In biology and ecology, extinction is the end of an organism or of a group of organisms (taxon), normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species’ potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly “reappears” (typically in the fossil record) after a period of apparent absence. The age of the Earth is about 4.54 billion years. The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. There are microbial mat fossils found in 3.48 billionyear-old sandstone discovered in Western Australia. Earlier physical evidences of life include graphite, a biogenic substance, in 3.7 billion-year-old metasedimentary rocks discovered in southwestern Greenland, as well as, “remains of biotic life” found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, “If life arose relatively quickly on Earth ... then it could be common in the universe.” More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth’s current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described.
Through evolution, species arise through the process of speciation—where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche—and species become extinct when they are no longer able to survive in changing conditions or against superior competition. The relationship between animals and their ecological niches has been firmly established. A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils, survive with virtually no morphological change for hundreds of millions of years. Mass extinctions are relatively rare events; however, isolated extinctions are quite common. Only recently have extinctions been recorded and scientists have become alarmed at the current high rate of extinctions. Most species that become extinct are never scientifically documented. Some scientists estimate that up to half of presently existing plant and animal species may become extinct by 2100.
Animals Going Exinct Giraffes are practically part of the landscape of Africa, standing tree-like in the grasslands. Most giraffe species are of no concern to conservationists, yet a sub-species (or, as some researchers propose a separate species), the Rothschild giraffe, a.k.a. Baringo Giraffe or Ugandan Giraffe, is endangered. Those living in the wild are found in protected areas in Kenya and Uganda, while about 450 individuals are found in zoos around the world. Howler monkeys are so common to Central and South America that it’s hard to think there is any risk for them. But with habitat loss and capture or predation by humans, there is indeed a problem for several species. The Guatemalan Black Howler Monkey is endangered and is expected to decline by up to 60% over the next 30 years. Meanwhile, the Red-handed Howling Monkey is critically endangered with less than 2,500 mature individuals remaining in the wild. The water buffalo is a surprise for this list as we think of it as a domesticaed animal, but like horses, it’s the
wild cousins of the domesticated beasts that are at risk. There are as few as 2,500 mature individuals left and researchers estimate the species has experienced a population decline of at least 50% over the last three generations. The major threats include interbreeding with feral and domestic buffalo, as well as hunting and habitat loss. Vultures aren’t usually the most attractive of birds, but the Egyptian Vulture, is a notable exception. The striking bird is found in Europe, Africa and India, however rapid and severe declines in the Indian populations as well as long-term decline in the European populations put the species at around 13,000-41,000 mature individuals. Hippopotamus, No, not the big, mean hippos famed for killing around 2,900 people a year. It’s their mini cousins on the Endangered Species list, the Pygmy hippo. These round and adorable hippos are nocturnal and not much is known about them because of their secretive ways. The last population estimate in 1990 put the species at 3,000 individuals and habitat loss since then suggests that even this estimate was (and is) too high. Meanwhile, there are about
303 animals in captivity. An icon of the African plains and a necessity in any wildlife documentary about lions going a’ huntin’, the zebra is actually in trouble. Well, really, it’s the Grevy’s zebra. There are several species of zebra in Africa, including the Plains zebra, Mountain zebra and the Grevy’s zebra. Among them, the Mountain zebra is listed as vulnerable but the Grevy’s is in dire straights with only about 2,500 individuals left in the wild. As with zebras, no documentary about the African savanna is complete without some gazelles being caught by lions or cheetahs. But that doesn’t mean several species are in more trouble than any number of feline predators could pose. The Cuvier’s Gazelle of northwest Africa is estimated at just 1,750 – 2,950 individuals. Meanwhile the Slender-horned Gazelle of the Sahara has only around 250 mature individuals left. The Speke’s Gazelle (pictured above) from the Horn of Africa now extinct in Ethiopia and remaining populations in Somalia are thought to be in the tens of thousands but they face severe pressure from hunting and habitat loss.
