Monday, 9 September 2013

Tian Tian, maybe definitely not

It is now virtually certain that Tian Tian, the female giant panda at Edinburgh Zoo, is no longer pregnant.

Following artificial insemination in April, the zoo has been tracking Tian Tian’s hormone levels. The one to watch is progesterone. At around the time of ovulation, there is a small rise, with levels remaining roughly constant for several months. At this stage, the embryo is fertilized but is not developing. Then, some 60 to 100 days later, progesterone levels jump again from around 250 ng to 2500 ng (per gram of faeces) and the embryo begins to divide. In a press release, tantalizing entitled “Panda update: definitely maybe!”, Edinburgh Zoo told us that this second rise occurred on 15 July.

According to the latest study of pandas whose pregnancies went to term, a female will give birth, on average, 38.8 days later. There is a large variation though, with the swiftest female giving birth just 26 days after the jump in progesterone and the slowest  female 55 days after. If Tian Tian were on the pacey side, she’d have dropped a month ago on 10 August. Even if she were more ponderous, she’d have given birth by now. She has not.

On Friday, Edinburgh Zoo’s chief executive issued a blog post that talked of “a flurry of new births” but made no mention – not even in passing – of Tian Tian’s pregnancy. Today, after much badgering, the zoo finally issued a brief update, saying that “we’re not out of the game." It goes on: 

We are continually analysing hormone and protein samples and, based on the latest results, our external experts now believe Tian Tian may have experienced her secondary progesterone spike two weeks later than the results previously available suggested.
I’m a journalist not a panda biologist, but looking at the graphs of what progesterone does in a pregnant panda, it is somewhat baffling that the zoo could have mis-identified such a massive change in progesterone. They do say that “Tian Tian is a panda whose behaviour and physiology appears to be more complicated than most!”

I suppose it’s possible that she’s still pregnant. Or, more likely I’m afraid, she’s not.

Monday, 19 November 2012

Lonesome George has relatives

Lonesome George might be have passed away but he’s still making the news. Less than six months after his death, with his carapace still interred in a Galapagos freezer, it appears he may not have been the last of his kind after all. There is now clear evidence of giant tortoises with Pinta ancestry on another island in the archipelago.

In a forthcoming study, geneticists from Yale University identify 17 hybrid tortoises with various combinations of Pinta genes on the nearby island of Isabela.

The existence of these Pinta-like tortoises came to light by chance when an initial sample of 27 tortoises from Isabela’s northernmost volcano Wolf turned up a youthful male with some unusual genes. This animal – officially dubbed PBR03 –appeared to be a first generation hybrid between a full-blown Pinta male and an Isabela female. "Lonesome George is not alone among Galapagos tortoises", the geneticists reported in Current Biology back in 2007.

Since then, they have worked hard to expand on this initial finding. Within a couple of years, they were able to return to Isabela, the Galapagos National Park mounting a huge expedition to extract blood from as many of Wolf Volcano’s tortoises as possible. The geneticists came away with samples from more than 1660 tortoises.

Earlier this year,
the Yale team demonstrated that some of these tortoises had signs of Floreana ancestry, another species thought to have disappeared in the mid-19th century. In Table S1, buried in the supplemental information for the paper, they reported a cluster of seven tortoises with a strong affinity to the Pinta species.

The forthcoming paper, due to be published in Biological Conservation, extends this number to 17 individuals. Four of these look like they are first generation hybrids (F1), with one or other of their parents being of full Pinta stock. The rest seem to be second-generation (F2) hybrids. Several of the Pinta-like tortoises appear to be siblings, which seems reasonable for a species that lays clutches of up to 20 eggs at a time.

Given that the sampling may only have captured around 1/5th of the tortoises roaming on Wolf Voclano’s inhospitable flanks, the geneticists extrapolate to estimate there could be some 60 to 70 Chelonoidis abingdoni hybrids yet to be discovered. As five of the 17 tortoises are juveniles less than 20-years-old, it is also possible that there is still a purebred Pinta tortoise out there and breeding. If there are, however, the geneticists have not yet stumbled upon them.

The hybrids they have come across are only known from their blood. The actual animals still roam free. But there is a plan afoot to go and get them.
“Our goal is to go back this spring to look for surviving individuals of this species and to collect hybrids,” says Adalgisa “Gisella” Caccone, senior author on the study, in a Yale University press release. “We hope that with a selective breeding program, we can reintroduce this tortoise species to its native home.”

