Biodiversity and Conservation: A Hypertext Book by Peter J. Bryant

Chapter 3: EXTINCTION AND DEPLETION FROM OVER-EXPLOITATION

 

 LATE PLEISTOCENE EXTINCTIONS

 SURVIVORS FROM THE PLEISTOCENE
 
HISTORICAL EXTINCTION EVENTS

    Aurochs
    Steller's Sea Cow
    Great Auk
    Carolina Parakeet
    Passenger Pigeon 

THE FUR TRADE
    The Russian Fur Trade
         Sea otters
    The American Fur Trade
         Beaver 
         American Buffalo

 SEAL HUNTING

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LATE PLEISTOCENE EXTINCTIONS

In late Pleistocene, during the last 50,000 years, there were mass extinction events in many different parts of the world, involving at least 200 genera (plural of genus = a group of related species). But this was different from previous episodes of mass extinction:

1. It was much more selective, involving mainly the megafauna: the large herbivores (mammoths, mastodons, huge ground sloths, cave bears, woolly rhinoceros, other rhinoceroses, etc.) and the carnivores that fed on them, the dire wolves and saber-tooth cats. There was no accelerated extinction of smaller terrestrial species, plants, or marine organisms.

The following disappeared from America, Europe and Australia:

All herbivores

> 1000 kg

75% of herbivores

100-1000 kg

41% of herbivores

5-100 kg

< 2% of herbivores

< 5kg

2. It occurred at different times on different land masses:

Time of start of
major extinction episodes
(years before present)

Africa and S.E. Asia

50,000

Australia

50,000

North Eurasia

13,000

North America

11,000

South America

10,000

West Indies

4,000

New Zealand

900

Madagascar

800

This excludes any global catastrophe or climatic change as an explanation.

In all of these cases except Africa, the extinctions occurred shortly after the first arrival of prehistoric humans.  The first humans were faced with animals that had evolved in the absence of human predators, and the animals were probably easily overcome. Therefore, the most plausible explanation is that these extinctions were caused by overexploitation by human hunters.

In Africa, massive extinction does not coincide with the arrival of humans. Humans had been evolving there for millions of years without causing mass extinctions (they may not have been as carnivorous as their descendants in other parts of the world) but it does coincide with the maximum development of advanced early Stone Age hunting cultures.

Many authors have remarked that to see what the Pleistocene was like, you should go to Africa. Africa still has more large herbivores (including elephants, hippos, rhinos, etc.) than any other place on earth. But, even in Africa, the big game we see today is only about 70% of the genera that were present in mid-Pleistocene. About 50 genera disappeared about 40,000 years ago.

It is paradoxical that the region where humans have existed the longest (Africa) retained a wide variety of big game whereas the areas where humans arrived more recently have suffered a more complete loss.  Perhaps the African big game had time to evolve defensive behavior, whereas species elsewhere were caught defenseless and naive by a newly arrived advanced hunting culture.

Australia once boasted a spectacular megafauna including giant wombats as big as grizzly bears and giant kangaroos.  But the continent was colonized by humans (already Homo sapiens) around 55,000 years ago and subsequently lost all of its large and medium-sized mammals; in fact all except some kangaroos.  All 19 species exceeding 100 kg and 22 of 38 species 10-100 kg disappeared, along with three large reptiles and the 450lb flightless bird Genyornis.  Miller et al. used eggshell dating to show that Genyornis disappeared suddenly around 50,000 years ago, very shortly after the first arrival of humans.  This does not necessarily mean that the animals were simply hunted to extinction.  The humans brought to the continent the use of fire as a hunting tool, and this may have destroyed so much vegetation that many herbivores were deprived of their food and could not survive.  Although some authors have claimed that the Australian megafauna was wiped out quickly after the arrival of humans, careful analysis of the ages of various remains suggests that man may have coexisted with the Australian megafauna for over 10,000 years.  More discussion.

