Behavioral Responses to Combinations of Timed Light,Food Availability,and Ultradian Rhythms in the Common Vole (Microtus arvalis)

Light is the main entraining signal of the central circadian clock, which drives circadian organization of activity. When food is made available during only certain parts of the day, it can entrain the clock in the liver without changing the phase of the central circadian clock. Although a hallmark of food entrainment is a behavioral anticipation of food availability, the extent of behavioral alterations in response to food availability has not been fully characterized. The authors have investigated interactions between light and temporal food availability in the timing of activity in the common vole. Temporally restricted food availability enhanced or attenuated re-entrainment to a phase advance in light entrainment when it was shifted together with the light or remained at the same time of day, respectively. When light-entrained behavior was challenged with temporal food availability cycles with a different period, two distinct activity components were observed. More so, the present data indicate that in the presence of cycles of different period length of food and light, an activity component emerged that appeared to be driven by a free-running (light-entrainable) clock. Because the authors have previously shown that in the common vole altering activity through running-wheel availability can alter the effectiveness of food availability to entrain the clock in the liver, the authors included running-wheel availability as a parameter that alters the circadian/ultradian balance in activity. In the current protocols, running-wheel availability enhanced the entraining potential of both light and food availability in a differential way. The data presented here show that in the vole activity is a complex of individually driven components and that this activity is, itself, an important modulator of the effectiveness of entraining signals such as light and food. (Author correspondence: vanderveen@nd.edu)     

棕色田鼠血液生理生化指标的测定

报道了棕色田鼠指名亚种的正常血象值及几项血液生化值。结果表明,各项备注学和血液生化学参数值在成年个体间无性别差异（附红细胞数、血红蛋白浓度、红细胞压积外,但此三项指标尚未达到极显著差异水平）。与其它仓鼠科动物的血液生理生化参数值相比较,棕色田鼠除红细胞数、血红蛋白浓度及中性粒细胞略低外,其它各项参数虽有差异,但均无统计学意义。     

Road verges as habitat for small mammals in Britain

There are 370 000 kilometres of roads in Great Britain, mostly bordered by a verge that is potential habitat for small mammals. The present study assessed the importance of road verges as small mammal habitat and investigated the influence of some key features on rodent abundance. Five rodent and three shrew species were live‐trapped on 14 road verges in late summer 1994 and nine verges in autumn 1996 in north Cambridgeshire, UK. On average, between three and four species were captured per verge. Bank Voles Clethrionomys glareolus, Wood Mice Apodemus sylvaticus and Field Voles Microtus agrestis were the most abundant species, with mean densities of 45.5, 40.2 and 29.5 animals km^–1 in summer and 52.8, 181.9 and 47.2 animals km^–1 in autumn. Numbers varied between verges and this was significantly correlated with particular features on the verge. Bank Vole and Field Vole numbers showed a significant positive correlation with the dimensions of hedges and the width of the tall grass area, respectively. Wood Mice were also more numerous on verges with big hedges but the relationship between mouse abundance and verge structure was complex. The number of mice in 1994 was positively and significantly correlated with hedge features and with the width of the short grass sightline, whereas, in autumn 1996, they were only significantly correlated with total verge width (positive association) and ditch width (negative association).     

Ongoing ultradian activity rhythms in the common vole,Microtus arvalis,during deprivations of food,water and rest

