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SMALL MAMMALS (INSECTIVORA, RODENTIA) IN THE AREA OF THE BARRAGE SYSTEM GABCIKOVO

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Jan KRISTOFIK, Peter MASAN

Institute of Zoology, Slovak Academy of Sciences, Dubravska cesta 9, 84206 Bratislava, SLOVAKIA

CONCLUSIONS: The community structure of small mammals living in the within-dike zone indicates that the species typical for the ecosystems survive there up to present. The conditions in the monitored area remain still within the limits of ecological tolerance of the studied species. The number of individuals of the species occurring in the monitored localities varied within the limits of the amplitude of their population fluctuation cycles. With regard to the rather wide amplitude of fluctuation cycles of the small mammal populations and their length taking usually 4-6 years, the significant data concerning the influence of the changed hydrological regime on the small mammals in this area can be obtained not earlier than after 10-15 years.

#### MATERIAL AND METHODS

Small mammals were caught in four localities: Dobrohost (Dunajske kriviny), Bodiky (Bodicka brana, Kralovska luka) and Klucovec (Sporna Sihot) during 1991-1994. The locality Dobrohost was represented by a swampy area and shallow oxbow with a natural willow stand. The locality Bodiky - Bodicka brana was predominatly represented by a willow stand surrounding a partly silted oxbow. The localitry Bodiky - Kralovska luka was represented by an oxbow separated from the Danube main stream and surrounded by a narrow reed stand neigbouring with a small willow stand separating it from an extensive poplar monoculture. The locality Klucovec was represented by a poplar monoculture growing on margins of a shallow branch of the Danube. The small mammals were caught by means of the Svedish-type traps and snap traps. In each locality, 25 Svedish type traps and 50 snap traps were exposed in a line during two consecutive nights. Annualy, 8-10 catches were taken in each locality.

#### RESULTS

Altogether 5,439 individuals of small mammals belonging to nine species (Table 1) were caught in four localities.

In Dobrohost, Clethrionomys glareolus dominated (62.6 %) during all four years of investigation. This was followed by Apodemus flavicollis (14.1 %), A. sylvaticus (10.5 %) and Sorex araneus (9.5 %). Other species were represented by a small number of individuals only: Microtus arvalis (2.1 %), Sorex minutus (0.6 %), Crocidura leucodon and Micromys minutus (0.3 % each).

In Bodicka brana, C. glareolus was also found to bo the most dominant species (58.7 %), followed by A. flavicollis (20.4 %), A. sylvaticus (11.3 %) and S. araneus (7.6 %). On the contrary, the species M. arvalis (1.5 %), S. minutus (0.6 %) and M. minutus (0.1 %) were represented by a small number of individuals.

In Kralovska luka, the dominant species was C. glareolus (65.5 %) followed by S. araneus (13.3), A. flavicollis (12.2 %) and A. sylvaticus (6.5 %). Other species were represented by a minute number of individuals (M. minutus and M. arvalis 1.1 % each, M. oeconomus 0.2 %, C. leucodon and S. minutus 0.1 % each).

Also in Klucovec the dominant species was C. glareolus (49.2 %). It was followed by A. flavicollis (21.6 %), A. sylvaticus (12.7 %), M. arvalis (10.9 %) and S. araneus (5.0 %). A small percentage of the caught individuals was represented by S. minutus (0.5 %) and M. minutus (0.1 %).

Among the species occurring in the studied localities only C. glareolus, a highly abundant species in the floodplain forests, can be regarded as a typical representative of floodplain forest fauna. The species A. flavicollis and A. sylvaticus have a wide ecological valency and prefer mesohygrophilous mature woods with a well developed shrub stratum. They occure relatively abundatly in floodplain forests. The species S. araneus (Insectivora) is regarded, in the central European conditions, as a hygrophilous species with a wide ecological valency. It prefers the moist habitats and occurs relatively abundatly in floodplain forests of all types. S. minutus also belongs to the species with a wide ecological valency, but it occurs rarely in the Danube within-dike zone. The species C. leucodon is one of the rarely occuring animals. In central Europe it inhabits rather an open landscape with shrub formations than the floodplain forests. M. minutus prefers humid habitats in highlands or lowlands with a typical cover of the shore vegetation, above all reed and reed-mace. A typical habitat of M. arvalis are drier fields and meadow of the middle and lower altitudes. Under the pressure of intraspecific competition, it can penetrate also into the floodplain forests representing, however, an unsuitable habitat type for M. arvalis. It was the case of the locality Klucovec, where the sampling plot lays in the vicinity of a meadow. A typical habitat of M. oeconomus, a glacial relict, are the water shores or marsh margines covered by reed, reed-mace and sedge. M. oeconomus survives on such habitats in several localities in the Podunajska nizina lowland.

