Largest of all the cats and on top of the food chain, tiger is one of the most culturally important animals on this planet. But with as few as 3,200 surviving in the wild in the year 2010 (WWF), there is fear that they may face extinction by the next Year of the Tiger in 2022.
The total tiger habitat in the world today (2013) is about staggering 11 lakh (1.1 million) sq.km dispersed among Asia’s 13 countries. Eric Dinerstein, Chief Scientist and Vice President of conservation science of the WWF, says, “Assuming two tigers for every 100 square kilometres, that’s a potential 22,000 tigers.” That seems like a lot of land. Yet, tigers have lost some 93% of their historic range compared to five centuries ago. Now they occupy roughly 7 % of their former range. At present fewer than 3,500 may be left in the wild, whereas, by sad contrast, China and the United States are thought to have 10,000-15,000 in captivity.
Aggression amongst adult male tigers can be influenced by number of reasons. Number of tigers in a given area (density) and whether there is a social disruption in which males are competing to take control of a territory. The intensity of aggression increased when there are high tiger densities for a given area because there is more competition of resources and mating opportunities. Resident male territory-holders may be challenged by other young males for possession of the territory or the young males may challenge each for ownership if the resident male has vacated or dies. The strongest male will take possession of the territory. These times of social disruption may also cause aggression between females.
Hair & Coloration
Hairs of tigers provide camouflage, warmth and protection from cold. There are two types of hairs on the body of tigers – guard hairs and underfur. First one is longer and more durable than the underfur and mainly acts as a protective cover. The primary function of these hairs is to provide warmth in colder season. The underfur traps air which insulates the tiger’s body thereby keeping it warm. Grooming is an important part of the tiger’s day. They use their rasping tongue to remove loose hairs and dirt from their fur. The grooming process keeps the tiger’s coat in good condition by using their tongues to spread oils secreted from their glands.
Probably the most easily recognized of all wild cats, tigers are the only large cats to have distinctive striping located on both the hair and the skin. Their fur ranges from orange to brownish yellow with white chest and belly is covered with broken vertical black/dark brown stripes. Males of all the sub-species exhibit longer fur in the form of ‘ruff’ around the back of the head. This is especially pronounced in the Sumatran males.
Many tigers possess stripes on their face, sides, legs and stomach. The striping is varied in width, length, whether they are single or double-looped, coloration from a light brown to dark black and are not symmetrical from one side of the tiger to the other. Stripe pattern on top of the animal’s head resembles the Chinese character of “wang” which means “king.” Many tigers possess light yellow-orange to deep reddish-orange background coloration.
Tigers have distinctive white circular spots on the backside of their ears. There are two ideas as to the function of these eye-spots. One of which is that they function as “false eyes”; making the tiger seem bigger and watchful to a potential predator attacking from the rear. The other idea is that they play a role in aggressive communication because when threatened tigers may twist their ears around so that the backs face forward. This prominently displays the distinctive white markings. The function of the white markings is probably a combination of both ideas.
Tigers have much less rigid climate needs, but they have special attraction for water that is why they are never away from the water source. When both lions and tigers were widespread in Asia, perhaps, tigers’ liking for water may have kept them out of more arid areas favoured by lions. Strong swimmers with love of bathing in pools and lakes in summers in hotter regions, tigers are adapted to most types of forests and grasslands broken by woods, swamp margins beyond woodland areas and they are seldom found in wide-open country. Basically, they are nocturnal hunters; however, in protected areas – away from human intervention – they are often active during the day. Their striped coat blends well into sun-dappled vegetation. If it is approached from the rear, it sometimes is possible to spy the vivid white spot that stands out against the black fur on the back of each ear. They usually frequent water holes at dusk and dawn – the time when most animals come there to quench their thirst. Although the habitat dictates the type of animal that the tiger would hunt, but it has special liking for larger prey species, such as buffalo, deer, wild boars and monkeys. Occasionally they go even for fish and various other small mammals if there is scarcity of preferred food. Packed with muscles that ripple forcefully when the animal walks, the tiger’s forelimbs are extremely strong, equipping the animal well for killing large prey.
