L. Forró szerk.: Miscellanea Zoologica Hungarica 12. 1998 (Budapest, 1998)

Horváth, Gy.: Population dynamics and trappability of four rodent species in a forest habitat

was not significant. This phenomenon can be explained with the adaptation of the animals. In 1997 the trappability of the animals on the first four days of the trappings was again determined by adaptation in that the initially low capture numbers were followed by a sudden increase. Significantly more data were recorded on the 4th and 5th days than on the first two, both in respect of mean number of captures and, in two of the species, in the proportion of recaptures. However, four- and five-night samplings cannot be compared, because in 1995-1996 much fewer traps were used in a grid with different parameters, and a drastic collapse of number of individuals was observed in 1995-1996. Even earlier studies (Begon 1979, Otis et al. 1978) suggest a minimum of four nights per period as the criteron for the acceptability of trappping results. When introducing the robust model, Pollock (1982) calculated population sizes using data from five-night periods. Based on our results we also deem five-night trapping periods as more appropriate for small mammal population studies. Acknowledgements The studies were funded by the OTKA grant No. F 021184. References Andrzejewski, R. & Wroclawek, H. (1961): Mass occurrence of Apodemus agrárius (Pallas, 1771) and variation in the number of associated Muridae. - Acta Theriol. 5: 173-184. Andrzejewski, R., Bujalska, G., Ryszkowski, L. & Ustyniuk, J. (1966): On a relation between the number of traps in a point of catch and trappability of small rodents. - Acta Theriol. 11: 343-349. Aulák, W. (1967): Estimation of small mammal density in three forest biotypes. - Ekol. pol. (A) 15: 755-778. Babiska-Werka, J., Gliwicz, J & Goszczyski, J. (1981): Demographic processes in an urban population of the striped field mouse. - Acta Theriol. 26: 275-283. Barnett, A & Dutton, J. (1995): Expedition field techniques: small mammals (excluding bats). - Expedition Avisory Centre, London, England. 126 pp. Bateman, J. (1971): Animal traps and trapping. - David and Charles, Newton Abbot. Begon, M. (1979): Investigating animal abundance. - London. 97 pp. Bondrup-Nielsen, S. (1983): Density estimation as a function of live-trapping grid and home range. -Can, J. Zool. 61: 2361-2365. Boonstra, R. & Krebs, C. J. (1978): Pitfall trapping of Microtus townsendii. - J. Mamm. 59: 136-148. Csizmazia Gy. (1980): A Tisza magyarországi hullámterén végzett mammológiai-ökofaunisztikai vizsgálatok I. [Mammalogical and eco-faunistical studies in the Hungarian backwater area of river Tisza I.]. - Juhász Gy. TF. Tud Közi. 19-38. Dalby, P. L. & Straney, D. O. (1976): The relative effectiveness of two size of Sherman live traps. -Acta Theriol. 21: 311-313. Demeter A. (1979): Kisemlősök populációdinamikája egy erdei fenyvesben [Population dynamics of small mammals in a scotch pine forest]. - M. Sc. thesis, Eötvös University, Budapest. Demeter A. (1981): Egyedszámbecslési kísérletek kisemlősökkel [Population size estimation of small mammals]. - Doctorate thesis, Eötvös University, Budapest. Flowerdew, J. R. (1976): Ecological methods. Mamm. Rev. 6: 123-159. Getz, L. L., Cole, F. R. & Verner, L. (1986): Effectiveness of multiple-capture live traps for field behavioral studies of microtine rodents. - Psychonomic Society 24:12-1 A. Gliwicz, J. (1981): Competitive interactions within a forest rodent community in a forest-floor small mammal fauna. - Oikos 37: 353-362.