Biology Term Paper

– Tigers Essay, Research Paper

The tiger is part of the kingdom Animalia, phylum Chordata, class Carnivora, family Felidae, subfamily Panthernae, genus/species Panthera tigris. Tigers have round pupils and yellow irises

(except for the blue eyes of white tigers). Due to a retinal

adaptation that reflects light back to the retina, the night vision of

tigers is six times better than that of humans. Like domestic

cats, tiger claws are retractable. Tiger scratches on trees serve

as territorial markers. No one knows exactly why tigers are

striped, but scientists think that the stripes act as camouflage (See diagram A), and help tigers hide from their prey.

The Sumatran tiger has the most stripes of all the tiger subspecies, and the Siberian tiger has the fewest stripes. Tiger stripes are like human fingerprints; no two tigers have the same pattern of stripes. The tiger’s head often carries the Chinese mark of wang or king on the forehead. Most tigers have an orange coat with dark brown or black stripes accented with white. Tigers that live in cold climates (Siberian tigers) have thicker fur than tigers that live in warm climates. A tiger’s tail is 3 to 4 feet long, about half as long as its body. Tigers use their tails for balance when they run through fast turns. They also use their tails to communicate with other tigers.

Where did tigers come from. Tigers (and all other carnivores) are descended from civet-like animals called miacids that lived during the age of the dinosaurs about 60 million years ago. These small mammals, with long bodies and short flexible limbs, evolved over millions of years into several hundred different species, including cats, bears, dogs and weasels. Approximately 37 cat species exist today, including Panthera tigris, the tiger. Tigers evolved in eastern Asia, and while some of the earliest tiger fossils have been found in Siberia and China, the tiger’s exact place of origin is unknown.

Adult tigers are solitary animals that establish their territories in areas with enough prey, cover and water to support them. The difficulty of locating prey in tiger habitat makes it more efficient for tigers to hunt alone. As a result, they do not tend to form social groups like lions. A female tiger and her cubs are the exception to this. The territory of a tiger usually ranges in size from about 26-78 sq. km, although the territory of a Siberian tiger may be as large as 310 sq. km. The size of a tiger’s territory depends on the amount of prey available. Tiger territories are not exclusive. Several tigers may follow the same trails at different times, and a male’s territory usually overlaps those of several females. Both male and female tigers spray bushes and trees along their route with a mixture of urine and scent gland secretions. This is a way of declaring their territory. They also leave scratch marks on trees, and urinate or leave droppings in prominent places.

Female tigers called tigresses reach maturity when they are about 3 years old, males a year or so later. In temperate climates, a tigress comes into estrus only seasonally; however in tropical climates, she may come into estrus throughout the year. She signals her readiness with scent markings and locating roars. The brief act of copulation occurs continually for a five day period. Tigers are induced ovulators, and must be stimulated through frequent copulation in order to become pregnant. To help stimulate ovulation, the male tiger’s penis has spines. This explains in part why the female roars and lashes out at the male immediately following copulation. Following mating, the gestation period for tigers is approximately 103 days. The average litter size of tigers is 2 or 3 cubs, the largest is 5. One usually dies at birth. Tiger cubs are born blind and weigh only about 1 kg, depending on th subspecies. They live on milk for 6-8 weeks (See diagram B) before the female begins taking them to kills to feed. Tigers have fully developed canines by 16 months of age, but they do not begin making

their own kills until about 18 months of age. Young tigers live with their mother until they are two to three years old, then they find their own territories. Females tend to stay closer to the mother’s range than males.

Over much of the tiger’s broad geographic range, wild pig, wild cattle and several species of deer are its major prey. All prey are forest or grassland ungulates that range in size from 30-900 kg. Tigers are ambush hunters, stalking their prey, approaching as closely as possible, and then charging the animal from behind. They usually bite the neck or throat of their prey. The neck-bite, which severs the spinal cord, is typcially used on small or medium sized prey, while the throat bite, which causes suffocation, is used on larger animals. After killing their prey, tigers drag the animal to a safe place, consuming it over the course of several days. Typically, wild tigers gorge themselves on fresh kills, and can eat as much as 18 kg of meat at one time. Several days may pass before they are hungry enough to hunt again.

The life span of tigers in the wild is thought to be about 10 to 15 years. Tigers in zoos live to be between 16 and 20 years old. Tiger hair length varies geographically. In the southern subspecies the hairs are short, approximately 7 to 20 mm on the back and 15 to 35 m