Дата публикации: 21 сентября 2021
Автор(ы): Vyacheslav ROZHNOV, Viktor ORLOV, Natalya PAKLINA, Natalya SPASSKAYA →
Публикатор: Научная библиотека Порталус
Рубрика: БИОЛОГИЯ →
Источник: (c) Science in Russia, №4, 2011, C.32-37 →
Номер публикации: №1632216232
Vyacheslav ROZHNOV, Viktor ORLOV, Natalya PAKLINA, Natalya SPASSKAYA, (c)
by Vyacheslav ROZHNOV and Viktor ORLOV, Drs. Sc. (Biol.); Natalya PAKLINA, Research Assistant of A. Severtsov Institute of Problems of Ecology and Evolution, RAS; Natalya SPASSKAYA, Dr. Sc. (Biol.), Scientific Research Zoological Museum of Moscow State University
Anthropological changes have affected natural populations of many animals: they have decreased so dramatically as to become almost extinct without human intervention. The famous Przhewalski horse (Equus przewalskii) is one of the endangered species. It is being raised in special nurseries and zoos-today this is the only way of preserving its population. However, the final objective of scientists is to put these steppe aboriginals back to their natural habitat.
SPECIES OR SUBSPECIES?
This wild Asian horse was discovered by Nikolai Przhewalski, an outstanding Russian explorer of Central Asia (Honorary Member of St. Petersburg Academy of Sciences from 1878). He appeared to be the first among Europeans to reveal these animals during the expedition of 1876-1877 on the way from the Bulugun River to Lake Barkul. The first scientific description of the species was made by Ivan Polyakov, curator of the Museum of Zoology in St. Petersburg, who named it in honor of the famous explorer (Equus przewalskii Polyakov, 1881). According to the data available at that time, the wild horse inhabited Dzungaria*: in the north this region was bounded by the Urungu (head of the Cherny Irtysh River) and the northern slopes of Mongolian Altai Mts; in the south--by Tien Shan Mts. This is where all Przhewalski horses have been caught for zoos and museums.
But was this area the only habitat of the animals? Scientists discovered fossils of the wild horse in the deposits of the late Pleistocene. A number of morphological characteristics show this species was formed in dry steppes, forest-steppes or similar landscapes on the foothills of Central Eurasia. Even though the pale-ontological findings are scarce, they still prove a widespread occurrence of the Przhewalski horse in Mongolia and Northern China, in the territory of present-
* Dzungaria is in the northwest of China and borders on the Mongolian Altai mountains in the north and east, and the Tien Shan mountains in the south. It is a desert passing into Mongolian Gobi eastwards.--Auth.
day Kazakhstan and Russia. According to the historical documents, in the 17th-18th centuries the distribution range of the species also included Northern Kazakhstan and the interfluve of the Volga and the Ural--perhaps the wild horse reached there from Dzungaria through the Zaisan depression*. In Siberia, the animal frequently occurred in the early 17th century on the right bank of the Irtysh (a tributary of the Ob) and in the steppes of the Kuznetsky District of the Tomsk Region.
At the same time, up to the late 19th century, in the south and southwest of Russia there lived the "tarpans" (Equus gmelini Antonius, 1912) ("wild horses" in Turkic). This word has analogues in the Kazakh, Tatar and Bashkir languages.
A logical question rises: could the Asian wild horse and the European tarpan be one and the same species? According to some scientists, for example, Ronald Nowak from John Hopkins University (USA), Peter Grubb from the Zoological Society of London, and a well-known national zoologist Academician Vladimir Sokolov, there are some geographical races of the same species, namely Equus caballus przewalskii, Equus caballus gmelini. In this context, the Przhewalski horse is sometimes called Dzungaria tarpan (this name first appeared in the publications of 1955 and 1961 by Vladimir Heptner, Dr. Sc. (Biol.), professor of Moscow State University). But this horse has a number of mor-
* Zaisan depression is in Kazakhstan, between the South Altai mountain chains in the north and the Tarbagatai and Saur in the south.--Ed.
Science in Russia, No.4, 2011
phological and genetic characteristics that make it a separate species. We stand for this interpretation as well.