Extinct Animals Wolly Mammoth An enormous mammal, believed to be closely related to the modern-day elephant. Its ancestors migrated out of Africa about 3.5 million years ago, spreading across northern Eurasia and North America; it is thought the Woolly Mammoth first appeared more than 400,000 years ago. The creature could reach heights of 4 metres or more and could weigh over 6 tons! Covered in fur with an outer covering of long hairs, short ears and tail to minimise heat loss and frost bite, it was well adapted to the cold environment it existed in during the last ice-age. Its curved tusks could easily be up to 5 metres long! The Woolly Mammoth eventually disappeared from its mainland range 10,000 years ago, the cause of this is most likely through a combination of hunting by humans, climate change (rapidly melting ice had an enormous impact on their demise) and the disappearance of its habitat. The last of the isolated woolly mammoth populations is believed to have vanished from Wrangel Island in the Arctic Ocean around 1700BC.
Sabre-Tooth Cats Often called Sabre-toothed Tigers or Sabre-toothed Lions they existed 55 million to 11,700 years ago. Sabre-tooth Cats were carnivores named for the elongated bladelike canine teeth in their upper jaw, which in
some species were up to 50cm long. Quite bear-like in build, they were believed to be excellent hunters and hunted animals such as sloths and mammoths. These felines could open their jaws at an angle of 120 degrees – almost twice as wide as a modern lion! It is thought the Sabre-tooth Cat’s extinction may be linked to the decline and extinction of large herbivores, which were replaced by smaller and more agile ones like deer. Being specialized at hunting large prey they may have been unable to adapt. Other explanations include climate change and competition with humans.
Great Auk A large and flightless bird that was found in the North Atlantic and as far south as northern Spain. It had an average height of 75-85 cm and weighed about 5kg. The Great Auk was flightless but was a powerful swimmer which aided hunting in the water. Humans hunted the Great Auk for more than 100,000 years using the bird as fishing bait and as a food source, this resulted in the bird’s numbers being reduced. High demand for the bird’s feathers in Europe almost eliminated the European population during the mid-16th century. The last colony of Auks lived on the island of Eldey, southwest of Iceland, in 1835 - they were killed for their skins. The last of these birds in the British Isles was killed on St Kilda, Scotland in 1844; three men caught it and kept it alive for three
days. A large storm arose and believing that the auk was a witch and caused the storm, they killed it.
Pyrenean Ibex One of four subspecies of the Spanish Ibex or Iberian Goat that was found in the Iberian Peninsula. It tended to live in rocky habitats with cliffs and trees on high mountain slopes in summer and warmer valleys during the winter. The Ibex had greyish brown fur that grew thicker in winter with the males having black colouring on their legs, neck and face. The males also had large, thick, ridged, curving horns but the females were much shorter and thinner. The Ibex would grow to a height of 60-76cm at the shoulder and weigh 24-80 kg and fed mainly on grasses and herbs. They were thought to have numbered 50,000 historically, but by the early 1900s its numbers had fallen to fewer than 100. The exact cause of the Pyrenean Ibex’s extinction is unknown; scientists think a number of different factors contributed including poaching, disease and the inability to compete with other mammals for food and habitat. The last Pyrenean Ibex was found dead in northern Spain in the year 2000, killed by a falling tree.
Dodo An extinct flightless bird that inhabited the island of Mauritius, the Dodo was about one metre tall and may have weighed 10–18 kg. The Dodo’s appearance is evidenced only by illustrations and written accounts from the 17th century but because these vary considerably, its exact appearance in life remains unresolved. It is presumed that the Dodo became flightless because of the ready availability of abundant food sources (seeds, bulbs, nuts, roots and fallen fruits) and a relative absence of predators on Mauritius. The first recorded mention of the dodo was by Dutch sailors in 1598. In the following years, the bird was hunted to extinction by sailors, their domesticated animals, and invasive species introduced during that time. The last widely accepted sighting of a Dodo was in 1662.
Tasmanian Tiger Native to Australia, Tasmania and New Guinea during prehistoric times, the Tasmanian Tiger was a large carnivorous marsupial which became extinct on the Australian mainland around 2000 years ago but survived on the island of Tasmania until the 1930s. Not related to tigers, the creature had the appearance of a medium-to-large-size dog (it weighed around 30kg with a nose to tail length of almost 2 metres) but dark stripes that radiated from the top of its back gave it a tiger-like appearance. It is believed to have been hunted to extinc-
tion – this was encouraged by bounties – but other contributing factors could have been human encroachment into its habitat, the introduction of dogs and disease. The last wild Tasmanian Tiger was killed between 1910 and 1920 with the last captive one dying in Hobart Zoo, Tasmania in 1936.
