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Why Do Animal Species Become Extinct?

overhuntingThe process of extinction involves many factors, such as weather, habitat loss, environmental toxins, disease, and shrinking population dynamics.

These factors can be analyzed to predict extinction risks and rates for endangered species. But some species may become extinct much faster than predicted because scientists have not updated the standard extinction prediction model.

Ecologists Alan Hastings at the University of California, Davis, and Brett Melbourne at the University of Colorado in Boulder have recommended a re-evaluation of the risks to wildlife based upon the proportion of males compared with females in a dwindling population, and the differences in reproductive success between individuals and birth rates in the group.

When these additional aspects are factored into risk assessments for particular species, the danger of extinction substantially increases. Missing factors such as the number of males to females and variations in the number of offspring are capable of causing unexpected large swings in the size of a population. At times, the swings may cause a population to grow, but they also may cause a population to contract.

Hastings and Melbourne contend that older extinction models could be erroneously underestimating the time to extinction. They predict that some species could go extinct 100 times sooner than expected.

Dr. Becker's Comments:

Extinction is defined as the end of an organism. The moment of extinction is the death of the last individual of a species.

It’s disturbing to contemplate that an entire species like the magnificent Sumatran tiger or the smallest member of the bear family, the Malayan sun bear could soon simply disappear from our world.

Causes of Extinction

Extinction of an entire species can happen very suddenly or gradually over thousands of years.

Causes of extinction are both natural and man-made.

Man-made causes of extinction include:

  • Overharvesting and overhunting. Overharvesting is when humans make use of a species at a rate greater than the species can reproduce itself.
  • Pollution in the form of chemicals and energy is another man-made cause of extinction.
  • Habitat destruction involves demolishing a natural environment, thereby displacing or wiping out the organisms that lived there. Destruction occurs through clearing habitats for agricultural purposes and through activities like mining and logging.
  • Introducing new predators and food competitors. Humans have the ability, whether intentionally or unintentionally, to introduce exotic species into new environments where they are able to prey on native species or compete with them for food.

The process of natural extinction is slower than man-made extinction. Natural triggers for extinction include climatic heating and cooling, changes in sea levels and currents, acid rain, disease epidemics, and the spread of invasive species.

A Few Creatures Recently Lost

Passenger Pigeon. This species of pigeon was wiped out in less than 100 years. The last passenger pigeon on earth died in a zoo in Cincinnati in 1914. Her name was Martha.

Japanese Sea Lion. Primarily found in the Sea of Japan, and may or may not have been a subspecies of the California Sea Lion. The last sighting of a colony of these sea mammals was reported in the 1950’s – the last confirmed record is of a single juvenile captured in 1974.

Tasmanian Tiger. Also known as the thylacine, this animal looked like a cross between a tiger and a dog, but it was actually a marsupial complete with pouch. The last one of its kind died in 1936 in Australia.

Baiji White Dolphin. A freshwater dolphin native to China, the Baiji had very poor eyesight but was highly intelligent. It is believed this dolphin was fished to extinction within just the last five years.

Species Currently in Danger of Extinction

According to the International Union for Conservation of Nature (IUCN), the species at highest risk of extinction in the immediate future are the following:

The group facing a very high risk of extinction in the near future includes the Dhole, the Blue Whale, the Ethiopian wolf, the Giant Panda, the Snow Leopard, the Crowned Solitary Eagle and the Orangutan.

How to Get Involved in Animal Conservation Efforts

You and I will have to leave the science of extinction to the ecologists. However, there are things you can do as an individual to get involved in the conservation movement.

There are several excellent organizations dedicated to conservation studies. Learn more about them and what you can do help:

World Wildlife Fund

African Wildlife Foundation

Endangered Species Coalition

U.S. Fish and Wildlife Service Endangered Species Program

National Zoo

Animal Planet’s R.O.A.R. (Reach Out, Act, Respond)

+ Sources and References