The sixth mass extinction. These five species were recently declared extinct

Currently 28% of all assessed species on earth – more than 42,100 out of 150,388 – are endangered, according to the Red List of Threatened Species, edited by the International Union for the Conservation of Nature (IUCN).

For decades, the IUCN would declare a species extinct if it were not observed in the wild for 50 years. Classification now instead states there to be “no reasonable doubt that the last individual member has died.”

Extinction describes the phenomenon of a species dying out due to cataclysmic events, evolutionary problems, or human interference such as the destruction and fragmentation of habitats resulting from taking land and water for growing human populations, pollution of land, sea, water, and climate change, including global warming. Now we are witnessing the so-called sixth mass extinction.

To counteract this phenomenon, the United Nations called for a biodiversity peace pact with nature. During the recent 2022 United Nations Biodiversity Conference (COP15) in Canada, nearly 300 countries discussed agreements that could allow reversing environmental destruction.

The declaration of the summit focuses on measures allowing the prevention of the extinction risk by protecting 30% of land and sea to protect degraded ecosystems by 2030, as well as eliminating billions of dollars in environmentally damaging governmental subsidies.

Baiji Dolphin

The last Lipotes vexillifer was seen in 2002. It was when QiQi, the last known river dolphin of this species, died. The baiji had unique features regarding their skeleton and stomach anatomy that were not shared with any other whale or dolphin species. They were the last representatives of the ancient Lipotidae family, which is now lost.

The baiji were freshwater dolphins native to the Yangtze River in China, which was their home for millions of years. They emerged in the Palearctic realm, which is the largest in the history of Earth. Baijis were social animals who lived in pairs or small groups of up to 10 individuals. They were carnivores active in the daytime, hunting for freshwater fish. Baiji reproduction season was from February to April, with calves becoming independent at around 8-12 months.

Despite having a special, spiritual meaning in the region of the Yangtze river – the Baiji was regarded as a symbol of peace and prosperity and nicknamed ‘the Goddess of Yangtze’ by local fishermen and boatmen.

The baiji are the first cetacean likely to have gone extinct due to humans. Overfishing as a result of food shortages removed smaller prey for the baiji and many of the baiji became entangled in fishing nets and drowned. As the Yangtze river is one of China’s major economic trade routes, the dolphins were also exposed to significant shipping traffic resulting in noise pollution which increased the chances for the baiji to hit ship propellers.

The IUCN still lists the Baiji dolphin as critically endangered, but in 2006, after a two-week search for the dolphins, the scientists from the Baiji.org foundation found no evidence of the animal, declaring with its circumstances, even if a few individuals remain “there’s no hope to save them”.

Splendid Poison Frog

On the IUCN’s list of endangered species, Oophaga speciosa was first classified as endangered in 2004 due to decreasing sights of this species. The frog was last spotted in 1996 and, following an assessment in 2018, finally declared extinct in 2020.

The splendid poison frog belongs to the family of poison dart frogs, one of the most brightly coloured animals on earth. Its colours are theorised to function as a visual warning – easy to be spotted, these animals taught predators to recognise them as poisonous. The frog would gain their toxicity by eating insects that feed on toxins. Despite each poison frog developing a unique kind of poison, touching or eating these amphibians can cause swelling, nausea, and paralysis.

The habitat of Oophaga speciosa was known to be in Panama, where it could be found in a small geographic range near the western Cordillera de Talamanca Central, bordering Costa Rica. There, it lived in the humid lowlands and very wet mountain forests. The female frogs laid eggs in leaf litter and, once they hatched, carried the tadpoles to small accumulations of water, putting them in the leaf axils of plants.

The main threats to the Splendid Poison Frog were habitat degradation and loss resulting from deforestation conducted by humans for construction and settlement.
Another cause of the frog’s extinction was for them to be poached and traded as pets. One of these instances, in 1992, was actually one of the last times the species was documented.

Bonin Pipistrelle

This bat, officially known as Pipistrellus sturdeei, belongs to a family of microbats called vespertilionidae. The only known specimen was a female observed in 1889 in Bonin Islands in Japan. It was officially recorded in 1915 by a British zoologist Thomas Oldfield, according to whom the Bonin Pipistrelle had a head-to-torso length of 3.7 cm and a tail length of 3.1 cm. The bat has not been seen since for the last 100 years, the IUCN officially declared it extinct in 2020.

The Bonin Pipistrelle was considered endemic to Hahajima Island in the Japanese Bonin Islands archipelago. The more recent analysis, however, placed doubt on the origin and taxonomy since because the bat was only sighted once, there is limited information on this species’ habitat.

Microbats are, in general, known to live in open country and woodlands and sleep in houses, hollow trunks and rock caves. The bats can be found in groups of up to twelve and usually search for food – in most instances, insects – in the evenings. The female microbats give birth to one or two 1-2 bubs after a gestation period of 40-60 days and raise them.

Insular bats are very vulnerable. Human introduction of numerous invasive species, including goats and various rodents, is presumed to be a reason for the bats becoming extinct. This conjecture is derived from the fact that invasive species introduced to the Bonin Islands have already caused other indigenous animals – Bonin Pigeon, Bonin Grosbeak – to die out.