North America. 12,000 years ago, North America had an amazing Megafauna including condors with a sixteen-foot wingspan, ground sloths as big as hippos, three kinds of elephants, three kinds of cheetah and five other kinds of big cat, several kinds of pronghorn antelopes, long-legged, antelope-like pigs, an assortment of camel, llama, deer, horse, and bison species, giant wolves, giant bears and giant armadillos.  North America has been called a "super-Serengeti" with more big animal species than you would find in Africa.

But 11,000 years ago, nearly all of these big animals  - 70 species or 95% of the megafauna - disappeared completely. This is exactly the time when humans (Paleo-Indians) colonized North America, and their arrival and skill as hunters at that time is documented by the appearance of artifacts.

The disappearing mammals in North America included all of the following: 

*Some of these fossils are directly associated with human artifacts in archaeological sites.

The carnivores on the list were probably not hunted directly, but were dependent on the large herbivores for food, so soon followed them to extinction.

In some cases accurate dating methods have shown that certain species became extinct at exactly the times that humans arrived. Giant ground sloths and mountain goats in the Grand Canyon both went extinct 11,100 years ago, which is the time that the human hunters arrived (within the accuracy of dating methods, which is +200 years).

There is also direct evidence for killing by humans. The human archeological sites from 11,000 years ago have stone projectile points, which were presumably used in hunting the large mammals. One mammoth skeleton has eight stone spear points among its ribs. Some of the large mammals were trapped in pits, and some were cornered using fire. La Brea tar pits and the Page Museum is an excellent place to see the fossils and reconstructions from this period.

Mammoth Trumpet (a newsletter about the first Americans)

Detailed study of late Pleistocene extinctions in North America (Martin, 1986) suggests that they happened over just a few hundred years. This explains why there is so little archaeological evidence for hunting of mammoths in the New World. The total number of mammoths from archeological sites in North America is 38; in Asia, where mammoths were hunted for many thousands of years, there are many more mammoth remains -e.g. remains of 1000 mammoths at just one site in Czechoslovakia and of 100,000 horses at another site.

Paul Martin has suggested that the human population quickly expanded south from the Bering land bridge, and exterminated the big game as they went ("Blitzkrieg" model).

Martin, P. S.1986. Refuting late Pleistocene extinction models. In Elliot, D.K. (ed) Dynamic extinction. Wiley & Sons, NY. 1073-130.

Other authors have disputed the idea that human hunting finished off the Pleistocene megafauna of North America.  For example, Donald Grayson, an archaeologist at the University of Washington, suggests that climate shifts and associated vegetational changes could have been responsible.  Grayson disputes two of aspects of the overkill hypothesis:

Paul Martin responds that the Pleistocene megafauna had survived several climatic changes during the previous million years, some more severe than the one that occurred at the end of the Pleistocene.  Yet these changes did not cause multiple extinctions.

South America was also colonized by humans about eleven thousand years ago, and since that time it has lost 80% of its genera of large mammals, including ground sloths, horses, and mastodons.

SURVIVORS FROM THE PLEISTOCENE

In North America, the only surviving herbivores of the megafauna are bears, elk, moose, buffalo and mountain lion.  The horse also survived, but only through its domestication and preservation overseas. The moose was hunted to near extinction but has recovered to a population of about 1 million.  Yellowstone moose decline due to hunger, not predators, ENN Daily News -- 10-6-1999

HISTORICAL EXTINCTION EVENTS

Some survivors from the Pleistocene have been driven to extinction during historical times by over-exploitation:

Aurochs

A European member of the cattle family, the Aurochs, was a long-horned, forest-dwelling ancestor of modern domestic cattle. Its last holdout was in a private game reserve in Poland, but poachers killed it off. The last one died in 1627.

Sea Cow

This was heavy, slow-swimming marine mammal related to the manatee and dugong (Sirenians), but much larger (25-30 feet long). It was discovered in 1741 in the ocean around the Pribilof Islands in Bering Sea (far north Pacific Ocean). It was used as food by visiting sea-otter hunters, and was extinct by 1768, 27 years after its discovery.

