A population is considered to be “a collection of individuals of one species that occupies a certain space for a long time and reproduces itself over a large number of generations” (BES, 1983).

The word “population” comes from the Latin “populus” - people, population, livestock. From this we can derive the very definition of this term. Population ecology is a young branch of environmental science. Although the components of this science can be found in essentially any autecological work, real research began only in the first quarter of the twentieth century. The progenitor of this branch is considered to be Charles Elton, who first identified and isolated this movement in 1927. Fundamental generalizations appeared in print only in the second half of the twentieth century. For the first time, a special chapter on populations was placed in the fundamental work of W. Olley et al. in 1949 (.

Population, like any other concept, has its own criteria, let's try to consider some of them.

A population, as a group association, has a number of specific properties that are not inherent in each individual individual. Group characteristics are the basic characteristics of a population. Maintaining optimal characteristics under given conditions is called population homeostasis. Homeostatic capabilities are expressed differently in different populations and species. They are realized through the relationships of individuals with each other. The population turns into a relatively integral genetic system, since during sexual reproduction the amount of genetic information is partially transferred to the next generation. In any case, populations have laws that allow them to use limited environmental resources in this way to ensure the preservation of offspring.

Among the characteristics of the population, first of all, it is necessary to note the demographic indicators of the population. These include: 1) number - the total number of individuals in the allocated territory; 2) population density - the average number of individuals per unit area; 3) birth rate - the number of new individuals appearing per unit of time as a result of reproduction; 4) mortality - an indicator reflecting the number of individuals who died in a population over a certain period of time; 5) population growth - the difference between birth rates and deaths; 6) growth rate - average increase per unit of time" (Chernova, Bylova, 1988).

Individuals in a population are united into various groups that make up the social structure. In different species, the social structure can be represented in different ways. Let us mention the structures in horses as the object of my research.

The general name for all associations of several animals with interconnected behavior can be a group, and if there is no connection, then a cluster. Among the groups one can also distinguish (according to Baskin, 1976; Panov, 1983):

• family - a group of individuals related by blood. In horses, this is a harem group (harem) or school, represented by a stallion, several mares and their offspring of several years.
• company - a group of individuals who are mutually attached or spend time together; and/or partial group - a group of familiar animals. This category includes bachelor groups consisting only of stallions of different ages who do not have their own harem.
• herd (herd) - an association of schools with complex mutual behavior.

Individuals or groups in the territory occupied by the population are not evenly distributed. “The spatial structure of populations is expressed by the nature of the placement of individuals and their groupings in relation to certain elements of the landscape and each other, and reflects the type of use of the territory characteristic of the species. The regular distribution of individuals in space has important biological significance and, in essence, is the basis of all forms of normal functioning of the population."

The constant use of the same places by animals to satisfy their needs leads to the emergence of a habitat. A concept described by Darling in 1937 and defined by him as a space that satisfies the daily needs of an animal. Even saigas, which are considered nomads in the animal kingdom, use grassland in a fairly orderly manner when staying in one area for several days (or even weeks). The use of habitat by animals is determined not only by their personal experience, but also by traditions inherited from previous generations. The structure of a habitat area arises as a result of many years of use of this territory by this population. It is part of the biological signal field, which helps animals navigate in space, using the experience of their ancestors. This was approved and proven by Naumov in 1973. This spatial structure is characteristic of all species of animals, and ungulates are no exception.

The spatial structure and behavior of horses differs little from ungulates in general. During part of the seasons, horses graze in the same areas, however, their food resources at different times are very different. This can be associated with their migration in different seasons of the year. The transition of horses to another pasture in a certain season does not cause any special difficulties in organization. Scientists have noted strong pre-migration anxiety if the transition was made late. It is interesting that the desire to move to a pasture of a different season occurs in the early morning or at the time of spending the night; often individual individuals break away from the herd and leave along a familiar route. Having woken up, the animal immediately leaves along the migration route, moving almost non-stop for 2-3 days, covering 100-150 km. More often, such behavior is observed in old horses (Baskin, 1976).

But in addition to spatio-temporal migration, some attachment to a place can also be identified. Several years ago it was discovered that horses and other equids have a space-time system of activity. Consequently, any activity is associated with a certain place in the living space. Horses, for example, eat not only at a certain time, but also in a certain place, they also doze and sleep in certain places. They also get used to being kept in a stall, perceiving it as their own habitat, just like we do our apartment.

The studied population of feral horses is currently the largest and, apparently, the only island population in Russia. This puts it on par with such well-known populations of feral horses as on Sable Island (Newfoundland, Canada), Chincoteague and Assateague Islands (Virginia and Maryland, USA). This group of feral horses was discovered and became known thanks to the research of N.V. Paklina in 1984–1988. .

