Mutants are natural variations which occur due to spontaneous genetic changes or the expression of recessive (hidden) genes. Recessive genes show up when there is too much inbreeding. As well as anomalous colours, there are abnormally large or small individuals, longhaired individuals, short-tailed or even tail-less individuals. All of these occur in domestic cats so why are they less common in big cats? Wild cats displaying these traits may be less likely to survive to pass on the traits. In captivity, humans control which traits are bred, hence the multitude of domestic cat colours and types. In the wild, nature selects against any trait which does not enhance the animal's survival chances.

In the past, the obvious reaction to any unusual big cat was to shoot it for the trophy room. As a result, many interesting mutations may have been wiped out before the genes were passed on. Some colour mutations which would disadvantage a wild big cat are bred in captivity and are not viable in the wild. It is questionable whether these mutants should be perpetuated for the sake of curiosity or aesthetics alone.

I am grateful to Paul McCarthy for researching and providing extensive material, information and corrections.


Blue tigers have been recorded. They have slate grey or black stripes on a pale grey body. Normally blue dilution makes the colour lighter e.g. black becomes blue-grey; it doe not transform orange into grey. Blue tigers have been sporadically reported in the mountains of the Fujian province in China. It is described as maltese (bluish-grey or slate-blue) with white patches on the face and black stripes. Other normally tawny cats have blue or grey colour forms e.g. the bobcat so it would not be impossible to have blue/grey mutations in the tiger. A solid grey tiger could be caused by the non-agouti gene (causes melanism or solid black colour) and the colour dilution gene (converts colour to a washed out hue i.e. black to blue); this would result in grey tigers with darker grey stripes.

A smokey blue pseudomelanistic tiger was born in Oklahoma in the 1960s, the preserved speciment is shown in the section on black tigers.

In 1910, while in south-eastern China American Methodist missionary and renowned tiger hunter Harry R. Caldwell described a tiger coloured deep shades of blue and grey-blue. It was described as having a bluish-grey base colour which changed to deep blue on the undersides and stripes similar to those of a normal orange tiger. Caldwell, an experienced hunter and reliable eye-witness, wrote: "I glanced at the object, which appeared to be a man dressed in the conventional light blue garment and crouching. I simply whispered to the cook 'Man,' and again turned my attention to watching the goat. Again the cook tugged my elbow, saying 'Tiger, surely a tiger,' and I once more looked. Now focussing on what I had altogether overlooked in my previous hurried glances, I saw the huge head of the tiger above the blue which had appeared to me to be the clothes of a man. What I had been looking at was the chest and belly of the beast." Caldwell attempted to shoot the tiger, but noticed two boys collecting plants nearby so he moved to a safer location from the shot. Unfortunately, the tiger disappeared. He wrote about the blue tiger in his book "Blue Tiger" in 1925 and noted that other sightings had been reported in the region.

There had been sporadic sightings of blue tigers in the Fujian Province of China since the early 1900s. Caldwell called the tiger "Bluebeard" and it became a personal mission to shoot the animal for its pelt. Although he never caught the cat, villagers confirmed the presence of "black devils" roaming the area. Caldwell sent out a telegram: "Come and help me kill the blue tiger. New York offers 500 gold for pelt." Later on, Caldwell, accompanied by his son John C Caldwell, carried out unsuccessful searches in search of the blue tigers. On several occasions John noted seeing maltese colored hairs along the mountain trails they were searching, but he did not catch sight of a live blue tiger. Another account of the same hunt is contained in "A Narrative Of Exploration, Adventure, And Sport In Little-Known China" written by his hunting companion, Roy Chapman Andrews (Associate Curator Of Mammals In The American Museum Of Natural History And Leader Of The Museum's Asiatic Zoölogical Expedition Of 1916-1917) and Yvette Borup Andrews (Photographer Of The Asiatic Zoölogical Expedition) published in 1918. Chapter 7 "Blue Tiger" contains the following account (abridged to remove travelogue):

'We had a most agreeable surprise when we sailed out of Foochow in a chartered house boat to hunt the "blue tiger" at Futsing. [...] In the evening we talked of the blue tiger for a long time before we spread our beds on the roof of the boat and went to sleep under the stars. [...] Mr. Caldwell's Chinese hunter, Da-Da, lived at Lung-tao [...] Tigers often come into this village. Only a few hundred yards from our camp site, in 1911, a tiger had rushed into the house of one of the peasants and attempted to steal a child that had fallen asleep at its play under the family table. All was quiet in the house when suddenly the animal dashed through the open door. The Chinese declare that the gods protected the infant, for the beast missed his prey and seizing the leg of the table against which the baby's head was resting, bolted through the door dragging the table into the courtyard.