Summary The timing mechanism underlying ultradian (2–3 h) activity patterns in the common vole, Microtus arvalis, was studied using behavioural deprivation experiments. These were aimed at distinguishing between a homeostatic control mechanism, in which the rhythmic behaviour itself is part of the causal loop, and a clock mechanism, independent of the behaviour.In 175 experiments, deprivation of food during 3 ultradian cycles in (subjective) daytime did not result in significant changes in the ultradian periodicity of attempts to obtain the food, compared with ad lib. access to food and water. A minor, but significant increase in ultradian activity time () occurred in the course of the deprivation, but this was compensated by a shorter ultradian rest (). These results were obtained both in intact animals (n = 24), which showed ultradian and circadian rhythmicity in behaviour, and in animals (n = 21) with electrolytic lesions aimed at the suprachiasmatic nuclei (SCN), which lacked the circadian modulation of behaviour. Simultaneous deprivation of water and food in 8 voles without circadian rhythmicity during 40 experiments also did not lead to any change in the ultradian periodicity of feeding attempts.Rest deprivation was studied in 5 SCN lesioned voles, by forcing running wheel activity to continue following spontaneous running. Thus, the experimental activity bout was artificially lengthened to 2–9 h in 67 experiments. The onset of the subsequent rest episodes occurred independent of the duration of the preceding . The duration of was dependent on the preceding, experimental in a periodic fashion. The interval experimental (=lengthened +following ) was equal to one, two or three times the control (obtained on nonexperimental days). This result fits the prediction of a clock model and is in conflict with a monotonicincrease of with , as expected in a homeostatic, restorative process.It is concluded that the ultradian timing of activity in the common vole can be explained neither by homeostatic hunger or thirst mechanisms nor by homeostatic rest/activity regulation. The results strongly suggest an independent clock system generating ultradian feeding rhythms in the common vole.Abbreviations DD continuous darkness - LD light-dark regime - LL continuous light - RCA retrochiasmatic area - ARC arcuate nucleus - SCN suprachiasmatic nuclei - ultradian period - ultradian activity time - ultradian rest time     

The first born,their dispersal,and vole cycles

Summary On the basis of some empirical data and the existing theory of vole cycles, a new hypothesis is proposed. It explains cyclicity as an effect of obligatory dispersal of the first seasonal cohort of young (Y1) from their natal (optimal) habitats into vacant (suboptimal) habitats. This behaviour could evolve, because it increases contribution of genetic lineages with dispersing Y1, to subsequent generation. It is assumed that the dispersal of Y1 is common among vole species, it does not change during consecutive phases of the cycle, and it does not vary between cyclic and non-cyclic populations. It results in multiannual cycles only under a certain set of spatial and climatic conditions, which are discussed in a paper. Otherwise it results in annual dynamics.     

Lifetime reproductive success in reproductively suppressed female voles

A population of the grey red-backed vole, Clethrionomys rufocanus bedfordiae, was investigated on a 1 ha control grid and a 1 ha grid on which the voles were fed within a 2.1 ha outdoor enclosure in Hokkaido, Japan by live trapping from 1984 to 1986, for testing the Reproductive Suppression Model of Wasser and Barash (1983)-females can optimize their lifetime reproductive success by suppressing reproduction when future conditions for the survival of offspring are likely to be sufficiently better than present ones as to exceed the costs of the suppression itself. Age at the first pregnancy more varied in a higher density population on the experimental grid and females could be classified into the early and the late reproductive type in two generations (A: females born from February to June 1985; B: females born from September to November 1985). Lifetime reproductive success (the number of pregnancies, the number of successful litters, and the number of offspring) was not different between the early and the late reproducing females. The late reproducing females lived for longer periods than the early reproducing females, so that the loss by delayed start of reproduction was compensated for by a longer life span. Life span was not different between offspring of the early and the late reproducing females. These facts supported the Reproductive Suppression Model.     

Environmental,parental and adaptive variation in egg size of Tengmalm's owls under fluctuating food conditions

