Why does animals become endangered

Humans are largely responsible when animals become extinct, endangered or threatened. Here are some reasons why animals become endangered:. Humans destroy precious habitat--the natural environment of a living thing--when they fill swamps and marshes, dam rivers and cut down trees to build homes, roads and other developments. Oil spills, acid rain and water pollution have been devastating for many species of fish and birds.

When animals or plants arrive into a new habitat from a foreign place they sometimes introduce diseases that the native species can't fight. Many violet species are likely to become threatened. Vulnerable Species The definitions of the three threatened categories vulnerable, endangered, and critically endangered are based on five criteria: population reduction rate, geographic range, population size, population restrictions, and probability of extinction. Threatened categories have different threshold s for these criteria.

As the population and range of the species decreases, the species becomes more threatened. This decline is measured over 10 years or three generations of the species, whichever is longer. A generation is the period of time between the birth of an animal and the time it is able to reproduce. Mice are able to reproduce when they are about one month old.

Mouse populations are mostly tracked over year periods. An elephant's generation lasts about 15 years. So, elephant populations are measured over year periods.

A species is vulnerable if its population has declined at least 50 percent and the cause of the decline is known. Habitat loss is the leading known cause of population decline. A species is also classified as vulnerable if its population has declined at least 30 percent and the cause of the decline is not known.

A new, unknown virus, for example, could kill hundreds or even thousands of individuals before being identified.

An area of occupancy is where a specific population of that species resides. This area is often a breeding or nesting site in a species range. The species is also vulnerable if that population declines by at least 10 percent within 10 years or three generations, whichever is longer. A species is vulnerable if it is restricted to less than 1, mature individuals or an area of occupancy of less than 20 square kilometers 8 square miles.

These formulas calculate the chances a species can survive, without human protection, in the wild. Vulnerable Species: Ethiopian Banana Frog The Ethiopian banana frog Afrixalus enseticola is a small frog native to high- altitude areas of southern Ethiopia. It is a vulnerable species because its area of occupancy is less than 2, square kilometers square miles. The extent and quality of its forest habitat are in decline.

Threats to this habitat include forest clearance, mostly for housing and agriculture. Vulnerable Species: Snaggletooth Shark The snaggletooth shark Hemipristis elongatus is found in the tropical , coastal waters of the Indian and Pacific Oceans. Its area of occupancy is enormous, from southeast Africa to the Philippines, and from China to Australia. However, the snaggletooth shark is a vulnerable species because of a severe population reduction rate.

Its population has fallen more than 10 percent over 10 years. The number of sharks is declining due to fisheries, especially in the Java Sea and Gulf of Thailand. They are sold in commercial fish markets, as well as restaurants.

Galapagos kelp is classified as vulnerable because its population has declined more than 10 percent over 10 years. Climate change is the leading cause of decline among Galapagos kelp. El Nino , the natural weather pattern that brings unusually warm water to the Galapagos, is the leading agent of climate change in this area.

Galapagos kelp is a cold-water species and does not adapt quickly to changes in water temperature. Endangered Species 1 Population reduction rate A species is classified as endangered when its population has declined between 50 and 70 percent.

A species is classified as endangered when its population has declined at least 70 percent and the cause of the decline is known. A species is also classified as endangered when its population has declined at least 50 percent and the cause of the decline is not known. When a species population declines by at least 20 percent within five years or two generations, it is also classified as endangered. Endangered Species: Siberian Sturgeon The Siberian sturgeon Acipenser baerii is a large fish found in rivers and lakes throughout the Siberian region of Russia.

The Siberian sturgeon is a benthic species. Benthic species live at the bottom of a body of water. The Siberian sturgeon is an endangered species because its total population has declined between 50 and 80 percent during the past 60 years three generations of sturgeon. Overfishing, poach ing, and dam construction have caused this decline. It is an endangered species because it has a very small population.

The bird is only found on a single island, meaning both its extent of occurrence and area of occupancy are very small. The Tahiti reed-warbler is also endangered because of human activity.

The bird nests in bamboo and feeds on flowers and insects that live there. As development and invasive species such as Miconia destroy the bamboo forests, the population of Tahiti reed-warblers continues to shrink.

Ebony is an endangered species because many biologists calculate its probability of extinction in the wild is at least 20 percent within five generations.

Ebony is threatened due to overharvest ing. Ebony trees produce a very heavy, dark wood. When polished, ebony can be mistaken for black marble or other stone. For centuries, ebony trees have been harvested for furniture and sculptural uses such as chess pieces.

Most ebony, however, is harvested to make musical instruments such as piano key s and the fingerboard s of stringed instruments. A species is classified as critically endangered when its population has declined at least 90 percent and the cause of the decline is known. A species is also classified as endangered when its population has declined at least 80 percent and the cause of the decline is not known.

A species is also classified as critically endangered when the number of mature individuals declines by at least 25 percent within three years or one generation, whichever is longer.

It is critically endangered because its extent of occurrence is less than square kilometers 39 square miles. The major threat to this species is loss of its cloud forest habitat. People are clearing forests to create cattle pasture s. The Transcaucasian racerunner is a critically endangered species because of a huge population decline, estimated at more than 80 percent during the past 10 years.

Threats to this species include the salination , or increased saltiness, of soil. Fertilizers used for agricultural development seep into the soil, increasing its saltiness.