HISTORY OF EXTERMINATION
Habitats of the European tarpan and the Przhewalski horse must have ovelapped in the territory of the present-day Orenburg and Samara Regions. This hypothesis is proved by historical documents and diaries of travelers: these animals concurrently inhabited steppes and semi-deserts of the Volga-Ural interfluve at least before the mid-19th century. But in the southern area of the Ural steppe these fast horses of wild plains disappeared much earlier. At the same time, eastward of the Ural River they lived on and were more numerous--the Bashkirs brought flocks of horses from there. The Daurian steppes, in the basins of the Onon and Argun Rivers, were the eastern border of the habitat of wild runners in Russia for the whole 18th century. Desert areas of Dzungaria Gobi became their last shelter upon their ouster from formerly vast habitats.
Less than 100 years after their discovery, wild Przhewalski horses were nearly totally exterminated. This
sad story is quite instructive. Before the 1940s a viable population of wild horses still existed at the southern foothills of the Mongolian Altai Mts and in the border areas of southwestern Mongolia. According to most conservative estimates, there lived some hundreds of animals with a habitat of 20,000 km2. A drastic reduction in the number of "takhi" (local name for the Przhewalski horse) began in the winter of 1944-1945 that followed a dry summer known as "Year of the Monkey Jute". Such harsh periods are not common in these parts, they occur once in a century. Many families lost all their livestock and had to hunt for survival. This natural disaster in the area of Dzungaria Gobi coincided with the militarization of Mongolia, when local defense detachments were formed and about one thousand Muslim Kazakh families moved in from China. The government equipped them with weapons to repel probable attacks of the Chinese army. Since they had no cattle of their own, both the refugees and the local tribes survived by hunting. But the newcomers brought modern weapons and vehicles destructive to the population of wild horses. Pernicious hunting practices resulted in a catastrophe: Przhewalski horses were noticed in Mongolia for the last time in 1969; as for China, the animals had disappeared there long before.
Yet we are speaking about the only and the last species of the wild horse. Clear phenotypic and genetic characters make it possible to rank the Przhewalski horse as a separate species. It has a short, standing mane without a forelock, a tail covered with short hair in the upper part, and with long hair toward the tip. Chestnuts (horny formations on the inner part of the legs under the wrist joint and below the ankle joint) are characteristic only of the forelegs, not all of the legs as it is in domestic horses.
The latter have only 64 chromosomes, while the species under consideration has but 66. Kurt Benirschke, member of the Zoological Society of San Diego (USA), in his detailed research works dated 1965 and Viktor Orlov, one of the authors of this article, have proved: the karyotype* of domestic horses was formed as a result of fusion of ancestral chromosomes, i.e. the ancestors of domestic and wild horses, in particular, the Przhewalski horse, were close relatives. This enabled them to interbreed and produce fertile hybrids. At the same time, as found by mitochondrial DNA studies, Equus przewalskii has unique genetic markers not ever registered in domestic horses, even in the Mongolian breed living side by side for centuries.
In late 19th-early 20th centuries, a number of expeditions to Western Mongolia were organized to catch
*Karyotype-a combination of characters (number, size, shape, etc.) of a complete set of chromosomes typical of the organism of a certain species.--Auth.
wild horses for zoos. The animals were very rare and were in great demand; young horses were distributed in many countries, singly or in pairs. Askania Nova, a steppe zoo in Ukraine, was one of the first to purchase such horses in 1899. It was there that pioneer experiments on seminatural breeding were initiated: the horses lived in big yards of 1.5 thous. ha, not small cages, where they could freely grass in the open air all year round. This is how the largest Przhewalski horse breeding center in the USSR originated--in Askania Nova, there lived over a hundred animals or about 60 percent of the whole herd available in our country.
NEW THREAT OF EXTINCTION
After the disintegration of the USSR, and the proclamation of Ukraine and other former Soviet republics independent, Russia lost a greater part of the living collection of wild horses. In 1995, nine national zoos had only 44 animals: 11 and 9 horses lived in Moscow and St. Petersburg zoos followed by Rostov-on-Don and Penza zoos. In recent years their population has not increased, it has even decreased to 40 animals; the palm was yielded to Rostov-on-Don with 8 horses in the collection. Other zoos keep not more than 2-5 animals.
