The number of mammal species is relatively small. The theriofauna of the Reserve includes 34 species belonging to 7 orders: Insectivora (4), Chiroptera (8), Lagomorpha (1), Rodentia (8), Carnivora (9), Pinnipedia (1), Artiodactyla (3). However, with the exception of non-resident or unconfirmed species, the site-specific mammal group consists of 20 species, a fifth part of which are introduced species showing no genetic affinity to the Volga Delta. The distinctive features of the Reserve’s mammal fauna are high productivity and dynamism of populations of some species. The life of some species, such as common vole, water vole, Old World harvest mouse, field mouse, common weasel, wild boar, otter, Crocidura suaveolens, Crocidura leucodon, European beaver, ondatra, racoon dog, American mink, is closely connected to natural conditions of extrazonal coastal landscapes. Other species are widespread throughout the Reserve’s area: house mouse, common rat, fox, gray wolf. The third group of species include those occasionally observed in the Reserve (Caspean seal, saiga and elk). The Insectivora is represented by 3 species: eared hedgehog, a permanent resident of the Reserve, and Crocidura suaveolens and Crocidura leucodon, both are quite abundant. Russian desman (Desmana moschata) is listed in the Red Data Book of the Russian Federation (status 2), Astrakhan Region, and the IUCN Red Data Book (status VU). The information is very scarce about this species. It is a decreasing, rare relic species of Russia. The Lagomorpha is represented by the only species – European (brown) hare (Lepus europaeus). It is a typical representative of the steppe-desert faunal complex. During the ice-free period it can be found at fire breaks and in the buffer zone of the Reserve. In winter, as the ice-cover developes, the brown hare enters the Reserve’s territory through channels and eriks, and returnes back to its summer habitat in spring. The Chiroptera, an underexplored order of the Reserve’s mammals, is represented by Pipistrellus kuhli, Pipistrellus nathusii, Eptesicus serotinus, Vespertilio murinus and Nyctalus noctula. Some of the abovementioned species visit the Reserve only during their seasonal migrations. Pipistrellus nathusii is a permanent resident, though not abundante. The status of other species is unknown and requires special studies. Only those few mammals able to swim across extensive water areas and to migrate to flood-free areas and back when needed, prolific, reproducing before the
high water period and flexible in feeding behavior, manage to live in humid environment of the Lower Delta. Two out of total of 9 species of Rodentia found in the Reserve are naturalized species (European beaver and ondatra), the other 7 species are native ones. European beaver (Castor fiber) was imported from the Voronezhsky State Reserve. Rodentia usually dwell in lodges and holes they build in eriks, and are less common in channels near kultuks. The beaver population has been shrinking since 1975. In 1987 the only beaver colony left, containing 3-5 animals. Currently there is no beavers in the Reserve. The main cause of its extinction is the increase in water level in the Delta in winter season as a result of the evacuation of water from the Volgograd Water Power Plant that causes the inundation of lodges and animal loss. Ondatra (Ondatra zibethicus) was introduced to the Volga Delta in 1953-1954. By now the species has – independently or by means of several target in-regional introductions – occupied the entire Delta area and has become an integral component of the Reserve’s biocenosis. It lives in holes in the banks of channels and eriks, but best hydrological regime and best conditions for its protection, breeding and feeding are in the kultuk area, especially in the avandelta. Currently the size of the ondatra population is steadily declining. Arvicola terrestris was common till the late 60-s; now its number reduced. Microtus arvalis is commonly found in meadow, willow-motley grasses, reed grass and reed grass-sedge grass stations, though in the last two it is found more often. The fauna of Muridae includes 4 species: Apodemus agrarius, Mus musculus, Micromus minutus and Rattus norvegicus. It the years with a favorable hydrologic regime the Reserve’s populations of Apodemus agrarius and Mus musculus reach a high level. For a full year witness to the presence of a common rat can be found at cordons and in the nature. Meriones tamariscinus was for the first time discovered 1989 on a salt marsh near the Babyatsky erik in the Damchiksky sector. Today large colonies of Meriones tamariscinus thickly settled in the northern part of the Damchiksky sector of the Reserve. In dry years the animals distribute themselves over a significant part of the Reserve’s area, however most of them die when high water comes next year. The Carnivora is represented by 3 families: Canidae, Mustelidae and Felidae. Among the Canidae, Nyctereutes procyonoides is the most abundant species. It was naturalized in the Delta in 1936 and in 1939. The Nyctereutes procyonoides’s best habitats are located in the lower zone of the subaerial Delta – exactly where there is the Reserve’s area, which is well protected and has plenty of food. A small number of raccoon dogs inhabit the avandelta’s reedbeds and macereed thickets located many kilometers far from land.
