The vaquita, a small porpoise found only in Mexico’s Gulf of California, is the most endangered animal on Earth right now. As few as 10 individuals remain, down from around 600 in 1997. No other known mammal is closer to total extinction in the wild, and the species continues to decline despite decades of conservation efforts.
Several other animals are not far behind. A handful of species now number in the low dozens or hundreds, each facing threats that show no sign of letting up. Here’s where the most critical cases stand.
The Vaquita: Down to Roughly 10
The vaquita is a shy, elusive porpoise about five feet long, with dark rings around its eyes. It lives nowhere else on the planet except a small stretch of the upper Gulf of California. Surveys of its full range documented about 600 animals in 1997 and roughly 200 by 2008, a steady decline driven by legal fishing with gillnets. Then things got much worse.
Around 2011, illegal fishing for a large fish called the totoaba surged dramatically. Demand from China for the totoaba’s swim bladder, which is prized in traditional medicine, created a black market that flooded vaquita habitat with gillnets. Because vaquitas and totoaba are similar in size, the nets are perfectly sized to trap and drown the porpoises. The population crashed by nearly 50 percent per year during this period. Recent estimates from 2017 through 2024, based on monitoring within a small protected zone called the Zero Tolerance Area, put the number at around 10 surviving animals.
Mexico has taken steps to address the crisis. A two-year emergency gillnet ban was announced in 2015, and a permanent ban on most gillnets followed in 2017. Illegal fishing for totoaba was also made a felony punishable by imprisonment. But enforcement has been weak. As of 2017, no one had been jailed for illegal totoaba activity. The conservation group Sea Shepherd, working alongside the Mexican Navy, has pulled many totoaba nets from the gulf, yet illegal fishing persists. Scientists are unanimous: for vaquitas to survive, gillnet fishing must end completely within their habitat.
One small piece of encouraging news is that the remaining vaquitas appear healthy. With so few animals left, some researchers worried about inbreeding or food shortages in the tiny protected area. But the IUCN’s Cetacean Specialist Group has noted that with only about 10 vaquitas in the zone, a lack of food is implausible. The question is whether enforcement can outpace poaching before the last animals are gone.
Javan Rhino: 50 Left After Poaching Surge
The Javan rhino was already one of the rarest large mammals on Earth, with an estimated 76 individuals living in a single national park on the Indonesian island of Java. Then poaching gangs killed at least 26 of them, a loss confirmed through an investigation by Indonesian police. That dropped the population to roughly 50, a staggering 33 percent decline.
Unlike the vaquita, which is threatened by accidental bycatch, Javan rhinos are targeted directly. Their horns are valuable on the illegal wildlife trade market. The species has no backup population in captivity, and every remaining animal lives in Ujung Kulon National Park at the western tip of Java. The IUCN’s Asian Rhino Specialist Group has called for the creation of a National Rhino Task Force under direct government leadership to steer recovery efforts. For now, the Javan rhino’s survival depends entirely on whether Indonesia can secure that single park.
The Saola: A Ghost of the Forest
The saola is sometimes called the “Asian unicorn,” though it actually has two long, straight horns. Discovered by scientists in Vietnam only in 1992, it may already be functionally extinct. The last confirmed sighting was in 2013, when a camera trap captured an image of one in a forest in Vietnam’s Quảng Nam province. No verified evidence of a living saola has emerged since.
Nobody knows how many saola remain, if any. They live in dense, mountainous forests along the border of Vietnam and Laos, terrain that makes surveys extraordinarily difficult. Habitat loss from logging and infrastructure development, combined with snare traps set for other animals, are the primary threats. The species has never been held successfully in captivity, so there is no captive breeding population to fall back on. Conservation groups are working to establish protected areas and remove thousands of wire snares from saola habitat each year, but without a confirmed sighting in over a decade, the window for saving this species may already be closing.
Northern White Rhino: Functionally Extinct
Only two northern white rhinos are alive, both females, both living under armed guard at a conservancy in Kenya. Neither can carry a pregnancy. The species is considered functionally extinct because natural reproduction is no longer possible.
Scientists are pursuing an ambitious last resort: creating embryos through IVF using preserved sperm from deceased males and eggs harvested from the two surviving females, then implanting those embryos into southern white rhino surrogates. A major milestone came when the first successful rhino embryo transfer through IVF was achieved using a southern white rhino surrogate. The embryo did not survive due to an infection, but the procedure proved the concept works. Whether this technology can produce a viable northern white rhino calf remains uncertain, but each attempt brings researchers closer.
Other Species on the Brink
The Cross River gorilla, a subspecies found along the border of Nigeria and Cameroon, numbers between 200 and 300 individuals. They live in fragmented patches of mountainous forest, separated by farmland and roads that prevent groups from mixing. Hunting and habitat loss continue to chip away at the population, though community-based conservation programs have shown some promise in recent years.
The Amur leopard, native to the forests of far eastern Russia and northeastern China, was once down to fewer than 40 adults. Thanks to sustained conservation work, including habitat protection and anti-poaching patrols, that number has climbed to an estimated 130 mature individuals as of 2023. It remains one of the rarest big cats on Earth, with likely fewer than 200 in the wild total, but it’s one of the few species on this list showing a genuine upward trend.
What Makes a Species “Most Endangered”
The IUCN Red List, the global authority on species conservation status, classifies animals as critically endangered when their populations are extremely small or declining rapidly. A species qualifies under the most severe criteria when fewer than 50 mature individuals remain, or when the population has declined by 80 percent or more within three generations and the cause hasn’t stopped. The vaquita meets both thresholds.
But raw numbers don’t tell the whole story. A species with 300 individuals spread across fragmented, unprotected habitat may be in more immediate danger than one with 100 animals in a well-guarded reserve. The trajectory matters as much as the count. The vaquita’s population is still shrinking. The Javan rhino just lost a third of its numbers to poaching. The saola may already be gone. Meanwhile, the Amur leopard, despite tiny numbers, is actually recovering. “Most endangered” is ultimately a combination of how few remain, how fast they’re disappearing, and whether anything is effectively slowing the decline.