Snow evens fragmentation effects and food determines overwintering success in ground-dwelling voles

Climate instability strongly affects overwintering conditions in organisms living in a strongly seasonal environment and consequently their survival and population dynamics. Food, predation and density effects are also strong during winter, but the effect of fragmentation of ground vegetation on ground-dwelling small mammals is unknown. Here, we report the results of a winter experiment on the effects of habitat fragmentation and food on experimental overwintering populations of bank voles Myodes glareolus. The study was conducted in large outdoor enclosures containing one large, two medium-sized or four small habitat patches or the total enclosure area covered with protective tall-grass habitat. During the stable snow cover of midwinter, only food affected the overwintering success, body condition, trappability and earlier onset of breeding in bank voles. However, after the snow thaw in spring, habitat fragmentation gained importance again, and breeding activities increased the movements of voles in the most fragmented habitat. The use of an open, risky matrix area increased along the habitat fragmentation. Our experiment showed that long-lasting stable snow cover protects overwintering individuals in otherwise exposed and risky ground habitats. We conclude that a stable winter climate and snow cover should even out habitat fragmentation effects on small mammals. However, along prolonged snow-free early winter and in an earlier spring thaw, this means loss of protection by snow cover both in terms of thermoregulation and predation. Thus, habitat cover is important for the survival of small ground-dwelling boreal mammals also during the non-breeding season.     

Effects of female kin groups on reproduction and demography in the gray-tailed vole, Microtus canicaudus

I conducted an experiment with gray-tailed voles, Microtus canicaudus , to test the hypothesis proposed by Charnov and Finerty that populations of voles comprised of female kin groups would grow more rapidly and reach higher densities more quickly than populations in which female kin groups were disrupted. The experiment was conducted in 0.2-ha semi-natural enclosures planted with mixed grasses. In four enclosures, females were unmanipulated (control) and in four enclosures all newly caught females were removed from their natal enclosures and replaced with females of comparable age from another enclosure, such that juvenile females did not settle near their siblings or parents (treatment). I found no significant differences in survival, reproduction, juvenile recruitment, population growth rates, or population size between control and treatment populations. The only difference was the time to sexual maturation for young females, which was 3.1 weeks for control enclosures compared with 4.2 weeks for treatment enclosures. I could not measure reproductive success for individual females, but my results did not support the hypothesis that the presence or absence of kin groups resulted in any biologically meaningful population-level effects. Female voles that have nesting territories adjacent to relatives may accrue some individual benefits, but these benefits are unlikely to contribute to population regulation in gray-tailed voles.     

放牧对布氏田鼠主要食物选择的影响

动物的食物选择受食物资源量、质量和喜好度决定。尽管放牧可减少鼠类的喜食植物的数量和质量,但其如何影响鼠类的食物选择尚不清楚。本研究于2014年5月至10月,在内蒙古锡林郭勒盟锡林浩特市毛登牧场的大型试验围栏内进行了布氏田鼠的食物选择实验。利用大型实验围栏内5年连续放牧处理所构建的植被变化条件,采用扣笼试验,调查了布氏田鼠对其三种主要植物的取食情况。研究发现：连续放牧后,糙隐子草的盖度增加,而羊草、克氏针茅盖度降低;糙隐子草的盖度显著高于羊草、克氏针茅,成为各季节的优势植物种类。放牧对布氏田鼠取食羊草、克氏针茅和糙隐子草的绝对取食频次均无显著影响。在季节上,布氏田鼠对克氏针茅和糙隐子草的取食在三个季节均无差异,但布氏田鼠对羊草取食的绝对频次夏季显著高于春季和秋季;布氏田鼠对三种植物的喜好程度依次为羊草>克氏针茅>糙隐子草,但季节和放牧因素对布氏田鼠对这三种植物的喜好度无显著影响。结果表明,布氏田鼠的食物选择及食物组成相对稳定,表现为其对放牧或季节因素造成的喜食植物资源量的变化具有很好的适应性,推测是其调整取食努力来实现食物组成的平衡。     

Direct interference or indirect exploitation? An experimental study of fitness costs of interspecific competition in voles

