Tetrapod Zoology

The mysterious tree-creature revealed

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So what was the mysterious beast shown in the photo? As usual, the Tet Zoo readership proved too clever to be fooled by such a rubbish trick. That white blurry streak in yesterday’s photo was…

…. not a fox, lynx, marten, white carrier bag, draft excluder, house cat, tree trout, rhinogradentian, dormouse, slug, ent, iguana, arboreal monitor lizard, tree octopus, kitten, raccoon, tree-eel, kite skeleton, nor, sadly, a late-surviving, modern-day, dwarf arboreal gorgonopsian (wow – an impressive list of in-jokes there). It is nothing more than, as some of you correctly guessed, a lowly Grey squirrel Sciurus carolinensis, but an albino one. I saw it from the bus, and leapt off and gave chase. The little bugger evaded me and vanished. Later that same day, Richard Hing and I went in quest of it: it was still hanging around at the same place (this all happened in Portsmouth’s Victoria Park), but despite my best efforts I was unable to get a good photo. And, hey, the photo was taken with my mobile phone, so I wasn’t exactly working with the best equipment. Given that the photo is so awful, I thought identification of the object of interest might prove a challenge. Well done Douglas Gogerty, Epicanis, Paul Barrett, Nick and everyone else who correctly identified it.

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Albino Grey squirrels aren’t really a big deal – they’re routinely reported in British urban populations, particularly those in southern England (Kent, Surrey and Sussex in particular), and people have been seeing them in and around Victoria Park for ages. There are also various places in the country with high proportions of melanistic Grey squirrels (Muirhead 1998): Hertfordshire is most strongly associated with melanism in the species, mostly because 12 melanistic individuals were introduced to Woburn [adjacent photo taken by Lindsay Abbas].

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As, I suppose, everyone knows, the Grey squirrel is a native of south-eastern Canada and eastern USA, but as early as the 1820s it was being introduced to Britain. The first reported British sighting is from Denbighshire in Wales and dates to 1828 – there are other Welsh records that are said to predate 1830, but the details are vague (Lever 1977). The problem is that no-one knows who introduced these squirrels, or where they came from. And no, I don’t think there’s a good case to make that this North American endemic might have been an overlooked Welsh native. Documented introductions first occurred in Cheshire in 1876, and by the early 1900s people were introducing them all over the place. Virtually all of these squirrels came from North America of course, but we know of one individual (a female released in Buckinghamshire in 1909) who came from the South African colony: these had been introduced to Groote Schuur by Cecil Rhodes in about 1880. Despite a setback that occurred during the 1920s and another that happened in 1932, Grey squirrels increased their range between 1930 and 1945 and today they’re essentially ubiquitous, absent only from some islands (including the Isle of Wight), the Scottish highlands, and much of Ireland (Gurnell 1987, Matthews 1989) [accompanying range map borrowed from here: the forest research grey squirrel management site].

Grey squirrels are mostly a bad thing here in Britain. Some people (Bill Oddie among them) argue that they get a lot of people interested in wildlife, as they’re among our most familiar, personable mammals. But they’re a significant menace to forestry (they strip bark and kill saplings) and have been recently shown to have a major negative impact on passerines: believe it or don’t, they routinely eat passerine chicks, and might be one of the most important factors in passerine decline.

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It is widely alleged that the spread of the Grey squirrel has resulted in the decline of Britain’s only native squirrel, the smaller, tufted-eared Red squirrel S. vulgaris [shown in adjacent image: from here]. This is a complex issue and even now it is argued as to what has really resulted in red squirrel decline. Grey squirrels do not hunt down and kill reds, nor are greys necessarily any better at adapting to life in urban places, as the Regent’s Park red squirrels in London seem to be doing fine, despite living alongside greys (Gurnell 1987), nor are reds doing badly because they’re limited to coniferous woodlands (they are equally at home among broadleaved trees). However, it does indeed seem that greys can replace reds: an established population of greys will lower the recruitment rate of juvenile reds into the population (Wauters et al. 2000). Greys also act as a vector for the transmission of the parapox virus: this kills red squirrels and can extirpate whole populations, yet greys typically show high sero-prevalance for antibodies to the virus and don’t die from it (Shuttleworth 2003).