Old theory on formation of tiger stripes validated
Validating a theory on formation of tiger stripes and leopard spots that famous code-breaker and mathematician Alan Turning put forth in 1950s, researchers at King’s College London have provided the first experimental evidence in the early 2012 to show how tiger stripes or leopard spots are formed. Turning had proposed that regular repeating patterns in biological systems are generated by a pair of morphogens that work together as an ‘activator’ and ‘inhibitor’. Researchers studied the development of the regularly-spaced ridges found in the roof of the mouth in mice.
Carrying out experiments in mouse embryos, the team identified the pair of morphogens working together to influence where each ridge will be formed. These chemicals controlled each other’s expression, activating and inhibiting production and therefore controlling the generation of the ridge pattern.
They showed that when these morphogens’ activity is increased or decreased, the pattern of the ridges in the mouth palate are affected in ways predicted by Turing’s equations.
About Alan Turning
Alan Turing was one of the great unsung heroes of World War II. Known as the father of modern computing he broke German military’s secret codes – created using the famous Enigma machine – that helped British Intelligence stay one step ahead of Hitler, allowing the Navy to defeat his U-boats and win the Battle of the Atlantic. He also played a seminal role in defining the emerging field of artificial intelligence, prescribing the still used ‘Turing Test’ to determine whether a machine has become intelligent.
Turing’s work even laid the foundation for the creation of modern computers. When the war ended, Turing went to work programming some of the world’s first computers, drawing up-among other things-one of the earliest chess games. Time magazine named him one of the 100 most important people of the 20th century. ‘Everyone who taps at a keyboard, opening a spreadsheet or a word-processing program, is working on an incarnation of a Turing machine,’ it said.
Alan Turing was gay, and 1950s Britain punished him with a criminal conviction, intrusive surveillance and hormone treatment meant to extinguish his sex drive. He made no secret of his sexuality, and being gay could easily lead to prosecution in post-war Britain. In 1952, he was convicted of “gross indecency” over his relationship with another man. Besides thrown out of job he was stripped of his security clearance, subjected to monitoring by British authorities, and forced to take estrogen to neutralize his sex drive – a process described by some as chemical castration. Depressed and angry, Turing committed suicide in 1954 at the age of 41.
On 24 December 2013 Turing, was formally pardoned by Queen Elizabeth II, 59 years after he committed suicide. He was granted pardon under the Royal Prerogative of Mercy by the Queen, following a request from the justice secretary, Chris Grayling. “Turing was an exceptional man with a brilliant mind,” Grayling said in a statement released on his pardon. Describing the treatment meted out to him as unjust, Grayling said the code breaker “deserves to be remembered and recognized for his fantastic contribution to the war effort and his legacy to science.” In 2009 then British Prime Minister Gordon Brown had apologized for the way Turing was treated.
Territory and Communication
The size of tiger territory varies greatly by prey density (the amount of prey in a given area), locality and season. In areas where prey is in abundance the territories tend to be smaller in size because sufficient food is available in smaller vicinity. For male tigers in Ranthambhore Tiger Reserve in India; the prey concentrations are high and male tigers have territories that range in size from 5 to 150 sq km. In Siberia the prey concentrations are much lower and male tiger territories range in size from 800 to 1200 sq km. Seasonality in terms of prey migrations, food availability and weather may also affect prey populations and therefore the size of tiger territories.
Males’ territory usually encompasses that of more than one female and is rigorously protected against intrusion from other neighbouring males. An adult male’s territory will usually overlap several females’ territories. The larger area contains more than enough food, water and shelter resources and also accommodates more females’ territories. Therefore, females are the most coveted resource for males. Tigresses’ territories are smaller than that of males but focus on vital resources required for rearing young. Tigresses usually occupy territories adjacent to or take over parts of their mother’s territory.
Tigers assert and maintain their control over their territories by continuously patrolling them, but this is not the effective method to guard such a vast area so they have devised a very powerful but silent communication system to convey the other individuals about its movement and announcing the territorial claim. Spray-marking is one such method in which tiger, male or female, while walking turns its hindquarters towards a tree, bush, or a big stone or pole and with vertically raised tail will shoot out spray of fluid. This strong musky smelling fluid is a mixture of urine and a secretion from the anal glands.