Studies on competing mammalian species in the past have focused mainly on the competitive exclusion of one species from the preferred habitat of the other. Investigations on effects of competition and coexistence on individual fitness are rare . In this study we were able to measure effects of interspecific competition on major fitness components, using a system with two vole species in asymmetric competition. Survival, reproduction and space use of bank vole Clethrionomys glareolus females were monitored in 32 enclosed populations over four replicates of eight parallel run enclosures. Into half of the enclosures we introduced an additional number of field voles Microtus agrestis , a dominant competitor.
Survival of bank vole females was lower under competitive conditions. Total number of breeding females was lower in populations coexisting with competitors. Territory size of bank vole females decreased. Females body weight and litter size bank vole litters conceived during the experiment were not affected by interspecific competition. These characteristics should respond to differences in food resources, and territory size should increase if food was scarce, thus we found no indication of direct exploitation competition between the two species. Space use was overlapping between the species, but individuals of both species were never caught together in the same trap, indicating avoidance behaviour.
We conclude that adult bank vole females do suffer fitness consequences through interference competition with field voles, probably basing on increased number of aggressive encounters in the presence of the dominant species. Our results suggest, that direct interference rather than indirect exploitation competition may be the cause for observed fitness decrease in bank vole females.     

储草期增加食物对布氏田鼠越冬存活率的影响北大核心CSCD

布氏田鼠(Lasiopodomys brandtii)是内蒙古典型草原区主要鼠种之一。该鼠种在秋季将食物储存在储草仓内,以此来度过植被贫瘠的冬季。为探究储草期增加食物对布氏田鼠越冬存活率的影响,2004年10月,于内蒙古阿巴嘎旗白音图噶苏木的布氏田鼠鼠害草场随机选取两块100 m×200 m的样地,分别设为增食样地和对照样地。增食样地内给每个布氏田鼠洞群补充食物,每天补充500 g小麦,连续补充2 d共计1000 g。对照样地内则不做任何处理。2004年10月,采用标志重捕法调查两块样地内布氏田鼠种群数量,调查显示,增食样地和对照样地内,布氏田鼠数量分别为310只和318只,以该结果作为计算其越冬存活率的基数。2005年5月,返回样地再次进行标志重捕,分别计算两样地布氏田鼠的越冬存活率。卡方检验显示,储草期增加食物能显著提高布氏田鼠越冬存活率。增食样地布氏田鼠越冬存活率为41.3%,显著高于对照样地布氏田鼠越冬存活率(24.2%,P<0.01)。增食样地雌性和雄性布氏田鼠越冬存活率分别为45.4%和37.3%,均显著高于对照样地雌性和雄性布氏田鼠越冬存活率(25.8%和22.6%,P<0.01)。但样地内雌性和雄性越冬存活率均无明显差异(P>0.05)。本研究结果表明,补充食物可大幅度提升布氏田鼠冬季存活率,增加布氏田鼠越冬存活基数,对来年种群增长起重要作用。     

A demographic analysis of population responses to the manipulation of adult males in <Emphasis Type="Italic">Calomys venustus</Emphasis> (Rodentia,Sigmodontinae)

In many species of mammals, adults play an important role in influencing the survival and/or reproduction of juveniles. Adult males could have a negative effect on population density when their absence becomes a limiting factor in female fertilization. We tested the hypotheses that the absence of overwintering males (adult males) reduces the population growth rate through a delay in the onset of reproductive activity of Cohort 1 females in Calomys venustus populations. The study was carried out in two control and two experimental enclosures (0.25 ha). Adult males were removed after their offspring were born. Weekly trapping sessions were carried out from spring to autumn. To estimate population growth rates (λ), apparent survival (ϕ) and seniority probability (γ) were estimated using capture–mark-recapture models. Models were constructed with these two parameters and recapture probability (p) constrained to vary as a function of time, enclosure and/or treatment. We derived estimates of population growth rates through the estimates of ϕ and γ. The best models for ϕ and γ did not show a treatment effect. Variability between the four enclosures was greater than between control and experimental enclosures. Enclosures had different growth rates at the beginning of the study but were equaled at the end. Temporal variation in population growth rates was a result of temporal variation of γ. The two controls showed the highest growth rates earlier in time. The results did not support the hypothesis tested in this study. It seems that the number of overwintering males do not affect the population growth rate.     

