Rarest Animals in the World: 10 Critically Endangered Species

Elephants are one of the most iconic animals in Africa, but they’re becoming increasingly rare. One African elephant species in particular is considered critically endangered: the African forest elephant.

Once lumped together as a single species, scientists and conservation groups now recognize African forest elephants (Loxodonta cyclotis) as a distinct species.

In fact, a 2017 genetic analysis of elephant DNA suggested that the forest elephants, which are about half the size of African savannah elephants (Loxodonta africana), may be more closely related to their extinct ancestors than living savannah elephants.

Sadly, both species are threatened. The 2016 African Elephant Status Report estimated a continental population of 415,428 for both the endangered African savannah elephant and the critically endangered African forest elephant combined.

“Conservation efforts to protect savannah elephants have seen many populations begin to recover, but sadly the same is not true for forest elephants, which remain under intense pressure from habitat loss and poaching,” said Andrew Terry, Director of Conservation at the Zoological Society of London, in an IUCN press release.

Ivory poaching, which peaked in 2011, caused so much harm to elephant populations that some elephants actually evolved to be tuskless.

If you want to see an African forest elephant, you’ll need to travel to Gabon or the Republic of Congo, home to the largest remaining populations, thanks to conservation efforts in both countries.

Still, it might be tricky to spot these rare animals. According to National Geographic, they live in small herds of only a few individuals and “are considered to be rather elusive” for their impressive size.

Lemurs, the big-eyed, long-tailed primates that live only in Madagascar, have long fascinated nature enthusiasts. Sadly, most lemur species are endangered or critically endangered due to loss of their natural habitats.

One of the rarest species is Prolemur simus, the greater bamboo lemur. As its name suggests, its primary food source is bamboo. Cutting down of bamboo, in addition to climate change, hunting, illegal logging, mining and slash-and-burn agriculture, has led to significant population decline — about 80 perceny in the past three decades.

In 2015, there were 1,000 greater bamboo lemurs left in the wild.

The Tapanuli orangutan (Pongo tapanuliensis) is the rarest of the Great Apes, with an estimated population of less than 800. To see it, you’ll need to travel to the Batang Toru forests in Sumatra, Indonesia.

Tapanuli orangutans were identified as a separate species in 2017; before then, scientists and conservationists recognized two species of orangutan: the Sumatran orangutan (Pongo abelii) of Indonesia and the Bornean orangutan (Pongo pygmaeus) of Malaysia, both also critically endangered.

“It is rather amazing that this population of orangutans differs so much from the orangutans in the north of Sumatra and that even today, after many decades of intensive research on Great Apes, a new species of this primate family can still be discovered” Dr. Ian Singleton, Director of the Sumatran Orangutan Conservation Programme (SOCP), shared in an IUCN press release.

Gorillas are some of our closest relatives, but they’re increasingly rare.

“Gorillas face numerous threats in the wild, from disease to the bushmeat trade, but habitat loss hits their populations especially hard,” says Josh Meyerchick, Lead Keeper in Primates at Zoo Atlanta. “Agriculture, forestry and mining push gorilla populations into smaller and smaller tracts of land.”

Both the western gorilla (Gorilla gorilla) and the eastern gorilla (Gorilla beringei) are critically endangered, with decreasing populations. Each species has two subspecies.

Cross-river gorillas (Gorilla gorilla diehli) are the rarest, with an estimated population of 250-300, followed by mountain gorillas (Gorilla beringei beringei), with an estimated population of 1,000. There may be 3,800 Grauer’s gorillas, also known as the eastern lowland gorilla (Gorilla beringei graueri).

The population of western lowland gorillas (Gorilla gorilla gorilla) is the largest, at an estimated 316,000 individuals according to IUCN.

The northern hairy-nosed wombat (Lasiorhinus krefftii) is one of the rarest mammals in Australia. When its population dropped to just 35 individuals, the Queensland Parks and Wildlife Service built a fence around an area of the Epping Forest National Park to keep out dingoes and wild dogs, which prey on the wombats.