This scent serves many purposes. Besides discouraging many it also encourages some young tigers to take on the resident male to usurp the territory. Strayed cubs can search out their mother by her spray-markings. Not only that, males can pinpoint a tigress in oestrus. Fresh markings can indicate a dangerous encounter between males while the old ones are signal that one can go ahead, but with care. It has been observed that the passer-by will always sniff the spray-markings of earlier animal and will invariably re-spray it, perhaps to assert his claim on the area.
Faeces along with the raked marks, scratching on trees and clawing are some other tools of communication. All these activities, including spray-marking, are found with higher frequency and intensity usually on the animal paths, nallahs, streams, specific trees, poles and stones etc. Perhaps the reason is such paths and belts act as natural boundaries, demarcating areas and ranges, especially for resident males.
Another means of communication is roar which is blood-chilling for humans and other animals alike, but for tigers it is a voice of a male asserting his territorial right. It is a long distance communication among jungle cats and definitely has greater intensity and regularity when the animals are asserting themselves.
Roar is produced in a variety of situations such as taking down large prey, signalling sexual receptivity and females calling to their young. These roars may be heard from distances over 3 km (1.8 mi.). Moaning is described as a subdued roar made while tigers are calmly walking with their heads in a downward position. This vocalization is audible for distances less than 400 m (440 yd.). Chuffing are friendly vocalizations that generally consist of a soft ‘brrr’ sound. This is primarily used for greetings between tigers and only audible at close range.
Tigers use their tails, which can be about a meter long, to communicate with one another. A tiger is relaxed if their tail is loosely hanging. Aggression is displayed by rapidly moving the tail from side to side or by holding it low with occasional intense twitches. Tigers may enhance their olfactory communication by using visual markings such as scrapes on the ground and trees.
Scent & Touch
Adult males and females both communicate to one another by marking their territories. An adult tiger will usually define the boundary of its territory by spraying urine because of the strong odour associated with it can last up to two months but they may also use faeces for marking. Smell is also a very accurate indicator to other tigers of how recently a tiger has passed by, and whether or not the territory is occupied.
All cats, including tigers, have a distinct scent associated with them due to their individualized scent glands. The individualized scent helps cubs track their mother’s path and serves to identify particular individuals. Cats have scent glands between their toes, tail, anus, head, chin, lips, cheeks, and facial whiskers. The animal’s intention is to leave its individualized scent to communicate with other animals of its species, mark its territory and belongings. The scientific community is currently trying to train dogs to detect some individualized tiger scents to assist with the estimation of wild tiger populations.
Scent glands between a tigress’s toes leave behind an individualized scent that enables a cub to follow its mother’s footsteps.
Sense of Touch: Vibrissae or Whiskers
Like all cats tigers too have a well-developed sense of touch, which they use for many purposes including navigation in darkness, detect danger and attack prey. They have five different types of vibrissae, commonly known whiskers, which detect sensory information and are differentiated by their location on the body. Whiskers differ from guard hairs in the sense that they are thicker, more deeply rooted in the skin and surrounded by a small capsule of blood. The root of whisker displaces the blood when it comes in contact with something, thereby amplifying the movement. Sensory nerves detect this movement and send signals to the brain for interpretation. Whiskers are so acutely sensitive that if they move 5 nanometers (a distance 2000 times less than the width of a human hair) its sensory nerve sends a signal to the brain.
