fishers as much as the number of eels present – eel fishers are highly mobile and target just the areas where eels can be most easily caught, which can mask pervasive declines in the population.

There appears to be a difference of opinion between MPI and the Parliamentary Commissioner for the Environment as to whether the longfin population is at a harvestable level, and whether it is continuing to decline. It would seem impossible to allow a commercial fishery until, at the very least, both of these questions are settled to the satisfaction of the research community.

My opinion, speaking as a scientist, is this:

  1. The South Island longfin quota for 2016 should be reduced to zero (0) tonnes, and maintained thus for 20 years, during which longfin populations will be monitored to determine if they are in fact recovering.
  2. The quota should be uniform for the entire South Island, as elvers do not return to a specific stream, and so the entire breeding population of New Zealand is a single management unit, with harvestable eels in a few areas supporting the eel population of the entire country. It seems odd to allow effectively unrestricted harvest of longfins in areas like the West Coast (LFE 16) when these populations are supplying elvers, and thus determining stock levels, for the rest of the South Island.
  3. If the quota is not reduced to zero, it should be reduced to a level well below the current commercial take, as one of the few methods available to immediately help reverse the decades-long decline of longfins. The “nominal catch” levels indicated for LFE 11, 12, 13, & 14 would be appropriate, and should be extended to LFE 15 and 16, instead of the proposed levels of half the current average commercial catch (LFE 15) or an unrestricted continuing commercial catch of 25 tonnes (LFE 16).
  4. MPI should take the initiative in supporting a research programme, run by all fisheries biologists and ecologists with expertise in longfin eels, that will clearly determine a) a population level of longfins able to support a commerical harvest (for example, 30% of the pre-fishery stock) and b) robust, well-accepted methods of determining whether that level has been reached.
  5. Until those methods have been settled on, and until the population has recovered to that agreed level, the TACC should remain at 0 or nominal.
  6. This research programme should be totally or substantially funded not by the New Zealand taxpayer, but by the commercial longfin industry. If the commercial eel industry is not willing to help determine if longfin stocks can be sustainably harvested, they should no longer be allowed the privilege of taking and exporting this publicly-owned resource. Other extractive industries are responsible for determining the environmental impact of their activities: the eel fishery should be no exception.
  7. Recreational and traditional quota should remain unchanged if not reduced to a nominal level, but a consultation and education programme should begin with iwi to give each region the option of setting traditional harvest levels to 0 – effectively, a rahui – for a similar period, and working with ecologists to monitor the health and population levels of their local longfin stocks.

Quite apart from the scientific arguments, though, about methods for assessing stock levels, I would like to propose another reason why the South Island longfin quota be set to zero.

It is abhorrent.

I believe that if most New Zealanders understood the population trends and breeding biology of longfins, and that this species was nevertheless still being caught and exported for profit, they would vote to shut the industry down tomorrow. If it were similarly-threatened native birds being harvested for export, there would be public outrage. Future generations will shake their heads in disbelief that we allowed a commercial longfin industry to carry on into the 21st century, long after the decline of this species was clear; just as we do today when we recall New Zealand was still carrying out commercial whaling into the 1960s.

Thank you for considering this submission. I am happy to be heard in person in support of it if required.

Dr Mike Dickison
Whanganui Regional Museum


Some useful info:

Sympathy for the Wētā

Mercury Islands tusked weta on Korapuki Island, May 2016. Photo by Rob Chappell/DOC

Mercury Islands tusked weta on Korapuki Island, May 2016. Photo by Rob Chappell/DOC

The Mercury Islands tusked wētā is an insect the size of a mouse. Its long curving tusks are weapons that males use to joust and grapple with each other in ritualised combat over mates. This bizarre species was discovered in 1970, living on one small island off the Coromandel Peninsula in northern New Zealand. It very nearly went extinct, saved in the nick of time by heroic conservation work, yet hardly any New Zealanders have even heard of it.

Middle Island is tiny, only 15 hectares, but in 1970 had the distinction of being the only one of the Mercury Islands with no introduced mammalian predators; in particular, the Polynesian rat or kiore. In the decades after tusked wētā were discovered on Middle Island there seemed to be plenty of them living there – you could see dozens in a single night. Then in the 1990s the population plummeted to less than 200, possibly because of a severe drought. Fewer and fewer were recorded each year. The last time a tusked wētā was spotted on Middle Island was in 2001: eight subsequent searches between 2009 and 2012 turned up nothing. Just 31 years from discovery to demise.

