Extinction is a normal process in the course of evolution. Species have slowly evolved and disappeared throughout geologic time as the result of climate changes and the inability to adapt to survive competition and predation. Since the 1600s, however, the rate of extinction has accelerated rapidly because of human population growth and human resource consumption. Today, most of the worlds habitats are changing faster than most species can adapt to through evolution, or natural selection. The current global extinction rate is exponentially greater than the background (normal rate of extinction in the process of evolution) extinction rate. Many biologists believe that we are in the middle of the greatest mass extinction episode since the disappearance of the dinosaurs 65 million years ago.
Causes of extinction There are a number of reasons that can contribute directly or indirectly to the extinction of a species or group of species. The primary causes of species extinction or endangerment are habitat destruction, commercial exploitation (such as plant collecting, hunting, and trade in animal parts), damage caused by non-native plants and animals introduced into an area, and pollution. The survival of ecosystems (plant and animal communities and their physical surroundings) such as forests, coral reefs, or wetlands depends on their biodiversity, or variety of plants, animals, and habitats, as well as the many interactions among these species. The removal or disappearance of one or several species may irreversibly damage the ecosystem and lead to its decline.
JAVAN TIGERJavan Tigers were a subspecies of tigers which were limited to the Indonesian island of Java. In the early 19th century Javan tigers were so common, that in some areas they were considered nothing more than pests. As the human population increased, large parts of the island were cultivated, leading to a severe reduction of their natural habitat. Wherever man moved in, the Javan tigers were ruthlessly hunted down or poisoned. Natives carried much of the hunting out, a surprising thing since they considered the tiger a reincarnation of their dead relatives. The last specimen to have been seen was sighted in 1972, although there is evidence from track counts that the animal had lingered into the 1980’s. The last track counts to yield evidence of the tigers was held in 1979, when just three tigers were identified. The leading cause of their extinction was agricultural encroachment and habitat loss, which continues to be a serious concern in Java.
Habitat and Ecology At the end of the 18th century, tigers inhabited most of Java. Around 1850, the people living in the rural areas still considered them a plague. Until 1940, tigers had retreated to remote mountainous and forested areas. Around 1970, the only known tigers lived in the region of Mount Betiri, with an altitude of 1,192 m (3,911 ft) the highest mountain in Javas southeast, which had not been settled due to the rugged and slopy terrain. In 1972, the 500 km2(190 sq mi) area was gazetted as wildlife reserve. The last tigers were sighted there in 1976.
Javan tigers were very small compared to other subspecies of the Asian mainland, but larger in size than Bali tigers. Males weighed between 100 and 140 kg (220 and 310 lb) on average with a body length of 200 to 245 cm (79 to 96 in). Females were smaller than males and weighed between 75 and 115 kg (170 and 250 lb) on average. They usually had long and thin stripes, which were slightly more numerous than of the Sumatran tiger. Their nose was long and narrow, occipital plane remarkably narrow and carnassials relatively long. Based on these cranial differences, the Javan tiger was proposed to be assigned to a distinct species,Panthera sondaica. Classically it is considered to be a subspecies of tiger Panthera tigris. The smaller body size of Javan tigers is attributed to Bergmann’s rule and the size of the available prey species in Java, which are smaller than the cervid and bovid species distributed on the Asian mainland. However, the diameter of their tracks are larger than ofBengal tiger in Bangladesh, India and Nepal.