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Mammalian Biology 76 (2011) 570–576

Contents lists available at ScienceDirect

Mammalian Biology

journa l homepage: www.e lsev ier .de /mambio

riginal Investigation

raditional and diversified crops in South Moravia (Czech Republic): Habitatreferences of common vole and mice species

va Janovaa,∗, Marta Heroldovaa, Adam Konecnya, Josef Bryjaa,b

Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czech RepublicDepartment of Botany and Zoology, Faculty of Science, Masaryk University, Brno, Czech Republic

r t i c l e i n f o

rticle history:eceived 9 September 2010ccepted 14 April 2011

eywords:icrotus arvalis

podemus sylvaticusgroecosystemsgricultural landscaperop

a b s t r a c t

Substantial changes in the composition of crops in Central Europe during the last two decades (increasingareas of maize, rape and sunflower fields) have significantly influenced the structure and dynamics ofanimal communities, though there is a lack of data available for small rodents. In this study, we assessedthe importance of these three crops for rodents and compared it with traditional crops (alfalfa, barley,wheat). We observed that herbivorous species (especially the common vole) do not live in crops whichdo not have green leaves near the ground (e.g. sunflower, maize), while mobile granivorous species caninhabit all types of crop. We confirmed the presumed differences in habitat preferences; however werejected the hypothesis of a general increase of rodent abundance during the vegetative season in man-aged fields. We found that (1) maize and sunflower had no importance for common voles, but they were

favored habitats for wood mice; (2) numbers of wood mice in rape decreased during the season, whileabundances of common voles increased; (3) common vole populations tended to increase during theseason in all suitable crops (alfalfa, barley, wheat, tendency in maize and rape); (4) wood mice popula-tions seemed stable in all crops; i.e. without a seasonal increase. It can be concluded that even if the newcrop fields are an important part of the agricultural landscape, they are only a temporal habitat for smallmammals, especially granivorous species.

sellsc

© 2011 Deutsche Ge

ntroduction

Many changes in agricultural land usage have occurred duringecent decades in Central Europe. New practices, such as privatiza-ion and the introduction of the Agri-Environmental Scheme (AES)nder the European Union, have influenced agricultural manage-ent. For example, based on data from the Czech Statistical Office

www.czso.cz; Fig. 1) areas planted with wheat have been stableince the 1970s, while areas of barley and alfalfa increased in the970s and 1980s and subsequently decreased slightly in the last0 years. Notwithstanding these changes, these crops have tradi-ionally been the main agricultural crops planted in Central Europe.owever, the area used for the cultivation of rape, sunflower andaize has significantly increased in the Czech Republic since the

980s and 1990s in response to the increasing demand for theserops. The area of maize has increased fivefold in the last decade,

nd the area covered by rape has increased continuously duringhe last 20 years, making it one of the dominant crops in the Czechepublic. Sunflower is widely grown in the south-east of the Czech

∗ Corresponding author. Tel.: +420 543422549; fax: +420 543211346.E-mail address: janova.eva@seznam.cz (E. Janova).

616-5047/$ – see front matter © 2011 Deutsche Gesellschaft für Säugetierkunde. Publisoi:10.1016/j.mambio.2011.04.003

haft für Säugetierkunde. Published by Elsevier GmbH. All rights reserved.

Republic (South Moravia), although its total production in the entirecountry is not high (Fig. 1).

There are numerous studies on the occurrence and dynamics ofsmall rodents in agroecosystems from Scandinavia (Loman 1991)and the UK (e.g. Tew and Macdonald 1993; Tattersall et al. 1999a,b;Tew et al. 2000; Todd et al. 2000), but these regions are outsidethe range of the common vole, which is one of the most importantrodent pests in Central Europe (e.g. Kratochvil et al. 1959; Babinska-Werka 1979; Zapletal et al. 2001; Zejda et al. 2002). Therefore, itis difficult to compare the composition of rodent communities andtheir effects on agricultural production in different geographicalregions. The majority of studies from Central Europe were carriedout some time ago and do not reflect recent changes in crop com-position. They are usually focused on small mammals in traditionalcrops, while only partial (and often unpublished) data are availableabout rodents in “new” crops (i.e. maize, rape and sunflower).