But not quite. In the 1990s the NZ Department of Conservation ruled out relocating any tusked wētā to other islands, worried about the effect of taking even a few from the tiny population still surviving. Instead, they captured two females and a male and tried to breed them in captivity – without success. They tried again with three more wētā in 1998, but this time everything went right: the insects bred prolifically, producing 181 hatchlings. In 2001, just as the species was going extinct on Middle Island, DOC released young wētā on two other islands in the Mercury group they’d newly cleared of mammals through poisoning and trapping. Since that release, hundreds more wētā have been bred and released onto four other pest-free islands, and all seem to be doing well. Every Mercury Islands tusked wētā in the world is descended from those three individuals captured in 1998, in a last-ditch, and fortunately successful, attempt at captive breeding.

This is a particularly New Zealand story: a species gets down to a handful of individuals and is heroically pulled back from the brink. It’s almost our trademark: we don’t get out of bed until the species is down to double figures. But when we do heroic conservation feats with birds, like the kākāpō and black robin, sponsors line up to be associated with the rescue, and TV crews fly in from all over the world to make inspiring documentaries. Even though the Mercury Islands tusked wētā story is just as inspiring, even though DOC’s earnest publicity drive in the ’90s managed to get it onto a postage stamp, it isn’t a household name.

UnknownThat’s a shame, because the wētā story is much more representative of what we’ll need to do to save New Zealand’s biodiversity. Most of our endangered species are not birds. They are fungi, lichens, insects, worms, shrubs, and snails: things TV crews overlook. They don’t require heroic multi-million-dollar conservation battles. Rescuing the tusked wētā cost a few thousand dollars a year; they were reared in recycled ice cream containers. Many of our critically-endangered species could be saved by similarly small projects: potting up cuttings in a back yard, fencing a patch of forest to keep cows out, trapping all the predators on a tiny island.

With its budget being reduced almost every year, DOC simply doesn’t have the personnel or funding anymore to rescue everything, and increasingly depends on the public’s help. The small-scale projects that could save obscure endangered species would be perfect for these sorts of partnerships. But instead, the public conversation about conservation seems obsessed with saving cuddly celebrity animals, ones people would perhaps secretly like as pets. It’s as if we don’t trust New Zealanders with the facts.

Slugs and spiders are just as endangered, and count just as much, as penguins and dolphins. If we’re tallying biodiversity, a species is a species. Last year I wrote about how we can prioritise species conservation to get the biggest bang for the buck, and Jesse Mulligan interviewed me about it on the radio. Jesse got quite impassioned about the neglect of uncharismatic species, and started a Critter of the Week slot with DOC’s Nicola Toki to highlight the plight of the rare and overlooked; these days I help by beefing up the corresponding species’ Wikipedia page each week. Perhaps by telling these stories we can help people care about all New Zealand’s threatened flora and fauna. Even the prickliest wētā.

(A version of this piece originally appeared in the Wanganui [sic] Chronicle, 16 May 2016, unfortunately stripped of all its carefully-applied macrons.)

Can We Rank New Zealand’s Environmental Record?

Freshwater biologist Mike Joy has been in the news recently for claiming New Zealand is not all that clean and green. He’s pointed out that most of our lowland rivers are contaminated with faecal bacteria, our lowland lakes are polluted, and two thirds of our native fish species are threatened with extinction. But Joy repeatedly goes further, claiming New Zealand’s whole environmental record is dubious: “We are now much much closer to the bottom than the top of global comparisons on environmental performance.”

For this, he was slammed in a New Zealand Herald editorial for “exaggerating” New Zealand’s environmental woes. Joy had told the paper, “We are nowhere near the best in the world, we are not even in the top half of countries in the world when it comes to clean and green.” The Herald took issue: “Whatever its deficiencies, it is nonsensical to place this country in the company of the world’s more polluted nations.”