Surviving relatives

A smaller (12 feet long) relative of the sea cow that is endangered by human activities is the Manatee (West Indian or Florida Manatee), a slow-swimming, friendly marine mammal that feeds on sea grass and lives in the coastal waterways of Florida and in other coastal areas around the Caribbean. There are about 2,000 animals in the population, but at least 200 die each year, mainly from collisions with speedboats. Florida's response to this problem has been to post "go-slow" signs on the waterways, and to rely mainly on voluntary compliance. They have also established some very small sanctuaries.  These efforts are not working very well. The death rate has not declined; in fact collisions with boats killed a record number of 82 manatees in 1999.  Save the Manatee Club is now filing lawsuits to try to get the government agencies to better enforce the laws protecting manatees. Read updates at MANATEE - Website For Manatee Watchers

Manatee deaths in Florida

Year

Manatee deaths

From boat injuries

1996

415

60

1997

242

54

1998

231

66

1999

268

81

2000

272

78

Despite the manatee's precarious situation, a consortium of Florida business interests is lobbying to get the mammal removed from the federal Endangered Species list.  

The other surviving relative of the sea cow, the dugong, is also in serious trouble.  Dugongs are found in a huge area from the Red Sea to the Pacific Coast of Australia and the Solomon Islands.  They are so dispersed that accurate population counts have not been possible.  The Australian dugong population is estimated at 85,000, but the numbers have fallen by between 50% and 80% since the early 1980s, due to habitat loss, entanglement in fishing nets and nets used to protect swimming areas from sharks . The Great Barrier Reef Marine Park Authority has established a chain of dugong sanctuaries to try to protect the remaining animals.  Recent News items

Great Auk

The Great Auk was a 3-foot tall penguin-like flightless seabird. It was a very fast underwater swimmer, but clumsy on land. Hundreds of thousands of these birds lived in the North Atlantic. They were hunted between 1785 and 1844, mainly for their feathers which were used for mattress and pillow stuffing. The last breeding pair was killed by two fishermen, who also smashed the last egg.

Carolina Parakeet

The Carolina Parakeet was the only endemic parrot of North America. Unfortunately, these birds fed in large flocks on fruit and other crops, and were shot in huge numbers by farmers.  They were also collected for their feathers and for sale to zoos.  The last pair survived in the Cincinnati zoo until 1917-18.

Passenger Pigeon

The passenger pigeon was an attractive bird with a blue back and a pink breast that existed in huge populations. In fact, it may have been the most abundant bird ever to have lived. John James Audubon observed a flock of pigeons passing over a period of three days at a rate he estimated at over 300 million birds an hour. The passage of large flocks created a roar of wings that could be heard 6 miles away. The pigeons nested in long narrow colonies that could be 40 miles long and several miles across. They occurred throughout Eastern North America where they fed on acorns and beechnuts.

Early settlers in the United States developed a taste for passenger pigeon and commercial hunters devised many different ways of killing large numbers of the birds. They were suffocated by burning grass or sulphur below their roosts; fed grain soaked in alcohol; beaten down with long sticks, blasted with shotguns, caught in nets or trapped using a decoy pigeon tied to a perch called a stool (this is the origin of the term "stool pigeon").

By the 1880's the huge flocks were gone from the coastal states and were dwindling everywhere else. The last wild passenger pigeon was seen in Michigan in 1889 and the last captive bird ("Martha") died in the Cincinnati Zoo in 1914.

THE FUR TRADE

The hunting of animals for their hides (for leather) or fur played a very important part in the exploration and history of Europe, Asia and North America. It also led to a drastic reduction in the abundance of (though fortunately not the extinction of) many kinds of fur-bearing animals.