Traditional crops such as alfalfa and winter wheat are importanthabitats for overwintering and reproduction in small mam-mals (e.g. Zejda and Nesvadbova 2000; Heroldova et al. 2005;Aschwanden et al. 2007). The lack of information for the new crops;

in particular whether rodents reproduce in these fields and howmuch their densities increase during the vegetative season, makesit difficult to predict the impact of new agricultural practices onsmall mammal populations and vice versa. Fragmented evidence

hed by Elsevier GmbH. All rights reserved.

E. Janova et al. / Mammalian Biology 76 (2011) 570–576 571

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ig. 1. Areas (ha) of main agricultural crops in the Czech Republic from 60s to theresent. Data from www.czso.cz.

uggests that rape has a positive influence on overwintering andeproduction of the common vole (Truszkowski 1982; Balmelli et al.999; Zejda and Nesvadbova 2000; Heroldova et al. 2004), but isot preferred by mice during the vegetative season (Macdonaldt al. 2000; Todd et al. 2000). On the other hand, no such publishedtudies exist for maize and sunflower plots.

Crops with high abundances of rodents could be a source of pestsfter ploughing (Tew and Macdonald 1993; Jacob 2003; Jug et al.008) and high spring abundances in perennial crops could meanhat these crops are important sites for overwintering of small

ammals (Babinska-Werka 1979; Truszkowski 1982; Heroldovat al. 2004). Rodent species can successfully move from these fieldso other crops according to food supply (Ylonen et al. 1991; Ouint al. 2000). Empirical data about the effect of crop type on the pop-lation growth of rodent abundance is required and has enormous

mportance for agro-management.The aim of this study was to compare the rodent communities

ver two seasons occurring in three “new” planted (maize, sun-ower, rape) and three “traditional” (alfalfa, barley, wheat) crops.wo hypotheses were tested: (1) That there would be differencesn abundances of small mammals in particular crops (traditionalnd new) at any given time and that abundances in “new” crops (orn some of them) are comparable with abundances in “traditional”rops (or in some of them). These could be a reflection of the avail-bility of a favorable food supply and shelters and food preferencesf particular species. (2) We tested the hypothesis that habitat suit-bility for reproduction and population increase is directly reflectedn the increase of rodent abundance during the season. Therefore,he increase of small mammal abundance was not expected to behe same in the all crops. In case that the crop offers good conditionsor reproduction and survival the numbers of small mammals wasxpected to increase considerably from spring till harvest time.

We predicted an increase in the numbers of small mammalsn crops providing a stable food supply and low level of tillageespecially alfalfa). However, corn and crop with oily seeds suchs sunflower and maize could be attractive preferentially for mices a seasonal food supply.

aterial and methods

The small mammals were studied in the years 2004–2006 in therop fields in South Moravia, the Czech Republic. The study lastedhree years, however the year 2006 was a year with very low small

ammal densities. The total number of fields where one or morendividuals was captured in the whole year was only ten, thus 2006

as not included in the analysis. The studied fields were situated inbroad strip around the highway from Brno to Breclav, GPS coor-inates 48◦40′N–49◦06′N and 16◦29′E–16◦53′E (Fig. 2), the size oftrip was approximately 40 × 12 km and the difference in eleva-

Fig. 2. The study area.

tion was up to 80 m. All fields were in a flat landscape. The studyarea formed the northernmost part of Panonia lowland and 67.5% ofthe area of the studied region is used as arable land (www.czso.cz).Small mammals were captured in alfalfa, spring barley, maize, win-ter rape, sunflower and winter wheat crop fields. Between 6 and 13different fields of each crop were sampled each year (Table 1). Westudied 49 fields in 2004 and 63 fields in 2005, 20 of them wereinvestigated in both years.

We tried to sample fields with each crop equally spread in thewhole region. The trapping of small mammals was performed twiceper year, at the beginning of the vegetative season of each crop andbefore the harvest (Table 2). We realize that the results could bebiased by the different sampling times and by temporal variationssuch as weather, stage of moon cycle, etc. which may influencecapture rates, nevertheless in the time of sampling we were limitedby the stage of crops.

