There are animal species worldwide whose populations have now shrunk to just a few dozen or even only single individuals. Many of them stand on the brink of extinction and survive only in small refuges or through elaborate conservation programs. The main cause of their decline is humans, for example through habitat destruction, poaching, invasive species, or climate change. Nevertheless, for some of these extremely rare species there is still hope that their final loss can yet be prevented.
7 animal species with fewer than 50 individuals – overview
Image: Tom Parkin, CC BY-ND 4.0
Image: Tokudaia muenninki (Johnson, 1946) Observed in Japan by orthoptera-jp, CC BY-NC 4.0, via GBIF
Image: Paula Olson, NOAA, Public domain, via Wikimedia Commons
Image: Ceratotherium simum subsp. cottoni Lydekker, 1908 Observed in Kenya by Royle Safaris, CC BY-NC 4.0, via GBIF
Image: Merulaxis stresemanni Sick, 1960 Observed in Brazil by Luiz Alberto Santos, CC BY-NC 4.0, via GBIF
Image: haithanh, CC BY 2.0, via Wikimedia Commons
Image: Red Wolf Recovery Program, CC BY 2.0, via Wikimedia Commons
Kungaka skink: one of Australia’s rarest lizards
The skink Liopholis mutawintji, scientifically described only in April 2026 and called Kungaka (“the hidden one”) by the Wiimpatja Aboriginal people, is already considered one of Australia’s rarest reptiles. So far, the species is known exclusively from a single moist gorge in the arid Mutawintji National Park in western New South Wales. It lives there in isolation, around 500 kilometers from its closest relatives.
For a long time, researchers considered the animals merely an isolated population of White’s skink (L. whitii). Only genetic analyses and examinations of body structure and scale traits showed that it is a distinct species. Researchers suspect that the Kungaka skink is a relict from earlier, wetter climatic periods in Australia. While large parts of the continent became increasingly dry, the Kungaka may have survived in the cool, moist rock refuges of the Mutawintji area.
The landscape, shaped by red rocks, scrubland, and periodic drought, appears hostile to life, yet the Kungaka skink has been able to survive to this day in a single cool and wetter rock gorge.
Image: Doug Beckers, CC BY-SA 2.0, via Wikimedia Commons
The population has already been discovered and monitored for about 25 years in cooperation among scientists, rangers, and the local Wiimpatja traditional owners. Intensive monitoring programs have been underway since 2019.
Today, researchers assume that fewer than 20 individuals may still exist, which is why some specialists even describe the Kungaka skink as “functionally extinct”. That means the population may already be too small to sustain itself in the long term.
Among the biggest threats to the newly discovered skink species are feral goats that destroy vegetation and damage rocky areas, invasive predators such as foxes and cats, as well as increasingly frequent droughts and the effects of climate change in Australia’s already dry interior. Researchers propose classifying the Kungaka skink as Critically Endangered (CR) under IUCN Red List criteria.
Okinawa spiny rat: a relict species in shrinking rainforest
The Okinawa spiny rat (Tokudaia muenninki) occurs exclusively in the Yanbaru region in northern Okinawa, one of the last larger subtropical forest areas of Japan’s Ryukyu Islands. Its habitat has been heavily fragmented over recent decades by deforestation, especially through state-supported forestry programs. In addition, introduced predators such as feral domestic cats, small Indian mongooses (Herpestes auropunctatus), and black rats (Rattus rattus) are putting pressure on the rare Okinawa spiny rat.
After an animal had been captured on Mount Yonahadake in 1974, the species remained almost absent for decades. A survey in 1994 was unable to detect a single individual at the same site. It was not until March 2008 that researchers succeeded in catching a wild animal again for the first time in more than 30 years. Despite intensive trapping between 2007 and 2009, only 24 individuals were detected in total, all in an isolated forest fragment estimated to cover only one to three square kilometers. The small number of records makes clear how small and fragmented the population has become; today, fewer than 50 individuals probably remain.
The genus of the Ryukyu spiny rats includes three species, each living on different islands of the archipelago. The Okinawa spiny rat is listed in the IUCN Red List as Critically Endangered (CR), while the other two are listed as Endangered (EN).
The rodent species endemic to Okinawa reaches a body length of up to 31 centimeters (including tail) and carries striking black bristle hairs on its back, a trait that gave it its name.
Image: Tokudaia muenninki (Johnson, 1946) Observed in Japan by patrickkuhn, CC BY-NC 4.0, via GBIF
Vaquita: the rarest porpoise in the world
The vaquita (Phocoena sinus) is not only one of the smallest, but also one of the most endangered marine mammals in the world. The species occurs exclusively in the northern Gulf of California in Mexico. While 567 animals were still counted in 1997, the population had shrunk to about 30 individuals by 2016. In the latest survey in 2024, there were finally only six to eight animals left. Acoustic monitoring programs confirmed an extremely rapid population decline: between 2011 and 2018, numbers fell by an average of around 45% per year.
