模拟条件下布氏田鼠对草原植被的作用1——植被生物量的影响

2007年5-10月在模拟条件下研究了不同密度的布氏田鼠Lasiopodomys brandtii啃食对草原植被生物量、植物补偿生长量的影响。结果表明:1）植被生物量与布氏田鼠密度关系呈现了“低-高-低”的变化趋势;鼠密度每100 m2<5只时,植被生物量呈增加趋势。鼠密度每100 m2为5只时,其植被生物量增长达到最高值,随鼠密度的增加,植被生物量下降。2）植物补偿生长量与布氏田鼠密度相关呈单峰型曲线,鼠密度每100 m2为8只时植被的补偿生长量最高。3）植被生长可承受的鼠密度每100 m2 为4只(折合400只/hm2),鼠密度每100 m2≤4只时刺激植物生长,且可稳定植被群落结构。     

布氏田鼠栖息地特征的研究

依据2008-2010年在中蒙2国的实地调查,研究了布氏田鼠(Lasiopodomys brandtii)对栖息地的选择特点,以期为该鼠的综合防治提供依据。选择316个样点,记录每个样点的布氏田鼠密度,并随机调查5～10个1m×1m的样方,记录海拔、植被盖度、植被高度、枯草盖度、植被优势种、郁闭指数和退化级别。利用相关性分析及因子分析选取布氏田鼠栖息地选择影响较大的因子。结果表明:布氏田鼠密度与植被盖度、枯草盖度、退化等级及郁闭指数相关;冷蒿(Artemisia frigida)、羊草(Leymus chinensis)和多根葱(Allium polyrhizum)3种植物多度、枯草盖度、植被盖度、草场退化程度和植被郁闭指数5个因子对该鼠选择栖息地影响显著,即布氏田鼠倾向于选择以冷蒿、羊草、多根葱为优势种,放牧利用程度高、植被低矮的退化草场。     

Browsing preference and ecological carrying capacity of sambar deer (Cervus unicolor brookei) on secondary vegetation in forest plantation

The browsing preference and ecological carrying capacity (ECC) of sambar deer (Cervus unicolor brookei) in acacia plantations for management and conservation of the ecosystem were investigated at Sabal Forest Reserve in Sarawak, Malaysia. The identification of the species browsed by the sambar deer was based on an observation of the plant parts consumed. ECC estimation was based on body weight (BW) and the physiological stages of animals browsed in six fenced 4‐ha paddocks. Sambar deer were found foraging on only 29 out of 42 species of secondary vegetation in the acacia plantation. The remaining species are too high for the deer to reach. Planted species, Shorea macrophylla are not palatable to the deer. This augurs well for the integration of sambar deer into shorea plantations. The most frequently exploited plants were Ficus spp. Sambar deer preferred woody species more than non‐woody species and they are browser animals. By producing metabolizable energy of 19 000 to 27 000 MJ/ha, the ECC was five head/ha to 5.25 head/ha. Given its contribution to the conservation of wildlife and its capacity to sustain the ecosystem, the sambar deer integrated farming system offers a promising strategy for the future of tropical forestry management.     

Browsing of Grewia occidentalis by domestic stock in a South African savanna: the influence of bush clumps

In South African karoo categorised by multi-species bush clumps, skirted shrub species appear to physically defend the palatable shrub Grewia occidentalis against browsing by eland (Taurotragus oryx). Skirted shrubs appear to defend G. occidentalis by preventing access to plants and by reducing the accessibility of G. occidentalis foliage to the large muzzle of eland. Compared to eland, domestic stock such as goats, have a smaller body and muzzle, and these features may allow them to overcome the physical defence offered by skirted shrubs against the browsing of G. occidentalis. Our study of G. occidentalis browsed by domestic stock indicated that mature and seedling G. occidentalis typically occurred with skirted shrub species. Mature and seedling G. occidentalis growing with skirted shrubs had lower intensities of browsing than other G. occidentalis, and mature G. occidentalis growing with skirted shrubs had greater numbers of fruit than other G. occidentalis. In our study area, a non-selective grazing/browsing system is used and camps are grazed/browsed until a high proportion of forage is removed from most plants. Under this system, mature and seedling G. occidentalis are common within the study area and skirted shrubs appear to provide adequate defence for G. occidentalis against browsing by domestic stock.     