We studied egg size variation of Tengmalm's owls in western Finland during 1981–1990. The owls fed on voles whose population fluctuated in a predictable manner: low (1981, 1984, 1987, 1990), increase (1982, 1985, 1988) and peak (1983, 1986, 1986) phases of the cycle occurred every third year. Eggs were largest in the increase phase of the vole cycle, even though that voles were more abundant and egg-laying started earlier in the peak phase than in the increase phase. This suggests that owls invest mostly in egg size when vole abundance increases along with survival chances of offspring. Territory quality and female age had no effects on egg size, but egg size decreased with laying data in the increase phase of the vole cycle. Egg size was significantly positively related to the male age in the increase phase, but the opposite relationship was significant in the peak phase of the vole cycle. The partners of adult males also decreased their egg volume from the increase to the peak phase, whereas the partners of yearling males produced their largest eggs in the peak phase of the vole cycle. This suggests the importance of experience in prevailing food fluctuations. Possibly male Tengmalm's owls can adjust the intensity of courtship feeding not only in relation to the food abundance on their territories at the time of egg laying, but also to the survival prospects of their offspring. Phenotypic plasticity seems to play a substantial role, as the egg size repeatabilities of individual females and partners of individual males were low. Obviously, under cyclic food conditions, predictability and inter-generational trade-offs are important to life history traits.     

Variation in the diet composition of a generalist predator, the red fox, in relation to season and density of main prey

Diet composition of a generalist predator, the red fox (Vulpes vulpes) in relation to season (winter or summer) and abundance of multi-annually cyclic voles was studied in western Finland from 1983 to 1995. The proportion of scats (PS; a total of 58 scats) including each food category was calculated for each prey group. Microtus voles (the field vole M. agrestis and the sibling vole M. rossiaemeridionalis) were the main prey group of foxes (PS = 0.55) and they frequently occurred in the scats both in the winter and summer (PSs 0.50 and 0.62, respectively). There was a positive correlation between the PSs of Microtus voles in the winter diet of foxes and the density indices of these voles in the previous autumn. Other microtine rodents (the bank vole Clethrionomys glareolus, the water vole Arvicola terrestris and the muskrat Ondatra zibethicus) were consumed more in winter than in summer. The unusually high small mustelid predation by red foxes (PS = approx. 0.10) in our study area gives qualitative support for the hypothesis on the limiting impact of mammalian predators on least weasel and stoat populations. None of the important prey groups was preyed upon more at low than at high densities of main prey (Microtus voles). This is consistent with the notion that red foxes are generalist predators that tend to opportunistically subsist on many prey groups. Among these prey groups, particularly hares and birds (including grouse), were frequently used as food by foxes.     

Does time after pair bond disruption affect subsequent reproduction in the socially monogamous woodland vole (Microtus pinetorum)?

Disruption of the pair bond between socially monogamous animals leads to changes in behavior, which may have reproductive consequences. There are two alternative hypotheses to explain the effect of the length of time since pair bond disruption on subsequent reproduction. One hypothesis predicts that voles housed immediately with a new opposite-sex conspecific will be as likely to produce litters and will produce them as quickly as voles separated from their initial mate for longer. Alternatively, if attachment between mates is enduring, we expect that more voles separated longer from their previous mates will produce litters and produce them sooner than voles re-paired immediately after separation from their initial mates. Woodland voles, paired with opposite-sex conspecifics, remained together until parturition. Mates were then separated for 0, 7, or 14 days until re-pairing with an opposite-sex conspecific. Pair bond disruption did not prevent males and females from mating subsequently, which was consistent with data from our breeding colony. In addition, the length of time an individual remained alone after pair bond disruption did not affect the latency to produce a litter. Our results show that having been paired previously does not affect subsequent reproduction in this socially monogamous vole.     

Progesterone and testosterone concentrations during oestrous cycle and pregnancy in the common vole (Microtus arvalis Pallas)

