Wplyw dodatkowego pkarmu na populacje nornicy rudej Clethrionomys glareolus (Schreber, 1780) i innych gryzoni lesnych

Influence of supplementary food upon bank vole Clethrionomys glareolus (Schreber, 1789) and other forest rodent population

Warsaw

2005

83 S.

12 Abb., zahlr. Lit. Ang.

Bandaufführung

83-7244-649-0

11195

127604

The paper presents research results and literature review dealing with the relationship between forest rodents and their food coming from various sources. The bank vole, Clethrionomys glareolus (Schreiber, 1789) is the most common rodent species in forests and therefore natural food resources of rodents and the effekt of supplementary food were discussed on the example of this species. Bank vole is polyphagous, feeding on green parts of plants, but complementing its diet with seed, fruits and invertebrates. Variable in time and space natural food resources cause specific response by rodents. They respond by seasonal and long-term changes in numbers. The impact of bump seed years of deciduous trees, such as oak and beech, is crucial in long-term scale. Abundant production of seed by these trees causes in the bank vole population fluctuations with top years each 4-7 years. There are two sources of supplementary food for forest rodents. First of them appeared to be food bait used in capturing rodents in live-catching traps. In these programmes CMR (catch, mark and release) technique is used and oats grain most often serves as bait. Oats is prebaited before traps are installed in order to attract rodents and then offered in live-catching traps. These traps are arranged in a network. An area with so arranged traps presents a patch of habitat with enriched food basis for rodents. While manipulating with different numbers of baited traps I studied relations of rodents with such a new source of food. Following questions were answered: how soon the new food is located by rodents, what rodents do when food is exhausted, how the quantity and distribution of food in habitat affect the spatial behaviour of rodents, what kind of senses facilitates the finding of food by rodents. The new food appearing in habitat is quickly located by rodents. On the other hand when the source of food is exhausted, voles seek another source, but always may be back again to check whether there is anything to eat. When food is abundant everywhere, voles restrict their mobility and exploit the nearest source of food. While having at disposal new food in the form of bait in traps, they utilize the portion located at closest. Consequently, vole move within the closest range of traps. When the food is less abundant and ist distribution in habitat is patchy, then voles, while searching after it, move at great distances, several hundreds of meters from burrow or nest. Under such conditions the range of spatial acitivty of rodents is remarkable. It is therefore the researcher studying rodents on small areas with live-catching traps with food bait and arranged as network, who restricts their mobility. Only studying small mammals on bigger pieces of land, above several hectares, permits to reveal their greater range of spatial activity. Traveling by rodents over long distances is facilitated by the fact that they move in fields along paths marked by urine and faeces, as well as by exudates of their glands. The phenomenon of homing, i.e. ability of animal to return to its home range, may be also explained by the existence of scent trail used by rodents to find their way to burrow or nest. Food introduced to habitats in the cource of experiments is another source of supplementary nourishment for rodents. In temperate zone populations of small mammals are frequently restricted by food. When their food resources are enrichted, a 2 to 3-fold increase in rodent numbers occurs. On the other hand there are nor changes in general models of number dynamics, even if a number of indices are altered, e.g. breeding, survival, immigation indices. While analyzing the impact of supplementary food upon forest rodents in the present paper, the attention paid to food bait in traps is considered as particularly important. Easiness of manipulation with them enables numerous experiments, which may reveal still other responses of rodents to supplementary food.