The Russian Fur Trade

The Fur Trade began in earnest in medieval times in Europe, when it involved the hunting of European animals to stock the wardrobes of the nobility and royalty. It involved mainly small animals such as squirrels, martens, ermine (=white phase of weasel), sable and foxes, and they were usually trapped alive so that their furs could be collected undamaged. Several hundred squirrel pelts were needed to make one cloak, so the numbers killed were enormous. Eventually, by the early 16th century, the populations of fur-bearing animals in Western Europe were almost exhausted, and this led to the exploration of the northern forests of Russia and the development of an international trading system. This trade was a major driving force behind the Russian expansion into Siberia, and the fur trade became Russia's economic foundation. It is estimated that, at the height of the squirrel trade (14th-16th centuries), Novgorod (one of three main centers) was exporting half a million squirrel skins a year. The fur-bearing animals of the vast Siberian forests were virtually eliminated by the end of the 18th century.  In the 1920's the American mink was introduced into Europe because of its superior fur compared to the native European species. Now, at least in part because of this introduction, the European mink is the continent's most endangered mammal. An "Island retreat" has been established in the Baltic Sea to try to rescue this species from extinction.

Sea Otters

When the Russian traders had exhausted the terrestrial fur-bearing animals they turned their attention to the sea otters that were discovered in 1741 in the north Pacific, on the Russian and Alaskan coasts.  At that time, there were between 150,000 and 300,000 otters living along the north American coast from Alaska to Baja California. From 1750 to 1790 most of the animals were killed by hunters, then they were too scarce to be worth hunting (they had reached "commercial extinction") and the trade collapsed. By 1911, when the otters received some protection through the International Fur Seal Treaty, there were only 1-2,000 animals left throughout their range. The population recovered well and the Alaskan (Aleutian Island) population reached a peak in the mid-1970s of about 50,000-100,000 animals. But from 1992 to 2000 it declined by 95% and now as few as 6,000 otters may remain in the entire Aleutian chain. This is just one part of a catastrophic ecosystem collapse that is occurring in the area.

Another population of about 2,400 sea otters survives along the California coast between Point Conception and Monterey Bay.  They are coming into increasing conflict with inshore fisheries for sea urchins.

The American Fur Trade

Partly because of the decline of the Russian fur bearing animals, from the earliest days of European settlement in North America, the fur trade has been one of the main incentives for westward expansion. For a long time, the colonists simply traded their goods for furs that the Native Americans collected. Later the Europeans became trappers as well as traders.

The strategy of the trappers in North America was similar to what had been responsible for depletion of these animals in Europe and Russia - they would exploit an area until the animals were so scarce that it was no longer profitable to hunt them, then they would move on to other areas and repeat the cycle.

One of the favorite targets of the trappers in North America was the beaver, the largest of the North American rodents. It was once extremely abundant throughout most of the continent but went into decline as early as 1638, mainly because the great insulating qualities of beaver fur made it the best material for hat manufacture. Beaver-fur hats were fashionable until the early nineteenth century, and the hunting pressure during this time virtually wiped out the species east of the Mississippi.

At the beginning of the 19th century, the fur trade in North America moved on to its last frontier, west of the Mississippi. In 1805 when the first explorers (Lewis and Clark) crossed the Rocky Mountains and continued on to the Pacific coast they reported that the area was "richer in beaver and otter than any other country on earth". The fur trappers were close behind the explorers, and in less than 40 years they had virtually cleared the area of both beaver and otter. By 1840 the beaver had been overexploited to the level where it was no longer worth hunting. The trappers had nowhere else to go, but they could switch to less desirable species. For a few years the trade was sustained by muskrat and marten furs, but these were also soon depleted.

Beavers have been protected in the 20th century and are now doing quite well on both sides of the Rocky Mountains. Now the beavers that still exist are often considered pests because they dam up creeks and cause flooding that leads to property damage. Oregon's beaver population causes about $250,000 in damage to roads, crops and businesses each year; the population is controlled mainly by professional trappers who catch about 5,000 beavers a year. In New York State bills have recently been introduced that would legalize underwater traps that kill beavers by drowning.

Not only beaver, but many other wildlife species in this country were almost eliminated by the fur trade. The Hudson's Bay Company was responsible for promoting the hunting of hundreds of thousands fur-bearing animals every year in North America, and exporting the hides and furs to Europe. The most valuable were the various members of the weasel family including the short-tailed weasel in its white or "ermine" phase, the otter, mink, pine marten, fisher, and wolverine. Of these animals, only weasels, otters and mink remain widespread, and the weasel is the only one that is still abundant. These animals were reduced initially by the fur trade, but most of them have also suffered from reduction in their forest habitat.