Serum progesterone and testosterone concentrations were measured during different stages of oestrous and pregnancy in paired and unpaired female common voles (Microtus arvalis). Hormone concentrations were measured by ELISA, and cycle stages were determined by vaginal smears. Paired females usually had serum progesterone concentrations of more than 10 ng/ml in the oestrous cycle. A significant maximum was detected in prooestrous (51.70 +/- 7.84 ng/ml, mean +/- S.D.). Serum progesterone concentrations increased from about 40 ng/ml at the beginning of pregnancy to about 70 ng/ml on days 15 and 16. The last 2 days before parturition (days 19 and 20) were characterised by a decrease of progesterone concentrations to ca. 30 ng/ml. The maximum concentration of testosterone was found in prooestrous (1.58 +/- 0.31 ng/ml). Concentrations during pregnancy varied between 1.5 and 2.1 ng/ml. In two of three cases unpaired females exhibited progesterone values below 10 ng/ml, but with varying vaginal smear patterns. The combination of progesterone concentrations and vaginal smear patterns was found to be regular in only 23.8% of the cases. The most frequent cycle stage found was the oestrous (44.2%). Mean concentrations of progesterone (10.43 +/- 13.81 ng/ml) and testosterone (0.85 +/- 1.11 ng/ml) in unpaired females were significantly lower than in paired females, thereby denoting reproductive inactivity in the former. The study presents basic data for several parameters of the reproductive biology in the common vole and confirms the importance of combining hormone assays and vaginal smear monitoring in reproductive research.     

An estimate of the impact of predators on the British Field Vole Microtus agrestis population

The productivity of the British Field Vole population is estimated to be between 677 000 and 982 000 voles per year, depending on the precise basis of the calculation. The total consumption of Field Voles by all the major predators, mammalian and avian, is estimated to be around 980 000, if the very uncertain consumption by Feral Cats is included. Two specialist vole predators (Weasel, Kestrel) and two generalist predators (Red Fox, Feral Cat) consume 85% of the total between them, the other 10 species share the rest between them. However important voles might be for owls, owl predation is unimportant to voles. The slight evidence for cyclicity in Field Vole populations in Britain might be explained by the overall take of voles by the predators, and by the rather generalized diet of even the vole specialists.     

SARS-CoV对幼年和成年布氏田鼠的感染研究

采用鼻腔喷雾法(CCID50=105.7)研究了SARS冠状病毒(SARS-CoV)对成年和幼年布氏田鼠的感染效果.成年动物攻毒后出现死亡,表现为口鼻有出血,肠道出血;肺组织呈出血性间质性肺炎改变,肝、脾、肾、胰腺组织均呈淤血性改变;存活动物肺组织呈间质性肺炎,局灶出血及肺气肿改变,其他脏器未见明显病变.幼年动物攻毒后未见死亡但行动较为迟缓,主要脏器未见明显异常;早期肺组织有局限性肺炎改变,且病毒分离为阳性;同居对照组的一只动物有肺组织局灶性肺炎.结果表明,SARS-CoV可以很强地感染布氏田鼠;成年布氏田鼠比幼年动物对SARS-CoV更敏感;布氏田鼠有望成为一种比较理想的小型SARS动物模型。     

Ural owl sex allocation and parental investment under poor food conditions

Parents are expected to overproduce the less costly sex under poor food conditions. The previously regular 3-year cycle in the abundance of voles, the main prey of the Ural owl, Strix uralensis, temporarily disappeared in 1999–2001. We studied Ural owls' parental feeding investment and sex allocation during these poor-quality years. We sexed hatchlings and embryos in unhatched eggs of all 131 broods produced during these years. Population wide, the owls produced significantly more males (56%). The parental food investment in the brood was estimated by sorting out the prey remains in the bottom of nest boxes. Food delivered to 83 broods without chick mortality showed no clear sex-specific investment. Nestling mortality was equal in both sexes. Thus, evidence for an investment-driven sex allocation is weak. Neither laying date, brood size nor the female's condition correlated with offspring sex ratios. In these poor years, parents provided less food per chick and the fledging weight of daughters was reduced more than the weight of sons compared with years of high food abundance (1983 and 1986). We discuss, in relation to published studies, the possibility of a sex-allocation scenario where, under poor food conditions, a daughter's long-term fitness is reduced more than a son's.     

Does feeding effort of Tengmalm's owls reflect offspring survival prospects in cyclic food conditions?