We are aware that the pre-crop (Zejda and Nesvadbova 2000)has an effect on assemblages of small mammals. Nevertheless therest of pre-crops were cleared off at the end of summer and thefields were ploughed – this leads to the moving of small rodentsto adjacent habitat (Ouin et al. 2000). At the time of the springsampling there were six or more months since the last pre-cropbiomass was present in the field. We think that this justifies thefact that the influence of pre-crop was omitted from our analysis.

The sampling was performed by snap trapping because thematerial of rodents was examined to check the presence of hanta,arena and cowpox viruses in the same time (Heroldova et al., 2010).Snap trapping is a method which is commonly used for the rela-tive abundances estimating in United States (e.g. Krebs et al. 2002),Fennoscandia (e.g. Norrdahl and Korpimaki 2002; Ecke et al. 2010)as well as in the central Europe (e.g. Heroldova et al. 2005; Janovaet al. 2008).

Snap traps were baited with fried wicks (soaked in fat and flour).Trap lines began about 50 m apart from the borders of the field toavoid the edge effect (Chudoba and Huminski 1980). Traps wereexposed for one night in two lines in the same field; each line had25 traps spaced 3 m apart. The next day the traps were movedto another field of the same crops, so the each trapping action

lasted one week and crops were sampled during the whole weekfor multiple nights and fields. The one-night exposition of trapswas sufficient for our previous studies in alfalfa and set-aside plots(Janova et al. 2003; Heroldova et al. 2005; Janova et al. 2008). The

572 E. Janova et al. / Mammalian Biology 76 (2011) 570–576

Table 1The numbers of analyzed field plots, captured common voles (Marv), wood mice (Asyl) and others small mammals (others) in spring and harvest time 2004 and 2005.

Crop Fields Spring Harvest

Marv Asyl Others Total Marv Asyl Others Total

2004Alfalfa 9 0 10 6 16 74 28 4 106Barley 9 3 21 5 29 13 8 12 33Maize 10 0 11 0 11 2 18 9 29Rape 6 0 10 1 11 7 1 1 9Sunflower 6 0 3 0 3 1 14 6 21Wheat 9 1 8 0 9 16 10 3 29

Total 49 4 63 12 79 113 79 35 2272005Alfalfa 12 4 7 0 11 113 6 5 124Barley 12 5 9 5 19 15 7 6 28Maize 10 0 6 0 6 6 15 1 22Rape 7 4 1 0 5 9 0 1 10Sunflower 9 0 17 1 18 5 4 4 13

dtt

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fiTdaTTwsaw

TT

Wheat 13 1 2 0

Total 63 14 42 6

istances between trap lines in the same field as well as distanceso lines in the nearest crop were long enough to make us considerhe trap lines as independent.

The small numbers of traps in each field, placing the trap linesn the spring in different places than in the autumn, leaving a longnough period between spring and autumn trappings for popula-ion recovery and especially a low trapping intensity and the lowatio of traps to field area (no field was smaller than 5 ha) was suf-cient to believe that the previous snap-trapping had no effect onhe subsequent results in the field and that captured individualsere soon replaced by recruitment and immigrants.

The population size was estimated as relative abundance (rA),.e. the number of individuals caught in a particular field per 50rap-nights. For analyses, we used relative abundance for all cap-ured species – rA all, or separately only for the most often capturedpecies – the common vole (Microtus arvalis, Pallas, 1778) – rA Marv,he wood mouse (Apodemus sylvaticus, Linnaeus, 1758) – rA Asyl,nd other species than the common vole or the wood mouse – rAthers. In order to restore the original variation in the data thatas presumably lost due to the “saturation effect”, the numbers of

aptured individuals of appropriate species (N) was transformedo rA index by assuming a random (Poisson) distribution of small

ammals, i.e. rA = (−ln(1 − Nx/100))100 (Caughley 1977).The similarity of datasets from years 2004 and 2005 were con-

rmed by Mann–Whitney test for each crop, season and species.his enabled us to increase the sample size by the combiningatasets from years 2004 and 2005. The effect of crop on rodentbundance was analyzed separately for spring and harvest time.he numbers of captured individuals in the field was often null.he non-normal distribution of the resulting dataset meant that

e had to use non-parametric Kruskal–Wallis tests for the analy-

is. Analyses were designed as test of difference between relativebundances of the small mammal species in the crops. Each cropas represented by 6–13 various fields. Because extremely large

able 2he dates of spring and harvest time sampling: the height and cover of particular crops.