The American Buffalo (also called American Bison; taxonomically correct name = American Plains Buffalo) was brought almost to extinction by overzealous hunters.  In the 1800's, about 65 million buffalo roamed the prairies of the Great Plains. Herds were described up to 25 miles long, containing 12 million animals. Possibly the high population was a result of the elimination of other large herbivores that competed with the buffalo for food and space. Native Americans hunted the buffalo for thousands of years without making a dent in the population.

The great buffalo slaughter started with the arrival of settlers from Europe and especially the railroads in the 1860's. As the railroads pushed west, huge numbers of buffalo were killed for meat and hides, and to starve out the Native Americans. A representative of the Intertribal Bison Cooperative describes the buffalo slaughter as a calculated military strategy designed to force the Native Americans on to reservations. Professional hunters shot the animals for their tongues and hides and often left the carcasses to rot. About 2.5 million buffalo were killed annually between 1870 and 1875, and by 1883 the last large herd containing about 10,000 buffalo was slaughtered. Domestic cattle diseases may have also had a major impact on the herds. By 1890, less than 1000 buffalo remained in the U.S. The final refuge for the species was Yellowstone National Park, established in 1872.

Loss of the buffalo and other big prey animals caused wolves to turn their attention to farm animals, leading to organized efforts to exterminate them.  Now they are an endangered species and subject of a controversial reintroduction program.

The total buffalo population has been built back up so that now the species is not endangered. About 200,000 exist in public and private herds in the U.S. and Canada. Most of them are being raised like cattle on big ranches to provide beef for buffalo burgers. A confederation of American Indian tribes (the Intertribal Bison Cooperative) is also heavily involved in re-establishing buffalo populations (39 tribes, 8000 buffalo). They are finding that buffalo are much better adapted to North American winters than domestic cattle are, and that they are less likely to overgraze their pasture (cattle tend to concentrate on the patches of best forage and overgraze those patches, causing erosion; buffalo graze more lightly and keep moving). A recent study shows that grazing by bison increases biodiversity of the prairie habitat. 

Recommended book: Bring Back the Buffalo! : A Sustainable Future for America's Great Plains by Ernest Callenbach (1995).  Island Press, 250pp. 

The smaller European relative of the American buffalo, called the European Bison or Wisent, suffered a similar fate. Its population was down to 50 animals in 1921, but now it is back up to several thousands in private herds and zoos.

SEAL HUNTING

Fur seals.  The loss of furs from other sources was a major incentive leading to massive hunts for various types of seal. The animals were usually clubbed to death when they came ashore to breed. The pattern was familiar - the discovery of large populations of target species, the development of intensive hunting leading to extermination or depletion, the move to a new area. The first phase (1780-1820) was directed at the southern fur seal in many areas of the southern hemisphere and was carried out by sealers from Europe, Russia, Canada and the U.S. Each of the following areas was the site of a fur seal hunt until the population was either commercially extinct (depleted to the level where it was not profitable to hunt) or really extinct: 

Exhaustion of fur seal hunts  in the Southern Hemisphere, 1780-1820

1790-1791

Tristan da Cunha

1790-1791

Falkland Islands

1790-1791

Tierra del Fuego

1797-1803

Mas Afuera (Juan Fernandez Islands)

1800-1825

South Georgia

?

South Shetland Islands

1800-1825

Kerguelen Island

?

Australian coast

1810-1820

Macquarie Island

Off the west coast of Namibia in Africa, 40- 50,000 cape fur seal are taken each year.  This is about 10% of the world's sealing activity, and much of the profit comes from the sale of penises for the aphrodisiac trade in Asia.  Most of the seals are being killed by clubbing to death, which is claimed to be a humane method.  

In the North Pacific, the northern fur seal was hunted on the Pribilof Islands in the Bering Sea, first by the Russians using Inuit labor after they had wiped out the sea otters. The slaughter went from 127,000 in 1791 down to 7,000 a year in the 1820's after 2.5 million had been killed. The population recovered after the Russian hunters moved to other areas, but after Alaska was sold to the U.S. in 1867 the hunting level went back up to 250,000 per year. This reduced the population again so that in the 1890's the number killed was down to 17,000 a year. It is now illegal to hunt fur seals, except for an exemption allowing Indians, Aleuts, and Eskimos to continue to hunt at a subsistence level (about 2000 a year).