Entirely by coincidence, Erik Meijaard – yes, the Erik Meijaard – added a comment about squirrels to Tet Zoo ver 1 on Friday (go here). And one last thing – if you like squirrels this youtube video is mandatory viewing (warning: it includes a few swear words).

Back to normal business soon enough; sorry for yet another distraction.

Refs – –

Gurnell, J. 1987. The Natural History of Squirrels. Christopher Helm, London.

Lever, C. 1977. The Naturalized Animals of the British Isles. Hutchinson & Co, London.

Matthews, L. H. 1989. British Mammals. Bloomsbury Books, London.

Muirhead, R. 1998. Black squirrels in Britain. British Wildlife 10 (2), 102.

Shuttleworth, C. 2003. A tough nut to crack: red squirrel conservation in Wales. Biologist 50 (5), 231-235.

Wauters, L. A., Lurz, P. W. W. & Gurnell, J. 2000. Interspecific effects of grey squirrels (Sciurus carolinensis) on the space use and population demography of red squirrels (Sciurus vulgaris) in conifer plantations. Ecological Research 15, 271-284.

Comments

  1. #1 Erik Knatterud
    October 14, 2007

    So, that`s what happens when one focuses on the centre of the picture, believing Darren staged a Paxton trick having people guess wildly about those two “glowing eyes”. How was it possible to not detect that bushy tail flat against the branch? Excellent test.

  2. #2 Mark Lees
    October 14, 2007

    That explains why it looked so pale, but for some reason the scale still looks odd to me.

    On the broader matter, I did a bit of researching published material a couple of years ago on the grey/red controversy, I don’t recall the references (I still have some of the notes, but the references are very incomplete), but a few points worth mentioning.

    a. there is no evidence (beyond dubious anecdote) to suggest grey squirels are any more of problem for small birds than are red. Red squirels also took passerine chicks. The idea that they are to blame for decline of small birds seems to me one more search for a convenient scapegoat.

    b. while grey squirels do carry SQPV (squirel pox) and act as vectors there is no proof they introduced it, indeed there are accounts of apparent breakouts among reds predating the introduction of greys, and certainly there have been breakouts in areas where were not present at the time. This was probably an indigenous disease, albeit greys have made matters worse.

    c. both species often coexist for long periods. The balance tends to get skewed when some ‘catastrophe’ occurs, either an SQPV outbreak (which has major effect on reds, minor on greys) or a really bad winter which affects both. In either case the greys recover quicker, apparenly reducing the reproductive success of the reds, and colonise.

    d. Reds do have some advantage in some types of coniferous woodland – specifically the few notes I have to hand state that they make better use of larch and some types of fir (e.g. douglas fir) forest than do grey. Other conifers are useful to both species, Sitka spruce is a good example; while some conifers are poor habitat for both – our native Scots pine comes in to that category, though reds can hang on in it. Generaly broadleafed woodland is good habitat for both species – though greys obtain more nutrition from acorns than do reds. The value of conifer woodland as habitat is rather dependant on the age structure of the woods, and the practice of planting large areas with conifers of the same age has undermined the value of what could have been an excellent refuge for reds.

    e. Prior to the rise of the greys, reds were viewed as pests and killed. In some areas of the UK they were locally wiped out. In a few cases they were reintroduced, and not always with British red squirels. Indeed the UK population apparenly had a substantial injection of european (mostly I think Scandanavian) red squirel blood in the 19th century.

    As you map shows reds hang on in a few places in the southern half of UK, in South Wales they still occur in the Rheola Forest (huge mostly conifer woods), though very rarely seen. Interestingly there is evidence that pine martens also occur therer.

    Yes it would be better that greys hadn’t been introduced. But they are here. Get used to it. It isn’t their fault, and they aren’t the villains they are made out to be.

    And don’t get me started on mink… 🙂

  3. #3 Mike from Ottawa
    October 14, 2007

    As always, something to learn at TetZoo. I never thought about our red squirrels being different from yours, but they are a separate genus (which all makes sense). I don’t know how Euro red squirrels behave, but it is amusing to watch ours chasing the much larger grays around. You never see it the other way around.