Spring

Date Height (cm) State

Alfalfa mid-April 20–30 Continuous coveBarley late May 30–50 Continuous rowMaize late May 20–30 30% coverRape mid-April 30–60 Continuous coveSunflower late May 20–40 40% coverWheat mid-April 15–30 Continuous row

3 10 1 0 11

62 158 33 17 208

densities were found at some alfalfa fields which could affect thecomparison of different crops, we excluded the alfalfa field fromthe analyses in the second step. The importance of the crop forpopulation increase was analyzed by comparing spring and har-vest abundances in the same plot with a Wilcoxon paired test. Allanalyses were performed in Statistica 6.0 (StatSoft 2001).

All captured individuals were identified to species, weighted,sexed, measured and dissected. Since we suppose that in fieldswith less suitable living conditions or in crops with a shorter veg-etative period, higher proportions of young migrating males orlower breeding intensity could be found, we evaluated the sexratio and proportion of breeding females in the crops. Females withembryos or with visible maculee cyanea were considered as breed-ing, females without these marks of reproduction were recorded asnon-breeding. For the both species the differences in total numbersof males and females captured in the crops in spring and harvesttime were tested using a �2 test. Likewise the differences in theproportion of breeding and non-breeding females in the crops inspring and harvest time were tested using a �2 test.

The work complied with Council directive 86/609/EEC regula-tions on the experimental use of animals.

Results

New planted crops appeared to be an important habitat for smallmammals. In total 289 common voles, 217 wood mice and 70 indi-viduals of other species – 20 pygmy field mice (Apodemus uralensis,Kratochvíl et Rosicky, 1952), 32 yellow-necked mice (Apodemusflavicollis, Melchior, 1834), 15 house mice (Mus musculus, Linnaeus,1758), two common shrews (Sorex araneus, Linnaeus, 1758) and

one bank vole (Myodes glareolus, Schreber, 1780), were captured in112 fields during the years 2004 and 2005.

Even where the overall relative abundances were very low inthe majority of crops, the effect of the crop type was significant in

Harvest time

Date Height (cm) State

r end August 30–60 Continuous covers mid-July 50–60 Ripeness

end August 120–200 Nearly ripenr mid-July 100–170 Ripeness

end August 100–170 Nearly ripens mid-July 70–90 Ripeness

E. Janova et al. / Mammalian Biology 76 (2011) 570–576 573

Table 3The effect of crops on abundance of all small mammals (rA all), common vole (rA Marv), wood mice (rA Asyl) and other species (rA others) in spring (SprA) and harvest time(HarA) and in spring (SprA) and harvest time (HarNA) after removing alfalfa from the analysis. Analyses were performed by Kruskal–Wallis test; numbers of all analyzedfields (N), values of H (tested criterion) and p-values are noted in table.

N rA all rA Marv rA Asyl rA others

H p H p H p H p

SprA 112 14.841 0.011 11.081 0.049 9.806 0.081 17.849 0.003

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SprNA 91 14.787 0.005 10.500HarA 112 20.306 0.001 29.683HarNA 91 8.019 >0.1 11.738

oth seasons; after excluding the alfalfa, the differences betweenrops remained significant only in spring (Table 3). The differencesn abundance between crops were most noticeable for the commonole and much less for wood mice. Maize and sunflower (the lattern spring) were favored by wood mice; however the common vole

as rarely found in these crops. Rape was preferred by wood micen spring, but they were not found in this crop at harvest time. How-ver, the common vole was found infrequently in rape in spring butts abundance rapidly increased at harvest time.

