Analýza časně jarního vzorku populace hraboše polního (Microtus arvalis) [Analysis of the early spring sample from a common vole population (Microtus arvalis)]
Jan Zejda, Milan Zapletal, Marta Heroldová, Emil Tkadlec
An early spring sample from a common vole population controlled by poisoning on the 22 March in a winter rape field was analysed from the point of view of its relative density and sexual activity. The relative population density was high (three different methods for density estimation have been used). The sexual condition of both males and females was determined, regarding the following aspects. In males, the gvI index (length of glandula vesicularis multiplied by the length of the testis) was decisive to assess sexual activity. The male was regarded as sexually active when the gvI exceeded 50 and the cauda epididymidis and ductus epididymidis were relatively large. In females the stage of sexual activity was determined by the presence or absence of corpora lutea, of the vaginal plug, by the presence and size of maculae cyaneae and the form of the uterus. The studied population was found to be already sexually active, some over win te red females started to reproduce at the end of January and at the end of the second decade of March they nursed their second litters. On the other hand some overwintered females only started to reproduce (first gravidity). Early spring borne voles grew quickly in weight and body length and became fecund. The importance of such analyses for forecasting the further development of the common vole population is discussed.