Zoologist, media consultant, and science writer, Dr Karl Shuker is also one of the best known cryptozoologists in the world. He is the author of such seminal works as Mystery Cats of the World (1989), The Lost Ark: New and Rediscovered Animals of the 20th Century (1993; greatly expanded in 2012 as The Encyclopaedia of New and Rediscovered Animals), Dragons: A Natural History (1995), In Search of Prehistoric Survivors (1995), The Unexplained (1996), From Flying Toads To Snakes With Wings (1997), Mysteries of Planet Earth (1999), The Hidden Powers of Animals (2001), The Beasts That Hide From Man (2003), Extraordinary Animals Revisited (2007), Dr Shuker's Casebook (2008), Karl Shuker's Alien Zoo: From the Pages of Fortean Times (2010), Cats of Magic, Mythology, and Mystery (2012), Mirabilis: A Carnival of Cryptozoology and Unnatural History (2013), Dragons in Zoology, Cryptozoology, and Culture (2013), The Menagerie of Marvels (2014), A Manifestation of Monsters (2015), Here's Nessie! (2016), and what is widely considered to be his cryptozoological magnum opus, Still In Search Of Prehistoric Survivors (2016) - plus, very excitingly, his first two long-awaited, much-requested ShukerNature blog books (2019, 2020).

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Sunday, 10 April 2011


Green polar bear at Singapore Zoo in 2004 (Singapore Zoo)

Although very commonly exhibited by birds, reptiles, amphibians, fishes, and an immense variety of invertebrates, green as a predominant colour is only very rarely displayed by mammals. Bearing in mind that many mammalian species live (or spend at least part of their time) in trees, or remain hidden amid bushes or dense undergrowth foliage from predators, one might have expected a substantial number of green mammals to exist, having evolved green fur for effective camouflage. Yet, strangely, this particular adaptation for survival has seldom occurred.


One of the most notable of the few exceptions to this odd rule is West Africa’s green bush squirrel Paraxerus poensis. Its distinctive olive-green upperparts and greenish-yellow underparts do indeed provide it with efficient camouflage within its savannah and woodland habitat, protecting it in particular from predation by airborne squirrel-devouring eagles.

Green bush squirrel (Studio Creazioni Dami)

A marsupial counterpart of sorts is the green ringtail possum or toollah Pseudochirops archeri of northern Queensland, Australia. On 20 May 1961, a detailed analysis of the greenish-yellow colouration of this species’ fur was published by zoologists Drs Hobart M. Van Deusen and E.L. Stearns in the Journal of Mammalogy. This study revealed that its fur’s colour was due to a mingling of yellow, white, and black colours, produced in turn by the effects of varying amounts of melanism and xanthin (a yellow pigment) within individual hairs in combination with reflection of white light from the fur. Much the same effect is also responsible for the olive-tinted fur of the green (vervet) monkey Chlorocebus pygerythrus.


In addition to these naturally-green species, however, green colouration can also occur in mammals via botanical intervention. The most familiar example of this phenomenon is the green hue of sloths’ fur. The outer surface of each hair bears a number of diagonal ridges, and each of these ridges contains unicellular Cyanoderma and Trichophilus blue-green algae or cyanophytes. These thrive in the moist, warm climate of the sloth’s Neotropical rainforest habitat, and the sloth benefits from the effective camouflage that it gains from its alga-impregnated pelage. Consequently, the alga-sloth association is truly symbiotic, because both partners benefit from it.

Sloth on ground, revealing its fur’s green colouration

So far, therefore, all of the examples of green mammals presented here have involved species in which such colouration is, for one reason or another, a normal occurrence – nothing special or aberrant. Conversely, there are various other cases on record in which this particular hue’s occurrence is anything but normal, resulting in some decidedly strange and spectacular outcomes.

During the late 1970s, for instance, Canadian fur trappers were a source of considerable bewilderment to the international zoological community – because they insisted that they often encountered polar bears Ursus maritimus with bright green fur! Needless to say, such claims initially received short shrift from science, but the reports persisted – and eventually a green polar bear was actually captured!

At much the same time, and once again to the great surprise of zoologists everywhere, news emerged that polar bears in at least two California zoos (San Diego and Fresno) had turned green too. Detailed fur examinations took place, utilising hair samples not only from the captured green polar bear but also from the verdurous zoo specimens. The answer obtained from all of these specimens was the same, and involved a very curious twist to the trichological tale already documented here for the green sloths.