Interestingly, the 17 hybrids are not randomly distributed but are most concentrated on the southwestern flanks of the volcano. The proximity of this location to Bank’s Cove – a popular watering hole for whalers and sealers – leads the authors to speculate that humans were responsible for the introduction of Pinta tortoises to Isabela some time during the last few centuries.

As incredible as this sounds, the alternative - that the tortoises got there by natural means - is less likely still. Although the islands are just 37 miles apart, any tortoise entering the sea from Pinta would be carried away from Isabela on prevailing northwesterly currents. Even if, by some freak means, a tortoise had floated southwest from Pinta to Isabela, its descendants would be located on the northern and not southwestern side of the volcano.  

This important map should help the Galapagos National Park and Yale University geneticists as they attempt to relocate these hybrids for the purposes of captive breeding. I'd have liked to have seen George nonplus these relatives. That would have been entirely in keeping with his character. With his death on 24 June this year, this is a reunion that sadly can not take place.

Thursday, 28 June 2012

Lonesome George and the late Lord Devon’s helmet

On Monday, when news of Lonesome George’s death began to reach editors around the world, I was asked to write his obituary for the Guardian. As I had already sent in one to Nature, they sensibly got the very excellent John Vidal to do it instead.

John’s done a pretty good job and he generously cites my book Lonesome George: The Life and Loves of a Conservation Icon. I was, however, very puzzled to read that I’d reported that “George was irresistibly attracted to the late Lord Devon's wartime helmet, presumably because it resembled the shell of a young tortoise.” I’ve never reported anything of the sort.

What I think has happened here is that in researching his piece Vidal came across a rather lovely article about Lonesome George and my book that appeared in the Daily Mail in 2007. It is particularly nice because it’s by Rory Knight Bruce, who declares his interest in tortoises as the author of Timothy The Tortoise: The Remarkable Story Of The Nation's Oldest Pet. His book, Bruce explains, “recounts the life and times of the tortoise who lived at Powderham Castle, the family seat of the Earls of Devon, until his death in 2004 at the grand old age of 164.” The Daily Mail article draws on the similarities between the reptilian subjects of our respective testudinate biographies and his last sentence notes that Timothy, like George, did not mate “unless you accept his attempts to mount the late Lord Devon's wartime helmet.”

I understand that this kind of mistake is inevitable in a busy news room, though I am a little puzzled Vidal was not himself more puzzled that the late Lord Devon's helmet should have found its way over to Galapagos and into Lonesome George's enclosure. I thought about emailing the Guardian to get it corrected. Then I thought it’s such an irrelevant detail I wouldn’t bother. But here’s what happens in the internet age if you don’t get stuff like this put right. It gets picked up, replicated and in the replication acquires a new life, gravitas and authority.

I think I'd better let the Guardian know. 

Tuesday, 26 June 2012

The death of Lonesome George

Lonesome George as he was when I visited Galapagos in 2003.

A team of vets, technicians and scientists has just carried out an autopsy on Lonesome George's cold corpse. The early signs, according to a press release just issued by the Galapagos National Park, are that he suffered a cardiac arrest some time on Sunday morning. His posture suggests he was walking. 

I am guessing that the postmortem will not tell us much more about the cause of death. In all of the thousands of news stories that have covered Lonesome George's passing, including in a short obituary I wrote for the Nature blog, you'll read that George was thought to be around 100 years old. But I now think he was a lot older than this and had simply come to the end of a long and rather peculiar life. 

When I wrote my book on Lonesome George, I wondered whether it was possible to study the growth of a tortoise's shell and work out its age in much the same way as one does with the rings of a tree. I'm clearly not alone in imagining this might be possible, as Simon Levey made a similar suggestion to me after the ABSW awards at the Royal Society last night. I discovered that it is possible to ring-age a tortoise but only when it's very young. Once it's adult, which for giant tortoises is at around 30, the shell stops growing so there are no more rings. When George was discovered in December 1971 he was already an adult so we know he was 30 or more. But tortoise experts, looking at his relatively unblemished, moss-free shell figured he was still young, perhaps only 50 or 60. Adding on the 40 years that have passed since then, brings him to 90 or 100. 

Pinta tortoise at the Natural History Museum in London.