Extent of Stem Dieback in Trembling Aspen (Populus Tremuloides) as an Indicator of Time-since Simulated Browsing

Simulated browsing treatments were imposed on an important browse species of the North American moose (Alces alces L.) to see if the development and extent of subsequent stem dieback in trembling aspen (Populus tremuloides Michx.) could be used to determine the time of browsing during the growing season. Two hundred naturally growing aspen saplings of similar size and form were randomly selected in a 20-ha area near the endowment lands of the University of Northern British Columbia, Prince George, British Columbia, Canada. Plants were randomly assigned to treatment categories so that the apical meristems of 50 plants each were assigned to a control or were clipped on one of the following dates 6 weeks apart: 1 June, 16 July, and 30 August 2005. The leader of each aspen was clipped and dieback was left to progress until the onset of winter dormancy. Our results showed that the earlier the simulated browsing occurs in the growing season, the greater the length of stem dieback, up to the maximum of the subapical axillary node below the point of clipping. The average rate at which dieback progressed varied between treatments and decreased throughout the growing season. Our results suggest that the ratio of the actual length of stem dieback to the overall length of stem between the clip point and the subapical axillary node serves as a good indicator for estimating the time at which aspen meristems have been browsed during the growing season.     

Reservoir‐Driven Heterogeneous Distribution of Recorded Human Puumala virus Cases in South‐West Germany

Endemic regions for Puumala virus (PUUV) are located in the most affected federal state Baden‐Wuerttemberg, South‐West Germany, where high numbers of notified human hantavirus disease cases have been occurring for a long time. The distribution of human cases in Baden‐Wuerttemberg is, however, heterogeneous, with a high number of cases recorded during 2012 in four districts (H districts) but a low number or even no cases recorded in four other districts (L districts). Bank vole monitoring during 2012, following a beech (Fagus sylvatica) mast year, resulted in the trapping of 499 bank voles, the host of PUUV. Analyses indicated PUUV prevalences of 7–50% (serological) and 1.8–27.5% (molecular) in seven of eight districts, but an absence of PUUV in one L district. The PUUV prevalence differed significantly between bank voles in H and L districts. In the following year 2013, 161 bank voles were trapped, with reduced bank vole abundance in almost all investigated districts except one. In 2013, no PUUV infections were detected in voles from seven of eight districts. In conclusion, the linear modelling approach indicated that the heterogeneous distribution of human PUUV cases in South‐West Germany was caused by different factors including the abundance of PUUV RNA‐positive bank voles, as well as by the interaction of beech mast and the proportional coverage of beech and oak (Quercus spec.) forest per district. These results can aid developing local public health risk management measures and early warning models.     

Diet shift in bank voles induced by competition from grey‐sided voles?

Grey‐sided voles (Myodes rufocanus) and bank voles (Myodes glareolus) co‐exist in boreal forests in northern Scandinavia. Previous studies suggest that the 2 species interact interspecifically, the grey‐sided vole being the dominant species. We tested the hypothesis that bank voles shift their diet due to competition with the dominant grey‐sided vole by studying stable isotope ratios in both species. Muscle samples were taken from voles in patches of old forest occupied by only bank voles and patches of old forest occupied by both grey‐sided voles and bank voles. We found that: (i) stable isotope ratios of bank voles differed in areas with and without grey‐sided voles; and that (ii) the stable isotope ratios of bank voles were more similar to those of grey‐sided voles in areas where grey‐sided voles were absent. Our data suggests that grey‐sided voles forced bank voles to change their diet due to interspecific competition.     

Research note: Tests for inducible thorn defences against herbivory must consider plant growth strategies

Abstract

Thorn length and density on the latest year's growth were compared at three height (feeding) levels (<1m, >1m<2 m and >2 m) on individuals of Acacia karroo and Ziziphus mucronata in an area that was browsed by goats. Thorn length and density was greatest for branches within easiest reach of goats. However, there was no increase in thorn length or density on the latest year's growth of branches of A. karroo individuals protected from browsing. Thorns on distal ends of branches are relatively small and sparse and this is partly due to differences in internode length. Herbivores limit the extent of annual growth and this prevents development of small thorns characteristic of late season growth. Thus, browsed individuals which lack late season growth may have greater spinescence. This is only a passively induced response and is not due to the active production of larger thorns subsequent to browsing.     