Image: Pcb21 (original uploader at English Wikipedia), CC BY-SA 3.0, via Wikimedia Commons
By far the greatest threat to the vaquita is fishing gillnets. The small porpoises become entangled in them and drown as bycatch. Particularly problematic is the illegal fishery for the totoaba (Totoaba macdonaldi), whose swim bladder fetches high prices on the black market. As early as the 1990s, numerous vaquitas probably died in these nets every year, hitting the already small population enormously hard. Other possible threats such as low genetic diversity or environmental changes are still considered far less severe.
Today, the last vaquitas survive only in a small protected area in the Gulf of California, the so-called Zero Tolerance Area, which covers only 300 square kilometers. Fishing is officially banned there, yet illegal gillnets continue to be used. Despite international pressure, Mexico has so far failed to enforce the protective measures consistently.
Despite these alarming developments, hope remains: newer observations suggest that female vaquitas, unlike long assumed, may be able to give birth not only every two years but probably every year, similar to other porpoises. If it were possible to remove the deadly gillnets completely from their habitat, the population could at least theoretically recover slowly.
Northern white rhino: hope from the lab
The northern white rhino (Ceratotherium simum cottoni) is now considered functionally extinct. Since the death of the last male, Sudan, in 2018, only two females remain worldwide: Najin and her daughter Fatu at Ol Pejeta Conservancy in Kenya. Neither animal can carry offspring anymore.
Image: Ray in Manila, CC BY 2.0, via Wikimedia Commons
The subspecies was once widespread in parts of Central and East Africa, but decades of poaching and the destruction of its habitat led to the collapse of the population. Especially in the 1970s and 1980s, armed poaching caused a dramatic crash. In 2008, researchers no longer found any animals living in the wild.
Today, hope rests on modern reproductive medicine and stem-cell research. From Fatu’s egg cells and frozen sperm from deceased bulls, 39 viable embryos have now been created. In the future, these are to be carried by female southern white rhinos (C. s. simum) serving as surrogates.
An important step came in 2025 with the complete sequencing of the genome of the northern white rhino. The genetic map is meant to help select healthy embryos, preserve genetic diversity more effectively, and in the long term even produce egg cells or sperm from skin cells.
Despite all progress, the future of the subspecies remains uncertain. The procedures are technically demanding, expensive, and associated with many risks. In addition, it is unclear whether suitable and safe habitats for a later reintroduction even still exist.
Stresemann’s bristlefront: missing for decades
Stresemann’s bristlefront (Merulaxis stresemanni) is one of the rarest birds in the world. For a long time, it was known only from two museum specimens: the holotype was collected near Salvador da Bahia as early as the 1830s, and a second specimen was recorded in 1945 near Ilheus in the Brazilian state of Bahia. After that, the species was long considered lost.
Image: Ciro Albano (NE Brazil Birding), via Wikimedia Commons
It was not until 1995 that researchers succeeded in photographing a male on Fazenda Jueirana in Bahia and recording its song. Further searches at first remained unsuccessful. Only in 2005 did researchers discover another small population in the Jequitinhonha Valley in the state of Minas Gerais.
Stresemann’s bristlefront lives hidden in the undergrowth of mature, moist Atlantic rainforest. There it searches on the ground and among fallen trunks for small arthropods. The birds move mostly by running or with short flights through the dense understory.
The greatest threat is the massive destruction of the Atlantic rainforest. Large parts of the original forests have been logged or converted into cocoa plantations, eucalyptus stands, and pasture. Added to this are timber extraction, recurring fires, and introduced predators such as cats and dogs. In 2016, a major fire even destroyed the area of the only known breeding pair.
While BirdLife International once still assumed 50 to 250 individuals, more recent studies suggest that today fewer than ten adult animals may still exist. The IUCN therefore classifies the species as Critically Endangered (CR).
Yangtze giant softshell turtle: probably the rarest turtle in the world
The Yangtze giant softshell turtle (Rafetus swinhoei) is one of the most threatened turtle species on Earth. With a body length of more than one meter and a weight of over 100 kilograms, it is also one of the largest known freshwater turtles. Today, only two known individuals may still exist, both male.
In the past, the species was distributed in the Yangtze and Red River systems in China and Vietnam. But river engineering, dams, the draining of wetlands, water pollution, and decades of hunting led to a population collapse. The animals were hunted both for their meat and for traditional medicine. The IUCN assumes that the population has declined by more than 99% within two generations.