It sounds plausible and I went with this in my book. But I've always had a niggling concern about it. In museums around the world there are probably a dozen specimens of the Pinta tortoise, the type specimens at the Natural History Museum in London, a few more at Tring, several at the Smithsonian in Washington D.C. and three at the California Academy of Sciences in San Francisco. All of these are males, with the exception of one specimen collected in 1901 that is either a juvenile or a female. In 2003, an expedition to Pinta organized by the Galapagos National Park carried out an extremely thorough search for tortoises. They found 15, or more properly their bleached bones and weathered scutes, which was all that remained of them. Again, all but one was male. The small pelvis of specimen 14 (which together with a limb bone was all that was left) suggests it belonged to a female. Perhaps this was Lonesome George's mother and she laid her last clutch in around 1910. 

But perhaps not. There were so few, if any, females on Pinta in the 20th century, that it seems more likely to me that the last clutch - the one from which the young George emerged - was laid much earlier and George just took good care of his shell. If, for the sake of a simple sum, George hatched out in 1862, he'd have been 110 when he was captured and transferred to Santa Cruz in 1972 and 150 when he died on Sunday. Not only would this scenario help explain his death, as 150 is about as old as the oldest giant tortoise we know of, but might also account for his reticence to reproduce. We know nothing about the mating habits of senior tortoises. Perhaps they just don't do it. 

Whatever the postmortem reveals, the Galapagos National Park is clearly aware of Lonesome George's special role as communicator extraordinaire. According to the press release, he is going to be "embalmed" and put on show "so that future generations know him" in a new center named that will carry his name. Perhaps someone took note of the closing remarks of my book:

...there’s no reason why Lonesome George should not outlive us all, acting as a focus for Galápagos conservation for generations to come. I hope so. I like the thought that when my son grows up, I will take him to the Galápagos and introduce him to George.

It all depends on what happens in the archipelago in the next few years. The pace of social change is alarming and does not bode well for the future of the islands’ unique suite of species. Let’s hope the Special Law can tame the population expansion. Tourism in the Galápagos Islands currently generates at least $150 million a year. If more of this can be fed back into a sustainable future, then yes my son may yet see the same pristine, enchanting world I saw. That Darwin saw.

One day, of course, George will give up the tortoise ghost. Even then, he will be of immense value to the Galápagos. His remains should not be taken back to his native island. Nor should they be flown to Quito to act as a centrepiece in the Museo Ecuatoriano de Ciencias Naturales. Lonesome George must remain in the archipelago, at the research station on Santa Cruz. By then, this is where he will have spent most of his life; this is the place that Lonesome George would call home.

Even in death, it is here that he will have his greatest audience. I, for one, would like to see him again – alive or dead. I feel I’m just about getting to know this tortoise, and I like him.

Whilst I'm sorry of course that my son will never have the chance to see George in life, I am pleased the Galapagos National Park is thinking of ways to keep his powerful narrative alive. I am, however, a little concerned about this talk of embalming. I am guessing that many Europeans and North Americans (who make up a significant proportion of visitors to Galapagos) will find the idea of stuffing George all very 20th century and more than a little distasteful. Such was the case for other celebrity animals, like Guy the Gorilla (stuffed, after much controversy, in 1982) and Ham the Astrochimp (not stuffed but given a full-blown funeral, burial and headstone). As you can see from the photograph above, taxidermy is not a great look for a giant tortoise.

More powerful, I think, would be Lonesome George's shell on a plinth. Empty. 

Wednesday, 30 May 2012

The dance of the three-footed rhino

The rhinoceros stands on three legs. Her fourth – the front left – is shorter than the rest by an unlucky 13 cm and ends in a constricted knot of skin and bone. In a perfectly executed maneuver that incongruously brings a ballerina to mind, she shuffles her three good feet, as if on tip-toe, to a single point beneath her hefty frame. Her damaged limb begins to oscillate, looking more like a trunk as it swings backwards then forwards. Suddenly, and unexpectedly, she throws it upwards and her front limbs are cycling in the air. For a slow-motion instant, before her good foot hits the ground again, I see a rhino standing on two legs.

This is Puntung, a diminutive Sumatran rhinoceros who has come to embody the plight of her species. Like other animal ambassadors, she has plenty of charisma, but it’s her physical handicap, not to mention her severely damaged uterus, that make her such a potent symbol of how desperate things have now become. As she moves with awkward grace around her barred enclosure, a team of veterinary specialists draped in medical green is setting up a stall of anesthetics, probes, endoscopes and laptops on a series of rickety tables. If Puntung is to reproduce she will certainly need their help.