Nevertheless, the total number of wild horses in the territory of the former Soviet Union has been preserved even despite a 14 percent decrease of the population in Askania Nova--today it has but 87 horses. As many as 28 animals were moved to the off-limits zone around the Chernobyl Nuclear Power Station (Ukraine) to restore and enrich the biological diversity of the local ecosystem. Unfortunately, poaching in this area brings all efforts of scientists nearly to nil.
At the moment, Przhewalski horses are bred only in large centers and not as actively as before. This is because of the low demand for this species that is not exotic any more and lack of space for the upkeep. Thus, the zoos of Tashkent, Semipalatinsk (Semei), Riga and Lipetsk keep solitary or non-fertile horses, while the zoos of Kishinev, Karaganda, Termez and Chelyabinsk have lost their herd. The ageing of the man-bred population, especially in small nurseries, is of special concern.
At present, numerous national and foreign centers are successfully breeding hundreds of species of birds, reptiles and mammals. Zoos are able to hold and breed animals in almost ideal conditions: good food, no threat of predators; climatic conditions are more comfortable than in wild nature. Normally, living collections are replenished with animals caught in the wild, which is very important taking into account the low number of hand-reared animals. But if the species does not exist in wild nature any more and scientists are unable to bring wild animals to zoos and nurseries (Père David deer, for example), such animals are facing a high risk of extinction because of the changing
economic environment, inbreeding (cross-breeding of close relatives within one population) and the critical decline of genetic variability.
However, a group of animals reproducing in a zoo could be placed back to its natural habitat, provided their biotypes have not been affected significantly by anthropogenic changes and a breeding center has enough money for re-introduction. Such work has been initiated in the Caucasus to regenerate the population of the Fore Asia leopard that inhabited this region as late as 50 years ago. A similar program is envisaged for the Far Eastern leopard in the Primorye (Maritime) Territory.
A WAY TO SALVATION
All that applies to Przhewalski horse as well. It is placed in the Red List of the International Union for Conservation of Nature and in Attachment No. 1 to the Convention on International Trade in Endangered Species of Wild Fauna (CITES). Its population is monitored by experts of the UN Environmental Program, Food and Agricultural Organization, Inter-
national Union for Conservation of Nature and Natural Resources; specialists are keeping the International Herd Book. In the 1980s-1990s, four international symposiums on preservation of the Przhewalski horse were held; scientists discussed how to introduce wild horses from zoos to the natural environment. Resolutions adopted at the forums made it clear that the formation of large natural populations is the only way of ensuring survival of the species.
What with the transition to a market economy, the business activities on former virgin lands, the habitat of wild horses, have slackened due to the low playability of plant growing on the poor soil. Large fields turn into wastelands and are abandoned. Such territories will recover only in 40-50 years. But this process will speed up once the original steppe natives, especially big herbivorous animals, are back. That is to say, the steppe and Przhewalski horse need each other. How can we help them? A. Severtsov Institute of Ecology and Evolution, RAS, Institute of Steppe of Ural Branch, RAS, and Zoological Museum of Moscow State University have developed a joint project aimed at forming a wild population of the Przhewalski horse in the Ural Region.
The initial phase of the project will be implemented in the last single virgin feather-grass steppe area in Russia called Orel Steppe, 120 km away from Orenburg. Its area is 16,500 ha, which is quite enough for normal life of a self-producing population of wild horses. This territory borders on the Orenburg State Natural Reserve*; in addition, vast fallow lands in the south and southeast of the region are suitable for further extension of the habitat in case of successful réintroduction. The climate there is more comfortable than in Mongolia--the last natural habitat of the Przhewalski horse. At present the Orenburg Region is inhabited by different birds and little rodents, northern mole voles, hares, foxes, polecats and badgers. Only big hoofed animals are missing. The low population density and no horse breeding centers make these lands even more prospective for us.
Lack of funding is one of the main obstacles to this project. However, we hope that the commitment of scientists, the assistance and enthusiasm of interested people will make it possible to revitalize one of the lost species in Russia soon.
*The Orenburg State Natural Reserve comprises four isolated land plots in the territory of the Orenburg Region representing different steppe landscapes characteristic of this region at the junction of the East European Plain, Ural Mountains and the Turgai Plateau.--Ed.
Опубликовано на Порталусе 21 сентября 2021 года
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