Small mammals community in the south-east of Ukraine: analysis of long-eared owl (Asio otus) pellets

UDC 599:574.4

S. V. Zaika

Taras Shevchenko Luhansk National University, Luhansk, Ukraine, zaika_sv@ukr.net

УГРУПОВАННЯ ДРІБНИХ ССАВЦІВ
ПІВДЕННОГО СХОДУ УКРАЇНИ:
АНАЛІЗ ПЕЛЕТОК ВУХАТОЇ СОВИ (ASIO OTUS)

С. В. Заїка

Луганський національний університет ім. Тараса Шевченка, zaika_sv@ukr.net

Analysis of owl pellets allows to investigate a pattern of victim communities, main part of them are represented by small mammals. Series of pellets of the Longeared Owl (Asio otus L., 1758) from the “Khomutovsky steppe” Natural Reserve (leg. V. Timoshenkov) make up a basis sample, which was supplemented with two another series of pellets come from vicinity of the Luhansk city (locality “Rozkishne”) and from vicinity of Ivanivka village in Lutugine district. Owls pellets analysis shown that the small mammals make up more than 90 % of all owl’s preys. In general, 984 specimens of 12 species of small mammals (~ 700 pellets) were identified. On average, 1 or 2 prey items (max=3) were found in each pellet. Analysis of species composition of small mammals, which make up the Asio otus diet, demonstrates a wide spectrum of species-preys, which includes 12 species of small mammals of three ecomorphological groups: insectivores, seed-feeders, and herbivores. Species composition of these 3 victim groups is following:

 

Assessments of relative abundance of species, which are the victims of the Longeared Owl, were calculated for each investigated locality. So, most numbered species of small mammals among owl’s victims are 4 rodent ones, which prevail in all the samples: Microtus levis (47 % of remains), Mus musculus (20 %), Cricetulus migratorius (12 %), Mus spicilegus (6 %). There are some peculiarities of small mammal communities in 3 investigated localities.

Locality “Khomutovsky steppe”. The contents of about 450 pellets were analyzed, and 565 specimens of 9 species were extracted (species are listed in order of their frequency decrease): Mus musculus (157 sp.), Cricetulus migratorius (128), Microtus levis (90), Mus spicilegus (84), Sylvaemus arianus (48), S. uralensis (26), S. sylvaticus (17), Micromys minutus (12), Crocidura suaveolens (3). In this locality, the dominant group among small mammal community compose genus Mus (both species), C. migratorius, and M. levis. In codominant group there are two genus: Sylvaemus and Micromys. Among accident preys there is shrew Crocidura suaveolens.

Locality “Rozkishne”. The contents of about 40 pellets were analyzed, and 84 specimens of 6 small mammal species were identified: M. levis (44), M. musculus (22), C. migratorius (8), S. uralensis (8), S. sylvaticus (1), C. suaveolens (1). Two species prevail among owl’s preys here, Microtus levis and Mus musculus. The second position occupied by pygmy mouse Micromys minutus and gray hamster Cricetulus migratorius. Two species are accident preys, wood mouse Sylvaemus sylvaticus (s. str.) and shrew Crocidura suaveolens.

Locality “Ivanivka”. The contents of about 100 pellets were analyzed, and 237 specimens of 11 small mammal species were extracted: M. levis (174), M. musculus (15), S. uralensis (14), C. migratorius (10), Lagurus lagurus (5), S. sylvaticus (5), M. minutus (4), M. spicilegus (4), Myodes glareolus (3), C. suaveolens (2), Sorex minutus (1). Microtus levis is an absolute dominant in this locality. Codominant group in this sample consist of two species, C. migratorius and S. uralensis. Just like in the other samples, the shrews (2 species) are presented by single specimens. It should be pointed that this community includes three new species did not recorded in other studied localities, namely steppe lemming (Lagurus lagurus), pygmy shrew (Sorex minutus) and bank vole (Myodes glareolus).

Among Asio otus victims only one ecomorphological group prevails in each locality. So, victims of herbivorous level (consumer 1st level in food chain) prevail in all the sites. Herbivores sits the first position in the Luhansk and Ivanivka sites (north of studied region). In “Khomutovsky steppe” (south of region), the seed-feeders had prevail. In all the studied localities, insectivores (i.e. consumers of 2nd level) demonstrate very low relative abundance, not more than 1,5 % in owl’s feeding. Peculiarities of these ecomorphological groups of small mammals are the next.

Insectivores. Shrews (Soricidae) in the Longeared Owl diet did not take an important role; they occur rarely, but regularly. Among them, Crocidura suaveolens is relatively common victim identified in all samples, whereas the shrews (Sorex) were registered just in the locality “Ivanivka”. Therefore, shrews are the accidental preys.

Herbivores. Among owl’s preys, three species has belong to the herbivore group (all of them are from family Arvicolidae): Southern Vole (Microtus levis), Bank Vole (Myodes glareolus), and Steppe Lemming (Lagurus lagurus). Former species is absolute dominant with frequency in pellets varied from 15 to 50 % depending on its number in nature. In contrary, two other species (Steppe Lemming and Bank Vole) are very rare, and just few single registrations in “Ivanivka” locality were recorded.

Seed-feeders. There are 3 small mammal taxa among this ecological group: wood mice (Sylvaemus), common mouse (Mus) and gray hamster (Cricetulus). Wood mice are presented in studied samples by three species, and their portion reaches 10–15 % of prays. Mice (Mus musculus and M. spicilegus) compose more than 25 % of total sample, and they can substitute another important prey, namely Microtus levis, in the years of its low abundance in the Luhansk province, in Donetsk’s steppes M. levis is always dominates. Domination of seed-feeders as well as visible absence of another ecogroups of small mammals in owl feeding in “Khomutovsky steppe” can testify to considerable violation of environment in this natural reserve and can indicate the loss of steppe biomes in a fact.

The analysis of Asio otus feeding selectivity is provided by the way of comparison of obtained data with results of direct census of small mammals using traps. In this purpose, data on small mammal trapping in Luhansk province (database of Luhansk provincial SES) during 2006–2008 was concern, and the comparison of abundance of various systematic and ecologic groups in traps and owl pellets was carried out. For the correct comparisons, the series of pellets for analysis was taken from the same localities as data traps occur came from (see next Table).

 

It is arranged that the most small mammal species from the set of potential owl’s preys have a significantly different frequency of their occurring in traps and in owl pellets. Obtained data demonstrate that the basis of Asio otus diet consist of species of open habitats: M. levis, M. musculus, and C. migratorius. At the same time, some very abundant species (wood mice and bank voles) have a small part in owl’s diet in spite of their high portion in community according to the direct census by traps; frequency of each of them in pellets is never more than 10 %.

So, obtained results demonstrate possibility to use such data to analyzed both pattern of victim communities and predator’s feeding selectivity.

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Zoocenosis — 2009
Біорізноманіття та роль тварин в екосистемах: Матеріали V Міжнародної наукової конференції. – Дніпропетровськ: Ліра, 2009. – С. 332-334.