Is New Zealand’s environmental record really well below average? On the web, in print, and in a recent Media3 interview, Joy repeatedly quotes a recent study (Bradshaw, Giam, and Sodhi 2010) published in the open-access journal PLoS ONE, “Evaluating the Relative Environmental Impact of Countries”. The New York Times article that kicked off the latest kerfuffle quotes its most painful finding: out of 179 nations examined, New Zealand was the 18th-worst in its impact on the natural environment.

That’s a pretty terrible grade. But is it accurate? I took a close look at the study, and the report card it compiled on New Zealand, to see if it held up.

What are these rankings?

Bradshaw, Giam, and Sodhi (2010) were attempting to come up with an objective measure of environmental performance for countries so they could test the effects of social factors, like per capita wealth or governmental corruption, on environmental impact. Their goal was to put together a rough working database, not compile league tables for ranking all the world’s nations. But, surprise surprise, that’s how the study is being used in New Zealand.

To come up with a rank, the authors gathered data on seven different variables and took the log-average or geometric mean (not the same as an ordinary average, this stops extremely high or low values from having as big an effect). As long as there were data available for three of the seven variables, a country was ranked in the league tables (179 of the 228 countries examined qualified).

The results summarised countries’ absolute impact on the global environment—all the usual suspects (China, the USA, Brazil, Japan) scored badly, but New Zealand didn’t—as well as their relative ranking, corrected for size. The latter is where NZ appeared in the bottom 20 (Singapore was worst, in case you’re wondering); here’s the rogues’ gallery, from the original paper but with some social and population information edited out.

Edited data from Bradshaw, Giam, and Sodhi (2010), showing the 20-worst environmental baddies, and the seven variables used to rank them—each variable is explained below.

What exactly are these variables?

It’s worth examining the variables one at a time, to understand where the rank of 18th-worst came from. They seem perfectly reasonable at first glance, but the more I poked them, the more dubious I got. New Zealand is ranked out of a maximum of 228 countries, though usually fewer than that as data weren’t available for every country. The lower the number, the worse we are.

Natural Habitat Conversion
NZ rank: 89th

This is the percentage of the land that’s human-modified: urban areas, crops, and managed land. In New Zealand, almost all open land below the tree line should count as human-modified—lowland tussock grassland was created by Polynesian fires and maintained by sheep grazing—so we should probably be ranked worse than this.

Marine Capture
NZ rank: 73rd

Marine fisheries take, divided through by coastline to correct for country size. How did the study cope with countries that have no marine fisheries, because they’re completely landlocked? Rather than leave them out of the rankings, they’re awarded a perfect score. Part of the reason the Central African Republic, that paragon of environmental stewardship, got the second-best ranking in the world.

Water Pollution
NZ rank: 91st

The ranking used here is based on BOD, a estimate of total dissolved oxygen being consumed by aquatic bacteria, divided through by the total yearly waterflow for each country to keep things proportional. New Zealand no doubt does well because of our abundant rivers and high rainfall. I’m stumped as to why the ranking here bears no relation to the research Mike Joy cites, which found excessively high levels of bacteria, nitrogen, and phosphorus in most of the 300 lowland rivers sampled. It would be remiss, by the way, to not mention the irony of condemning NZ’s environmental record with a study that says our water quality is OK.

Natural Forest Loss
NZ rank: 98th

The authors looked at the change in native forest area between 1990 and 2005; they calculated this from FAO statistics, subtracting plantation forests from the total forest area. New Zealand is about the middle of the pack, because our amount of native forest didn’t change over that time. (I’ve updated the data to 2010.)

New Zealand (98th)1990200020052010
Total7720826683118269
Planted1261180918541812
Native6459645764576457

Wait a minute: according to the FAO stats, our forest area not only didn’t change; it stayed exactly the same, to the hectare. Dodgy data alert! And we know that’s not true: between 1997 and 2002 we lost at least 2000 Ha of native forest, according to satellite imagery; between 1990 and 2008 over 50,000 Ha was deforested, and a similar amount naturally regenerated. So the FAO data look suspicious.

To check it, I picked another couple of countries at random; Samoa, which had an exemplary deforestation ranking of 196, and Korea, with the bad boys at 23.