This was the work of the famous "blue tiger" which we had come to hunt and which had on two occasions been seen by Mr. Caldwell. The first time he heard of this strange beast was in the spring of 1910. The animal was reported as having been seen at various places within an area of a few miles almost simultaneously and so mysterious were its movements that the Chinese declared it was a spirit of the devil. After several unsuccessful hunts Mr. Caldwell finally saw the tiger at close range but as he was armed with only a shotgun it would have been useless to shoot. His second view of the beast was a few weeks later and in the same place. I will give the story in his own words:

"I selected a spot upon a hill-top and cleared away the grass and ferns with a jack-knife for a place to tie the goat. I concealed myself in the bushes ten feet away to await the attack, but the unexpected happened and the tiger approached from the rear. When I first saw the beast he was moving stealthily along a little trail just across a shallow ravine. I supposed, of course, that he was trying to locate the goat which was bleating loudly, but to my horror I saw that he was creeping upon two boys who had entered the ravine to cut grass. The huge brute moved along lizard-fashion for a few yards and then cautiously lifted his head above the grass. He was within easy springing distance when I raised my rifle, but instantly I realized that if I wounded the animal the boys would certainly meet a horrible death. Tigers are usually afraid of the human voice so instead of firing I stepped from the bushes, yelling and waving my arms. The huge cat, crouched for a spring, drew back, wavered uncertainly for a moment, and then slowly slipped away into the grass. The boys were saved but I had lost the opportunity I had sought for over a year. However, I had again seen the animal about which so many strange tales had been told. The markings of the beast are strikingly beautiful. The ground color is of a delicate shade of maltese, changing into light gray-blue on the underparts. The stripes are well defined and like those of the ordinary yellow tiger."

Before I left New York Mr. Caldwell had written me repeatedly urging me to stop at Futsing on the way to Yün-nan to try with him for the blue tiger which was still in the neighborhood. I was decidedly skeptical as to its being a distinct species, but nevertheless it was a most interesting animal and would certainly be well worth getting. I believed then, and my opinion has since been strengthened, that it is a partially melanistic phase of the ordinary yellow tiger. Black leopards are common in India and the Malay Peninsula and as only a single individual of the blue tiger has been reported the evidence hardly warrants the assumption that it represents a distinct species.

We hunted the animal for five weeks. The brute ranged in the vicinity of two or three villages about seven miles apart, but was seen most frequently near Lung-tao. He was as elusive as a will o' the wisp, killing a dog or goat in one village and by the time we had hurried across the mountains appearing in another spot a few miles away, leaving a trail of terrified natives who flocked to our camp to recount his depredations. He was in truth the "Great Invisible" [referring to elusiveness of tigers] and it seemed impossible that we should not get him sooner or later, but we never did. Once we missed him by a hair's breadth through sheer bad luck, and it was only by exercising almost superhuman restraint that we prevented ourselves from doing bodily harm to the three Chinese who ruined our hunt. Every evening for a week we had faithfully taken a goat into the "Long Ravine," for the blue tiger had been seen several times near this lair. On the eighth afternoon we were in the "blind" at three o'clock as usual. We had tied a goat to a tree nearby and her two kids were but a few feet away.

The grass-filled lair lay shimmering in the breathless heat, silent save for the echoes of the bleating goats. Crouched behind the screen of branches, for three long hours we sat in the patchwork shade,--motionless, dripping with perspiration, hardly breathing,--and watched the shadows steal slowly down the narrow ravine. It was a wild place [...] the only entrance was by the tiger tunnels which drove their twisting way through the murderous growth far in toward its gloomy heart. [...] I knew it was six o'clock and in half an hour another day of disappointment would be ended. Suddenly at the left and just below us there came the faintest crunching sound as a loose stone shifted under a heavy weight; then a rustling in the grass. Instantly the captive goat gave a shrill bleat of terror and tugged frantically at the rope which held it to the tree.