    And, a completely extraneous question for Darren: how much difference is there between the 1st edition of the DK dino book and the one you worked on? I have the earlier one, got some years ago.

  4. #4 SMC
    October 14, 2007

    One cannot properly honor Squirrels On The Internet without mentioning Foamy the Squirrel (link goes to flash animation. Warning: Naughty words.)

    Hooray! I got it right! So, what did we win? Money? Gold? A New Car?…

  5. #5 Darren Naish
    October 14, 2007

    Many thanks for the squirrely comments, in particular to Mark for the thoughtful set of opinions on the ‘reds vs greys’ issue. I see where you’re coming from Mark, but I’m not sure that I entirely agree that greys are as non-problematical as you imply. Here are my responses to the five points you raise…

    a. The contention that grey squirrels have a significant impact on passerine birds is not the result of scapegoat-searching, nor is it based on dubious anecdotes: it is based on studies of the impact of mammalian predators on British passerine populations, in particular on Roy Brown’s 2006 study ‘A review of the impact of mammalian predators on farm songbird population dynamics’ (free pdf available here). In this report (widely reported by the British media) Grey squirrels were found to have a significant impact on passerine density, and they accounted for more losses of eggs and nestlings than feral cats and raptors. Brown found that squirrels may predate on about 93% of the passerine nests in a given area and that ‘this evidence confirms the significance of Grey squirrels as a potentially wide ranging predator of both ground, hedge and tree nesting farm bird species’.

    b. It has indeed been argued that greys introduced the parapox virus, mostly because it’s unknown in continental reds (Harris 1997). I hadn’t heard that it might be indigenous to Britain. Regardless, the evidence is good that greys act as a reservoir for it, and pass it to reds, for which it is fatal. In places where the two species co-exist, the non-native grey is a problem if we want the red to persist (Sainsbury et al. 2000, Shuttleworth 2003).

    c. Reds and grey can coexist, and indeed reds have a competitive advantage over greys in conifer stands. But recent work indicates that an established populations of greys reduces the recruitment of young reds into the population – even in those conifer stands, greys can and do replace reds. This has happened at Cannock Chase in Staffordshire.

    d. Yes, it’s true that woodland management has made life more difficult for reds. The reduction in hazel coppice is a problem, for example. The take-home message here is that it’s not greys alone that have resulted in the decline of the red, but that factors like habitat loss and management changes have contributed too.

    e. Like several other native species (e.g., Red and Roe deer), yes, Britain’s surviving red squirrels are not necessarily the original native populations as you note. But if those populations aren’t native, it can still be argued that we should be trying hard to conserve a native species. British reds are supposed to represent an endemic subspecies (Sciurus vulgaris leucourus) and some recent studies have shown that the British population is indeed still distinctive compared to mainland Eurasian populations (Barratt et al. 1999). However, repeated introductions of European squirrels seem to have diluted the morphological distinctiveness of this taxon: pre-1980 reds were more similar to the original description of S. v. leucourus than post-1980 reds.. and the latter resembled continental reds more (Hale & Lurz 2003).

    Sure, it’s not the ‘fault’ of those little grey squirrels that they’re the problem that they are. But the data showing that they are a problem – and a problem for passerines and red squirrels in particular – is pretty good. If we care, we should do something about it.

    Refs – –

    Barratt, E. M., Gurnell, J., Malarky, G., Deaville, R. & Bruford, M. W. 1999. Genetic structure of fragmented populations of red squirrel (Sciurus vulgaris) in the UK. Molecular Ecology 8, 55-63.

    Hale, M. L. & Lurz, P. W. W. 2003. Morphological changes in a British mammal as a result of introductions and changes in landscape management: the red squirrel (Sciurus vulgaris). Journal of Zoology 260, 159-167.

    Harris, S. 1997. Squirrel under siege. BBC Wildlife 15 (5), 12-17.

    Sainsbury, A. W., Nettleton, P., Gilray, J. & Gurnell, J. 2000. Grey squirrels have high seroprevalence to a parapox virus associated with deaths in red squirrels. Animal Conservation 3, 229-233.

