Last March, the world’s last male northern white rhino, Sudan, died at 45 years of age.

Sudan – who is named for his country of birth and lived under the protection of armed guards at the Ol Pejeta Conservancy in Kenya, away from poachers – suffered from a degenerative muscle and bone condition and was euthanized.

Fortunately, scientists were able to gather genetic material that could one day be used to create more northern white rhinos through IVF. Sudan also left behind a daughter and granddaughter, so there’s a flicker of hope for the wildlife preservation community.

Even so, there are numerous other animal species and subspecies that are in danger of perishing for good. The Amur leopard and Sumatran elephant are just two of 19 species categorized as “critically endangered” by the World Wildlife Fund, while the white-rumped vulture, Philippine crocodile, and Chinese pangolin have been given the equivalent classification on the IUCN Red List.

The Amur leopard is one of the world’s most endangered wildcats, and native to the Russian Far East

This subspecies – which is also known as the Far East leopard, the Manchurian leopard, or the Korean leopard, despite being nearly extinct outside of the Amur River basin in eastern Russia – can run upwards of 37 miles an hour and jump as high as 19 feet in the air.

According to a 2015 census, there are only around 60 Amur leopards left, all living at Russia’s Land of the Leopard National Park.

In the the past 60 years, there has been a 50% decline in the Bornean orangutan population

Found only on the island of Borneo, Asia’s largest island, Bornean orangutans have broader faces and shorter beards than their arboreal Sumatran cousins.

There are three subspecies of Borean orangutans: Northwest, Northeast, and Central. The largest is the Central subspecies, of which there are an estimated 35,000. The most threatened is the Northeast subspecies: due to its habitat being decimated by logging and hunting, there are only about 1,500 extant Northeast Borean apes.

Scientists predict that the Bornean orangutan population will fall another 22% by 2025, bringing the total number down to 47,000.

It was once believed that mountain gorillas would be extinct by the end of the 20th century

At just under 900, the current population size is low, but conservationists are working to ensure that mountain gorillas don’t fall prey to human threats.

According to the African Wildlife Foundation, the greatest threats to mountain gorillas – an eastern gorilla subspecies – are political instability (mainly conflicts in the Democratic Republic of Congo), human encroachment, and forest degradation.

The remaining mountain gorilla population is spread out over three countries and four national parks, such as Bwindi Impenetrable National Park in Uganda, and Virunga National Park in DRC.

The saola, or “Asian unicorn,” wasn’t discovered until 1992

Native to a mountainous region of Vietnam and Laos, “saola” means “spindle horns” in Vietnamese.

Like antelope and bison, the saola belongs to the ruminant artiodactyl family Bovidae. According to the World Wildlife Fund, this enigmatic creature is super rare – scientists have only documented wild saola on four occasions.

Despite their international protected status, hawksbill turtles are killed for their prized shells

This sea turtle, which has a hawk-like pointed beak, can be found in tropical oceans around the world.

Humans pose a large threat to hawskbills, whose population has decreased by 80% over the last century. Despite their protected status under the Convention on International Trade in Endangered Species of Wild Fauna and Flora, people still eat their eggs and kill them for their flesh and colorful shells. They’re also susceptible to being ensnared in fishing nets.

The South China tiger population is functionally extinct, meaning these wildcats are only found in captivity

Back in the 1950s, there were an estimated 4,000 South China tigers. Although China banned poachers from hunting these wildcats in 1979, the population dipped to between 30 and 80 by the end of the 20th century.

About 100 tigers remain in captivity, Bloomberg reported in 2016.

The Yangtze finless porpoise is as intelligent as a gorilla

The Yangtze porpoise, native to China’s longest river, is a close relative of the most-likely-extinct Baji dolphin.

It’s estimated that between 1,000 and 1,800 of these intelligent, mischievous-looking porpoises remain.