As published on 29 March 1979 in the scientific journal Nature by San Diego-based researchers Drs Ralph A Lewin and Phillip T. Robinson, it transpired that just as with sloths, the polar bears’ green colouration was due to attached cyanophyte algae - but there the similarity ended. For whereas the sloths’ algae were sited externally upon their fur, those of the polar bears were located internally. That is, they were actually present within the medulla (the hollow tubular section) of certain hairs in the bears’ pelage – predominantly the wider, stiffer guard hairs of the bears’ outer coat.

On initial consideration, one might imagine that the bright green hue bestowed upon them by this algal infestation would put the affected polar bears at a very considerable disadvantage, by making them extremely conspicuous against their snowy-white Arctic surroundings. With the exception of humans, however, the polar bear, being the top predator in this region, is not preyed upon or killed by any other species (though they will sometimes attack one another and even resort to cannibalism). Consequently, the enhanced visibility caused by the algae is less deleterious than would otherwise be the case. As for the California zoos’ green polar bears, a salt solution was applied to rid them of their unwanted algae.

A similar outbreak of green polar bears took place at Singapore Zoo in 2004, but this time they were cured of their algae by bleaching their fur with a hydrogen peroxide solution. In addition, three polar bears at Japan’s Higashiyama Zoo became stained with green during July 2008 after swimming in a pond overgrown with algae. A YouTube video of one of these Japanese green polar bears showing its unusual condition can be accessed here.

Alga-stained green polar bear at Higashiyama Zoo, Japan (Higashiyama Zoo)

As it happens, scientists should not have been too surprised about reports concerning green polar bears. A decade earlier, they had already been baffled by comparable stories of green seals, which by coincidence also emerged from Canada. The species in question was the grey seal Halichoerus grypus, and subsequent investigations revealed that algae were indeed involved (specifically, Enteromorpha groenlandica), but this time growing among the hairs present on the seals’ backs. Moreover, various currently-unidentified green algae may sometimes colour the pelage of monk seals Monachus spp.


Very occasionally, reports of green dogs and cats appear in the media. Usually, of course, there is a perfectly straightforward explanation – often involving an unfortunate interaction with a pot of green paint! Much more mysterious, conversely, was a case highlighted by several newspapers during April 1984 (but not on 1 April, I hasten to add!), concerning the alleged birth in northern Italy of a puppy with green fur. Apparently it was one of six puppies born to a farmer’s gun dog, yet the other five puppies were all normally-coloured.

Bearing in mind the considerable novelty of this occurrence if found to be genuine, the zoological world was surprisingly uninterested and unwilling to investigate it, though some unnamed scientists did suggest rather non-specifically that it may be due to a spontaneous mutation. More memorable was the opinion proffered by an equally nameless vet that it may be a form of dandruff. Any pet owner faced with the dilemma of a dog with green dandruff could perhaps be forgiven for wondering momentarily whether they should treat their unfortunate pet’s fur with shampoo or with weedkiller!

After being alerted to its existence by a report in the local Middlesbrough Evening Gazette newspaper on 29 January 1987, English cryptozoological researcher Richard Muirhead was able to view a week-old green puppy when he visited the home of its owners. The peppermint-tinted individual in question was one of nine puppies born to a three-year-old Labrador x collie bitch. As with the Italian green puppy, however, all of its siblings were of wholly unremarkable colour. A vet suggested that the extraordinary hue of the Middlesbrough individual may be due to ‘utera verdi’ [sic], i.e. uteroverdin.

First documented back in 1830, this is a thick, dark-green discharge (lochia) released by the placenta into the womb (uterus), staining anything with which it comes into contact, and can be observed passing from the vulva at the time of parturition, indicating placental separation for one or more puppies, and reliably signalling that whelping should begin within a few hours for a term bitch. However, as Richard rightly pointed out, if uteroverdin were responsible for the green colouration of this puppy’s fur, why hadn’t it also stained the fur of the puppy’s eight siblings? All nine of the puppies had shared their mother’s womb at the same time, so all nine should have exhibited at least some degree of staining. Moreover, if uteroverdin were indeed responsible here, there should be numerous reports on file of other green newborn puppies, because uteroverdin secretion is a common, typical occurrence.


A no less extraordinary case, but this time featuring a bright green kitten, hit the news headlines in autumn 1995, just in time for me to prepare and include the following box feature concerning it in my book The Unexplained (1996):

‘Denmark’s Green Kitten’ (click the above box feature to read it directly in greatly-enlarged format)

During this viridescent kitten’s all-too-short time in the limelight (pun definitely intended!), I was kept up to speed regarding it by fellow zoologist and anomalous animals enthusiast Lars Thomas from Copenhagen University. By early February 1996, however, the remarkable saga itself was all but over, yet the mystery surrounding it remained unresolved, as noted by Lars in the last of various letters on this subject that I’d received from him during the previous weeks:

“Alas, the green cat is no longer green. Its colour has been fading all the time, and now you can only just, if the lighting is good, make out a weak greenish tinge on the legs and the stomach. And even that will probably disappear in a few weeks as well.