模拟条件下布氏田鼠对草原植被的作用2——鼠密度对植物群落结构及根系的影响

在模拟条件下研究了不同密度的布氏田鼠Lasiopodomys brandtii啃食对植物群落结构及根系生物量的影响。结果表明：1）低密度鼠对植被群落结构的影响不显著,而高密度鼠可改变草地植被群落结构,植被在每100 m2 5只出现退化演替表现为优质牧草的比例降低而其他杂类草的比例增高,使之向退化草地方向演替。2）鼠类啃食促进茎叶枯萎,加速植被演替。茎叶枯萎率与鼠密度呈线性正相关。3）植被根系生物量与布氏田鼠密度关系呈现“高-低-高”的变化趋势;鼠密度为每100 m2 8只时,根系生物量降至最低。随鼠密度的增加,其须根系植物所占比例降低,其他杂草类轴根系植物比例增加。     

Effect of ENSO-driven precipitation on population irruptions of the Yangtze vole Microtus fortis calamorum in the Dongting Lake region of China

The Yangtze vole (Microtus fortis Buechner, 1889) is a small herbivore species that inhabits lake beaches in the Dongting Lake region along the Yangtze River in Southern China. Its population shows strong oscillations during the wet season due to summer precipitation-induced immigration away from the lake into adjacent rice fields. The effect of El Niño-Southern Oscillation-driven precipitation on population abundance and growth of the vole species is not fully understood. We undertook an analysis of the combined data of 4 time series covering 1981–2006 from 4 different sites and a separate analysis on a single time series (1981–2006) from one site. Our results demonstrate that a dual effect of El Niño-Southern Oscillation-driven precipitation on the population abundance of voles is time-dependent: precipitation in the current year has a positive effect, whereas precipitation in the previous year has a negative effect. The dual effect of precipitation on vole population is well explained by the unique interactions among vole population, precipitation water level and the lake beach habitat around Dongting Lake. We found that drier than average weather of the previous year benefited voles because their breeding habitats, lake beaches, were exposed for long stretches of time. Wet weather was found to increase the number of voles inhabiting rice fields because as the water level of the lake rose they were forced from beaches into surrounding rice fields. Summer precipitation in the Dongting Lake region was found to be positively associated with the sea surface temperature (SST) of the eastern tropical Pacific Ocean of the previous year and winter SST and spring SST of the current year. Annual rates of increase in the vole population of the reconstructed time series are negatively associated with the vole abundance and autumn precipitation of the previous year and winter precipitation of the current years. These results suggest that both extrinsic and density-dependent intrinsic factors may affect population dynamics of the Yangtze voles.     

Voles and weasels in the boreal Fennoscandian small mammal community: what happens if the least weasel disappears due to climate change?

Climate change, habitat loss and fragmentation are major threats for populations and a challenge for individual behavior, interactions and survival. Predator–prey interactions are modified by climate processes. In the northern latitudes, strong seasonality is changing and the main predicted feature is shortening and instability of winter. Vole populations in the boreal Fennoscandia exhibit multiannual cycles. High amplitude peak numbers of voles and dramatic population lows alternate in 3–5‐year cycles shortening from North to South. One key factor, or driver, promoting the population crash and causing extreme extended lows, is suggested to be predation by the least weasel. We review the arms race between prey voles and weasels through the multiannual density fluctuation, affected by climate change, and especially the changes in the duration and stability of snow cover. For ground‐dwelling small mammals, snow provides thermoregulation and shelter for nest sites, and helps them hide from predators. Predicted increases in the instability of winter forms a major challenge for species with coat color change between brown summer camouflage and white winter coat. One of these is the least weasel, Mustela nivalis nivalis. Increased vulnerability of wrong‐colored weasels to predation affects vole populations and may have dramatic effects on vole dynamics. It may have cascading effects on other small rodent–predator interactions and even on plant–animal interactions and forest dynamics.     

Density-induced social stress alters oxytocin and vasopressin activities in the brain of a small rodent species

It is known that social stress could alter oxytocin (OT) and arginine-vasopressin (AVP) expression in specific regions of brains which regulate the aggressive behavior of small rodents, but the effects of density-induced social stress are still unknown. Brandt's voles (Lasiopodomys brandtii) are small herbivores in the grassland of China, but the underlying neurological mechanism of population regulation is still unknown. We tested the effects of housing density of Brandt's voles on OT/AVP system with physical contact (allowing aggression) and without physical contact (not allowing aggression) under laboratory conditions. Then, we tested the effects of paired-aggression (no density effect) of Brandt's voles on OT/AVP system under laboratory conditions. We hypothesized that high density would increase aggression among animals which would then increase AVP but reduce OT in brains of animals. Our results showed that high housing density induced more aggressive behavior. We found high-density-induced social stress (with or without physical contact) and direct aggression significantly increased expression of mRNA and protein of AVP and its receptor, but decreased expression of mRNA and protein of OT and its receptor in specific brain regions of voles. The results suggest that density-dependent change of OT/AVP systems may play a significant role in the population regulation of small rodents by altering density-dependent aggressive behavior.     

