Mammal Extinctions

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Mammal Extinctions
Cuba, Puerto Rico, Hispaniola and Jamaica had a variety of unusual native rodents and shrew-like insectivores prior to the arrival of European explorers and settlers in the 1600s; many were ancient species. When native Caribbean populations settled the islands after the Ice Ages, rodents as big as marmots inhabited the larger islands. A type of giant sloth lived in Puerto Rico, and a rodent nearly the size of the American black bear inhabited the small islands of Anguilla and St. Martin until it was apparently hunted to extinction by natives (Olson 1978). Cuba, Puerto Rico and Hispaniola were once attached to the mainland of Central America, but this large land mass became separated and drifted off into the Caribbean. Some of the native fauna and flora present more than a million years ago survived until a few thousand years ago, and tiny frogs and butterflies from that period persist today.
When Europeans colonized the Caribbean islands, they began cutting forests and replacing them with huge plantations of sugar cane, other crops and grazing land for livestock. They imported thousands of slaves to farm the land. Mongooses were brought on the islands to control snakes, but they preyed on native mammals and birds instead; rats arrived in ship holds and did the same. Fifteen mammals have become extinct on Hispaniola, the island divided between present day Haiti and the Dominican Republic – this island suffered the highest number of mammal extinctions of any Caribbean island. Forests have been nearly obliterated on Haiti, which is another cause of extinctions. Cuba, Puerto Rico and Jamaica have likewise lost the majority of their forest cover, as well as many native mammals, including bats, rodents and insectivores. Jamaica was home to a monkey (Xenothrix mcgregori), making it the only Caribbean island with a native primate. It was hunted and its forest habitat was cut by European colonists, and it died out in the 1750s. Various species of hutias, large rodents found on most major islands, became extinct as well. Hutias remain on a few Caribbean islands but are close to extinction from forest destruction and predation by introduced mammals.
Most of the 40 mammals that became extinct on Caribbean islands after 1600 were rodents and insectivores. A muskrat and a rice rat became extinct on Martinique when Mt. Pelee erupted in 1902 – one of the few examples of a naturally caused modern extinction. Hutias, large rodents that resemble South American agoutis, proliferated into a variety of species on the large islands of the Greater Antilles. Settlement, deforestation and hunting caused at least five species of hutias to become extinct, and the few remaining species are now highly endangered.
The first mammal to disappear after 1600 was a massive wild cow called an auroch (Bos primagenius). This species, native to most of Europe, lived in the deciduous forests that once covered most of the continent. The auroch was also hunted for its meat and died out about 1627. Several other wild cattle related to the auroch survive in Southeast Asia, but they are critically endangered. The tarpan (Equus gmelini), a wild horse of Europe, gradually became rare and restricted from hunting and destruction of its native forests during the Middle Ages. The last wild tarpans were killed off in 1851 (Day 1981). Both the auroch and the tarpan are depicted by Pleistocene humans in magnificent cave paintings found in southern Spain and France.
The Steller's sea cow (Hydrodamalis stelleri) was an enormous 24 to 30 feet long marine mammal, similar in appearance to the dugong and the manatee. The sea cow was larger, however, and swam in the cold arctic waters of the Bering Sea, enduring temperatures that would kill its closest relatives. The slow and sluggish sea cows were killed off only 27 years after their discovery. They were first seen by the shipwrecked crew of the explorer Vitus Bering in 1741 in the vicinity of Bering Island in the Commander Islands, off the eastern coast of Russia's Kamchatka Peninsula. These sea cows were tame and easy to spear and harpoon by the ship crews who killed most of the population, calculated at only about 1,500. This animal showed extreme protectiveness toward its fellows and strong bonds between mates. The naturalist Georg Wilhelm Steller, after whom the species was named, described their behavior on being harpooned.
. . . Some of them tried to upset the boat [when another sea cow was struck] with their backs, while others pressed down the rope and endeavored to break it, or strove to remove the hook from the wound in the back by blows of their tail, in which they actually succeeded several times. It is most remarkable proof of their conjugal affection that the male, after having tried with all his might, although in vain, to free the female caught by the hook, and in spite of the beating we gave him, nevertheless followed her to the shore, and that several times, even after she was dead, he shot unexpectedly up to her like a speeding arrow. Early next morning, when we came to cut up the meat and bring it to the dugout we found the male by the female, and the same I observed on the third day when I went there by myself for the sole purpose of examining the intestine (Day 1981).
Australia has been the scene of more mammal extinctions than any other continent or island group. Beginning in the 19th century, Australia's mammals disappeared in large numbers. Native marsupials and rodents were gradually eliminated by massive habitat destruction and predation from animals introduced by European settlers. Twenty-two mammals became extinct after 1600. A wide variety of marsupials, from small species to wallabies, was extinguished within a century of settlement. Some, like the thylacine, or Tasmanian wolf (Thylacinus cyanocephalus), were deliberately persecuted by livestock ranchers under the misapprehension that the species presented a threat to flocks.
The crescent nailtail wallaby (Onychogalea lunata) was native to the gum forests of western Australia where John Gilbert, a 19th century museum collector, found the animal common in thick scrub, "where it is occasionally seen sunning itself" (Strahan 1995). This small marsupial weighed less than 20 pounds and looked like a miniature kangaroo. It rested in hollows in soft ground beneath shrubs during the day, feeding mainly at night on roots and coarse grass (Nowak 1999). When chased, it would run to a hollow tree with a hole in the bottom and clamber up the sides until it got high up within the trunk; aborigines used smoke to chase them out and then killed them for food (Strahan 1995). The aborigines also hunted these animals by building brush fences and enclosures and driving the animals into areas where people waited with clubs (Strahan 1995). In spite of hunting, this wallaby was fairly common until 1900, and many were collected for museums (Strahan 1995). It disappeared from the southern portion of its range early in the century after intensive forest clearance and development of the country for agriculture. Gradually, it became very rare, and disappeared altogether from the wild in the 1960s (Nowak 1999, Strahan 1995). Some experts suggested the removal of the thickets where these wallabies sheltered during the heat of the day left them homeless and vulnerable to predation (Nowak 1999).
Millions of acres of eucalyptus forests and mulga woodlands of southern and western Australia were clearcut by settlers beginning in the 19th century, opening up the land to wildfires (Lines 1991). The devastation of these habitats was described in Taming the Great South Land. A History of the Conquest of Nature in Australia, by W.J. Lines (1991). The combination of this habitat destruction, hunting and introduced predators, such as feral dogs, was responsible for the extinction of the Crescent Nailtail wallaby and many other native marsupials.
Various endemic Australian rodents and bats died out as well, and many of the remaining native mammals are become confined to tiny islands off the coasts – the only habitats where introduced animals are absent. Australia is like an island in having been isolated from other land masses for millions of years, and the majority of its mammals are endemic to the continent. In fact, it is often referred to as the "Island Continent." If Australian extinctions are included among those on islands, 87 percent of all extinctions of vertebrates other than fish have occurred on islands.
In Asia, the freshwater baiji dolphin species was until recently found throughout the Yangtze River and its surrounding lakes and tributaries. Unfortunately, the exponential growth of the Chinese population posed a variety of threats to its survival. A lack of information, growing threats and the species' small population size eventually led to the baiji's decline, despite protective efforts. Baiji dolphins were last officially sighted in 2004, and a 2006 expedition deemed the species "functionally extinct."






©1983 Animal Welfare Institute

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