Comparisons of spring and harvest densities in the same croponfirmed that the abundances of the common vole have a ten-ency to increase (although significantly only in alfalfa, barley andheat) in all crops (Table 4, Fig. 3b). However, no uniform trendsere found for wood mice (Table 4, Fig. 3c). The total number of

aptured wood mice was nearly the same in the harvest time asn spring (Table 1). There was no significant increase in abundanceuring the vegetative season and the decrease in rape fields was oforderline significance. The high densities of the common vole inlfalfa during the harvest affected the results for the whole com-unity; after removing the alfalfa from the analysis of category “rA

ll”, there was no significant increase in abundance during the sea-on (z = 1.216, p = 0.224). Other species than the wood mouse andhe common vole showed a trend towards a slight increase in maizend sunflower (Table 4).

Similar sex ratios in the crops were found both for the commonole and the wood mouse in spring and in the late summer (allesults p > 0.1). The proportion of breeding females in the crops wasetween 50 and 100% in spring (totally 26 breeding/4 non-breedingemales of the common vole, 41/19 females of the wood mouse) and0–100% in harvest time (182 breeding/20 non-breeding females ofhe common vole; 42/14 the wood mouse). We found no differencesn the proportion of breeding females in any species or season (allesults p > 0.1).

iscussion

It is not surprising that we confirmed that small mammal com-unities in both spring and harvest time are influenced by crop

ype (Pelikan 1986; Heroldova et al. 2007). However we rejectedhe hypothesis of the clear increase of the rodent abundances dur-ng the vegetative season in all crops and rodent species. Very lowbundance was observed in spring in any crop. However, the veryigh autumn abundances of the common vole in alfalfa were incom-arable to any other crop. A comparable seasonal increase in woodice abundances was not detected in any crop. We found that

he new crops are important habitats for some rodent species –aize and sunflower have great importance as a temporal habi-

at for wood mice while common voles are almost absent there. Inape, both common voles and wood mice occurred regularly, how-ver, vole abundances increased while mice decreased during theegetative season.

Low densities occurred in spring. This could be a result of thegronomical techniques and tillage in autumn and spring, whichestroyed burrows and shelters, and therefore rodents died oroved to adjacent fallows (Tew and Macdonald 1993; Jacob 2003;

0.035 8.987 0.061 16.757 0.002<0.001 12.419 0.029 8.406 >0.1

0.019 10.732 0.029 8.019 0.091

Jug et al. 2008). This result is unlikely to be a consequence oflow densities from the previous year, because abundances of thecommon vole were at an average level in 2005 in the studiedarea (according to the data collected by the State PhytosanitaryAdministration, Holmanova et al. 2006). It is possible reducedattractiveness of the traps in spring (Gliwicz 1970) – i.e. the time ofgood supply of fresh herb leaves – may be a reason for the low num-bers of common voles we observed. Surprisingly low abundanceswere observed also in perennial alfalfa, although alfalfa fields aregenerally suitable habitats for overwintering of small mammals(Babinska-Werka 1979; Truszkowski 1982; Heroldova et al. 2004).Our results implied that the highest spring abundances of the com-mon vole and wood mice were in the spring barley. The green leavesof spring barley can be attractive for the common vole because oftheir high carbohydrates and sodium content – there is 1.5–2 timesmore carbohydrates and 1.5–3 times more sodium in leaves of bar-ley than in leaves of oil crops or alfalfa in spring (Zeman 1995).Mice are probably also attracted by the remains of the seed grainsin barley fields at the time of trapping. In addition barley fieldsare usually more infested by annual weeds and invertebrates occurat higher densities in this crop (Pysek et al. 2005), which attractsmice species and shrews (Watts 1968; Obrtel and Holisova 1979;Povey et al. 1993; Heroldova 1994). In spring wood mice were alsoquite often present in sunflower, rape and alfalfa. The relativelyhuge numbers of yellow necked mice were observed in barley inspring and in crops with oily seeds (sunflower, maize) in autumn.Fields of maize and sunflower were inhabited by wood mice despitethe fact that they form only small biomass at the time of springsampling. Possibly the seeds of these crops are attractive for mice.Rape is an important overwintering habitat of many rodents in gen-eral (Truszkowski 1982; Balmelli et al. 1999; Zejda and Nesvadbova2000; Heroldova et al. 2004).