不同密度布氏田鼠对内蒙古典型草原菌根真菌群落的影响

布氏田鼠是内蒙古典型草原的主要啮齿类动物,其活动既可以改变植物群落组成和多样性,又可以改变土壤理化性质,进而潜在影响与绝大多数草原植物共生的重要土壤微生物-丛枝菌根真菌（AMF）,但目前关于啮齿动物活动对AMF群落组成和多样性影响的研究鲜有报道。基于此,依托内蒙古自治区锡林浩特市毛登牧场的大型野外布氏田鼠围栏实验平台,选择其中3个田鼠密度处理（低、中、高密度,对应的初始投放布氏田鼠数量分别为12、24和48只·样地^-1）,利用Illumina Miseq测序技术分析不同密度布氏田鼠处理对AMF群落的影响,采用标准网格交叉法测定根系侵染率和土壤菌丝密度,探究布氏田鼠活动对典型草原AMF群落的影响机制和作用途径。主要结果表明：1）在土壤样品中共鉴定到6科9属的AMF,其中优势属为球囊霉属（Glomus）;2）高密度布氏田鼠处理显著降低了植物生物量、植被盖度、群落丰富度和多样性,显著降低土壤水分、pH,显著增加土壤硝态氮含量;显著降低AMF侵染率、菌丝密度、丰富度和多样性;3）相关性分析表明,菌丝密度与植物丰富度、多样性指数、土壤pH和含水量显著正相关,与硝态氮含量显著负相关;侵染率与植物多样性指数、土壤pH和含水量显著正相关;AMF多样性指数与土壤pH和含水量显著正相关,不同操作分类单元（OTU）丰富度与植物多样性指数和pH显著正相关;4）NMDS 和 PerMANOVA 分析显示AMF群落结构在低密度和高密度处理间差异显著,其中土壤NO₃^-和pH是影响AMF群落组成的主要因子。因此,布氏田鼠密度过高会导致植物群落生物量、多样性以及土壤养分含量下降,同时两者的改变导致了AMF群落多样性显著降低,可能会加速典型草原的退化。     

Development of transferred xenogeneic vole embryos in mouse uteri

An experimental model to study interspecific pregnancy using voles, Microtus arvalis, and green fluorescent protein gene‐induced transgenic mice is presented. Xenogeneic blastocysts from the vole were transferred into the uteri of pseudopregnant mice along with allogeneic blastocysts from green fluorescent protein gene‐induced transgenic mice. The uteri containing xeno‐allo combined transfers were examined from day 6 to 13 of gestation. Although the vole embryos implanted, the uteri containing vole embryos were smaller compared with those having allogeneic mouse embryos. On day 8, the uteri containing vole embryos hemorrhaged internally and no vole embryo was found in the pregnant uterus after day 11. Allogeneic mouse embryos developed normally despite the presence and abortion of the vole embryos. In uteri implanted with vole embryos, decidua were formed and numerous blood vessels were distributed around the embryo. Maternal blood cells infiltrated into the celomic cavity of the vole embryo through the discontinuous region of trophoblast. Periodic acid‐Schiff‐positive granulated metrial gland cells were remarkably increased in the decidual sites. These findings suggest that a disorder of embryo–maternal interaction might induce the appearance of numerous granulated metrial gland cells and rejection of the embryos.     

Further studies on leptospirosis in small rodents and shrews in Finland. A report of investigation made in 1963-64

In previous investigations on small mammals in Finland (Rislakki & al 1954, Rislakki & Salminen 1955, Salminen 1956), the Leptospira icterohaemorrhagiae-frequency in rats (Rattus norvegicus) was rather high (43.1 %). Leptospira-positive cases were also found in house mice (L. sejroe 23.3 %), harvest mice (L. hataviae 9.0 %), yellow necked field mice (L. poi 12.5 %), common voles (L. sejroe and L. bataviae together 12.1 %), field voles (L. sejroe and L. bataviae together 10.7 %) and in common shrews (L. poi 1.2 %). Specimens of other species sent in for investigation (Norway rat, common red backed vole, large tooth backed vole, northern red backed vole, root vole, water vole, wood lemming, Laxmann''s shrew, lesser shrew and water shrew) gave negative results.     