At the end of March, I flew out to Malaysian Borneo to report for Nature on the extraordinary efforts being made to get Puntung into reproductive condition. Officially, there are just 35-37 rhinos left in this part of the species’ range. There are probably more animals still surviving on Sumatra, but the species is still heading fast towards extinction.

Conservationists often talk about imminent extinction. Indeed, we are so used to it, I wonder if we have started to ignore these warnings. Puntung’s story - and the significant financial and emotional investment in her future - is a tragic illustration of what happens when we do so. It was a huge privilege to meet all those involved in this effort and to meet Puntung herself. If somehow they do manage to get her to reproduce, I will want to go back to see her again and to meet her calf. I suspect, however, this is unlikely to happen.
Look out for my feature, which will go online on the Nature News site this evening and appear in the print edition tomorrow. I also made a video of my trip, which you’ll find embedded into the online version and on the NatureVideoChannel.

Friday, 13 January 2012

Extinct Galapagos torotise has just been hiding

A species of Galapagos tortoise – thought to be extinct for over 150 years – may, in fact, be alive and well. This finding – made by geneticists at Yale University– is particularly surprising when you consider that this reptile is of giant proportions, measuring more than a metre from the front to the back of its shell and weighing more than 200 kg. How could such a behemoth have gone unnoticed for so long?

The answer, it turns out, is simple. They’ve been hiding. When Charles Darwin visited the Galapagos Island of Floreana in 1835, he found no sign of its native tortoise and assumed that whalers, pirates and human settlers had done them over. Since about 1850, there has never been a tortoise on the Island (bar one or two introduced animals kept as pets by the locals). It makes sense, therefore, that the IUCN should classify the Floreana tortoise Chelonoidis elephantopus (sometimes also Chelonoidis nigra nigra) as extinct.

A direct descendant of Chelonoidis elephantopus, alive and well on Isabela. Courtesy of Yale University

But the Yale geneticists now have good evidence that some purebred Floreana tortoises may still be alive on a different Island in the archipelago. For more than a decade, the researchers have been absorbed by the bizarre mixture of genes found in the tortoises on Wolf Volcano at the northern tip of Isabela, the largest Island in the volcanic chain. They began by studying mitochondrial sequences, which suggested that tortoises from the distant islands of San Cristobal and Espanola has somehow reached Wolf. Their guess was – and still is – that whalers and pirates were responsible. “Tortoises were occasionally stashed on various islands for safe-keeping and even tossed overboard in large numbers in nearshore areas to lighten cargo during flight or battle,” they wrote in 2002.

When I wrote my Galapagos book Lonesome George, I was fascinated by this possibility and looked hard for some first-hand evidence of such an introduction near Wolf volcano. I found it in the diaries of Captain David Porter, skipper of the infamous US frigate Essex that ruled Galapagos waters during the war of 1812.

David Porter, captain of the USS Essex
USS Essex in full sail

On 29 April 1813, with no wind to give chase, Porter sent several little boats out filled with armed men to capture the British ships Georgiana and Policy. What follows is lifted from my book:

Those on board the Georgiana and Policy were taken by surprise. If the rowing boats reached them, they would have to fight at close quarters and casualties could be heavy. With no wind, there was no escape. Their only hope was to blast the small boats out of the water. They were woefully unprepared, particularly as they had just stocked up on tortoises, which were getting in the way. ‘In clearing their decks for action, they [threw] overboard several hundred Galápagos terrapins’, wrote 12-year-old Essex midshipman David Farragut in his diary. Farragut was in one of the rowing boats closing on the Georgiana:

The appearance of these [land] turtles in the water was very singular; they floated as light as corks, stretching their long necks as high as possible, for fear of drowning. They were the first we had ever seen, and excited much curiosity as we pushed them aside.

As Farragut and his fellow men picked their way through a sea of giant tortoises, the cannon fire began. Back on the Essex at a safe distance, Porter looked on: ‘At two o’clock, the boats were about a mile from the vessels ... when they hoisted English colours, and fired several guns. The boats now formed in one division, and pulled for the largest ship, which, as they approached, kept her guns trained on them.’ None of the canons hit their mark. The boats ‘rowed up beneath the muzzles of the guns and took their stations for attacking the first ship’, Porter explained in a letter back to his superiors in Washington. The British struck their flag and stood down without a shot being fired. They then left a crew on board and took their stations for attacking the other vessel, the Policy; her flag was also struck.