“No one has been able to ascertain the reason for the cat’s rather strange colour. At first it looked like the colour was purely structural, i.e. it was caused by the light being reflected in a certain way from the uneven surface of the hairs. But further studies showed that it was the actual hairs being green.

“The general theory is that the colour is the result of something the kitten has eaten or drunk. And the reason the colour is now fading is because the cat is now a pet, drinking clean water and milk, and getting food from a tin. But as to the substance that caused the colour, no-one has the faintest idea. The forensic laboratory in the State Hospital in Copenhagen has been studying hair samples of the cat for several months now, but has not come to any conclusion yet...

“I did manage to get one of the doctors at the laboratory talking, and he suggested that the colour might be caused by some form of mild copper-poisoning. This is very difficult to believe, as the cat has always been very healthy. A few cases of humans developing greenish hair from drinking copper-polluted water are known, but they had white [i.e. blonde] hair, and even then, the [green] colour was very weak. This kitten’s natural colour is bluish-grey, and the green colour was very strong.

“So, as you can see, the mystery has still not been solved.”

And as far as I’m aware, the same is true even today – but just in case I am mistaken about this, over to you Lars...!


Finally, three green felids of differing yet equally exotic form. In his book Simba: The Life of the Lion (1962), C.A.W. Guggisberg briefly mentioned that a prospector had once claimed to have spied a green lion in the forests of western Uganda. Whether the said green lion was stalking pink elephants at the time is not recorded!

Exquisite painting of a green lion (Felipe Soltero, at www.redbubble.com/people/SolteroArt)

As an interesting (albeit wholly unconnected!) aside, in alchemy the symbol representing Nature’s green raw energy was a green lion. This was also used to symbolise aqua regis – a greenish-tinged liquid created by mixing nitric acid with hydrochloric acid, and so corrosive that it could even dissolve gold - the noblest of all metals to the alchemist. This chemical process was often illustrated in alchemical manuscripts by images of a green lion devouring the golden sun.

Green lion devouring the sun, from the Rosarium Philosophorum (1550), an important alchemical treatise

In 1996, residents of Balbriggan, a town in County Dublin, Ireland, were claiming that a glowing green phantom cat had been seen there. Bearing in mind that a popular nickname for Ireland is the Emerald Isle, any reports of a green-hued spectre there – feline or otherwise - are nothing if not appropriate!

Nor should we – or, indeed, could we – forget the transgenic glowing green cats (not to mention mice, rabbits, pigs, and even monkeys) that have been created by various scientific teams during the past two decades by introducing genes controlling bioluminescence in certain animal species into the DNA of feline and several other mammalian embryos. In October 2008, the world’s first transgenic glowing green cat – created by scientists at New Orleans’s Audubon Centre for Research of Endangered Species - was introduced to the media. Named Mr Green Genes, in ordinary light he looked just like any other six-month-old cat, but when viewed in ultraviolet light his eyes, gums, and tongue glowed a vivid lime green. The gene responsible for this uncanny effect was derived from a jellyfish.

Moreover, in 1995 the world’s first transgenic glowing mammals were produced by a Japanese research team from Osaka University’s Microbiology Disease Research Institute. They created mice that glowed green under artificial light by taking a gene controlling the production of a luminous protein called aequorin in Aequorea victoria, a species of Pacific jellyfish, and incorporating it into mouse embryos.

Happily, these luminescent mammals’ weird-looking ability to glow like jellyfishes has not been accompanied by a similar ability to sting like them too! Firefly genes controlling the production of luminous enzymes called luciferases have also been incorporated into various transgenic mammals to induce glowing.

Continuing this theme of exotic and unexpected green fauna, in the very next ShukerNature blog post I’ll be examining my all-time favourite mystery beast from classic cryptofiction, surveying some Celtic canids of the supernatural variety, and reporting an extraordinary new discovery in the real world that represents the most intimate phytozoological association currently known that involves a vertebrate species – so don’t miss it!

This present article is excerpted from one of my in-progress books, The Anomalarium of Doctor Shuker, scheduled for completion and publication in 2012.

1 comment:

  1. I couldn't help but wonder...has there been any research done on the effects of copper on cats? I figured that perhaps the kitten's unusual hue could still be attributed to copper, due to some characteristic of cat hair that humans do not possess?