Effects of fragmented breeding habitat and resource distribution on behavior and survival of the bank vole (Myodes glareolus)

Habitat fragmentation causes negative population trends or even local extinction in many species. Understanding the role of fragmentation on behavior and space use of animals is an essential part of revealing the mechanism behind observed population declines. We studied experimentally the effects of small-scale habitat fragmentation on the distribution and movement of bank voles (Myodes glareolus) in seminatural enclosures. We predicted that besides habitat structure, availability of two resources, food for both sexes, and receptive females for males, determine individual distribution. We manipulated female density (either 0, 4, or 12 per enclosure) and followed movements of radio-collared males. We also studied the effect of unequal food distribution between the fragments on vole distribution. The habitat of 0.25-ha enclosures was manipulated by forming either one large, two medium-sized, or four small habitat patches surrounded by an inhospitable matrix. Female density and distribution clearly affected male spacing behavior. Males had larger home ranges in the medium female density enclosures. Furthermore, the use of the inhospitable and risky matrix area increased with habitat fragmentation. Food supplementation improved individual condition measured as body mass but did not affect breeding success. Our experiments demonstrated that both small-scale habitat fragmentation and resource distribution affect the behavior and condition of individuals. Increased fragmentation led to increased risk taking in both mating and foraging behavior. This should have direct survival and fitness consequences, and therefore our results may be extrapolated to population-level consequences of habitat fragmentation.     

Effect of overwintering adults on juvenile survival of Calomys venustus (Muridae: Sigmodontinae)

Abstract The aim of this paper was to test the hypothesis that the presence of overwintering Calomys venustus males or females at the beginning of the breeding period reduced the survival of juveniles belonging to the first cohort of each year (C1). The study was carried out in four 0.25‐ha enclosures (two control and two experimental), each situated on natural pasture. This study was conducted between August 1997 and February 1999 and had two parts: removal of overwintering males (ROM) and removal of overwintering females (ROF). For the ROM treatment, overwintering males were removed immediately after C1 juveniles were born, in the ROF treatment overwintering females were removed after the C1 were weaned. Weekly censuses were taken for 3 successive days over 6 weeks. Juvenile survival was examined through a survivorship schedule. The survivorship values were compared by sex and treatment (removal of overwintering males or females) using repeated‐measures anova . Removal of overwintering males and females did not improve the survival of C1 juveniles. This result could be related to the delay in maturation of C1 juvenile males.     

Breeding state and season affect interspecific interaction types: indirect resource competition and direct interference

Indirect resource competition and interference are widely occurring mechanisms of interspecific interactions. We have studied the seasonal expression of these two interaction types within a two-species, boreal small mammal system. Seasons differ by resource availability, individual breeding state and intraspecific social system. Live-trapping methods were used to monitor space use and reproduction in 14 experimental populations of bank voles Myodes glareolus in large outdoor enclosures with and without a dominant competitor, the field vole Microtus agrestis. We further compared vole behaviour using staged dyadic encounters in neutral arenas in both seasons. Survival of the non-breeding overwintering bank voles was not affected by competition. In the spring, the numbers of male bank voles, but not of females, were reduced significantly in the competition populations. Bank vole home ranges expanded with vole density in the presence of competitors, indicating food limitation. A comparison of behaviour between seasons based on an analysis of similarity revealed an avoidance of costly aggression against opponents, independent of species. Interactions were more aggressive during the summer than during the winter, and heterospecific encounters were more aggressive than conspecific encounters. Based on these results, we suggest that interaction types and their respective mechanisms are not either-or categories and may change over the seasons. During the winter, energy constraints and thermoregulatory needs decrease direct aggression, but food constraints increase indirect resource competition. Direct interference appears in the summer, probably triggered by each individual's reproductive and hormonal state and the defence of offspring against conspecific and heterospecific intruders. Both interaction forms overlap in the spring, possibly contributing to spring declines in the numbers of subordinate species.     

Food Deprivation Suppresses a Preference for the Top-Scent Mark of an Over-Mark in Meadow Voles (Microtus pennsylvanicus)

Food availability affects whether mammals communicate their interest in interacting with opposite‐sex conspecifics. This study examined the responses of voles to over‐marks, and factors that influence the formation and maintenance of a preference for the top‐scent in an over‐mark. Specifically, we investigated how food deprivation affected the amount of time male and female voles exposed to an over‐mark, later responded to the marks of the top‐ and bottom‐scent donors when subsequently presented with the two scents side by side. Males and females that were not food deprived and males that were food deprived 6 h before exposure to an over‐mark later maintained a preference for the donor of the top‐scent mark compared with the donor of the bottom‐scent mark of the over‐mark. Females that were food deprived for 6 h before or after exposure of the over‐mark and males food deprived 6 h after the exposure to the over‐mark showed no preference for the top‐scent mark donor. Re‐feeding females that were food deprived for 6 h before exposure to an over‐mark was sufficient to restore their preference for the mark of the top‐scent male over that of the bottom‐scent male. The different responses of food‐deprived male and female voles to over‐marks of opposite‐sex conspecifics may be associated with differences in their tactics for interacting with potential mates and the higher energetic costs of reproduction in female voles than in male voles.     

