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2. Distribution of the common hamster in the Czech Republic after 2000: retreating to optimum lowland habitats

Creator:
Tkadlec, Emil, Heroldová, Marta, Víšková, Veronika, Bednář, Marek, and Zejda, Jan
Type:
article, model:article, and TEXT
Subject:
Cricetus cricetus, questionnaire, and Rodentia
Language:
English
Description:
Abundances of the common hamster in western Europe declined dramatically over the last 30 years. Recently, severe restrictions in distribution range have also been reported from central European countries. Here we update knowledge of the hamster distribution range in the Czech Republic based on information from six independent sources: (1) monitoring programme for the common vole carried out by State Phytosanitary Administration, (2) monitoring carried out directly by us, (3) questionnaire data from farming companies, (4) questionnaire data from district museums, (5) data from a public server BioLib for mapping species distribution, and (6) observations from nonrelated research activities and persons taking interest in hamsters. The comparison of locations detected after 2000 with those from the last survey > 30 years ago suggests that the range is severely reduced with hamsters retreating to the optimum lowland habitats along large rivers. These results suggest that the demographic mechanisms causing population decline in western populations operate in central Europe as well.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Is the eye lens method of age estimation reliable in voles?

Creator:
Jánová, Eva, Nesvadbová, Jiřina, and Tkadlec, Emil
Type:
article and TEXT
Subject:
age, calibration, eye lens mass, Microtus, and sexual differences
Language:
English
Description:
We examined the reliability of laboratory-derived calibration curves for age determination of field individuals of the common vole, Microtus arvalis. The sex-specific calibration curves for age determination based on the relationship between eye lens mass and age derived in the laboratory were applied to a live-trapped field population of common vole. When comparing the individual’s age to the length of its trapping history, we found a slight tendency for underestimation of real age. These errors were observed slightly more in females than in males and in individuals captured over a longer time. This could mean that growth rates in captive animals, especially older ones, and in females are greater than those from the field. The month of first trapping has no effect on the presence of the error. We suggest that, in population studies with a special concern for ageing individuals over the whole life span, other methods should be examined, such as those measuring insoluble eye lens proteins or calibration curves based on more than one predictor.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/

4. Measurement error in a burrow index to monitor relative population size in the common vole

Creator:
Lisická, Lenka, Losík, Jan, Zejda, Jan, Heroldová, Marta, Nesvadbová, Jiřina, and Tkadlec, Emil
Type:
article and TEXT
Subject:
bias, colonisation, dispersion, Microtus arvalis, precision, and sampling error
Language:
English
Description:
Various population indices are widely used to monitor relative population size of many pest and game species to aid their management. However, information on the level of uncertainty associated with their estimates is rarely available. Here we explore sampling and systematic error associated with the index of re-opened burrow entrances which is used extensively in central Europe for surveying common vole populations. We found that relative sampling errors were enormous for low-density populations, attaining almost 400%. However, in high-density populations and for large sample sizes, the relative error dropped below 10% and the estimate is quite reliable. The dispersion of burrow entrances became more clumped at low population densities enhancing further the sampling variation. We demonstrated that the index is related to population size in a non-linear fashion, overestimating the population change at high densities. Consequently, population dynamics of the common vole described by the untransformed burrow index appear more variable than they are in reality.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/

5. Set-aside plots - source of small mammal pests?

Creator:
Heroldová, Marta, Jánová, Eva, Bryja, Josef, and Tkadlec, Emil
Type:
article and TEXT
Subject:
abandoned fields, succession, and rodents
Language:
English
Description:
Succession of weeds and small mammal species was studied and compared on alfalfa field in two periods (cultivated 1996–1998 and set-aside 2001–2003). Composition of the plant community changed between the two periods of study. In the first period high biomass of green alfalfa biomass was available to the common vole which dominated small mammal community (88.7 %) and pronounced variation in maximal autumnal densities, typical of cyclic vole populations. Massive invasion of seed bearing weeds was stated after the field was set-aside and alfalfa biomass lowered. With the succession of weeds other rodent species such as Apodemus sp. increase their relative abundance (RA) and that of the pygmy field mouse was higher in the abandoned field compared with the common vole. The trend toward increasing RA was quite distinct (Z = 1.883; P = 0.060). Diversity of herb species and the small mammal species increased with abandonment. The monthly RA of the common vole was, on average, lower in the abandoned field than in the former period (Z = 2.353, P = 0.019). Also the cyclicity disappeared and RA of the population exhibited only seasonal oscillations. Biomass of the small mammal community decreased after the field was set-aside (Z = 3.021, P = 0.002).
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/