Cats can control the movement of their whiskers, especially the long and rigid ones, called mystacials that protrude sideways from the muzzle. Mystacials are used when attacking prey and navigating in the dark. Tigers use these long, sensory hairs also to locate the spot where they should inflict a bite. Since their eyes cannot focus well on objects that are very close, such as prey they hold in their mouth, cats will rotate these whiskers down and around to check the captive for signs of life. The chin and lip, or mandibular, whiskers help the cat direct the killing nape bite. While navigating during the night or through the darkness, when eyesight is not of much use, mystacial and mandibular whiskers are pushed forwards to be used as sensors and help the animal to feel its way through. They can register very small changes in air pressure thus enabling the cat to avoid objects whilst moving around in the dark. Interestingly, cheetahs who mainly hunt by day, have less developed whiskers than many other ‘night hunting’ cats. Cats are able to change the position of their whiskers depending on what they are doing – at rest the whiskers are elongated, at 90% to the head, whilst when walking they are tilted forward to aid their sensing ability. When eating or fighting, cats pull their whiskers back and out of food or harm’s way. Whiskers are also used to decide whether the animal can fit in a small space.
Superciliary whiskers, located above the eyes and Cheek or genal whiskers, located just behind the mystacial whiskers on the cheeks, are less rigid and distinctly less mobile than the mystacials. They play an important, but less spectacular role. Whenever they are touched, they cause the lids to blink, thus protecting the eyes from injury.
Carpal whiskers are located on the back of the tiger’s front legs. With their help cat can feel its prey and detect any escape attempts.
Tylotrich whiskers are located randomly throughout the body. Besides the whiskers, which can reach up to 15 centimeters (six inches) in length, the facial area of the tiger has numerous sensory neurons that can detect even the slightest change in air pressure when passing by an object.
Cats in general are more sensitive to high-pitched sounds than humans are. They can hear sounds up to 60 kHz whereas a human’s upper auditory range is about 20 kHz. This sensitivity enables them to detect high-pitched sounds emitted by prey and their movements. On the lower scale they are capable of hearing infrasound too, which are below the range of normally audible sound (20 hertz) for humans. Tigers use infrasound to communicate over long distances or dense forests because the waves of these sounds can pass through a variety of mediums such as trees and mountains.
Tiger’s sense of hearing is most acute of all its senses and is mainly used for hunting. Their ears are capable of rotating, similar to a radar dish, to detect the origins of various sounds such as the high-frequency sounds produced by prey in the dense forest undergrowth.
Tiger’s sense of smell is not as highly developed as some of its other senses and is generally not used for hunting. They have small amount of odour-detecting cells in their nose and a reduced olfactory region in the brain that identifies various scents. They use this sense mainly for communicating information with one another such as territories and reproductive status.
Like other carnivores, tigers too have a Jacobson organ in the roof of their mouth. It is a pouch-like structure located directly behind the front incisors. It has two small openings that direct scent particles from the air as the tiger inhales to nerves located within the structure. The nerves then transmit the message to the olfactory region in the brain that identifies the scent.
Tigers often exhibit a behavior called flehman, in which they pick up a scent on their upper lip and curl it upwards towards their nose to detect scents. This behavior makes the tiger appear to be snarling but without any sound.
Tigers seem to be able to taste salt, bitter and acidic flavors and to a lesser degree of sweetness. Cats in general possess only about 500 taste buds compared to a human’s 9,000. Therefore taste buds are speculated to have a minimal role in their survivability.
Tiger a Solitary or Family Creature ?
On top of the food chain tigers are usually very cautious, territorial and solitary hunters, patrolling and marking their territory with urine sprays and scrapes. Rarely is it seen in family groups, barring the tigress that remains with her cubs almost for two years. Valmik Thapar has mentioned about an incident, which he saw while following Laxmi along with her cubs, “My last moments with this family were in the presence of a mature male and on one occasion we saw him carrying a large chital doe into a stream bed, followed by Laxmi and her three cubs. I had a feeling then that he must have contributed significantly in providing food for the family.
From these descriptions of family life it seems that tigers have an exceedingly close-knit bond with each other while they grow up, and that the mother plays a role of total devotion in this process — sacrificing all so that her cubs may survive. Sometimes the bond between tiger and tigress can be strong enough for them both to be involved in raising the family, but this is the exception and not the rule.”
Although the ‘pride’ behavior, as is seen among lions, is not the part of tiger’s life, but there are instances where some non-family groups have been found following it. It is not clear whether it is a temporary phenomenon or continues life-long. Edward B. Baker wrote in his book, “Sport in Bengal” (1886), “This animal is not the unsociable creature it is commonly understood to be. On the contrary, it is fond of consorting with others, and not seldom three or four may be found together; a mother and nearly full grown cubs; both parents and half grown ones, or a charming party of young males and females living and hunting together for a considerable length of time.”