The community structure of small mammals in individual years of monitorig indicates that the species typical for the floodplain forest survive in the studied localities up to the present. The ecological conditions of the studied area are still within the limits of variability of ecological requirements of the above species of small mammals. In the studied localities, the number of individuals of the species studied varies within the natural fluctuation cycles of populations of indivudual species. With regard to the rather wide amplitude of these cycles taking usually 4-6 years, the significant data concerning the influence of the changed hydrological regime on the small mammals in this area can be obtained not earlier than after 10-15 years.

Among the found species, S. araneus, C. leucodon and M. oeconomus are included in the list of the protected species in Slovakia. The Red Book of Endangered and Rare Species regards M. minutus as a rare species (R) and C. leucodon and M.oeconomus as a criticaly endangered species (E).

Out of the species found during our investigation, the following species occur, althgough rarely, in the studied area, in the river side zone and on the islands in the branch system: Neomys fodiens (Pennat, 1771) and N. anomalus Canbera, 1907 [2] and further Crocidura suaveolens (Pallas, 1811), Apodemus microps Kratochvil et Rosicky 1952 and sporadically also Pitymys subterraneus (De Selys-Langchamps, 1836) [1,2].

#### REFERENCES

  [1] Brtek, L., 1986: Efect of the historical 1965 flood of the Danube on the population of small mammals. Ekológia (CSSR), 5:113-124.

  [2] Dudych, A., Lysy, J., Stollmann, A., 1985: Sucastne poznatky o rozsireni drobnych zemnych cicavcov (Insectivora, Rodentia) juznej casti Podunajskej niziny. Iuxta Danubium-Rerum Naturalis, 5 :157-186.

Table 1. Systematic survey of small mammals caught in the monitored localities in 1991-1994.

Specie | Dobrohost | Bodiky - Bodicka brana | Bodiky - Kralovska luka | Klucovec
--- | --- | --- | --- | ---
91 | 92 | 93 | 94 | sum | 91 | 92 | 93 | 94 | sum | 91 | 92 | 93 | 94 | sum | 91 | 92 | 93 | 94 | sum
Insectivora Soricidae
Sorex araneus Linnaeus, 1758 | 78 | 72 | 13 | 4 | 167 | 40 | 19 | 15 | 9 | 83 | 77 | 79 | 13 | 20 | 189 | 33 | 8 | 9 | 8 | 58
Sorex minutus Linnaeus, 1758 | 7 | 2 | 1 | 1 | 11 | 1 | 2 | 2 | 2 | 7 | - | - | 1 | - | 1 | 4 | 1 | 1 | - | 6
Crocidura leucodon (Hermann, 1780) | 3 | 1 | 1 | 1 | 6 | - | - | - | - | - | - | - | 2 | - | 2 | - | - | - | - | -
Rodentia Muridae
Micromys minutus(Pallas, 1778) | 1 | 2 | 1 | 2 | 6 | - | - | - | 1 | 1 | 1 | 12 | - | 2 | 15 | - | - | - | 1 | 1
Apodemus flavicollis (Melchior, 1834) | 40 | 141 | 47 | 21 | 249 | 15 | 106 | 65 | 35 | 221 | 3 | 65 | 54 | 51 | 173 | 27 | 150 | 37 | 36 | 250
Apodemus sylvaticus (Linnaeus, 1758) | 45 | 113 | 19 | 8 | 185 | 40 | 18 | 32 | 33 | 123 | 12 | 57 | 12 | 11 | 92 | 28 | 86 | 19 | 14 | 147
Arvicolidae |  |  |  |  |  |  |  |  |  |
Clethrionomys glareolus (Schreber, 1780) | 313 | 418 | 254 | 122 | 1107 | 39 | 247 | 237 | 118 | 641 | 171 | 303 | 343 | 115 | 932 | 87 | 155 | 222 | 105 | 569
Microtus arvalis (Pallas, 1779) | 5 | 11 | 15 | 6 | 37 | 2 | 4 | 7 | 3 | 16 | 1 | 1 | 9 | 4 | 15 | 28 | 43 | 35 | 20 | 126
Microtus oeconomus (Pallas, 1776) |  |  |  |  |  |  |  |  |  |  | - | - | 2 | 1 | 3 | - | - | - | - | -
SUM | 492 | 760 | 351 | 165 | 1768 | 137 | 396 | 358 | 201 | 1092 | 265 | 517 | 436 | 204 | 1422 | 207 | 443 | 323 | 184 | 1157