Hedgehogs Hog Hedgerows in Hebrides

Pudgy, snub-nosed, totally cute and only slightly prickly. Can there possibly be such a thing as too many hedgehogs? Apparently, the answer is yes, at least for small islands like the Hebrides west of Scotland, where hedgehogs only recently arrived.

And yes, this story is filed under climate change because the author traces a possible looming hedgehog bonanza as one nightmarish offshoot of the coming global warming. Now, I don’t normally like to poke fun at global warming alarmists – I mean, what’s alarmist about standing in a burning building and pulling the fire alarm? But he may be stretching things a bit here.

Nevertheless, introduced hedgehogs don’t confine themselves to politely rummaging under privet bushes. On tiny islands like South Uist they barge around like they own the place, cracking shorebird eggs with their little nubbin teeth and sucking out the contents. Their natural predators, foxes and badgers, are absent from the island, so apart from the odd death by recklessly driven Mini or wobbly hedgehog syndrome, there’s no stopping them.

A Journal of Zoology paper by the (aptly named) Digger Jackson estimated about 2,700 adult hedgehogs on the island and found up to 32 per square kilometer in some pastures. Come springtime, all that concentrated adorableness creates quite a bustle in your hedgerow, as adults churn out some 3,000 youngsters each year.

Most young die over the long, harsh North Atlantic winter, rendering the hedgehog population something of an annual crop, like arugula. But the Hebrides have warmed at an average rate of 0.06 degrees C per year over the last 20 years. With milder winters, earlier springs and warm, insect-filled summers, the author reports, hedgehog populations could be on the rise.

Image: hedgehog coffee mug by Judie Peters, on cafepress

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Rats vs. Rotifers on New Zealand Islands

Let rats loose on an island and they don’t just scamper around eating birds’ eggs, a study reports in a recent Ecology Letters. They cut nutrient levels, make the soil nearly 100 times less acidic, and topple populations of six out of eight kinds of – well, let’s call them creepy crawlies (springtails, rotifers, nematodes, snails, and so on).

It’s called a trophic cascade – the domino effect of the ecological world. And in this case, rats seem to have pushed against the sort of domino that sets several new rows falling.

The rats weren’t scarfing down tiny soil organisms themselves, or leaching nutrients through some ingenious filtration scheme. All they had to do was drive away the seabirds – graceful, wave-trotting shearwaters and the like – that nest here precisely because there are no predators around.

The study team, led by Tadashi Fukami and composed of scientists from New Zealand, Hawai’i, Alaska and Sweden, chose 18 very similar hunks of rock off northern New Zealand. Rats had jumped ship onto nine of these islands between 50 and 100 years ago. The other nine islands had no rats – and 24 times the number of seabird burrows.

Nitrogen isotopes measured in soil and plant leaves revealed the signature of marine nutrients on the rat-free, guano-splattered islands. Guano splattering is a good thing: carbon, nitrogen and phosphorus levels were at least 45% higher on the rat-free islands. When researchers grew plants in the same greenhouse using soil taken from each of the islands, plants growing in rat-free soil grew to 40% heavier.

Rats did seem to encourage plant growth, with bigger trees, more seedlings and more leaf litter found on invaded islands. The authors suggest that on the other islands, the seedlings may have been kept down by “seabird trampling,” a wonderful thing to imagine.

We live in a world where everything we see runs downstream. So it’s easy to understand problems caused by runoff (dead zones, for example). It’s less straightforward, but more fascinating, to learn of the various ecological rivulets that carry nutrients back up onto land.

In recent years, researchers have found the marine signatures of salmon flesh in Alaskan forests and pollutants concentrating at the feet of nest-cliffs in the otherwise pristine Arctic. Add this study to the list – a neat demonstration of both the seabirds’ ocean-harvesting ability and the shockingly simple way the system can be dismantled.

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Take the First Annual Scribble Readers’ Poll!

Maybe the occasional Scribble Reader has wondered just who in the heck this Scribbler is. But let me tell you, that ain’t nothin’ compared to how much I wonder who the heck you guys are.

But that’s the beauty of Web 2.0, ain’t it? No more agonizing over the wording of your letter to the editor of Omni Magazine in the hopes of seeing your name in print. Just hit the Comments button and fire away.

So here’s your chance to do some scribbling of your own and fill me in on one or more of the following 15 pressing questions:

1. How did you get here? (no need to get cosmic on this one)

2. Have you visited this site before?

3. Are you just here for the baby turtles? (you would not believe how many people search the Internet each day for baby turtles)

4. What kind of posts do you like the best? (a) ocean science (b) climate change (c) birding (d) surfing (e) other?

5. Are the posts (a) about right or (b) too damn long?

6. Would you like more coverage of (a) climate change (b) islands being devastated by rats (c) weird deep-sea creatures (d) earthquake-type stuff (e) celebrity feuds and/or adoptions (f) sex (g) atmospheric physics (h) other (please specify)?