    Shuttleworth, C. 2003. A tough nut to crack: red squirrel conservation in Wales. Biologist 50 (5), 231-235.

  6. #6 Mark Lees
    October 14, 2007

    I guess we are going to have to disagree on much of this. 🙂

    But just for clarity, I wasn’t suggesting that grey squirels don’t kill passerine chicks, just that reds also are recorded as doing so, and there is no evidence that greys are more of problem in this regard than reds. They may look cuter, but they still have the teeth of a killer if your a nestling!

    As to whether SQPV was introduced by grey squirels, most authorities say it was, but some are more cautious and say that it is uncertain. Pre nineteenth century records of diseases in wild animals considered pests are not particularly well recorded, but there is some suggestion of something similar before the greys got here. It has also been noted that, albeit post the introduction of greys to the UK, SQPV breakouts have occured in areas where no greys were known to occur at the time. So however it first got here, greys do not seem to be directly involved in all outbreaks.

    The point about the introduced red squirrels was that since most UK squirrels are no longer distinct – only those in Cumbria show the traits of Sciurus vulgaris leucourus, and as you noted they less so since 1980s – rather than waste excessive sums on large scale doomed to failure culls etc, why not introduce continental red squirrels to areas of UK where they are now absent and where the habitat favours them, preferably after a local cull of greys (to reduce populations and give the reds a fighting chance) and having inocculated them (the reds) against SQPV?

    I think that rather than try to go back to just having reds, we should accept the grey is here to stay, and try to find a viable 2 squirrel species solution.

    I go on a bit don’t I. I’m going to shut up now. Oh, and can we have the second part of your crypto talk?

  7. #7 Allen Hazen
    October 14, 2007

    The “New York Times” had an article, “The Squirrel Wars,” in its Sunday Magazine two (?) weeks ago about the effort to stem the spread of the Gray in Britain: probably still recoverable from the NYT’s WWWebsite (I’d suggest looking at the “Sciecne” section of the index). Nothing of Zoological interest beyond what has already been said in Darren’s posts and the replies, mostly “human interest” with an eccentric nobleman who leads a squirrel-trapping organization….

    So, the British (European, Eurasdian?) Red Squirrel is Sciurus vulgaris, eh? So– to the degree that genera are “natural” that means it is pretty similar to the American Gray Squirrel (Sciurus virginianus, where “virginianus” — referring to the U.S. state of Virginia and/or its colonial predecessor– shouldn’t be taken too seriously as a geographical guide: “virginianus” and “canadensis” were over-used as specific names for North American species early on). The American Red Squirrel (and, yes, they do chase the larger gray ones) is Tamiasciurus somethingorother, which I take it means the original describer thought they were somehow intermediate between standard squirrels and chipmunks (Tamias).

    I don’t think, in my years growing up in the U.S., that I ever saw an albino squirrel, but S. virginianus was about the third most-commonly spotted mammal species (after H. sapiens and C. familiaris). Different city parks in North America seem to have different proportions of standard-issue gray and melanistic individuals in their populations.

  8. #8 Sven DiMilo
    October 15, 2007

    I hit an albino carolinensis with my Jeep a couple years ago (eastern Pennsylvania; it was an accident, I swear!). I bet it’s still in a freezer someplace.

  9. #9 Jamie A. Stine
    October 16, 2007

    We have a small population of albino grey squirrels here on my college campus. There’s such a following that when one of them was eaten by a cooper’s hawk last spring, they had a funeral and an obit in our school paper. We even have an albino squirrel preservation society!

    Cute little buggers, but I’m under the distinct impression that it’s the SQUIRRELS that are running this university. That would explain the strange parking decisions and notable lack of tree trimming.

  10. #10 Stevo Darkly
    October 16, 2007

    Hmm, I didn’t even notice the “glowing eyes” in the original photo (just above the squirrel’s tail). If I had, I would have guessed it was a photo of an arboreal Jawa. We have quite a lot of those in the scrub forest near our moisture farm. At dusk you can hear their characteristic cry: “Taheeneeee!”

    [from Darren: strange, all the jawas round here say ‘utini!’]