‘Thus were two fine British ships ... surrendered, without the slightest resistance, to seven small open boats, with fifty men, armed only with muskets, pistols, boarding-axes and cutlasses!’ Porter boasted ‘that Britons have either learned to respect the courage of the Americans, or they are not so courageous themselves as they would wish us believe’.

As dawn broke a couple of days later, the Essex with her three prizes in tow was surrounded by about 50 live giant tortoises. They were rounded up and brought on board. According to Porter’s journal, ‘they had been lying in the same place where they had been thrown over, incapable of any exertion in that element, except that of stretching out their long necks’. He and his crew ate these tortoises in the coming months, but presumably some of those jettisoned by the embattled British ships were never recaptured. One or two, perhaps, made it to the nearest shore. We know from Porter’s letter to Washington that this would have been the northwest coast of Isabela, from which a beached tortoise could have made it to either Puerto Blanco or Puerto Bravo.
Here's David Farragut, presumably a little later in his career

It would be great to know where the Georgiana and Policy had been before they were captured, as this would give us the identity of the tortoise species they had on board. I never succeeded in locating their logbooks, which would have given this information but wouldn’t it be rather neat if they’d just come from Floreana carrying some of its last tortoises to a new life on Isabela? If anyone knows of the whereabouts of these logbooks – presumably captured by Porter and taken to the US along with the British vessels themselves – please, please let me know.

Anyway, back to the study on tortoises with which I began this post. With technological advances over the last decade and the tumbling cost of sequencing, so the Yale researchers have been able to mine the Wolf tortoise DNA in ever-greater depths. In 2007, they found evidence that this volcano might be harbouring close relatives of Lonesome George – the famed solitary survivor of the Pinta tortoise species. Using ancient DNA from museum-based specimens, they were also able to characterize the genetic signature of the Floreana tortoise and show that some Wolf tortoises have clear signs of this ancestry.

This latest study, published this week in Current Biology, takes this a step further by sampling a massive 1669 giant tortoises from Wolf, estimated to 20% of the volcano’s population. In amongst these, they have found 84 tortoises that have to have had a purebred C. elephantopus as one of their parents. They estimate that at least 38 founders would have been needed to leave the genetic footprint observed. Although most of these will have died out, it’s known that giant tortoises can live for more than 150 years and there’s a good chance there are still purebred Floreana tortoises out there.

The trouble is finding them. In 2008, it took a combined team of geneticists and rangers from the Galapagos National Park – some 40 people! – around 11 days of hard graft to sample 1/5th of the Wolf population. If purebred Floreana tortoises are still on the volcano, they are likely to be in very low numbers, says Ryan Garrick, Yale postdoc, now assistant professor at the University of Mississippi and lead author on the paper. “We would have to be very lucky to directly sample one of them.” Even if they can’t, however, their hybrid descendants could still be useful. "Hybrids may provide opportunities to resuscitate an 'extinct' species through intensive targeted breeding efforts,” he says.

It would certainly be of interest to those conservationists involved in Project Floreana, a huge initiative to put the island on a new, sustainable course, eradicating invasive species like cats and rats, restoring lost natives like the critically endangered Floreana mockingbird and bringing the island’s human residents on side. Wouldn't it be great to be able to include bona fide Floreana tortoises rather than just some stand-in surrogate?

The snag is that locating hybrid tortoises on Isabela’s Wolf volcano, transporting them to captivity and finding money to fund a back-crossing breeding programme over several decades would be seriously expensive. With Galapagos facing a multitude of pressures, not least from indirect impact that 30,000 residents and 170,000 annual visitors have on such a fragile place, is restoring the Floreana tortoise a priority? Or is it a luxury the cash-strapped conservation movement can ill afford?

This post is based on an article published on the Nature News blog on 9 January 2012.

Friday, 2 December 2011

A black and white Christmas

The pandas are coming!” announced Edinburgh Zoo’s press office on Monday morning. The reason, I discovered, was not to proclaim the transfer of seminal fluid from male to female panda (cause for celebration as that might be), but because the Royal Zoological Society of Scotland (RZSS) finally has a date set for the long-awaited arrival of a pair of giant pandas. When the FedEx Panda Express touches down in Edinburgh on Sunday, Tian-Tian and Yang-Guang will be the first giant pandas to set foot in Britain for 17 years.

