Top 10 Largest Natural Extinctions of the 20th Century

The extinction of the Zanzibar Leopard (sometimes referred to as the 'Zanzibar cat') remains a topic of much debate, as there is no conclusive evidence that it has completely disappeared, although there have been occasional reports of sightings. These leopards roamed the dense forests of Zanzibar in Tanzania, with the entire population eventually being wiped out by the local people.

Numerous researchers have since made efforts to confirm their existence by playing recorded sounds, setting up camera traps, and searching for any signs in the wild. However, none of these efforts have yielded any concrete proof. In 1932, British zoologist Reginald Innes Pocock described the Zanzibar Leopard as a subspecies of the spotted leopard, proposing its scientific name as Panthera pardus adersi. Many years later, in 1996, it was reclassified under the name P.p. pardus.

The West African Black Rhino was found across several countries in southeastern Africa. Measuring up to 3-3.8 meters in length and standing around 1.4-1.7 meters tall, this rhino could weigh between 800-1,300 kg. It had two horns, one measuring 0.5-1.3 meters and the other between 2-55 cm. Their diet primarily consisted of leaves and young shoots. Some people also believed that their horns had medicinal properties—though there is no scientific basis for this—which led to severe poaching.

Conservation efforts were initiated in the 1930s to protect the species, but the population continued to decline. The West African Black Rhino was last seen in Cameroon in 2006 and was officially declared extinct in 2011. Their extinction was primarily caused by poaching for their horns, which were highly valued on the black market and used in traditional Chinese medicine.

The Javan Tiger was a subspecies of tiger that once roamed the islands of Java, Indonesia. Hunting and deforestation are believed to be the primary causes of its extinction by the mid-70s or early 80s. Fossil evidence suggests that about 12,000 years ago, Javan Tigers also inhabited the islands of Borneo and Palawan in the Philippines. However, some experts believe specimens from Borneo were still present as recently as 200 years ago.

Compared to other subspecies of Panthera tigris that still exist in mainland Asia, the Javan Tiger was slightly smaller. However, male Javan Tigers could grow larger than Sumatra tigers. They had long, narrow stripes and a slim occipital region, along with a relatively long spine and narrow, elongated nose. These anatomical differences have led to suggestions that the Javan Tiger might have been a separate species, Panthera sondaica.

The Spanish Ibex Goat, or Iberian Ibex, is one of four subspecies native to the Iberian Peninsula. These goats typically reach a shoulder height of 60-76cm and weigh between 24-80kg, primarily feeding on grasses and herbs. Once thought to number around 50,000, their population drastically declined to under 100 by the early 1900s. Scientists managed to clone a Pyrenean Ibex, making it the first species to be revived from extinction, but it died shortly after birth due to a lung condition.

The exact cause of the Pyrenean Ibex's extinction is still unclear. Experts believe that poaching and competition for resources with other mammals played a major role. Ultimately, the last Pyrenean Ibex was lost in 2000, killed by a fallen tree in northern Spain. Its extinction was likely hastened by disease and illegal hunting.

In the early 19th century, the passenger pigeon was the most abundant bird in North America, and possibly the world, with an estimated population of around 5 billion. However, these birds were not evenly distributed across Mexico, Canada, and the United States. Instead, they traveled in massive flocks that could block out the sun, stretching for dozens or even hundreds of miles across the continent.

Hunters in the Midwest trapped and shot millions of these birds, transporting their carcasses eastward through the newly established transcontinental railroad. The female passenger pigeon laid only one egg at a time, in tightly packed nests atop the forests of northern U.S. and Canada. In 1871, naturalists estimated that a nesting area in Wisconsin spanned nearly 1,000 square miles, housing over 100 million birds.

The Tasmanian Tiger, also known as the Thylacine or Tasmanian wolf, wasn't a tiger or a wolf at all, but rather a marsupial closely related to the Tasmanian Devil. The last known Tasmanian Tiger died in 1936, though hundreds of unverified sightings have sparked investigations to determine if any still exist.

Its extinction marked the end of the only member of its genus, Thylacinus, and the largest known carnivorous marsupial of its time. The Tasmanian Tiger ranged in length from 100 to 130 cm, with a tail extending another 20 to 26 inches (50 to 65 cm). Weighing between 15 and 30 kg, it had a dog-like appearance with yellowish fur, black stripes on its body, and a thin tail resembling that of a rodent.

The Macaw Parrot is known as the giant of the parrot world. The long-tailed Macaw is the longest of all parrots, with lengths reaching up to 40 inches from head to tail. Macaws feature long tail feathers and large, curved beaks, ideal for cracking tough nuts and seeds. These parrots are long and slender, with vibrant plumage ranging from the green of the long-tailed parrot to the bright red of the scarlet Macaw. Some species also display facial patches.

Macaws are native to the southern part of North America (Mexico), as well as Central and South America. Evidence suggests that the Caribbean once had native parrot species, such as the extinct Cuban long-tailed parrot (Ara tricolor) and the St. Croix long-tailed parrot (Ara autochthones). They inhabit tropical rainforests, savannahs, and grassy woodlands. Many long-tailed parrot species and other macaws are native to the Amazon River basin.

The Madeiran Large White Butterfly was one of the many species last observed in the 20th century. Its extinction status remains uncertain, as the IUCN Red List often classifies it as critically endangered and possibly extinct. Sadly, for this butterfly, hope has dwindled: numerous search efforts on the relatively small island of Madeira since the late 1980s to find living specimens have all been unsuccessful.

Many sources list 1977 as the year of the last confirmed sighting, with the last specimens of the Madeiran Large White Butterfly collected in 1986 (by Antonio Aguiar). This butterfly once thrived in the laurisilva (laurel forest) of Madeira's northern valleys, where it fed on nectar-rich plants such as bedstraw, knapweed, and various cruciferous plants—the preferred host plants for its larvae. For many years, the Madeiran Large White (Pieris wollastonite) was considered a subspecies of the more common Large White (Pieris brassicae), but it is now recognized as a distinct species.

The Golden Toad B. Periglenes was once abundant in the misty cloud forests of northern Monteverde, Costa Rica, where it gathered in large groups in small ponds to breed during the short rainy season. Discovered in 1964, the species experienced a sharp population decline by 1987, affecting nearly half of the amphibian species in its 30km range. The last confirmed sighting occurred in 1989 when only a single male was found by researchers.

Some researchers believe the Golden Toad was the first species driven to extinction directly by climate change, as rising temperatures facilitated the spread of chytridiomycosis, a fungal disease that affects the vital skin functions of amphibians. In 1991, the IUCN formed a task force, the Amphibian Specialist Group, to study 30% of amphibian species at risk of extinction in an effort to prevent other species from suffering the same fate as the golden toad.

Baiji is native to China's Yangtze River. Historically, it inhabited both the central and lower reaches of the Yangtze, from Yichang in the west to the river mouth near Shanghai, as well as Poyang and Dongting Lakes and the smaller Qiantang River in the south. Baiji dolphins typically appeared in small groups of about 10 individuals, spending their days hunting for fish. They were quiet, shy, and elusive creatures.

The Baiji was a freshwater dolphin species that may have already gone extinct, and it is believed to be the first dolphin species driven to extinction due to human impact. Baiji dolphins had a light grayish-blue back and a white belly. They had a long, slightly upward-curved snout, with 31 to 36 cone-shaped teeth on each side of the jaw. The dorsal fin of the Baiji dolphin was low, triangular, and appeared like a bright flag when the dolphin swam just beneath the dark, murky waters of the Yangtze River, which earned them the name 'white flag dolphin.'