Korea (23rd)1990200020052010
Total6370628862556222
Planted173817811823
Native“6370”455044744399
Samoa (196th)1990200020052010
Total130171171171
Planted323232
Native“130”139139139

Notice there’s missing data from 1990; presumably there were actually plantations in Samoa and Korea before 2000. The researchers seemed to have assumed that no data mean no trees, so Korea is unfairly accused of massive forest loss (ranking it among the worst 15% of countries for deforestation). It looks like Samoa though has increased its indigenous forest area by 6.9% since 1990, giving it an overall environmental impact ranking, according to this study, of 173 out of 179. Not bad for a country that had one of the most rapid rates of deforestation in the world in the 1990s. Forest clearance is rampant in Samoa, these numbers are nonsense, and so is Samoa’s ranking. I picked these two countries completely at random—who knows how shonky the rest of the database is? At the very least, the researchers need to go through and recalculate ratings using only available data.

CO2 Emissions
NZ rank: 93rd

Why do we get off so lightly here? Because the only carbon emissions the study counted were fossil fuel usage and clearing land for agriculture. While those are the two biggest components of most countries’ carbon footprints, they’re not ours. Nearly half of our CO2-equivalent emissions are from agriculture and the digestive systems of cows; methane and NO2 aren’t counted by this study at all.

Fertiliser Use
NZ rank: 13th

New Zealand does use an awful lot of fertiliser, but are we really 13th-worst in the world? The problem lies with how the study calculates fertiliser use: total imports divided by area of arable (crop) land. Now, that’s fine for most countries, where fertiliser is applied mostly to crops. But in NZ most of our fertiliser is going onto pasture, and pasture makes up almost all of our agricultural land.

ArablePasture
NZ42511224
Denmark2332368
Thailand15200800

Dividing our fertiliser imports by just our arable land area overestimates the amount we use by a factor of maybe 10 or 20. No wonder we’re 13th-worst!

Proportion of Threatened Species
NZ rank: 1st

At last, a field in which New Zealand can be proud to say we’re number one! The species counted are amphibians, land mammals, and birds, and since all our frogs and bats are threatened, and 70 of our bird species, we do indeed take the title here. This ranking, more than all the others, is the reason we’re near the bottom in the PLoS study. Four things to ponder, though.

  1. We don’t have threatened species for the reasons most countries do: ongoing deforestation and pollution. Most of our extinction and species decline was happening 100 or 150 years ago, well out of the timeframe of this study. These days, increases in the proportion of threatened species in New Zealand occur because we’re actively studying the genetics of our native animals and discover small isolated populations are actually species.
  2. Extinction is really the thing we should be measuring, but it’s harder to count, as it’s difficult to know whether a species has vanished or is just very rare. In most countries, the number of endangered species is a good proxy for the extinction rate, but not in New Zealand. We haven’t lost a bird, frog, or bat species since 1972 (Bush Wren), and have pulled several back from the brink—the Black Robin from 11 individuals, the Kakapo from 50). It’s quite possible, thanks the the fine and underfunded work of the Department of Conservation, that none of them are in danger of going extinct in the future (which is more than most countries can claim).
  3. Why do we have so many threatened species? Because we’re a small island country. Small countries have a greater proportion of endangered species than large ones: the bigger your country, the harder it is to wipe out all of a species living in it. Islands have more threatened species than the mainland: there’s nowhere for native species to escape to, and evolving in island isolation makes animals more vulnerable to extinction. Both these points are not controversial in conservation biology (references coming!), but are tersely dismissed in the PLoS paper. Their evidence: one unpublished study by one of the co-authors that looks at plants not animals. It does seem a bit unfair that New Zealand is penalised for being a small island country, something I don’t think can be laid at the door of either Labour or National governments.
  4. Why do we have so many threatened species? Because Aotearoa is the last place humans settled: we arrived only 800 years ago. Every other country in the world has already suffered the mass extinction that occurs whenever humans encounter the local wildlife; we’re still working through the tail end of ours. If Europe had only been settled 800 years ago, the French would right now be battling at great expense to save their last endangered lions, leopards, and mastodons. Again, it’s not all that fair to condemn New Zealand for choosing to be settled so late.

So how accurate is our ranking?

Not very. One of the variables dominates all the others, but is a little unfair. One of our rankings is just a blunder. A couple of variables are calculated wrongly, one database looks pretty dodgy, and the whole issue of sustainable fishing when you don’t have a coastline skews all the results. Nevertheless, we can have a go at recalculating the ratings.