A.A. Dunbar Brander states in “Wild Animals in Central India“, “The largest party I have ever seen together consisted of six animals; one large male and two fully grown females accompanied by three young animals almost as big as the tigers.” Valmik Thapar observed one day in January of 1984 ‘ an adult group of three in Ranthambhore…… one was an adult male, accompanied by two adult females sitting at a distances of ten to twelve meters from each other.
Tigers’ behavior changing ?
Males becoming affectionate fathers
Male tigers are not known to play any part in rearing of their young. Many are even hostile towards their cubs, but in Ranthambore National Park tiger’s roar is becoming more and more “affectionate”. And this is becoming even “infectious”. Officials have recently recorded seven cases of male tigers in the park that have taken on a parental role and are helping the tigresses bring up young ones.
It started with a male called T-25. The tiger was seen roaming with the two orphaned four-month old cubs and protecting them from other tigers, panthers and hyenas after the mother T-5 died within 9 to 10 days of giving birth. T-25 was also sighted confronting a tigress, T-17, to protect the cubs.
It is a rare behavior among the male tigers, but as they say only change is permanent! After the above incident officials have recorded at least six more male tigers at the park that are playing the daddy’s role and are helping tigresses in bringing up the young ones. Generally, the mother takes care of the cubs till they are at least two-year-old while the father plays a mere visitor.
“What is now happening in Ranthambore will denote the sheer complexity of tiger behaviour. The trend of tigers preferring solitude is gradually changing at the park. In fact, we have witnessed a peculiar, astonishing and amazing breakthrough in the behaviour of male tigers,” said Rajesh Kumar Gupta, field director, Ranthambhore tiger reserve.
Gupta has documented the behaviour of these six tigers in the current publication (2012) of Project Tiger. “In Ranthambore National Park, T-19 female with three cubs are in the bigger home range of their presumed father T-28. The territory of T-28 has increased or varies with the movement of T-19 and her three cubs, signifying reach of parental protection by the males. On 18 March 2012, I sighted T-19 tigress with two cubs. One of them stood up and moved close to the male tiger T-28 and sat beside him for affection” wrote Gupta.
“On March 29, 2012, I spotted tigress T-8 and her two cubs while returning from night patrolling and also saw tiger T-34 near them. The cubs were again spotted with the tigress and the tiger few days later in the same area. It has been noticed that T-8 with her two cubs are residing within the home range of T-34 male in the Sawai Mansingh Sanctuary,” he says.
“Tigress T-26 with three cubs lives in the close vicinity of T-20, an aged tiger. T-31 with two cubs is frequently visited by tiger T-23. T-11 with three cubs is protected by T-33. T-30 with a litter of three cubs is protected by T-3 and T-9 with two cubs is protected by T-33, a male tiger,” he noted.
Gupta explains, “It could be that the father of the cubs are providing parental protection to prevent infanticide and establish ‘genetic supremacy’ in the park. However, what has become clear is that male tigers do display affectionate behavior, resorting to parental care. But research and observation should continue to reach a definite conclusion.”
Tigress eats its own dead cub
In a strange incident in Panna Tiger Reserve (PTR) in Madhya Pradesh (India), a tigress eaten her own cub, a couple of minutes after it was killed by an adult male the female tigress code named T2 was pairing with. The dead cub was spotted by villagers at Jardhova forest area of Rampura village in the morning of 2 February 2013 and informed the forest officials about the incident.
Officials found T2, shifted from Kanha National Park (Madhya Pradesh) in 2009, had eaten her own cub, born nine months ago. “The male P111, with which she was pairing, was sitting beside the carcass,” according to R S Murthy, park director. It was an unusual behaviour, the officer said, adding “theory that wild tigresses eat cubs has never been substantiated.” On the other hand a researcher said that such a thing is common among captive big cats. Hunger due to shortage of prey base may have driven the tigress to eat its cub.