Harp seal.  A massive seal hunt also developed in the North Atlantic, taking advantage of the huge harp seal population that breeds on the pack ice in winter around Labrador and Newfoundland. The sealers, from Newfoundland, focused on the newborn seals with pure white fur, although adults were also taken for their oil as well as fur. The Newfoundland sealing industry began in the early 19th century and peaked at about 600,000 animals per year in the 1850's. This ultimately led to reduction in the size of the herd to about one fifth of its original size, and the industry went into decline in the early 20th century. A 1998 study shows that the current level of hunting (350,000 animals killed in one season) is not sustainable, and 12 members of Congress have written to Secretary of State Madeleine Albright declaring their opposition to this hunt.  Again in 1999 Canada is being criticized for allowing 275,000 of these animals to be killed in spite of public opinion against it.  The adult harp seals are also hunted on a subsistence level further north by Inuit hunters, who use the meat for food but also sell the skins in order to pay for the snowmobiles, rifles, gasoline and ammunition that are used in their hunting activities.

Another herd of harp seals, at Jan Mayen Island in the Arctic ocean, was wiped out by a rapid boom and bust between 1840 and 1860.

Elephant Seals were hunted in the Pacific in the 1800s by whalers who wanted to supplement their catch. They were hunted for their oil rather than their fur or skin. Hundreds of thousands of these animals were killed in the southern ocean and along the coast of California. The southern population (a distinct subspecies) was saved when the Kerguelen and Macquarie Islands were turned into nature reserves, but in 1884 it appeared that the northern subspecies had been lost. However, a small colony of about 50-100 had survived on Guadalupe Island off the coast of Baja California.  The species was given protection by the Mexican and U.S. governments in the 1920s and the stock is now doing quite well. Today, there are approximately 160,000 northern elephant seals!  A large breeding population (~2000) now congregates on the beach at Ano Nuevo, fifty-five miles south of San Francisco, every winter (See today's minicam picture!). Seals and sea lions may have had many more breeding colonies on the mainland before they were eliminated by prehistoric hunting.

Walruses were killed for three centuries for their oil, skin, and ivory from their tusks. They were once abundant in the North Pacific, North Atlantic and the Arctic Oceans, but like the other seals, walruses were hunted almost to extinction. They are now protected in this country and the walrus population appears stable at about 200,000 individuals. 

Different Views

The most vociferous opposition to marine mammal hunting has come from anti-cruelty activists and animal welfare organizations including the International Fund for Animal Welfare and the Sea Shepherd Conservation Society.  They argue that clubbing animals to death or puncturing their skulls with an iron spike is inhumane.

The North Atlantic Marine Mammal Commission is conducting scientific studies on the best way to kill marine mammals.

Another form of opposition to marine mammal hunting has been based on the danger it poses to the survival of these species.  This viewpoint emphasizes that most hunts have not been sustainable, but have seriously depleted or wiped out the target population in a "boom and bust" cycle. 

The fact that many hunted populations have recovered quite well after we stopped hunting them leads to pressure to continue hunting and to try to manage the activity on a "sustainable" basis.  The High North Alliance was established to defend the right of coastal communities to utilize marine mammals sustainably.  You can post your opinions on their web site.

Walruses, seals and sea lions are protected in the U.S. by the Marine Mammal Protection Act, passed in 1972 (see Lecture 4). This Act established a moratorium on the taking and importation of various marine mammals, their parts, and products. The Act does allow various exceptions. For example, it allows Inuit and other Alaskan Natives to take walrus for subsistence, and to use their parts in making handicraft articles. 

The Act, and a European import ban in 1983, has removed a major source of income for the Inuit. 

 

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Copyright 2002  Peter J. Bryant (pjbryant@uci.edu), School of Biological Sciences,
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