Foraging patterns of voles at heterogeneous avian and uniform mustelid predation risk

Temporal variation of antipredatory behavior and a uniform distribution of predation risk over refuges and foraging sites may create foraging patterns different from those anticipated from risk in heterogenous habitats. We studied the temporal variation in foraging behavior of voles exposed to uniform mustelid predation risk and heterogeneous avian predation risk of different levels induced by vegetation types in eight outdoor enclosures (0.25 ha). We manipulated mustelid predation risk with weasel presence or absence and avian predation risk by reducing or providing local cover at experimental food patches. Foraging at food patches was monitored by collecting giving-up densities at artificial food patches, overall activity was automatically monitored, and mortality of voles was monitored by live-trapping and radiotracking. Voles depleted the food to lower levels in the sheltered patches than in the exposed ones. In enclosures with higher avian predation risk caused by lower vegetation height, trays were depleted to lower levels. Unexpectedly, voles foraged in more trays and depleted trays to lower levels in the presence of weasels than in the absence. Weasels match their prey's body size and locomotive abilities and therefore increase predation risk uniformly over both foraging sites and refuge sites that can both be entered by the predator. This reduces the costs of missing opportunities other than foraging. Voles changed their foraging strategy accordingly by specializing on the experimental food patches with predictable returns and probably reduced their foraging in the matrix of natural food source with unpredictable returns and high risk to encounter the weasel. Moreover, after 1 day of weasel presence, voles shifted their main foraging activities to avoid the diurnal weasel. This behavior facilitated bird predation, probably by nocturnal owls, and more voles were killed by birds than by weasels. Food patch use of voles in weasel enclosures increased with time. Voles had to balance the previously missed feeding opportunities by progressively concentrating on artificial food patches.     

Experimental tests of predation and food hypotheses for population cycles of voles

Pronounced population cycles are characteristic of many herbivorous small mammals in northern latitudes. Although delayed density-dependent effects of predation and food shortage are often proposed as factors driving population cycles, firm evidence for causality is rare because sufficiently replicated, large-scale field experiments are lacking. We conducted two experiments on Microtus voles in four large predator-proof enclosures and four unfenced control areas in western Finland. Predator exclusion induced rapid population growth and increased the peak abundance of voles over 20-fold until the enclosed populations crashed during the second winter due to food shortage. Thereafter, voles introduced to enclosures which had suffered heavy grazing increased to higher densities than voles in previously ungrazed control areas which were exposed to predators. We concluded that predation inhibits an increase in vole populations until predation pressure declines, thus maintaining the low phase of the cycle, but also that population cycles in voles are not primarily driven by plant-herbivore interactions.     

Determinants of reproductive success in voles: space use in relation to food and litter size manipulation

Spacing behaviour of female mammals is suggested to depend on the distribution and abundance of food. In addition, food limitation has been found to constrain the reproductive success of females. However, whether females maximize their reproductive success by adjusting space use in relation to current food availability and reproductive effort (e.g. litter size) has not been experimentally studied. We examined these questions by manipulating simultaneously food resources (control vs. food supplementation) and litter sizes (control vs. plus two pups) of territorial female bank voles (Clethrionomys glareolus) in large outdoor enclosures. Females with supplementary food had smaller home ranges (foraging area) and home range overlaps than control females, whereas litter size manipulation had no effect on space use. In contrast, the size of territory (exclusive area) was not affected by food supplementation or litter size manipulation. As we have previously shown elsewhere, extra food increases the reproductive success of bank vole females in terms of size and proportion of weaned offspring. According to the present data, greater overlap of female home ranges had a negative effect on reproductive success of females, particularly on survival of offspring. We conclude that higher food availability increases the reproductive success of bank vole females, and this effect may be mediated through lower vulnerability of offspring to direct killing and/or detrimental effects from other females in the population. Moreover, it seems that when density of conspecifics is controlled for, home range sizes of females, but not territoriality, is related to food resources in Clethrionomys voles.     