In 2019, a female died in China after several unsuccessful attempts at artificial insemination. In April 2023, the last known female was finally found dead in Dong Mo Lake in Vietnam. Since then, only two male animals are regarded as confirmed: one in Suzhou Zoo and another in Vietnam’s Xuan Khanh Lake.
Image: John Edward Gray and/or G.H. Ford, Public domain, via Wikimedia Commons
Despite everything, conservationists continue to search for surviving animals in remote lakes and river systems of southern China and northern Vietnam. In 2025, the Chinese NGO Endangered Species Fund even launched a public reward campaign: anyone who provides a credible photo or video of a wild Yangtze giant softshell turtle is to receive 100,000 yuan. At present, hopes are focused above all on the remote Honghe Basin in China’s Yunnan Province.
The search for the turtle species is made even more difficult by the fact that nobody knows what the juveniles look like. Experts therefore suspect that individual animals may have been overlooked in the past or confused with other softshell turtles.
Red wolf: back from extinction—and threatened again
The red wolf (Canis rufus) was once widespread across large parts of the southeastern United States. Intensive hunting, habitat loss, and persecution, however, led to the species going extinct in the wild around 1980.
Image: Steve Hillebrand, Public domain, via Wikimedia Commons
As early as the 1970s, the United States Fish and Wildlife Service (USFWS) began a rescue program. A total of 79 wild red wolves were captured, of which only 14 animals were classified as genetically “pure” and selected for a breeding program. Through breeding in human care, the complete extinction of the species could be prevented.
In 1987, reintroduction in North Carolina finally began. At the time, the area was considered almost free of coyotes and therefore seemed ideally suited. The population initially developed successfully: by the early 2000s, more than 150 red wolves were again living in the wild.
However, this success was only short-lived. Since the 1990s, coyotes have increasingly spread into the range. Crossbreeding between the two species became more and more frequent, which today is regarded as one of the greatest threats to the red wolf’s continued existence. There were also conflicts with landowners and a sharp increase in illegal shootings. The situation became even more problematic after coyotes could at times be legally hunted in North Carolina, because red wolves can easily be confused with them.
In the following years, the population collapsed again. At the beginning of 2021, only about ten wild red wolves were still known. Through renewed protection measures and releases, numbers later rose slightly again. Today, experts assume that probably only about 20 to 30 red wolves remain in the wild, confined to a small protected area in eastern North Carolina. The population in human care, by contrast, numbers around 250 animals and forms the most important basis for future conservation measures.
Sources
- BirdLife International (2021). Merulaxis stresemanni. The IUCN Red List of Threatened Species 2021: e.T22703477A161689029. https://dx.doi.org/10.2305/IUCN.UK.2021-3.RLTS.T22703477A161689029.en
- Emslie, R. (2020). Ceratotherium simum. The IUCN Red List of Threatened Species 2020: e.T4185A45813880. https://dx.doi.org/10.2305/IUCN.UK.2020-1.RLTS.T4185A45813880.en
- Fong, J., Hoang, H., Kuchling, G., et. al (2021). Rafetus swinhoei. The IUCN Red List of Threatened Species 2021: e.T39621A2931537. https://dx.doi.org/10.2305/IUCN.UK.2021-1.RLTS.T39621A2931537.en
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- Parkin, T., Swan, G., Marshall, L., et al. (2026). Phylogenomics, taxonomy and conservation of the White’s skink (Scincidae: Liopholis whitii) species complex in south-eastern Australia. Zootaxa 5792(3), 457–493. https://doi.org/10.11646/zootaxa.5792.3.2
- Phillips, M. (2018). Canis rufus (errata version published in 2020). The IUCN Red List of Threatened Species 2018: e.T3747A163509841. https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T3747A163509841.en
- Rojas-Bracho, L., Taylor, B.L. & Jaramillo-Legorreta, A. (2022). Phocoena sinus. The IUCN Red List of Threatened Species 2022: e.T17028A214541137. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T17028A214541137.en
- Strauss, M. (2026, April 24). Was Just Identified as a Brand New Species Thanks to Indigenous Knowledge. ZME SCIENCE.
https://www.zmescience.com/ecology/animals-ecology/new-hidden-one-lizard-australia/
About the author: Doreen Fräßdorf
Doreen Fräßdorf is the author and publisher of artensterben.de. She researches and writes about extinct and endangered species in the modern era, with a focus on red lists, scientific studies, historical sources, and current conservation efforts. The goal is a clear, evidence-based overview of biodiversity loss and species protection.
She is also the author of a non-fiction book about extinct modern-era mammals.
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