In an environment fluctuating in a predicatable manner with wide among-year variation in offspring mortality, fitness is largely influenced by the timing of reproductive investment. In vole-eating nocturnal Tengmalm's owls (Aegolius funereus), within-cycle variation in 1st-year survival of owlets is 3-fold as estimated by the recruitment probability of an offspring. It increases from the peak through the low to the increase phase of the vole cycle. We recorded prey delivery rates of males during a 3-year vole cycle using 4 h continuous recording at night. Males brought significantly more prey items per offspring in a low-vole year than in the increase and peak vole years. In the early night (10 p.m.–12 p.m.), males fed their families equally in the increase and peak vole years, whereas in the late night (0.01–2.00 a.m.) males reduced their feeding rate in the peak year but not in other years. Both prey number and prey mass per offspring were larger in the low and increase vole years than in the peak year, though in the peak phase food is most abundant. We suggest that feeding effort of site-tenacious, long-lived (mean lifespan 3.5 years) male owls culminates in the increase rather than in the peak phase of the vole cycle, because offspring survive better in the former phase.     

田鼠婚配制度的神经内分泌基础

作为繁殖行为的一种表现形式,婚配制度是通过长期进化而形成的,具有种属特异性及可遗传性。因此,不同的婚配制度具有不同的生理基础。这种生理基础由3级结构组成：神经直接启动并维持繁殖行为;激素或通过诱导特异神经通路的发育或直接激活神经传导影响繁殖行为;基因则可能是通过调节激素的代谢和作用方式来控制与繁殖行为相关的神经系统。田鼠脑中涉及婚配制度的区域集中在视前区中部（MPOA）,腹被盖区（VTA）,膈部及纹状体端部。起作用的激素主要是催产素（OT）和后叶加压素（AVP）。导致田鼠形成不同婚配制度的最终原因可能是这两种激素受体基因上的差异。受体基因调控区的启动子序列存在变异,导致脑中受体基因在表达区域上的差异,进而使激素激活不同的神经通路,产生不同的繁殖行为及婚配制度。     

布氏田鼠雄性的优势地位

在实验条件下对雄性成年布氏田鼠（Microtus brandti）相遇后的优势地位及生理指标的研究结果表明：布氏田鼠雄性之间存在严格的等级关系;优势雄鼠生理指标中睾丸重量和血清睾酮激素含量高于从属雄鼠,而血清中皮质醇激素的含量低于从属雄鼠。优势雄鼠的探究、攻击和修饰等行为频次显著高于从属雄鼠,而从属雄鼠在跳跃频次上多于优势雄鼠。随着观察时间的延长,不论优势个体还是从属个体,其探究频次都呈现明显的下降趋势,其他行为的频次则没有显著差异。相关性检验说明,除攻击行为可以作为判断区分雄鼠等级的依据之外,修饰行为也可以作为判断的依据。     

Climate change in Norway: warm summers limit grouse reproduction

Grouse and vole numbers may peak after peaks in the seed crop of bilberry (Vaccinium myrtillus) because of reduced levels of feeding deterrents in bilberry plants. We predicted that grouse reproduction depends also on summer (June–September) temperatures in the 2 previous years, because bilberry plants will be less exhausted after a high seed crop in or after warm summers, and thus rebuild their chemical defence more quickly. After berry peak years, population indices of capercaillie (Tetrao urogallus) and bank vole (Myodes glareolus) in southern Norway were negatively related to summer temperatures in the previous year or previous 2 years. Willow grouse (Lagopus lagopus) chick production in five areas in Norway was negatively related to summer temperatures in the 2 previous years when controlling for vole density. A similar pattern was found for the bilberry-feeding moth (Eulithis populata), an important prey for grouse chicks. In eastern Norway, autumn densities of capercaillie and black grouse (Tetrao tetrix) were more likely to peak in vole peak years at high altitudes, where summer temperatures are low. We conclude that high summer temperatures may limit grouse reproduction through the effect on bilberry plants and that a warm climate thus adversely affects population levels of grouse.