VariableDodgy?Better estimateComment
Habitat conversion89Depends of definition of “human modified”60?Only if other countries are reassessed too.
Marine capture73No coastline = perfect score!Omit from everyone’s rankings until this is sorted.
Water pollution93Doesn’t agree with recent studies50?Reconcile the two.
Natural forest loss98FAO data look shonky98 for nowDatabase needs to be checked, scores recalculated.
CO2 Emissions93Misses out agriculture50?
Fertiliser use13Wrongly calculated100?Need data for our fertiliser use on arable land.
Proportion of threatened species1Could correct for insularity, country size10?
RANK18RECALCULATED39-ish

That rank is still not great, but it puts us in the vicinity of South Africa, the UK, and France. Sure, my recalculation is just handwaving, but it’s definitely more justified than the rank of 18 the PLoS study gave us. Those global rankings are probably OK for testing broad-brush models of the effect of social variables on environmental performance. But the data are so dodgy that I wouldn’t dare use them at all for the purposes of grading a country on an environmental report card.

New Zealand’s environmental impact might well put us in the bottom half of the world league table, but we actually don’t know if it does or not, and this study is not much help. Our country has real environmental issues—and is not by a long shot “100% pure”, absolutely or relatively, despite what the PM says—but claiming we are 18th-worst in the world seems just flat-out incorrect. And if you continue to claim it after knowing how dodgy the data are, you’ve crossed a line from science into advocacy.

What, if anything, is a Maui’s dolphin?

Maui’s dolphin | © WWF & Will Rayment

Everyone wants to save the Maui’s dolphin. It’s either the world’s smallest dolphin or smallest marine mammal (depending who you read), and supposedly the most endangered: there are only about 55 left. A petition is doing the rounds to save the “most critically endangered marine species in the world” from extinction, partly by stopping iron ore mining on the seabed.

There’s one big problem, though. Maui’s dolphins don’t really exist, not in the same way that takahe or kakapo or short-tailed bats do. They’re not a distinct species, just a subspecies of Hector’s dolphins—in fact, it would be perfectly accurate to call them “North Island Hector’s dolphins”. And this has implications for their conservation.

Part of the problem is that people who should know better use technical terms like subspecies and species as if they were the the same thing, but there’s a world of difference. A subspecies is a population of animals or plants that looks a bit different from its relatives nearby. Critically, members of the subspecies are still perfectly-well able to breed with other members of their species. If a subspecies is isolated for long enough and become so different they it can’t interbreed any more, we call it, by definition, a different species. A species is a real thing, reproductively isolated and distinct from its nearest relative; a subspecies is just a formally-named variety, and what counts as a subspecies can be a matter of personal taste, reflecting how picky a biologist is. Some biologists refuse to even countenance subspecies and say, with some justification, that they’re not real.

Because biologists, like everyone else, are fond of large charismatic animals, it’s mostly mammals and birds that get fussily sorted into subspecies. This whole debate would be a non-issue if we were talking about an insect, or reptile, or fungus. The problem is if you split something into multiple subspecies you are almost guaranteed to create at least one rare, localised population, which then becomes in urgent need of conservation, and it’s problematic if ever-decreasing conservation funds have to be allocated to saving something that doesn’t really exist.

So what sort of thing is a Maui’s dolphin, then? Alan Baker and two colleagues measured bones of a dozen or so Hector’s dolphins from the North Island and few dozen from the South, and also compared their genetics. North Island Hector’s dolphins are a bit bigger, have a longer snout, and show some differences in their DNA—the sort of differences you would see if they’d been evolving separately from the southern dolphins for a few thousand years. (Thousands of years sounds like a lot, but it’s really nothing in evolutionary time.) Baker et al. (2002) named the northern population Cephalorhynchus hectori maui, and decided it would henceforth be called Maui’s dolphin, with the South Island population, confusingly, remaining Hector’s dolphin (Cephalorhynchus hectori hectori). Notice the triple-barrelled Latin names, which indicate both forms are just subspecies of Cephalorhynchus hectori.