The conservation effort has been successful, and there were 315 northern hairy-nosed wombats in May 2021, according to the Australian Wildlife Conservancy.

The kākāpō (Strigops habroptila) is a large, nocturnal, flightless parrot from New Zealand. With a mating call that can reach up to 132 decibels, it’s one of the loudest animals in the world. (For reference, a car horn is 110 decibels.)

Once abundant, kākāpō populations declined due to hunting. Despite conservation efforts, the population is declining, and in 2018, there were 149 known kākāpō in New Zealand.

The Sumatran rhinoceros (Dicerorhinus sumatrensis) is the smallest, hairiest and most ancient living rhino species. In 2019, there were approximately 80 Sumatran rhinos, but the population is decreasing.

However, there has been some success with breeding programs. In October 2023, Ratu, a 22-year-old Sumatran rhino, gave birth to a healthy calf — her third — at the Sumatran Rhino Sanctuary facility in Way Kambas National Park, Lampung, Indonesia.

Other endangered species of rhinoceros include Javan rhinos (Rhinoceros sondaicus) and black rhinos (Diceros bicornis).

The Hainan gibbon (Nomascus hainanus), only found in Hainan, China, is the world’s rarest ape, with a population of about 35 individuals.

Poaching and habitat loss have pushed this species, once found all over the island, into a 5.8-square-mile (15-square-kilometer) patch of forest in the Bawangling National Nature Reserve.

With such a small wild population, tracking is of the utmost importance. “If we can find out how many there are, and where they live, we can focus on protecting and reforesting those areas,” conservation scientist Jessica Bryant told National Geographic.

Listening to the gibbons sing is the best way to identify them. “Every gibbon species has a slightly different call,” Bryant said. “In my opinion, the Hainan gibbon’s haunting song is the most beautiful of all.”

The vaquita (Phocoena sinus) is a porpoise from the Gulf of California, a strip of water that separates Baja California from mainland Mexico. Its name means “little cow” in Spanish, thanks to its small stature (at 5 feet [1.5 meters] in length, it’s the world’s smallest cetacean) and unique markings.

With an estimated population size of 10-13 individuals, the vaquita is the world’s rarest marine mammal. “We’re at the end of the line for the vaquita,” Sarah Uhlemann, international program director and senior attorney with the Center for Biological Diversity, shared in an email interview with HowStuffWorks.

The vaquita has not responded well to captive breeding attempts, so the only option for saving this species is protecting the remaining population.

“The vaquita faces a single threat: entanglement in fishing gear set to catch shrimp and a giant fish called the totoaba,” Uhlemann explains. Fishing with these deadly gillnets is illegal in the vaquita’s habitat, but enforcement has been a problem.

In August 2022, the Mexican government installed concrete blocks with hooks designed to entangle fishing nets in the protected Zero Tolerance Area (ZTA), which seem to be deterring fishing activity.

The 2023 vaquita survey saw a 90 percent reduction of gillnetting in the protected areas compared to the previous survey in 2021, and conservationists want the government to add more of these deterrents to areas outside the ZTA where vaquitas are also found.

“Mexico must crack down and end illegal fishing now, or we’ll lose the vaquita forever,” Uhlemann says.

While it would be impossible to definitively rank the world's rarest animals, the saola (Pseudoryx nghetinhensis), also known as the “Asian unicorn” makes a pretty solid case for rarest animal species. Although there may be as many as 750 living in the wild, saola sightings are extremely rare.

A saola sighting in 2010 was the first confirmed record of the species since camera-trap images taken in 1999. The saola lives in dense forests in the Annamite Mountains of Laos and Vietnam and is notoriously shy, making observation very difficult. The 2010 sighting was of a saola captured in its natural habitat and brought back to a village, where it died within days.

“Our lack of knowledge of saola biology is a major constraint to efforts to conserve it,” Dr. Pierre Comizzoli, a veterinarian with the Smithsonian Conservation Biology Institute and a member of the IUCN Saola Working Group, said in a press release.

Dr. Comizzoli is hopeful that the preservation of the saola’s carcass will help conservation efforts.