Abundances of common voles increased in all crops except sun-flower from spring to harvest; the most intense population growthwas recorded in alfalfa, barley and wheat. Alfalfa is the crop withvery good conditions for the reproduction and the increasing of thesmall mammal densities, due to the stable food supply and min-imal agricultural intervention (Babinska-Werka 1979; Zejda andNesvadbova 2000; Heroldova et al. 2004).

Winter wheat and barley provide a suitable environment forcommon vole reproduction until harvest time (Truszkowski 1982;Zejda and Nesvadbova 2000; Aschwanden et al. 2007), howeverit prefers feeding on weeds than on ripening grain in these fields(Truszkowski 1982). We did not observe population growth ofwood mice in any crop, while there was a decrease of miceabundance in rape. This finding was surprising such as the cropsshould be the habitat with the high recruitment rate of wood mice(Tattersall et al. 2004). More than a half of the captured femaleswere gravid, so the decrease could not be caused by the absenceof reproduction. The present mice should be detectable by snap-trapping while they did not have upper stratum activity (Nordvig

et al. 2001). There are three possible explanations for the seasonallystable wood mice abundances in most plots: (1) “overestimation”of wood mice numbers in spring when attractive seeds for sowingwere available in fields and mice from adjacent areas move to the

574 E. Janova et al. / Mammalian Biology 76 (2011) 570–576

Table 4Comparisons of spring and harvest abundances rA all, rA Marv, rA Asyl and rA others in the crops by Wilcoxon matched pair test.

rA all rA Marv rA Asyl rA others

z p z p z p z p

Alfalfa 3.501 <0.001 3.439 <0.001 1.216 >0.1 1.185 >0.1Barley 0.994 >0.1 2.935 0.003 1.507 >0.1 0.471 >0.1Maize 1.894 0.058 2.023 0.043 1.287 >0.1 1.826 0.068

0.0>0.1

0.0

coaot

itbsecnct

Fa

Rape 0.945 >0.1 1.782Sunflower 1.289 >0.1 0.707Wheat 2.306 0.021 2.548

rop fields (Ylonen et al. 1991; Ouin et al. 2000); (2) in the timef fullest harvest wood mice moved to other habitats with a morettractive food supply – possibly more diverse or to crops with oilyr starchy seeds; (3) traps were not attractive for wood mice at theime of ripening.

Fields with new crops are important habitats for small mammalsn agroecosystems. Maize and sunflower are favorable habitats athe beginning and end of the vegetative season for granivorous miceecause of the high nutritional quality of the corn and sunflowereeds (Grodzinski and Savicka-Kapusta 1970; Hansson 1973; Toddt al. 2000; Zeman 1995; Heroldova et al. 2007). However, these

rops have negligible importance for the common vole, as they areot a suitable food supply for them. Sunflower and maize fieldsould be used as an isolating habitat between overwintering habi-ats and more attractive crops for common voles. Rape is (together

ig. 3. The relative abundances of all small mammals rA all (a), common voles – rA Marvlfalfa, ba – barley, ma – maize, ra – rape, su – sunflower, wh – wheat) in spring (–S) and

75 2.201 0.028 0.535 >0.10.070 >0.1 1.944 0.052

11 0.237 >0.1 0.707 >0.1

with alfalfa and fallow habitats) a refuge for rodents in winter(Zejda and Nesvadbova 2000; Heroldova et al. 2004) and a sourceof small mammals for adjacent fields in spring. Its green biomassprovides suitable conditions for reproduction of the common vole(Truszkowski 1982; Balmelli et al. 1999). Mice species could beattracted by weeds and in flowering time also by insect. How-ever, and in accordance with the published results from the UK(Macdonald et al. 2000; Todd et al. 2000), we registered only fewwood mice in this habitat at harvest time. This could be caused bythe fact that granivorous mice are repelled by mature rape seedswith high amount of sinapines and glucosinolates with a bitter taste

(Bouchereau et al. 1991; McDanell et al. 1988).