At the first sound Harry had breathed in my ear "Get ready, he's coming." I was half kneeling with my heavy .405 Winchester pushed forward and the hammer up. The blood drummed in my ears and my neck muscles ached with the strain but I thanked Heaven that my hands were steady. Caldwell sat like a graven image, the stock of his little 22 caliber high power Savage nestling against his cheek. Our eyes met for an instant and I knew in that glance that the blue tiger would never make another charge, for if I missed him, Harry wouldn't. For ten minutes we waited and my heart lost a beat when twenty feet away the grass began to move again--but rapidly and up the ravine. I saw Harry watching the lair with a puzzled look which changed to one of disgust as a chorus of yells sounded across the ravine and three Chinese wood cutters appeared on the opposite slope. They were taking a short cut home, shouting to drive away the tigers--and they had succeeded only too well, for the blue tiger had slipped back to the heart of the lair from whence he had come. He had been nearly ours and again we had lost him! I felt so badly that I could not even swear and it wasn't the fact that Harry was a missionary which kept me from it, either. Caldwell exclaimed just once, for his disappointment was even more bitter than mine; he had been hunting this same tiger off and on for six years.

It was useless for us to wait longer that evening and we pushed our way through the sword grass to the entrance of the tunnel down which the tiger had come. There in the soft earth were the great footprints where he had crouched at the entrance to take a cautious survey before charging into the open. As we looked, Harry suddenly turned to me and said: "Roy, let's go into the lair. There is just one chance in a thousand that we may get a shot." Now I must admit that I was not very enthusiastic about that little excursion, but in we went, crawling on our hands and knees up the narrow passage. Every few feet we passed side branches from the main tunnel in any one of which the tiger might easily have been lying in wait and could have killed us as we passed. It was a foolhardy thing to do and I am free to admit that I was scared. It was not long before Harry twisted about and said: "Roy, I haven't lost any tigers in here; let's get out." And out we came faster than we went in.

This was only one of the times when the "Great Invisible" was almost in our hands. A few days later a Chinese found the blue tiger asleep under a rice bank early in the afternoon. Frightened almost to death he ran a mile and a half to our camp only to find that we had left half an hour before for another village where the brute had killed two wild cats early in the morning. Again, the tiger pushed open the door of a house at daybreak just as the members of the family were getting up, stole a dog from the "heaven's well," dragged it to a hillside and partly devoured it. We were in camp only a mile away and our Chinese hunters found the carcass on a narrow ledge in the sword grass high up on the mountain side. The spot was an impossible one to watch and we set a huge grizzly bear trap which had been carried with us from New York. It seemed out of the question for any animal to return to the carcass of the dog without getting caught and yet the tiger did it. With his hind quarters on the upper terrace he dropped down, stretched his long neck across the trap, seized the dog which had been wired to a tree and pulled it away. It was evident that he was quite unconscious of the trap for his fore feet had actually been placed upon one of the jaws only two inches from the pan which would have sprung it.

One afternoon we responded to a call from Bui-tao, a village seven miles beyond Lung-tao, where the blue tiger had been seen that day. The natives assured us that the animal continually crossed a hill, thickly clothed with pines and sword grass just above the village and even though it was late when we arrived Harry thought it wise to set the trap that night. It was pitch dark before we reached the ridge carrying the trap, two lanterns, an electric flash-lamp and a wretched little dog for bait. We had been engaged for about fifteen minutes making a pen for the dog, and Caldwell and I were on our knees over the trap when suddenly a low rumbling growl came from the grass not twenty feet away. We jumped to our feet just as it sounded again, this time ending in a snarl. The tiger had arrived a few moments too early and we were in the rather uncomfortable position of having to return to the village by way of a narrow trail through the jungle. With our rifles ready and the electric lamp cutting a brilliant path in the darkness we walked slowly toward the edge of the sword grass hoping to see the flash of the tiger's eyes, but the beast backed off beyond the range of the light into an impenetrable tangle where we could not follow. Apparently he was frightened by the lantern, for we did not hear him again.