Horses have been living on the island since the 1950s and are apparently former farm horses of the Don breed and/or their crosses. Horses of the feral population are characterized by a massive (or dense) constitution. The predominant color is red (various shades), there are brown (also different shades) and dun. Most animals have various markings on the face (gray hair, stars, blazes, bald spots), and to a lesser extent there is whiteness on the legs, rarely rising above the carpal or hock joints.

In 1995, the territory of Vodny Island (Yuzhny) with the adjacent water area of ​​Lake Manych-Gudilo, with a total area of ​​4581 hectares, and three mainland areas, with an area of ​​​​990 hectares and up to 2182.5 hectares, became part of the organized State Nature Reserve " Rostovsky. The horses that lived on the island became an actual part of the steppe biocenosis; in other steppe reserves, grazing of farm animals, as well as any economic activity, is prohibited. In the Rostov Nature Reserve, the opportunity arose to study, under the conditions of a natural experiment, various aspects of the existence of a population of large phytophages in the steppe ecosystem.

The State Nature Reserve "Rostovsky" was organized by order of the Government of the Russian Federation No. 1292 of December 27, 1995 in the south-eastern part of the Rostov region for the protection of areas of indigenous steppe vegetation and part of wetlands (Ramsar Convention).< /p>

It consists of 4 independent sections, stretched in a chain in the latitudinal direction along the right bank of the Manych Valley and located 5–25 km from each other. The total area of ​​the reserve is 9464.8 hectares.

The largest site (4591 hectares) - Ostrovnoy - is located in the Oryol region, in the northwestern part of Lake Manych-Gudilo and includes the islands Vodny (Yuzhny) (3100 hectares) and Gorely (together 3491 hectares), the adjacent water area of ​​the lake and 10 hectares of mainland coast. The islands and mainland coast are covered with steppe. The site was allocated from the lands of the Orlovsky state breeding plant and the state water fund. According to the explication, the site territory includes 1848 hectares of pasture land, 2587.2 hectares under water, 38.9 hectares of swamps, 11.8 hectares of ravines, 5.3 hectares under buildings, 5.2 hectares of salt marshes and 4.6 hectares of roads.

The Krasnopartisan site (1,768.4 hectares) is located 5 km southwest of Starikovsky, in the Remontnensky district. The lands were transferred from the sheep-breeding state farm "Krasnopartizansky" and the collective farm named after. Lenin. Explication of land: pastures (steppe) - 1651.1 hectares, trees and shrubs - 7.2 hectares, arable land - 96.5 hectares, the rest - roads, buildings, under water.

The Starikovsky site (2115.4 hectares) is located in the east of the Oryol region. The lands were allocated from the district's land fund. The land includes, among other things, 1914.5 hectares of pastures and 34.0 hectares of hayfields, which are steppes.

The Tsagan-Khak site (990 hectares) is located in the south of the Remontnensky district and consists of the tract of the same name, which is a salt marsh flooded in the spring with small islands and capes jutting into the lake. The site includes 609 hectares of salt marshes and 381 hectares of pasture. Its borders, for the most part, lie at some distance from the coastline, in some places smoothing out its curves and, thus, capturing several capes with steppe vegetation. The lands were previously used by the Ovtsevod state farm.

Vodny Island (Yuzhny) - the habitat of the studied population, is part of the Ostrovny section of the reserve and is the largest island of Lake Manych-Gudilo, located in the Kuma-Manych depression. The salinity of the lake is 22.1–26.5 g/l, in the resulting bays up to 54 g/l. The area of ​​the island is 1903.4 hectares, of which about 1848 hectares are considered pasture land. The vegetation is represented by associations of dry fescue-feather grass and wormwood-fescue-feather grass desert steppe on dark chestnut and chestnut soils with varying degrees of salinity with communities of helophytes that are more xerophilic. There is no woody vegetation on the island. The climate is temperate continental, hydrothermal coefficient 0.7, annual precipitation 300–400 mm, frost-free period 185–190 days. The winds are quite constant, prevailing from the east (in winter) and west. The island is separated from the mainland by a channel, in a narrow place about 400 m wide. The lake freezes once every few years during persistent frosts, despite this, no cases of horses crossing the ice to the mainland or neighboring islands have been recorded.

The research was carried out using several methods.

The visual method involved direct observation of animals. For this method, optical instruments (binoculars) were used. In this case, observers followed the animals for a long time, usually during daylight hours, without letting them out of sight and recording all forms of behavior, changes in activity, movements, etc..

This method was supplemented by the use of a personal GPS navigator (Garmin eTrex) Global Positioning System. The system uses data from 24 satellites orbiting at an altitude of 20,000 km above the Earth's surface, and using a receiver receiving signals from at least 4 satellites, it is possible to obtain data on the exact location of the observer on the Earth's surface (3-dimensional location, error of about 5 m ). The use of this system turned out to be most productive in conditions of homogeneous landscape (steppe) and the absence of detailed maps of the territory (available map scale 1:200000).