(Maui’s dolphin is actually a pretty terrible name, as Maui didn’t identify, know about, or even see them, being, as he was, mythical. Baker et al. were naming them after the North Island, Maui’s fish—Te Ika a Maui—as that’s where they live, but the South Island is Maui’s canoe, and they live there too; it would be more appropriate, but a bad idea, to call them fish dolphins, or ika dolphins. Personally I think we should go back to cumbersome-but-accurate North Island and South Island Hector’s dolphins.)

Does all this pickiness about the difference between species and subspecies matter? Yes. Cephalorhynchus hectori are distinctive, unique beasts, not very much like other dolphins, and they’re only found here in New Zealand. Losing them would be a tragedy, because there’s no way to get them back. Maui’s dolphins are just those slightly-bigger Hector’s dolphins that live in the North Island, and if they died out the species would be be a little less varied, but, critically, it would still be here. It’s awful to lose a subspecies, but it doesn’t even compare to an actual species extinction; we’ve had plenty of those in New Zealand, and will be hard-pressed to prevent more.

It’s also important to look at these subspecies on a longer, evolutionary, timescale. The north/south split is, as you would guess, caused by Cook Strait; it isn’t a complete barrier, but Hector’s dolphins are coastal animals that prefer water less than 100 m deep, and most of the Strait is deeper. They can and do cross it, though, as the 2010 DoC survey found some South Island dolphins along the North Island coast. This species prefers cool water, so Maui’s dolphins are currently living close to the edge of their comfortable range, and population numbers might never have been very high.

But the North Island/South Island split is quite recent, and only temporary. Over the last couple of million years, New Zealand has been through about 20 ice ages, in which the world sea level dropped dramatically and our three main islands were joined into a single land mass. Back then, Hector’s dolphins would have lived as one continuous population in the cool waters around the entire coastline of that big island. Twenty times there has been a comparatively short warm period, called an interglacial (we’re in one right now), when the waters have risen, the islands have separated, and the North Island dolphins have been isolated from their kin and begun to evolve slightly differently. Twenty times they’ve been reabsorbed back into the fold. Maui’s dolphins have appeared and disappeared repeatedly for millions of years.

The species Cephalorhynchus hectori is in trouble: it’s been classified as Endangered since 2000 (IUCN 2011), and the population has dropped by 75% in the last 40 years, down to about 7000, largely from accidental bycatch in fishing nets. The response has been to ban commercial gillnetting in much of the dolphin’s habitat—coastal waters less than 100 m deep—though numbers continue to drop. I think it’s more important to stabilise the dolphin population than worry about whether or not they persist in the North Island. Most whales and dolphins, as their numbers recover, can recolonise their former range without assistance, and the fact that South Island Hector’s dolphins are still crossing Cook Strait suggests that would happen here too. Rather than worrying about seabed mining near Raglan, which is surely a comparatively minor threat, we should be fighting for Liz Slooten’s proposal: a gillnet and trawling ban across Cook Strait shallow waters so dolphins can get to the North Island unhindered.

Hector’s dolphin in Akaroa Harbour | Harald Selke / Tewahipounamu

Hector’s dolphins do need protection, but conservation organisations, journalists, and even the Department of Conservation are treating the North Island dolphins as if they were a distinct species about to go extinct, even comparing them to the moa. That’s irresponsible, and plays fast and loose with the facts at a time when we need to have those facts on our side.

References

Baker, Alan N., Smith, Adam N. H., and Pichler, Franz B. 2002. Geographical variation in Hector’s dolphin: recognition of new subspecies of Cephalorhynchus hectori. Journal of the Royal Society of New Zealand 32(4): 713–727

IUCN. 2011. Cephalorhynchus hectori. IUCN Red List of Threatened Species. Accessed 20 March 2012.

The Science Media Centre provides a good overview of recent stories on Maui’s dolphin, and the WWF has a series of fact sheets that are informative although they don’t agree with my argument above.


And for journalists who claim Cephalorhynchus hectori is the “smallest” or “rarest”:

  • Smallest marine mammal: the sea otter (Enhydra lutris), up to 45 kg.
  • Smallest cetacean: probably the vaquita (Phocoena sinus), from the Gulf of California, 40–55 kg.
  • Rarest cetacean species: the vaquita again (100–300 left).
  • Rarest other marine mammals: the Hawaiian monk seal (Monachus schauinslandi), 1100 remaining, and the Mediterranean monk seal (Monachus monachus), less than 600.

