These Animals Are About to Disappear From the Planet Forever

When a species becomes extinct, it's gone for good: the last surviving member has died.

Earth is currently experiencing the worst wave of species die-offs -- a mass extinction of plants and animals -- since the dinosaurs 65 million years ago, according to the Center for Biological Diversity. Scientists say that nearly all of the thousands of currently threatened species -- mammals, birds, fish, reptiles, amphibians, plants and invertebrates -- are at risk because of human activities, including habitat loss, introduction of non-natives, and the effects of climate change.

This list is based on the priorities of the World Wildlife Fund, a conservation organization that focuses on protection of species that are critical to their larger environment, and the The IUCN's Redlist, a comprehensive inventory of the conservation status of species around the world.

Here are 33 animals that are at risk of disappearing from the planet forever.

Pere David's Deer
Pere David's Deer

Pere David's Deer

Elaphurus davidianus

Status: Extinct in the Wild

Population: about 600

This semi-aquatic deer of China vanished around 1939 when the last wild one was shot and killed. The Pere David's Deer has been recovered from the edge of extinction after being reintroduced into captivity in China, according to the IUCN redlist. There are now four wild populations being established by escapees from a Nature Reserve during severe flooding in 1998, according to IUCN.

Photo: Tim Felce (Airwolfhound)/Wikipedia

Scimitar-horned Oryx
Scimitar-horned Oryx

Scimitar-horned Oryx

Oryx dammah

Status: Extinct in the Wild

The myth of the one-horned unicorn may have originated from this antelope, which was once widespread across northern Africa and was domesticated in ancient Egypt. Overhunting and habitat loss, including competition with domestic livestock, are the main reasons for the extinction of the wild population, according to the IUCN Redlist.

Photo: Charles Miller from Basingstoke, United Kingdom, Wikipedia

Guam kingfisher
Guam kingfisher

Guam kingfisher

Todiramphus cinnamominus

Population: about 146

Status: Extinct in the Wild

The Guam kingfisher is a species of kingfisher from the U.S. territory. The wild population was killed off by the non-native brown tree snake. It exists only in captivity. The male pictured here is at the Bronx Zoo.

Photo: Eric Savage/Wikipedia

Alagoas Curassow
Alagoas Curassow

Alagoas Curassow

Mitu mitu

Population: about 130

Status: Extinct in the Wild

Clearance of the lowland forests of Brazil for sugarcane, as well as poaching, have brought this glossy-black, pheasant-like bird to the edge of extinction. While the bird exists in captive breeding programs, much of its wild habitat has been destroyed.

Photo: Shutterstock

Guam Rail
Guam Rail

Guam Rail

Hypotaenidia owstoni

Population: about 150

Status: Extinct in the Wild

The last individual in the wild of this flightless but fast-running bird died in 1987, killed by the brown tree snake. Captive breeding programs in Guam and the U.S. may restore the population. Pictured is a Guam Rail at the Cincinnati Zoo.

Photo: Greg Hume/Wikipedia

South China Tiger
South China Tiger

South China Tiger

Panthera tigris amoyensis

Status: Critically Endangered (possibly Extinct in the Wild)

Population: 30-80

According to the World Wildlife Fund, the South China tiger population was about 4,000 in the early 1950s. In the next few decades, thousands were killed, hunted as a pest. Though the Chinese government banned hunting in 1979, by 1996 the population was estimated to be just 30-80 of these tigers. Today the big cat is considered to be "functionally extinct," as it has not been seen in the wild for more than 25 years.

Photo: J. Patrick Fischer/ Wikipedia

Amur Leopard
Amur Leopard

Amur Leopard

Panthera pardus orientalis

Status: Critically Endangered

Population: More than 84

A rare subspecies of leopard of the Russian Far East, the Amur leopard can run at speeds of up to 37 mph. It is frequently killed by poachers for its beautiful, spotted fur, according to WWF.

Photo: Shutterstock

Black Rhino
Black Rhino

Black Rhino

Diceros bicornis

Status: Critically Endangered

Population: 5,000 - 5,400

Killed in large numbers by European hunters and settlers, today rhinos are an important source of income from ecotourism in places like Namibia. World Wildlife Fund says this species has made a strong comeback from the brink of extinction, but poaching and black-market trafficking of rhino horn continues to threaten recovery. Pictured is a black rhinoceros in Kruger national park, South Africa.

Photo: Shutterstock

Orangutan, Sumatran Orangutan
Orangutan, Sumatran Orangutan

Orangutan

Pongo pygmaeus

Status: Critically Endangered

Population: About 104,700

Sumatran Orangutan

Pongo abelii 

Status: Critically Endangered

Population: 14,613

Highly intelligent, Orangutans share 96.4% of genes with humans. Female Orangutans are hunted most, and if caught with offspring, the young are often kept as pets.

Sumatran Orangutans live in the trees of tropical rainforests, and rarely travel on the ground.

Photo: Shutterstock

Cross River Gorilla
Cross River Gorilla

Cross River Gorilla

Gorilla gorilla diehli

Status: Critically Endangered

Population: 200 to 300 individuals

Cross River gorillas live in a region populated by many humans in Cameroon and Nigeria. As humans clear forests for timber, agriculture and livestock, the gorillas continue to lose habitat. They are also poached by hunters.