7. How educated are you: (a) made it out of high school; curious about the world (b) still interested in most things (B.S.) (c) able to detect the infantile flaws in some stories; peripherally interested in all the rest (M.S.) (c) basically humoring me (Ph.D.)?

8. Do you wish the words I use were (a) longer (b) shorter (c) funnier (d) snarkier (e) less stupid (f) rhyming?

9. Do you occasionally wonder what possesses me to spend an hour or so writing about such obscure topics?

10. More pictures? (Of what?)

11. Are you not leaving comments because (a) the posts arrive fully formed and inviolable (b) you never make it to the end of a post (c) it’s interesting, just not that interesting (d) try writing about something that matters (e) you have a lingering feeling that even though only a tiny fraction of the world’s population will ever look at a comments page, you might come off sounding stupid and someone, somewhere, might snicker at you from the lonely confines of their poorly lit hovel

12. If scientists were to turn their collective intellectual power toward designing one and only one robot animal, what animal should that be?

13. I am an heir/heiress and I would like to contribute ___ million dollars to further the Scribbler agenda

14. Do I know you? How?

15. Setting aside the surfing and the birding for a moment, if there was one thing in the world you’d like me to write about, what would it be?

I’m really not kidding about this. Answer as much or as little as you see fit. Post a comment – or – if you don’t feel like going totally public – send aphriza at gmail dot com an e-mail. Thanks for reading.

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Scribble Updates

 
News roundup, starting with sort of a “Where are they now?” for past Scribble posts:

The Alfred Wegener Institute’s ship Polarstern is back in port after riding along to the scene of the collapse (of the Larsen B ice shelf). Scattered along a seafloor uncovered for the first time in perhaps 12 millennia, the researchers found lots of new, if smallish, species, including an unassuming invertebrate with a towering name: Shackletonia (pictured).

Those Japanese scientists who found (Captain) Nemo (i.e., videotaped a live giant squid for the first time) have already been upstaged. After “giant,” the next squid size up is the improbably named and even rarer “colossal” squid. A team fishing Antarctica for Patagonian toothfish pulled up a colossal squid weighing half a ton. News reports delicately avoided mentioning that Patagonian toothfish is the same thing as the overfished and bottom-trawled Chilean seabass, so popular at upscale though clueless restaurants.

The Society for Conservation Biology keeps an eye out for cool science headlines on their new blog Journal Watch. Among recent offerings, eradicating rats from Ohinau, off New Zealand, let geckos bounce back much faster than researchers expected. Another reason to ask for your island without so much rat in it.

The folks at RealClimate found this funny site: cheatneutral. Their premise: If you just can’t stay faithful, now you can pay someone to be faithful for you while you keep on producing infidelity at an industrial clip. They’re hoping putting the problem this way will change your attitude about buying and selling carbon offsets.

My sister, Sophie, recently went to see an amusing display of dodo art by Harri Kallio. Slate, always one step behind the avant garde (here represented by my sister), has now written about the work and posted a slideshow. Check it out. Dodos may be dead, but they’re adorable in a hopeless sort of way.

The practice of DNA barcoding – or sequencing anything with a mitochondrion – is turning up new species faster than you can say “phylogenetic species concept.” Recent results suggest 15 new species of birds are hiding in plain sight – there may be more species of commonplaces like ravens and chickadees than we ever suspected. This story has been covered in several venues, but Scientific American gets a mention here for the sheer hopelessness and complacency of their coverage. They misspell the name of the gene under study (that’s “oxidase” with an “i”, folks) and then announce that “Some fish differ by just one arrangement of the various amino acids in the DNA….” That’s a train-wreck of an error, as most high-school science-fair participants could tell you. DNA uses bases to code messenger RNA to tell ribosomes to assemble amino acids into proteins. For a magazine that charges you six bucks a copy to read stories written to be as stuffy as possible, that’s inexcusable.

Icing on the cake? The article never actually tells us what the 15 new species are. C’mon folks, there’s a public out there that we’re supposed to be informing. Grrr.

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Mammals 2, Birds 0

Two regrettable recent stories, each with mammals in the villain’s role: The humble mouse terrorizes seabird populations on a remote island; and Dutch shorebirds abandon a marine reserve because of shellfish dredging.

In far and away the more macabre story, on tiny Gough Island in the South Atlantic, thousands of endemic albatrosses and hundreds of thousands of petrels are being gnawed to death by house mice run out of control. Sorry if it sounds like TV news hyperbole – it isn’t.

After escaping onto the island from fishing boats a century ago, the mice have bulked up to twice their normal body size and surged to an estimated 700,000 strong on the island (that’s about half again as dense as people in San Francisco). Through constant, aimless nibbling, one imagines, they learned that the docile chicks around them were full of protein and fat.