Mount John Blues

tekapo_small.jpg

I’m here on the top of Mt John, in the Tekapo Valley. The observatory here has scientist accommodation if you’re connected with Canterbury University; the décor is a bit Research Station Cinderblock (a Star Wars poster and a collection of interesting pine cones) but, hey, there’s wireless.

mt_john_map.gifMount John is rather grandly named; it’s more of a a solitary hill rising out of the Mackenzie Basin. You’re ringed by the Southern Alps, and look down on the amazing turquoise waters of Lake Tekapo. The lake and valley are both products of twenty or so glaciations, which scoured out the basin and left Mt John sitting like an increasingly battle-scarred veteran each time they retreated. The surrounding mountains do keep the clouds at bay, and make a good spot for an observatory (which, to my disappointment, consists mostly of people looking at monitors; computers are doing all the stargazing).

But walking round Mt John by day, when the astronomers are asleep, is an experience. Skylarks (Alauda arvenis) are all around, trilling as they ascend from sullen earth to sing hymns at Heaven’s gate, or at least they try when the wind is not howling too forcefully. It’s a bit blowy today, and I watched a surprised lark fly backwards. Supposedly there are chukor (Alectoris chukor) in the tussock, but I had to descend to the larch forest on the southern slope to see any other birds; various finches and grey warblers (Gerygone igata). spaniard.jpg

The vegetation has been sadly rather munted by rabbits and sheep, though pockets of subalpine native plants persist. In the rockfalls are various spiky and twiggy divaricating shrubs, the occasional nibbled-on native broom (Carmichaelia), and golden spaniard (Aciphylla)—even ferns (Blechnum penna-marina), perhaps the last things you’d expect to see on a wind-blasted, sunbaked mountain. I do love spaniard, with its ferocious spines and crazy yellow thatched flower spikes, just daring you to touch it. The spines don’t seem to work too well against mammals, but they almost certainly evolved as a defense against moa browsing, a poke in the eye for Megalapteryx.

This landscape used to be full of totara forest, but now the blasted emptiness of the tussock-clad basin is sublime. You could paint it with a very minimal watercolour kit; the tricky part would be getting the opaque blue of the lake. It’s almost like the blue of the sky at the horizon, perhaps because the fragments of quartz in the water scatter the light the way dust does in the atmosphere.

And you’ll see the mirror image of this if you ever have a chance to visit Mt John overnight: the lights of the lakeside town twinkle for the same reason stars do. As above, so below.

Ducks in the Avon

scaup.jpg When I was growing up in Christchurch, it seemed like the Avon River’s sole purpose was to drain the city’s inherent swampiness and look tidy while so doing. Its banks were kept neatly mowed, lined with willow trees and little else. In the 1990s, the city council changed their policy and began planting native grasses and shrubs along the banks and dialing back the mowing (a big ask for New Zealanders, with our innate ferociousness in the field of lawn care). And in just a few years, two species of native duck have returned to the Avon.

New Zealand scaup, or pāpango (Aythya novaeseelandiae), are little golden-eyed black ducks of classic rubber-duckie shape. They’re divers, happy to suddenly disappear underwater and pop up again ten seconds later. If you read the old guide books, you’ll find that our scaup are the inhabitants of high mountain lakes. Well, they don’t seem to be reading the field guides, because they make up about half the ducks on the Avon, and probably a good chunk of the world’s A. novaeseelandiae are swimming within a few miles of the Cathedral.

paradiseducks.jpgParadise ducks (technically shelducks, since they’re Tadorna variegata) are pūtangitangi in most of the country, and pūtakitaki hereabouts. Weirdly for ducks, the male is duller colored–the female has a white head contrasting with a russet body. You almost always see them in pairs–one, usually the male, keeping a lookout somewhere high. When you approach, they start calling to each other in a wheep-honk-wheep-honk chorus, but in Christchurch they’re used to people. This morning I was out walking and was able to touch one as it sat on a bridge pillar.

Who knows what’ll become common in years to come? Black swans? Shovellers? White herons? Native birds are obviously just waiting for us to meet them halfway. So if you live in a city with a river flowing through it, why not bring your representatives’ attention to an interim report archived here? You too could have scaup on your doorstep.