Canis lupus is a permanent resident of all the three sectors of the Reserve. For the ice-free season it prefers the northern parts of the Reserve’s sectors. Wolf’s dens are often found on salt marshes or in thinned reed thickets. When the flood period comes old wolves and broods leave their dens and make several new ones in reed heaps. No disturbance, safe and perfectly protected territory, high density of potential pray (wild boar and raccoon dog), all these factors attract wolves to the Reserve’s area. Vulpes vulpes rather belongs to the biocenosis of the Upper and Middle subaerial Delta, though is quite common in the Reserve, too. In summer the red fox lives in the northern part of the Reserve, in thinned reedbeds and salt marshes. In winter this animal or rather its footprints are found everywhere, even in the kultuk zone and in the avandelta. In the Reserve fox usually digs its brood burrows on natural or man-made elevations, near the edge of reed thickets. Canis aureus was for the first time registered in the Reserve in 1989 in the Damchiksky sector. Today 1-2 families permanently live in this sector. Encounters with this animal in the Obzhorovsky sector have also been reported. Mustella erminea, Mustella nivalis, Mustella vison and Lutra lutra represent the Mustelidae family. The most common is Mustella erminea. It is found in every of land biotopes. In contrast, Mustella nivalis is scarce in the Reserve. Mustella vison negatively affects some animal species and is not welcomed in the Reserve’s ecosystem in particular and in the Volga Delta in general because the Delta is of global significance as an important habitat of waterfowl and water-related bird species. M. vison is an introduced species, which appeared in the Delta in the early 70s as a result of the site-specific adaptation of animals escaped from fur farms. River otter is an indigenous species of the Delta, which is found throughout the Reserve but is the most abundant in the Damchiksky sector. The Reserve’s Records contain very limited records of Felis chaus. According to them, jungle cat was common in the Reserve till the middle 50s. Later it occurred more and more rare and now special research is required to find out any information about the destiny of this species in the Reserve. The Caspian seal is spotted in the Obzhorovsky and Damchiksky sectors of the Reserve in autumn and in springtime migrating in path of fish shoals, which come to their wintering or spawing grounds to the branches of the Volga River. During this period Caspian seal is found not only in the avandelta’s water area but also in the Delta’s channels. Since the sea level rose, individual seals are regularly spotted in the Delta’s channels almost every year. Three species of hoofed mammals have been registered within the Reserve, but only one of them, Sus scrofa, permanently lives there. This species is one of the key components of the Reserve’s biocenosis. It mainly lives on plants: reed grass, macereed, lotus, water chestnut, rush flower. The estrus period starts in the latter half of November and finishes in January. First piglets born in the end of March, mass ferrowing finishes by the middle April.
The wild boar is the only hoofed animal inhabiting the entare area of the Reserve from the subaerial Delta’s reedbeds to the avandelta’s islands. Thanks to well-developed hydrographic network and the presence of natural levees, the Reserve’s area is a «maternity home» for animals of the adjacent low-land «reed grass belt». In recent years from 400 to 800 boars were registered in the Reserve before the ferrowing period. Extensive reed and macereed thickets are very much fit the tastes of the wild boar. However, during the flood period the water rises up, and so it drives the wild boar out from the most low-lying places (kultuks and il’mens) and up to the levees. Thus, in May-June the bulk of boars gather on the levees. During the high water period, if the water is low or around the average level, adult boars and new-born piglets successfully survive flood gathering on ridges, salt marshes and other elevations. But if the water is high and the flood period is long, which happens in the Delta once in 6-8 years, in that case boars and other animals starve, die of cold or perish of inanition. To save animals earth mounds for supplementary feeding during the high water period have been built in the Reserve’s sectors. For the last two decades wintertime became another difficult period for wild boar as well as for the other mammals living in the Lower Delta. In winter quite unfavorable weather and feeding conditions become even harsher due to the high water level, flooding of islands and ice crust development. All these factors force animals to shift from place to place more frequently, which is often leads to their loss. Elk (Alces alces) and saiga (Saiga tatarica) are not the residents of the Reserve. Their sporadic winter visitations of the Reserve’s area are caused mainly by unfavorable weather conditions. Mammals are the key component of an ecosystem. In the Astrakhansky Reserve the composition of mammal species is almost equal for each sector. Hydrological regime is the main factor determining the status and dynamic characteristics of mammal populations.