Is this Tian Tian? It's a female I photographed in 2010 at Bifengxia. Copyright Henry Nicholls
I’ve thought a lot – probably too much – about giant pandas. In 2010, I published The Way of the Panda, a popular science-cum-history book that lays out the intertwined fortunes of giant pandas and modern China as they made their respective ways towards zoological and economic world domination. In it, I reached the conclusion that captive pandas are deceptive beasts, having more in common with the cuddly toys, the abstracted WWF logo or dressed-up darlings of many-a-successful advertising campaign than with the real, wild pandas that eke out a living in the dwindling bamboo forests of China.

The Edinburgh pandas illustrate this perfectly. When China’s vice premier Li Keqiang and Britain’s deputy prime minister Nick Clegg signed off on the panda deal in January, the pandas were the subject of widespread up-beat news coverage. But within weeks, any pretentions that these were zoological entities had vaporized as the media began to dig deeper. From February onwards, the pandas had become stars in a human drama, used to draw attention to a full-on scandal that brought the zoo’s management infrastructure to the brink of total collapse.

The precise details of what took place remain unclear but for those who missed it I wasted several hours putting together a detailed timeline of events as covered by the Scottish press. In short, an anonymous dossier of serious but as yet undisclosed allegations crippled the organization, triggering suspensions and dismissals from the board. As this scandal wrought its destructive course on individuals, families and the venerable institution that is Edinburgh Zoo, the repeated appearance of pandas in photographs gave the overall impression that their acquisition had triggered the management crisis. In the absence of any direct evidence, however, this seems to have been little more than speculation based on the assumption that where there are pandas, there are men in suits filling their seedy little pockets with grubby banknotes.

Sure, captive pandas have obvious commercial promise. There is, for instance, an established graph with visitor numbers on the y-axis and time since arrival of pandas on the x-axis. There is also a version of this that shows what happens to gate receipts if the pandas manage to procreate. The zoo shop can do a nice line in panda-related merchandise. There is always the hope of landing a private sponsor, though in the current climate this could be tricky. 

But the income that captive pandas can generate for a zoo is unlikely to match the expense. It cost Edinburgh Zoo £250,000 to construct a state-of-the-art panda enclosure on the site of the former gorilla exhibit. The RZSS will be paying China around £640,000 every year for ten years for the privilege of having pandas. It will have to fork out a further £70,000 each year for food, importing most of the required bamboo from a plantation on the outskirts of Amsterdam. Then there are the salaries of keepers that will dedicate their working lives to the pandas. 

If captive pandas are so costly, why does Edinburgh want them? There are many reasons I think, but few of them have very much to do with wild pandas. The more time that passes since writing my book, the more convinced I am that there is little, if any, overlap between the lives of captive and wild pandas. In theory, the annual fee that Edinburgh will pay to China must be used to those animals in the wild. In practice, it is spent on strengthening captive institutions in China. Should Tian-Tian and Yang-Guang procreate, there will be lots of excitement but without a means of reintroducing captive pandas into the wild – a feat that has yet to be achieved – any offspring will be destined to a life as a captive with only superficial resemblance to their real, wild counterparts. 

No, the real value of captive pandas lies not in their identity as pandas but in the colossal symbolic importance we humans have invested in this remarkable species. Any zoo that can boast the face of global conservation amongst its inmates will only enhance its standing as a serious conservation concern. A pair of pandas acts like an incredibly efficient, self-sustaining PR engine, generating the kind of press coverage – most of it generous – that most press officers can only dream of. These animals open up wide and fertile new vistas for educating the public, not just about conservation of pandas, not just about conservation in China but about global conservation, full stop. 

In spite of these benefits though, I feel duty bound to point out that captive pandas can be profoundly unpredictable too. Take the case of Wang-Wang and Funi, a pair of bears that have been on loan to Adelaide Zoo since 2009. It’s been estimated that during their first year in residence, they injected $57 million into the South Australian economy. At the zoo itself, however, the pandas have not had the same effect and the South Australian government and Westpac Bank have had to step in to save it from financial ruin.

Tian-Tian translates as “Sweetie” and Yang-Guang as “Sunshine”. Only time will tell whether the Edinburgh pandas live up to their names and bring sweetness and light to the fortunes of Edinburgh Zoo and the wider city or whether the undoubtedly risky panda adventure will have a dark and bitter ending. 

An edited version of this article (with the jokes taken out) appears on the Guardian's Comment Is Free website