The device includes many different functions, such as: compass, altimeter, map and many other features. The coordinates of backwater places, dried puddles, remains of dead animals were also marked, and the lengths of trails and routes for moving horses were plotted and measured (the starting point of the route and its trajectory were marked on the map, after which the length of the route was estimated).

The data obtained during the study using the OziExplorer and MapInфfo (for Windows) programs were presented for further analysis in graphical form.

Using GPS, data were obtained on the size of the herd (from 300 to 1000 m), the location of social groups of animals in it (the distance between groups is from 5 to 30 m), and individual distances between animals within social groups (0–10 m).

The research revealed some features that are unusual for other populations of feral horses. Horses in the population stay in a common group throughout the day and at different times of the year, demonstrating weak tendencies towards separation and territoriality.

During my work, I noticed that in the herd (herd) there are no clear boundaries between social groups: the individual distance between them is practically minimal, there were no aggressive actions or herding reactions to maintain the integrity of the groups in the summer. Previous studies (Klimov, Paklina, 1990) also noted that harems on the island unite to form a new structure called a herd.

It can be assumed that the reasons for this behavior may not only be the convenience of protection, since there are no large predators on the island. Obviously, this phenomenon can be associated with a small territory and the use by animals of a limited, narrowly localized resource - fresh water sources.

Study of the use of island space during the day.

The data was obtained by following a herd with an estimate of the route length using GPS.

In summer (and spring), the movement of the herd during the day across the island is insignificant and amounts to 3–6 km. In autumn, the daily movements of animals increased significantly - up to 10–15 km.

Climatic conditions may be the reason for the observed differences. In summer, the average daily temperature was +40–450С. Active movement at high temperatures threatened to overheat the body and dehydration. When the temperature dropped below 00C and a steady wind increased this factor, active movements, on the contrary, contributed to additional warming of the animals. In the spring, temperature conditions were quite comfortable. But the low motor activity of the animals could be explained by the large number of newborn foals, the peak of which occurred in April–May.

Study of the use of island space in different seasons of the year.

Using GPS, the coordinates of dried puddles and backwater areas were determined and plotted as routes for trails on the island. In the OziExplorer and MapInfo (for Windows) programs, the obtained data was processed and maps of the predominant location of animals by season were compiled.

The limiting factor for the existence of horses on the island and determining their territorial distribution is the presence of fresh water sources. In the autumn-spring period, horses use sediment accumulation in relief depressions. During this period of the year, the herd is located in the central part of the island. The more heterogeneous terrain here helps shelter the horses from bad weather and the prevailing east wind in winter. With the onset of the dry period (July-October), the horses are watered using a water supply piped from the mainland. The artificial watering hole is located in the north-eastern part of the island, and during this period of the year horses prefer to be nearby (.

Horses use different parts of the island in different seasons of the year, which is apparently connected not only with the location of watering places, but also with the intensity of grazing. Thus, we can talk about some seasonal movements across the territory and a preserved strategy for the optimal use of pastures. The use of the central part of the island for a long time (during the spring-summer period) is apparently due to the preservation of lush vegetation here and its more intensive growth due to the accumulation of a sufficient supply of fresh water in the depression of the relief.

During the research on Vodny Island, some characteristic features of large horse populations were discovered:

• The presence of an extensive trail system. In the work of N.V. Paklina and V.V. Klimov (1990) indicates that no trails were observed on the territory of the island with a population size of up to 120 individuals. With a current population of 400 individuals, trails appear. L.M. Baskin (1976) also confirms that most ungulates have paths along which they tend to move.
• The phenomenon of seasonal changes in pastures. L.M. Baskin (1976) points out that even domestic horses kept in herds themselves move to different pastures in different seasons of the year. N.V. Paklina (Klimov, Paklina, 1990) on the same population confirms that, according to her observations, in the 1980s horses supported seasonal migration across the island. Our observations in 2006 confirmed the change of pastures in different seasons of the year.

Different localization of animals by season may be due to several reasons. Firstly, the location of watering holes: in summer, an artificial watering hole is located on the north-eastern tip of the island, and horses prefer to stay on the eastern part; in spring and autumn, separate puddles are located in the central part of the island and horses stay right there. Secondly, the shift of horses in spring and autumn to the central and western parts of the island can be explained by the reduced relief here and the animals’ attempt to hide from the eastern winds that prevail at this time of year.

As a result of the work, the features of the spatial structure and organization of feral horses of this population were determined and the factors influencing the distribution of horses across the island were identified. The data obtained during the study allow us to draw conclusions about the emergence of environmental adaptations associated with the island habitat. It should also be noted that the research carried out must be continued, since not all issues of interest have been clarified and the assumptions and hypotheses put forward need to be verified.

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