We have to mention that the detected abundances and trappa-bility of the small mammals can be influenced not only by the foodsupply of the crops but also by the time of sampling as well as anti-

(b), wood mice – rA Asyl (c) and other species – rA others (d) in specific crops (al –in harvest time (–H).

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E. Janova et al. / Mammal

redating behavior. Small rodents were more active (and thereforeore detectable) in the higher vegetation than in mowed or short

egetation as they perceive it the less risky (Jensen and Honess995; Jacob and Brown 2000; Macdonald et al. 2000; Jacob andempel 2003), which could cause underestimation of abundances

n crops without proper vegetation cover – sunflower, maize andlso barley in spring. Different densities of individual species inrops could be also influenced by presence/absence of weeds (theommon vole – green parts; mice – seeds and insect). In the sameime the age of fodder crop (alfalfa) can influence the small mam-

al community, because the amount of weed increases togetherith the succession of crop.

Other potential bias of our study could be influence of the sur-ounding habitat and adjacent crops on abundances in crop fields.his should be minimized by the fact, that our trap lines were situ-ted more than 50 m from the boundary of the field and there wereo forests or hedgerow in the direct contact with the field in addi-ion the field boundaries were usually formed by crops fields orarrow balks. However there are different movement patterns ofice and vole. Mice are more mobile and select habitat according

o its actual food supply (Ylonen et al. 1991; Tew et al. 1992; Ouint al. 2000). On contrary the common vole, which tends to long termtilization of the habitat, is likely to prefer one site and its homeange is smaller (Mazurkiewicz and Rajska-Jurgiel 1998; Brinert al. 2005). There is strong seasonal dispersion of mice from hedgeso crops in the beginning of vegetation season (Ouin et al. 2000),hich means that the surrounding habitat especially hedgerows

nd forests (although there are sparse in agricultural landscape ofouth Moravia) can influence density of mice in fields. The resultsay be also affected by the trappability differences between the

elds. This feature is influenced by the dispersion and by the move-ent which are dependent on the crop (Macdonald et al. 2000) and

re affected by tillage (Jacob and Hempel 2003) and breeding (Corpt al. 1997; Tew and Macdonald 1994).

Other alternative limitation of our study could be the rolef competitive interactions of small mammals. There is nothingnown about interactions between the common vole and the woodouse, however there was not observed any habitat shift related

o competitive release in the bank vole and the wood mouse, evenhe removing of wood mice affected bank vole density (Fasola andanova 2000). Wood mice and yellow-necked mice have tendencyo be segregated vertically (Hoffmeyer 1973) which could affect theumbers of yellow-necked mice estimated from ground snap-traps.

We expected that breeding would be more intensive in cropsith more abundant-stable populations (mainly alfalfa) and that

ndividuals in crops with lower observed numbers could benly randomly dispersed individuals. Mainly younger individuals,specially males who are seeking their own territory should beispersing (Kozakiewicz et al. 2007; Gauffre et al. 2009). These pre-umptions were not confirmed as we did not find any differencesn the proportion of breeding females or the sex ratio in the cropseither at the common vole nor the wood mouse.

We can assume that the new crops are not a “desert” for smallammals. The crops include long term refugee for small mammals

rape) as well as habitats inhabited only for a short time for theuration of an attractive food supply (sunflower and maize). Den-ities of small rodents in these crops are comparable with densitiesn traditional crops. We confirmed the differences in the habitatreferences of rodent species; however a general increase of rodentbundance was not detected. Populations of herbivorous commonoles tended to increase during the vegetative season in all suit-ble crops; however, populations of the granivorous wood mouse

ppeared stable in all crops. For agroecosystems management aso decrease the numbers of common voles it is recommended tose sunflower and maize crops as an isolating habitat between itsverwintering and attractive habitats or crops.

logy 76 (2011) 570–576 575

Acknowledgements

The project was supported by the Grant Agency of the CzechRepublic, the grant no. GA CR 521/08/P529 and by the Long-termResearch Plan (MSM 0021622416) of the Masaryk University.

References

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