Racerunners live in and among the rocks and soil, and cannot adapt to the increased salt in their food and shelter. The racerunner is also losing habitat as people create trash dumps on their area of occupancy. Critically Endangered Species: White Ferula Mushroom The white ferula mushroom Pleurotus nebrodensis is a critically endangered species of fungus.

The mushroom is critically endangered because its extent of occurrence is less than square kilometers 39 square miles. It is only found in the northern part of the Italian island of Sicily, in the Mediterranean Sea. The leading threats to white ferula mushrooms are loss of habitat and overharvesting. White ferula mushrooms are a gourmet food item.

Farmers and amateur mushroom hunters harvest the fungus for food and profit. Extinct In The Wild A species is extinct in the wild when it only survives in cultivation plants , in captivity animals , or as a population well outside its established range.

A species may be listed as extinct in the wild only after years of surveys have failed to record an individual in its native or expected habitat. Extinct in the Wild: Scimitar-horned Oryx The scimitar-horned oryx Oryx dammah is a species of antelope with long horns. Its range extends across northern Africa. The scimitar-horned oryx is listed as extinct in the wild because the last confirmed sighting of one was in Captive herds are now kept in protected areas of Tunisia, Senegal, and Morocco.

Scimitar-horned oryxes are also found in many zoos. Extinct in the Wild: Black Soft-shell Turtle The black soft-shell turtle Nilssonia nigricans is a freshwater turtle that exists only in one man-made pond, at the Baizid Bostami Shrine near Chittagong, Bangladesh. The to turtles that live at the pond rely entirely on humans for food. Until , black soft-shell turtles lived throughout the wetland s of the Brahmaputra River, feeding mostly on freshwater fish.

Unlike other animals that are extinct in the wild, black soft-shell turtles are not found in many zoos. The reptiles are considered to be the descendants of people who were miraculously turned into turtles by a saint during the 13th century. Extinct in the Wild: Mt. Kaala Cyanea The Mt. Kaala cyanea Cyanea superba is a large, flowering tree native to the island of Oahu, in the U. The Mt. Kaala cyanea has large, broad leaves and fleshy fruit. Geological Survey USGS have discovered a population of the endangered desert pupfish Cyprinodon macularius in constructed ponds along the southeastern shore of the Salton Sea, in south-central California.

A highly endangered native Hawaiian bird species has taken a small but significant step back from the brink of extinction. USGS biologists monitoring 14 captive-reared puaiohi released into the wild earlier this year by The Peregrine Fund say the birds are nesting and have already fledged four young. Pima pineapple cactus and vegetative offshoot, commonly called a pup, in the Altar Valley of south-central Arizona November A green and black endangered Sonoran tiger salamander Ambystoma mavortium stebbinsi on a tree branch.

Malaria transmission is tied closely to the effects of temperature on development of malarial parasites within their mosquito. USGS biologists are leading the monitoring and reintroduction effort of the Southern California mountain yellow-legged frog -- federally listed as endangered with only wild adults remaining in the mountains surrounding Los Angeles County.

The Colorado River basin supports one of the most distinctive fish communities in North America, including the federally endangered humpback chub Gila cypha. The number Grand. Listen up—it's Endangered Species Day, and we have two podcasts for you: giant, invasive predators that eat endangered animals, and the tiny Devil's Hole pupfish, which lives on a watery shelf no bigger than a walk-in closet. Skip to main content. Search Search. Biology and Ecosystems.

Learn more: Endangered Species Act. Apply Filter. This is an issue of great concern, as these populations are already struggling to survive in the current environment. If some of these species are more vulnerable to fatal WNV infection, WNV may ultimately lead to their extinction or significantly set back the progress of the recovery programs.

Where are salmon most endangered? Certain populations of sockeye salmon, coho salmon, chinook salmon, and Atlantic salmon are listed as endangered. Sockeye salmon from the Snake River system are probably the most endangered salmon. Coho salmon in the lower Columbia River may already be extinct. Salmon are not endangered worldwide. For example, most populations in Alaska are Are salmon endangered worldwide? No, salmon are not endangered worldwide. For example, most populations in Alaska are healthy.

Some populations in the Pacific Northwest are much healthier than others. These healthy populations usually occupy protected habitats such as the Hanford Reach on the Columbia River and streams of Olympic National Park. Learn more: Questions and Answers What are the differences between endangered, threatened, imperiled, and at-risk species? What is an invasive species and why are they a problem? An invasive species is an introduced, nonnative organism disease, parasite, plant, or animal that begins to spread or expand its range from the site of its original introduction and that has the potential to cause harm to the environment, the economy, or to human health.

A few well-known examples include the unintentional introduction of the Filter Total Items: 9. Year Published: Early action to address an emerging wildlife disease A deadly fungal pathogen, Batrachochytrium salamandrivorans Bsal that affects amphibian skin was discovered during a die-off of European fire salamanders Salamandra salamandra in Adams, M.

Camille; Grear, Daniel A. View Citation. Geological Survey Fact Sheet , 2 p. Year Published: Birds of a feather Greater sage-grouse Centrocercus urophasiunus, hereafter sage-grouse are broadly distributed, occupy a diversity of sagebrush habitats, and face multiple threats.

Knick, Steven T.