Photo: Shutterstock

Eastern Lowland Gorilla
Eastern Lowland Gorilla

Eastern Lowland Gorilla

Gorilla beringei graueri

Status: Critically Endangered

Population: Unknown-Possibly as few as 8,500

Poaching, disease, habitat destruction and years of civil unrest in the Democratic Republic of Congo have impacted the population of this gorilla.

Photo: Shutterstock

Hawksbill Turtle
Hawksbill Turtle

Hawksbill Turtle

Eretmochelys imbricata

Status: Critically Endangered

Population: n/a

Hawksbills feed in coral reefs, helping to maintain the health of reefs and sea grass beds. Their existence is threatened by wildlife trade of their shells, habitat loss, egg collection, pollution and development on coasts, where they lay their eggs. They often get caught on fishing hooks or tangled in gillnets, causing them to drown.

Photo: Shutterstock

Javan Rhino
Javan Rhino

Javan Rhino

Rhinoceros sondaicus

Status: Critically Endangered

Population: 58-68

With just 58-68 of these rhinos that live in Ujung Kulon National Park in Java, Indonesia, these are the most threatened of all rhinos. Most were killed by trophy hunters during colonial times. Vietnam's last Javan rhino was poached in 2010. They are killed for their horn, which is coveted in parts of Asia for its supposed medicinal qualities and as an ornament. Even in the park, poaching remains a threat.

Photo: Lena Lir / Shutterstock

Malayan Tiger
Malayan Tiger

Malayan Tiger

Panthera tigris jacksoni

Status: Critically Endangered

Population: 250-340

This tiger is found only on the Malay Peninsula and in the southern tip of Thailand. It is threatened by loss of habitat to logging operations and road development, as well as illegal wildlife trade and sometimes angry villagers who retaliate for loss of livestock.

Photo: Shutterstock

Mountain Gorilla
Mountain Gorilla

Mountain Gorilla

Gorilla beringei beringei

Status: Critically Endangered

Population: 880

The remainder of these gorillas live in the Bwindi Impenetrable National Park in Uganda. These animals have endured years of war, hunting, habitat destruction and disease. Conservation efforts have helped increase the population, according to WWF.

Photo: Richard Ruggiero/USFWS

Saola
Saola

Saola

Pseudoryx nghetinhensis

Status: Critically Endangered

Population: Unknown

Often called the Asian unicorn, little is known about the rarely seen saola. None exist in captivity. They are found only in the Annamite Mountains of Vietnam and Laos. Scientists have documented saola in the wild on only four occasions.

Photo: Silviculture at Vietnamese Wikipedia

Sumatran Elephant, Asian Elephant
Sumatran Elephant, Asian Elephant

Sumatran Elephant (pictured)

Elephas maximus sumatranus

Status: Critically Endangered

Population: 2,400 - 2,800

Asian Elephant

Elephas maximus indicus

Status: Endangered

Population: Fewer than 50,000

Elephants are victims of deforestation and poachers who kill them and sell their tusks on the illegal ivory market. Elephant numbers have declined by 80% in less than 25 years, according to the World Wildlife Fund.

Photo: Shutterstock

Sumatran Rhino
Sumatran Rhino

Sumatran Rhino

Dicerorhinus sumatrensis

Status: Critically Endangered

Population: Fewer than 100

Much smaller than other rhinos, (they weigh up to 2,000 pounds, while other rhinos can weigh over 5,000 pounds) Sumatran rhinos are also known as the hairy rhinoceros for their long hair. Poaching for their horn has driven these animals to near extinction.

Photo: Shutterstock

Sumatran Tiger
Sumatran Tiger

Sumatran Tiger

Panthera tigris sumatrae

Status: Critically Endangered

Population: Less than 400

Habitat destruction from deforestation forces tigers into human-populated areas in search of food, where they are often killed by villagers. They are victims of illegal wildlife trade, prized for their bones and their pelts.

Photo: Shutterstock

Vaquita
Vaquita

Vaquita

Phocoena sinus

Status: Critically Endangered

Population: 30

The rarest marine mammal in the world is on the edge of extinction, and could be gone by this year, according to World Wildlife Fund. This relatively small porpoise lives in Mexico's Gulf of California, where they are often caught and drowned in gillnets used by illegal fishing operations in marine protected areas, despite efforts by Mexico to protect it. In August, a U.S. federal judge ordered a fishing embargo against Mexico to protect the vaquita, according to media reports.

Photo: Paula Olson/NOAA

Western Lowland Gorilla
Western Lowland Gorilla

Western Lowland Gorilla

Gorilla gorilla gorilla

Status: Critically Endangered

Population: Unknown

Living in some of the most dense and remote rainforests in Africa, large numbers of these gorillas died from the deadly Ebola virus. They are also killed for bushmeat or during the capture of their babies for pets. Populations still exist in isolated parts of the Republic of Congo. Pictured is a gorilla at the Prague zoo.