West African Black Rhinoceros The West African Black Rhinoceros is a sub-species of the Black Rhinoceros which was found in several countries towards the southeast region of Africa. Measuring 3-3.8 metres long and 1.4-1.7 metres in height this rhino would have weighed 800-1,300 kg. It had two horns, one measuring 0.5-1.3 metres and the other between 2-55cm. Their diet included leafy plants and shoots. Some people believe their horns had medicinal properties – though this had no grounding in scientific fact - this lead to heavy poaching. Preservation actions were taken in the 1930s to try to protect the dwindling Rhino numbers but since these protection efforts declined over the years, so did the number of rhinos. By 1980 the numbers were in the hundreds and further widespread poaching brought the species to extinction. The last West African Black Rhino was seen in Cameroon in 2006. It was declared officially extinct in 2011.
Stellers Sea Cow Named after George Steller, a naturalist who discovered
the creature in 1741, Stellers Sea Cow was a large herbivorous mammal that had a seal-like appearance with a tail which resembled that of a whale. It is believed that Stellers Sea Cow which grew to at least 8-9 metres and weighed around 8-10 tons, inhabited the Near Islands, southwest of Alaska and the Commander Islands in the Bering Sea. Its closest living relatives are the Dugong and the Manatee. It is believed that the mammal was tame and spent most of its time eating kelp; this, and the fact that it was unable to submerge its enormous body, is possibly what made it so vulnerable to human hunters. Within 27 years of discovery by Europeans, the slow-moving Steller’s Sea Cow was hunted to extinction.
Passenger Pigeon Native to North America and once the most abundant birds in the world, the Passenger or Wild Pigeon has been extinct since the early 20th century. It is estimated 3 to 5 billion Passenger Pigeons were in the US when Europeans arrived in North America, but their settlement led to mass deforestation resulting in habitat loss and a reduction in the bird numbers. In the 19th century pigeon meat was commercialized as a cheap food for slaves and the poor, which resulted in hunting on a massive scale. The Passenger Pigeon died out in the wild around 1900 with the last survivor dying in captivity in 1914.
Extinction of Species · Every 20 minutes, the world adds another 3,500 human lives but loses one or more entire species of animal or plant life - at least 27,000 species per year. · At the present rates of extinction, as many as 20% of the world’s 7-15 million species could be gone in the next 30 years. This rate of extinction has been unprecedented since the disappearance of dinosaurs 65 million years ago
the much prized rhino horn more than 5 times the price of gold. · 5 -10 million African elephants existed in 1930. Less than 1% of that number (approximately 600,000) remained when they were added to the international list of the most endangered species in 1989. · Demand for ivory combined with loss of habitat from human settlement led to these huge declines in population.
· Human population reached 1 billion by 1800. Over 6 billion by 2000. Conservative estimates predict that our population will reach 9 billion people by 2050 (Source: Population Reference Bureau). · The hourly destruction of an estimated 240 acres of natural habitat is directly attributable to the growth in human populations.
· Listed as one of the worlds most endangered canids, and the most endangered predator in Africa, there are now only between 4,000-5,000 African wild dogs in the wild.
· 80% of the decline in biological diversity is caused by habitat destruction. Plight of Rhinos
Today, pack size averages about 10, and the total population on the Serengeti is probably less than 60 dogs.
· Of the dozens of species of rhino that once roamed the earth, only 5 now exist.
· Due to their large home ranges, African wild dogs are particularly vulnerable to habitat destruction.
· Where there were once over 100,000 black rhinos on the plains of Africa, there are now only 2,707 on the entire continent. · The staggering decimation of the rhino population is due to poaching, to satisfy the demand for the horn for use in Eastern traditional medicines and as dagger handles. · Prices up to US$40,000 a kilo have been recorded for
· A century ago, African wild dog packs numbering a hundred or more animals could be seen roaming the Serengeti Plains.
· They are widely regarded as pests, and poisoned, shot, trapped and snared in many areas. · Their most serious threat, though, is introduced diseases. Burgeoning human populations have brought the African wild dogs into frequent contact with domestic dogs, many of which carry canine distemper and rabies.