After nearly a month of disappointments such as these Mr. Heller joined us at Bui-tao with Mr. Kellogg. Caldwell thought it advisable to shift camp to the Ling-suik monastery, about twelve miles away, where he had once spent a summer with his family and had killed several tigers. This was within the blue tiger's range and, moreover, had the advantage of offering a better general collecting ground than Bui-tao; thus with Heller to look after the small mammals we could begin to make our time count for something if we did not get the tiger. [...] Caldwell and I always spent the afternoon at the blue tiger's lair but the animal had suddenly shifted his operations back to Lung-tao and did not appear at Ling-suik while we were there.

Both Caldwell and I lost from fifteen to twenty pounds in weight during the time we hunted the blue tiger and each of us had serious trouble from abscesses. I have never worked in a more trying climate--even that of Borneo and the Dutch East Indies where I collected in 1909-10, was much less debilitating than Fukien in the summer. The average temperature was about 95 degrees in the shade, but the humidity was so high that one felt as though one were wrapped in a wet blanket and even during a six weeks' rainless period the air was saturated with moisture from the sea-winds.

[...] It was hard to leave Fukien without the blue tiger but we had hunted him unsuccessfully for five weeks and there was other and more important work awaiting us in Yün-nan. It required thirty porters to transport our baggage from the Ling-suik monastery to Daing-nei, twenty-one miles away, where two houseboats were to meet us, and by ten o'clock in the evening we were lying off Pagoda Anchorage awaiting the flood tide to take us to Foochow. We made our beds on the deck house and in the morning opened our eyes to find the boat tied to the wharf at the Custom House on the Bund, and ourselves in full view of all Foochow had it been awake at that hour.'

Caldwell wrote in his own book: "The markings of the animal were marvellously beautiful. The ground colour seemed to be a deep shade of maltese, changing into almost deep blue on the under parts. The stripes were well defined, and so far as I was able to make out similar to those of a tiger of the regular type." and his son wrote in "Our Friends The Tigers" (1954) of finding maltese (grey-blue) hairs of Futsing's blue tigers along the mountain trails when accompanying his father during his many searches for the blue tigers.

Richard Perry, in his book "The World Of The Tiger" reiterated that China's blue tigers were called blue devils because they were so often man eaters. More recently, there have been occasional reports of blue tigers in a mountainous region on the border between North and South Korea. Because North Korea does not welcome outsiders, it is not currently possible to investigate sightings. Slate-coloured tigers may represent a montane population of tigers where the colour has become fixed in a small, isolated and inbred population. Caldwell's hunting expedition indicates that blue tigers, if they are a separate race, prefer inaccessible regions where they are less likely to be encountered by humans. There are no blue tigers in captivity today - if there were, the recessive gene would make it easy to fix the trait. If a smokey blue tiger was born in the Woodland Park Zoo, this would be the only captive blue tiger. There are no blue tiger pelts in museums or private collections and the images here are artist's impressions. Note: the term "Maltese" means "slate grey" and comes from the domestic cat world; it does not refer to Malta as the origin of the blue tigers.

Is it possible that blue tigers are due to a manifestation of the chinchilla gene known as "shaded silver"? The Amur tiger is found in north eastern China and northern North Korea and Siberia and has produced white tigers. The South China tiger whose range covers Fujian province (near Taiwan) has not produced white tigers though the historic ranges of the Amur and South China tigers may have overlapped resulting in inter-breeding. The South China tiger is supposedly the "stem species", from which all other tigers evolved so it is just about possible that the chinchilla mutation occurred in the South China tiger where it causes the bluish shaded colour morph and has been inherited by its descendent species where it has combined with other genes to produce white tigers.




Textual content is licensed under the GFDL.

For more information on the genetics of colour and pattern:
Robinson's Genetics for Cat Breeders & Veterinarians 4th Ed (the current version)
Genetics for Cat Breeders, 3rd Ed by Roy Robinson (earlier version showing some of the historical misunderstandings)
Cat Genetics by A C Jude (1950s cat genetics text; demonstrates the early confusion that chinchilla was a form of albinism)

For more information on genetics, inheritance and gene pools see:
The Pros and Cons of Inbreeding
The Pros and Cons of Cloning

For more information on anomalous colour and pattern forms in big cats see
Karl Shuker's "Mystery Cats of the World" (Robert Hale: London, 1989 - some of the genetics content is outdated)