The knee-high, 20-pound chicks, for their part, remain flummoxed, never in their evolutionary past having dealt with mammalian predators attacking from below. Scientists estimate the carnage at more than 700,000 chicks each year. New Scientist has the story, which hit the South African newspapers as well. (thanks Charles)

Some 6,500 miles to the north, in Holland’s Wadden Sea, even good intentions lead to bad news. Resource managers tried to allow shellfish dredging on the same mud flats where half of Europe’s red knots (see picture) feed for – you guessed it – shellfish.

The science of the study is ferociously good. The authors sampled shellfish availability in 2,800 different locations in each of five years. They traipsed across those same mud flats scraping up red-knot droppings to analyze what they’d been eating. They captured the birds and put bands on their legs to track their yearly survival – and while they were at it they even measured the birds’ gizzards with an ultrasound, for crying out loud. (Knots swallow mussels whole, then crunch up the shells in their gizzards to get to the flesh.)

Dredging didn’t reduce shellfish numbers appreciably, but it did hurt their quality as knot food – more shell and less flesh. Analysis showed that unless a knot could expand its gizzard capacity during the season, it likely could not eat enough food to meet its energy requirements. The result, the scientists calculated, was 58,000 knot deaths over five years, and the departure for parts unknown of four out of every five knots that used to frequent the Wadden Sea.

The good news is that the Dutch government halted dredging in 2004. But the bad news is not just bad for shorebirds. It’s bad news for conservation, because one of the encouraging selling points of marine protected areas is the idea that we can balance resource extraction (and jobs) with habitat protection. This study adds to the evidence that it’s simply harder than that.

(from PLoS Biology: news story and research article; image: Varnamo bird club)

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Rabbits make life hell for penguins, seabirds

The World Wildlife Fund warns that a population explosion of rabbits is threatening a remote Australian island’s seabird populations. That’s right, rabbits. We Americans think of them as cute, harmless long-eared friends that occasionally lay chocolate eggs or hybridize with antelopes. But in That Other Hemisphere, they are threatening a 4-million-strong seabird colony using little more than those sinister buck teeth.

Seal hunters introduced rabbits to Macquarie Island around 1880 (presumably because they were tired of eating seal). By 1960, scientists were calling rabbit grazing “catastrophic” in the Journal of Ecology and warning that if left unchecked, the rabbits could chew their way to major landslides. That’s because the dominant grasses had roots strong enough to collect several feet of peaty soil and hold it in place on steep slopes. Once those roots died, the scientists warned, the soil would slip.

Rabbit numbers had reached about 10,000 by the 1980s, and there was nowhere to go but up. Macquarie reached the 100,000-rabbits mark in recent years. And now, the World Wildlife Fund and Reuters report, the land has started to slip – 20 slides in the last month. Right down onto the nests of thousands of breeding albatrosses, petrels, and royal penguins, not to mention about 100,000 momma and baby seals.

The Australians are suitably concerned — one researcher has called for a $10 million rabbit-riddance campaign (large vacuum cleaner, perhaps?). But it’s interesting that even in the 1960 article, the authors noted that once the grass dies and slips begin, they will be hard to stop.

It’s a familiar arc – a population starts small on an idyllic patch of ground, uses God-given gifts (in this case, excellent nibbling skills) to get ahead, slowly goes from thriving to burgeoning, and eats up all its surroundings. At which point the island falls in on itself, chucking the rabbits into the cold Southern Ocean along with most of the other species that live alongside it. Sound like anyone you know?

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I’d like a small island without so much rat in it

Invasive species are a major problem in our modern world. That’s because we’re generally happy with the way things are and less happy when some vagabonding drabcoat like a starling or a wild pig or even a smallish purple thistle moves in and starts carpeting the place. Also, frequently enough, the invaders got a lift over from us, and so we feel a lingering sense of guilt over the whole fiasco, at least those of us who haven’t made pots of money off not worrying about it.

And so it has gone with pigs, goats, cane toads, zebra mussels, nutria, rabbits, eucalyptus, kudzu, privet, tamarisk, all manner of ballast-water hitchhikers, brown tree snakes, lake trout, fire ants, house finches, leafy spurge, scotch broom, big jellyfish, uncomfortably large sea urchins. There’s even evidence we were carting fruit bats from island to island nearly a thousand years ago, for God’s sake.

And then of course there’s the original: the rat. The consummate invader has made mincemeat of island oddities ever since the first one dragged its creepy hairless tail off a sailing ship and started infiltrating nests of helpless birds (like the flightless kakapo, a New Zealand parrot the size of a toddler).