Effect of adults on juvenile reproduction of Calomys venustus (Muridae: Sigmodontinae)

Abstract We tested the hypothesis that adult overwintering Calomys venustus inhibit maturation and reproduction in young‐of‐the‐year from the first cohort. The study was carried out in four 0.25‐ha enclosures (two control and two experimental), each situated on natural pasture. This study was conducted between August 1997 and March 1999 and had two parts: removal of overwintering male (ROM) and removal of overwintering female (ROF). For the ROM treatment overwintering males were removed immediately after the first cohort of juveniles were born, in the ROF treatment overwintering females were removed after the first cohort were weaned. Weekly censuses were taken for three successive days over 6 weeks. The sexual maturation and reproductive condition of juveniles were compared between treatments (overwintering male or female removal) using repeated‐measures anova . The repeated measures factor was the age of juveniles. Removal of overwintering males and females did not affect sexual maturation of juveniles, however, overwintering males influenced the onset of reproductive activity of juvenile females at the beginning of the breeding period.     

实验检验东方田鼠学习能力的性别差异

东方田鼠选择从禾本科植物叶片的不同部位采食会引起食物摄入率的巨大差异,这项具有明显的认知和学习行为的觅食活动是否存在性别差异。在由带两片叶的新鲜马唐茎秆配置的密集食物斑块上,测定东方田鼠觅食马唐叶片的行为序列、过程及参数,检验其在学习能力上的性别差异。结果表明,雌鼠和雄鼠的觅食决定时间尽管均随觅食学习天数的增加而减小,但雌鼠的觅食决定时间显著地高于雄鼠的;雌鼠和雄鼠均由从对叶片部位无差别选择和采食转向偏爱从叶片基部采食。学会这项采食技能后,雌鼠从叶片基部采食的选择指数显著地高于雄鼠的;二者的摄入率均随觅食学习天数的增加极显著地增大,但雌鼠的摄入率却极显著地高于雄鼠的。研究结果充分验证了提出的假设:雄鼠较雌鼠能更快地习得从禾本科植物叶片的基部采食和收获食物;但当二者习得这项采食技艺后,雌鼠较雄鼠能获得更高的食物摄入率;同时也说明,新建立的评价小型植食性哺乳动物认知和学习能力的实验方法,具有可靠的有效性和实用性。     

小型啮齿动物种群系统调节复合因子理论的野外实验研究：食物可利用性和捕食对根田鼠种群空间行为的作用模式及其对种群调节的探讨

本项研究在野外围栏条件下,采用析因实验设计,测定食物可利用性和捕食对根田鼠（Ｍｉｃｒｏｔｕｓｏｅｃｏｎｏｍｕｓ）种群空间行为的作用模式。检验的特定假设为,高质量食物较大的可利用性能降低田鼠的攻击行为和活动;捕食能减少田鼠的活动。研究结果表明,食物可利用性能间接地和直接地影响根田鼠的空间行为。附加食物种群具有较高的密度和较小的巢区,且在诱捕期间具有较少的长距离活动和较低的攻击水平。捕食者的存在不直接影响攻击行为,但能影响诱捕期间的长距离活动,此为根田鼠对捕食者存在作出的直接反应。在阐明田鼠种群动态时,应仔细考虑上述因子相互作用的效应。     

Effects of forage availability on growth and maturation rates in water voles

1. In populations of small mammals, food supplementation typically results in higher population densities, body weights, growth rates and reproductive rates. However, few studies have demonstrated a relationship between forage levels and demographic rates in wild populations in the absence of supplementation. 2. We examined the association of levels of available forage with individual growth rates and time to sexual maturity in eight re-introduced and three naturally occurring populations of water voles (Arvicola terrestris). 3. Range sizes were smaller at sites with higher population densities. Mean forage availability and individual growth rates covaried with range size at each site. 4. The weight at which water voles became sexually mature was 112 g for females and 115 g for males and did not vary between study sites. Differences in growth rates therefore translated into differences in the time taken to reach maturity between sites. 5. In the re-introduced populations, mean days to maturity varied inversely with mean range length. Females took 7 days (18%, range 40-47 days) longer and males 5 days (13%, range 40-45 days) longer to reach breeding condition at the sites with the shortest mean range lengths. 6. Evidence from this study suggests a possible mechanism by which increased population densities may reduce maturation rates in water voles through a reduction in mean range size, thereby limiting the availability of forage to each individual.     

