Demografická struktura a procesy v přírodní populaci křečka polního (Cricetus cricetus) na Olomoucku [Demographic structure and processes in a natural population of the Common Hamster (Cricetus cricetus) in the Olomouc region (Czech Republic
Emil Tkadlec, Jitka Hříbková, Lenka Lisická, Jan Losík
In last decades, populations of the common hamster (Cricetus cricetus L.) have suffered a widespread decline all over Europe. In the Czech Republic, the hamster became endangered in the 1970s and 1980s but its real demographic status is largely unknown. Between 2001 and 2006, we carried out the first intensive live-trapping capture-mark-recapture study in a natural population (25 ha area) located in the periphery of the Olomouc city, central Moravia. We used the Jolly-Seber model to estimate population size and fi tted constrained linear models (Cormack-Jolly-Seber) to estimate survival rates with respect to sex and age. We found that the population was constant over the study period, with the mean spring abundance of about 1.6 individuals per hectare. The maximum density of 8 ind./ha was observed in the summer 2005. The sex ratio in juveniles appeared to be female-biased while being male-biased among adults. The mean month survival rate was 0.8, with less than 10% of individuals surviving beyond one year of age. During the breeding season, females survived better than males. Whereas no male attained sexual maturity before the first hibernation, few females did complete maturation in the year of their birth(the probability of maturing being 0.128). Overall, the results do not indicate a decline in the investigated population as relatively high mortality rates are well compensated by good reproductive performance.