  11. #11 Steve Bodio
    October 16, 2007

    There is a funny link to a debate on squirrels in the House of Lords in Querencia.

    Greys at least are delicious.

  12. #12 David Marjanovi?
    October 16, 2007

    Hmm, I didn’t even notice the “glowing eyes” in the original photo (just above the squirrel’s tail).

    Oh, there’s where they are! I missed them, too.

  13. #13 Nick
    October 16, 2007

    Albino Grays are supposed to be common in parts of Illinois, New Jersey, and South Carolina. Melanistic Grays are common in Ontario and have been introduced to parts of British Columbia (I’ve seen them both in Toronto and on the University of British Columbia campus in Vancouver).

  14. #14 DDeden
    October 16, 2007

    Oh, funny that, I didn’t notice it before. That’s a critically endangered big red ellipse, isn’t it?

  15. #15 Stevo the Darkly
    October 17, 2007

    strange, all the jawas round here say ‘utini!’

    Oops! That’s really what I meant.

    Bo chuuuuuudaaaaaa.

    [from Darren: Bo shueda. Kaa bazza kundee hodrudda! Ches ko ba tuta creesta crenko ya kolska]

  16. #16 David Marjanovi?
    October 18, 2007

    What is that? Huttish?

    [from Darren: well, Huttese, yes. I don’t waste my time with those, you know, real non-English languages… ducks, runs]

  17. #17 Stevo Darkly
    October 19, 2007

    Arrenday isay evenay iggerbay erdnay anthay emay.

    [from Darren: maybe. Or maybe I’ve just watched the Star Wars film too many times 🙂 ]

  18. #18 Neil
    October 29, 2007

    Hi darren a nice article as ever, but (for the first time that I can recall) there is one mistake. There are definately no red squirrels in Regents Park or in any of the Royal Parks in London. This I can personally vouch for (I at UCL these day 5mins from Regents Park). Just lots and lots of grey squirrels causing havoc. I read somewhere that they tried to reintroduce them in the 1980s but it was unsuccessful.

    And there no doubt in nmy mind Greys are bad news. Ive seen photos of red squirrels with lower jaws fallen off due to ‘squirrel pox’ which as you said is carried by the greys. And in my local park on the outskirts of London the greys are in very hign numbers due to people feeding them and the only passerines in this area are the crows that are big enough to fight off the squirrels – and Ive had bird boxes robbed by greys too – so there bad news for birds too

    As for the white squirrel in Victoria park I shall have to drag Mr. Hing to go have a look when Im next in town 🙂

  19. #19 Darren Naish
    October 30, 2007

    Hi Neil – thanks for the comment…

    Hi darren a nice article as ever, but (for the first time that I can recall) there is one mistake. There are definately no red squirrels in Regents Park or in any of the Royal Parks in London. This I can personally vouch for (I at UCL these day 5mins from Regents Park). Just lots and lots of grey squirrels causing havoc. I read somewhere that they tried to reintroduce them in the 1980s but it was unsuccessful.

    Very kind of you to say it, but that’s hardly the first mistake I’ve made on Tet Zoo! My source on the Regent’s Park red squirrels was squirrel worker John Gurnell, who wrote about them in his 1987 Helm book The Natural History of Squirrels. He stated (p. 164) that native red squirrels were still present in Regent’s Park in 1942, and that they were reintroduced there (presumably after local extinction) in 1987. At the time of writing he stated that the reds ‘appear to be surviving very well’. If you’re right that they’re not there now, then Regent’s Park has lost its reds again. How sad.

    The whole reds vs greys issue was covered on British TV last week (in The Nature of Britain, presented by Alan Titchmarsh). They made bold and direct statements about how the decline of reds was due to competition from greys, though didn’t mention squirrel pox.

  20. #20 Rob
    November 25, 2007

    BTW, in the u-tube video the “sparrow” being eaten is likely a waxwing, judging by the yellow feather tips.

  21. #21 Neil
    December 18, 2007

    Me a richard went for a hunt in victoria park and saw the guy on the ground but he ran up the tree before I could get a photo. So the resulting photo I have is it in the shade of the only leaved tree in Victoria park.

    http://flickr.com/photos/ukwildlife/2120427497/

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