Maternal Food Restriction During Lactation Affects Body Weight and Sexual Behavior of Male Offspring in Meadow Voles (Microtus pennsylvanicus)

Little is known about the occurrence of individual variation in sexual behavior and how maternal nutrition can affect this variation. We tested the hypothesis that male offspring of female meadow voles, Microtus pennsylvanicus, that were 30% food restricted (FR) during days 1–7 of lactation (FR 1–7), days 8–14 of lactation (FR 8–14), or late days 15–21 of lactation (FR 15–21) lactation show persistent, negative effects on their sexual behavior as adults relative to male offspring of females that were not food restricted. We measured three components of sexual behavior, attractivity, proceptivity, and receptivity, beginning when the males were 98 d of age. Food restriction during middle lactation (FR 8–14) but not during early (FR 1–7) and late lactation (FR 15–21) was sufficient to induce adult male voles to produce anogenital marks that were not as attractive as those produced by control males. Food restriction during lactation did not affect the proceptive behavior of male voles but did affect their receptivity. Only four of 12 FR 8–14 male voles mated compared to nine of 12 FR 1–7 males, eight of 12 FR 15–21 males, and eight of 11 control males. However, no differences existed in their copulatory behavior among the males that did mate. The body weight of FR 1–7 and FR 8–14 males was lower than that of FR 15–21 and control males when they were between 22 d of age (weaning) and 48 d of age (puberty) but was similar when the males were 98 d of age. Food intake was similar for the FR and control males between day 22 and day 98. It remains unclear, however, whether this type of maternal effect represents strategic programing of offspring behavior in response to the environment experienced by mothers or is a product of developmental processes of food restriction prior to weaning (Evolution 58 , 2004, 2574).     

Spacing behaviour of juvenile corn mice, Calomys musculinus, at the beginning of the breeding period, in absence of adult males

This research was carried out to examine the hypothesis that the absence of fathers promotes a different spacing behaviour in juveniles Calomys musculinus at the beginning of the breeding period. The study was carried out in four 0.25-ha enclosures (two control and two experimental), in a natural pasture, between November 2003 and February 2004. In this study the fathers were removed from the experimental enclosures after juveniles were born. Home-range size depended on sex of juveniles and treatment (father removal). In control and experimental enclosures, female home-range sizes were always smaller than male home-ranges. Male home-ranges were always larger in experimental enclosures than in control enclosures. Treatment and overlap type (intra- and inter-sexual) were not independent. The overlap proportions of male home-ranges were greatest in experimental enclosures than in control enclosures, in both the overlap types (male/male, males/females). The intra- (females/females) and inter-sexual (females/males) overlap proportions of female home-ranges were independent of treatment. In C. musculinus, at the beginning of the breeding period and in absence of adult males, juvenile males increase their home-range size and therefore the degree of inter- and intra-sexual home-range overlap as a mechanism for enlarging the number of receptive females that they encounter.     

瑞士西部农田周围生态保留带中小型兽类种群结构特征及数量动态的初步研究

为了评价生态保留带对小型兽类种群的影响,2003年7月至2004年6月在瑞士西部Salavaux,chevmux和Montbrelloz 3个地区采用标志重捕方法对小型兽类种群进行了研究。在3个生态保留带中,共发现6种1206只小型兽类,其中普通田鼠、小林姬鼠、中麝晌捕获数量多。普通田鼠为优势种。普通田鼠的种群数量在生态保留带间有差异,但具有相同的季节性波动趋势,一般种群数量随着植被覆盖度和食物丰富度的增加,春季末开始出现增加,仲夏达到最高水平。种群中雌雄个体年龄结构之间有明显的差异,成体和亚成体的数量比幼体多,雄性亚成体的数量比雌性多,雌性成体数量比雄性多（X^2=44．09,df=10,P〈0．001,N=203）。普通田鼠种群中雌雄个体体重之间有明显的差异,雄性的体重比雌性大（t一检验：t=5．011,df=162,P〈0．05,N=213）。种群性比之间有明显的月间变化,雌性的捕获次数比雄性大。普通田鼠只在短距离范围内活动,在生态保留带中的巢区为350～400m^2,雌雄个体的巢区大小之间没有显著性差异。