But today’s post isn’t about bad news. It isn’t about scurrilous rats with their insatiable appetite, their lust for expansion, their pyramid schemes and gleaming steel shrines to capitalism. It’s about community, faith, and grit. A small band of determined locals. And a shearwater.

Wedge-tailed shearwaters nest, among other places, on a 3-acre scrap of lava off O’ahu, Hawai’i, called Mokoli’i Island, in burrows that they somehow etch into the rocky soil. Unfortunately, rats have burrows pretty well figured out, and in the years 1999-2001 exactly one shearwater fledged from all the nests on the entire island.

Some University of Hawai’i researchers enlisted the help of concerned locals and started an e-rat-ication campaign in earnest. By May 2002, the team had scattered 354 blocks of poisoned bait, captured 18 rats, and could find no lingering ratty traces on Mokoli’i.

That same year the island’s shearwaters produced 126 young. For those of you who are impressed by large percentages, that’s a 37,800 percent increase (over the previous annual rate of 1/3 of a shearwater per year). The next year the tally went up another 50%, to 185. The researchers also noted, though a bit less scientifically, a definite increase in tidepool animals, native plants, and an endangered grass after the rats were removed.

There you are, some good news for a change. Now, if we could just get the rats out of the other 33.3442 billion acres (not counting Antarctica) of land on the planet.

Images: thanks to the University of Hawaii’s Project Ant (a whole other story in itself) and the USGS… and in other shearwater news: last week we found out that the sooty shearwater flies 40,000 miles in a lazy figure-8 around the Pacific every year, the longest animal migration yet documented.

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Urchins uber abalone

Climate change is being felt in and around Tasmania, reports the Hobart Mercury. Among the noticeable effects, ocean temperatures along Tazzie’s east coast have warmed by a full degree Centigrade since 1940. A report commissioned by the Australian Greens party warns of impending damage to Tasmania’s fisheries and agriculture, including its Atlantic salmon farms (not that farmed Atlantic salmon is a good thing, you understand – just search Google on the topic.)

Already, the warmer water temperatures have been blamed for the arrival of the long-spined sea urchin. Scads of these invasive aquatic pincushions have moved into the (not quite so) cold waters and laid waste to the $150 million (Australian) abalone fishery. Interestingly, the long-spined sea urchin’s southern range extent, until recently, was around Sydney. That’s ABOUT 500 MILES NORTH of Tasmania.
And this news hits me fresh off a showing of An Inconvenient Truth, where Al Gore fingers climate change as a disruptive agent that allows species to become invasive. And I thought he was stretching the point at the time.

Once again, the photo above is not the real long-spined sea urchin – to see one of these basketball-sized specimens click the urchin link above. My image comes, once again, from the NOAA Photo Library. Thanks, NOAA!

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What’s next? Jellyfish and chips?

A swath of Namibian waters favored by fishing fleets seems to have been taken over by jellyfish – big ones, and lots of them. A new scientific survey found more than four times as much jellyfish (by mass) than fish in a 30,000 square mile stretch of once-prime fishing grounds. And 99% of the jellyfish sample was made up Aequorea forskalea, a once-rare whopper that can be a foot or more across and weigh as much as a wet chihuahua.

 

Now, I’m just as enthralled by jellies’ strange beauty as the next envious landlubber. But the sudden appearance of prizewinning jellies in Namibian waters seems to have come at the expense of fish stocks – perhaps even as a price of overfishing.

The Benguela current nourishes the Namibian waters with strong upwelling that brings nutrients to the surface and kick-starts binges of productivity by phytoplankton. That starts off a feeding frenzy among all the little copepods and other zooplankton, and the party continues all the way up the food chain until, in normal circumstances, you end up with shimmering schools of fat, happy mackerel, hake, and herring. (Kathleen Wong has a nice article on upwelling in the new Bay Nature.)

Overfishing subtracts, via nets wriggling with fish, a big, visible piece of this scenario. But it adds something too: scads of choice prey in the form of uneaten copepods, larvae and small fish. Enter the jellies. You can almost see them smiling and rubbing their tentacles together.

Research cruises in the 1950s rarely reported large jellies, as Christopher Lynam (Ph.D. student, University of St. Andrews, UK) and his coauthors note in this week’s Current Biology paper. Now, an estimated 12 million metric tons in the authors’ study area are clogging power plant intake pipes, covering fish catches with a layer of stinging slime, and even fouling diamond mining equipment.

The authors suggest a more worrying possibility, too. With scores of jellyfish eating fish food as well as fish larvae, the depleted stocks of market fish may not soon get the chance to rebuild their numbers. I suppose we can only wait and see. And start working on beer batter that makes jelly-guts taste good.

Photo disclaimer: Not being able to run over to Namibia to snap a picture of A. forskalea, I used a stand-in jelly. It’s a purple-striped jelly photographed in Monterey Bay National Marine Sanctuary. From the NOAA Photo Library.

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