Photo: Shutterstock

Yangtze Finless Porpoise
Yangtze Finless Porpoise

Yangtze Finless Porpoise

Neophocaena asiaeorientalis ssp. asiaeorientalis

Status: Critically Endangered

Population: 1,000-1,800

This highly intelligent porpoise lives in China's Yangtze River, the longest river in Asia. Their decline is caused by overfishing, which decreases their food supply, as well as pollution and ship movement. Above, in Jiangxi, China, Poyang Lake, the largest freshwater lake in China, and fed by the Yangtze, shrunk due to drought. Reconnecting floodplain lakes helps restore seasonal flows and allows the migration of species like the finless porpoise, according to WWF.

Photo: humphery / Shutterstock

African Wild Dog
African Wild Dog

African Wild Dog

Lycaon pictus

Status: Endangered

Population: 6,600

World Wildlife Fund calls the African Wild Dog one of the world's most endangered mammals. The largest populations are in southern Africa, Tanzania, and northern Mozambique. They are often killed by humans, accidentally and intentionally, as well as viral diseases like rabies and distemper. Habitat loss and competition with larger predators like lions is also a threat.

Photo: Shutterstock

Amur Tiger, Bengal Tiger
Amur Tiger, Bengal Tiger

Amur Tiger

Panthera tigris altaica

Status: Endangered

Population: As many as 540

Bengal Tiger

Panthera tigris tigris

Status: Endangered

Population: more than 2,500

Also known as the Siberian tiger, the Amur tiger was driven to the brink of extinction in the 1940s with no more than 40 left in the wild. Bengal tigers are found mainly in India, with smaller populations in Bangladesh, Nepal, Bhutan, China and Myanmar. Tigers are threatened by habitat loss, illegal wildlife trade, and conflict with humans.

Photo: Shutterstock

Humphead Wrasse
Humphead Wrasse

Humphead Wrasse

Cheilinus undulatus

Status: Endangered

Population: N/A

This huge fish is important to the health of the coral reefs where it lives. These fish can be over 6 feet long and live 30 years. Habitat loss and illegal fishing threatens the existence of the humphead wrasse, which is considered a delicacy in Southeast Asia, one of the most expensive live reef fishes in the world. Pictured is a humphead wrasse in an aquarium in Japan.

Photo: Mokkie/Wikipedia

Black-footed Ferret
Black-footed Ferret

Black-footed Ferret

Mustela nigripes

Status: Endangered

Population: Approximately 370 in the wild

This little ferret is one of the most endangered mammals in North America. It was once thought to be globally extinct. It continues to be threatened by habitat loss and disease. The ferret feeds on prairie dogs. State and federal agencies, zoos, Native American tribes, conservation organizations and landowners have given black-footed ferrets a second chance for survival, the World Wildlife Fund says.

Photo: Shutterstock

Blue Whale
Blue Whale

Blue Whale

Balaenoptera musculus

Status: Endangered

Population: 10,000-25,000

Blue whales are harmed by ship strikes and fishing gear. Climate change has had an impact on krill, their food supply. The largest animal in the world (they can weigh up to 200 tons) blue whales are at the top of the food chain and important to the health of the marine environment.

Photo: Shutterstock

Bluefin Tuna
Bluefin Tuna

Bluefin Tuna

Thunnus spp

Status: Endangered

Population: n/a

Populations of Bluefin tuna, a highly sought-after delicacy for sushi and sashimi, are harmed by overfishing and illegal fishing. According to the Center for Biological Diversity, the bluefin has been overfished to less than 3% of its historic population

Photo: Shutterstock

Bonobo
Bonobo

Bonobo

Pan paniscus

Status: Endangered

Population: 10,000 to 50,000

Similar to chimpanzees, Bonobos are smaller, leaner and darker. They live in forests south of the Congo River in the Democratic Republic of Congo. Civil unrest, poaching, and habitat loss threaten these primates.

Photo: Shutterstock

Borneo Pygmy Elephant
Borneo Pygmy Elephant

Borneo Pygmy Elephant

Elephas maximus borneensis

Status: Endangered

Population: Approximately 1,500

This baby-faced subspecies of Asian elephant inhabits northeastern Borneo, in Indonesia and Malaysia. They are actually not much smaller than other Asian elephants, but they tend to be more gentle-natured. The species is threatened by loss of habitat to oil palm plantations.

Photo: shankar s. from Dubai, UAE/Wikipedia

Galapagos Penguin
Galapagos Penguin

Galapagos Penguin

Spheniscus mendiculus

Status: Endangered

Population: fewer than 2,000

This is the only penguin species found north of the equator and in the Galapagos. Their population is threatened by pollution, bycatch and climate change.

Photo: Shutterstock

Red Panda
Red Panda

Red Panda

Ailurus fulgens

Status: Endangered

Population: less than 10,000

Red pandas live in the Eastern Himalayas. Slightly larger than a house cat, they are poached for their pelts. Much of their forest habitat is being cleared, and they are often killed when they get caught in traps meant for other animals.

Photo: Shutterstock

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This article was written by a staff member of TheStreet.

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