First insights into Puumala orthohantavirus circulation in a rodent population in Alsace,France

In‐depth knowledge on the mechanisms that maintain infection by a zoonotic pathogen in an animal reservoir is the key to predicting and preventing transmission to humans. The Puumala orthohantavirus (PUUV), the most prevalent orthohantavirus in Western Europe, causes a mild form of haemorrhagic fever with renal syndrome (HFRS) in humans. In France, this endemic illness affects the north‐eastern part of the country. We conducted a 4‐year capture–mark–recapture study in a bank vole population, combined with molecular analyses, to explore the epidemiological situation of PUUV in Alsace, a French region where human cases have occurred, but for which no studies have been conducted on this reservoir host. PUUV‐infected bank voles were detected in the 2 years that showed high bank vole density with a prevalence of 4%. The individual PUUV sequences identified in this study were similar from year to year and similar to other French sequences. On a very small spatial scale, the distribution of seropositive bank voles was very heterogeneous in time and space. The short distances travelled on average by bank voles resulted in spatial clusters of seropositive rodents, which spread only very gradually throughout the year.     

Nutritional composition of three fodder species browsed by camels (<Emphasis Type="Italic">Camelus dromedarius</Emphasis>) on arid area of Tunisia

Browsing camels have access to different plant species in relation to the kind of pasture they can reach. A study was conducted in an arid region of Southern Tunisia to determine the dietary preference and forage quality of free ranging camels. Foliage consisting of leaves from Limonium pruinosum, Retama raetam and Stipa tenacissima, was collected during the dry season to evaluate the chemical characteristics and nutritional value of these browse fodder species. The dietary preference was studied using 15 adult camels which were selected from a herd of 50 animals appropriately marked for identification. There was a significant difference in the chemical composition and nutritional value of plant species collected. Based on crude protein (CP) content and nutritional value, the three fodder species browsed can be recommended as good-quality food source for camels under pastoral management.     

Pellet Accumulation as a Proxy for Herbivore Pressure in a Mediterranean Ecosystem

Human activities have dramatically altered the distribution and density of large herbivores worldwide, particularly on islands. For example, thousands of goats were abandoned to the mountains on Majorca Island, Spain, during the tourism boom in the 1960s. Though this mammal is common throughout the Majorcan mountain range, the impact of goats on the main mountain plant communities has not yet been evaluated. To fill this gap, we recorded goat fecal pellet accumulation and assessed the degree of browsing of 9 363 shrubs and trees located within 231 25-m² strips systematically distributed in two mountain regions of Majorca. We also recorded the degree of regeneration of woody plants inside the same strips. The environmental factors that significantly influenced pellet accumulation were altitude, rock cover, distance to roads and paths, distance to water, and slope. The correlations between the pellet index and degree of browsing depended on species palatability and abundance. Finally, the natural regeneration of plants was heterogeneously distributed and negatively correlated with pellet accumulation. This study indicates that high levels of browsing of unpalatable species in less preferred areas are a clear indicator of strong herbivore pressure, whereas the presence of nonbrowsed palatable species could indicate low herbivore presence. Moreover, this work demonstrates that the relative abundance of fecal pellets is a good indicator of the pressure exerted by feral goats on vegetation at a fine scale. The simple pellet index used in this work correlates strongly with vegetation damage; thus, it could represent a valuable innovative tool to inform sustainable management of feral goat populations in not only Majorca but probably also other Mediterranean islands.     

Behaviour of goats, sheep and cattle on natural pasture in the sub-humid zone of West Africa

The behaviour of sheep, goats and cattle on a shrub and tree savannah in the sub-humid zone of West Africa was studied during the dry (February to May), rainy (June to September) and cool season (October to January). Two mature females per animal species were followed by two observers during 3 days per month and behaviour activities were recorded every 15 min of the daily grazing time. When browsing, the plant name, plant part and plant height reached during prehension were recorded. The distance travelled and the grazing circuits were recorded with a step counter and a Geographic Position System device. The knowledge of farmers concerning appreciated browse species relative to the browse species consumed by animals in the area was also investigated.

During the dry season sheep, goats and cattle spent around 25% of their time browsing and 20%, 16% and 31%, respectively, of their time grazing. During the cool season, goats (17%) browsed more than sheep (7%) and cattle (5%) (P < 0.05). During the rainy season, sheep browsed 20% of the time while cattle spent only 7% of their time browsing, while goats were tied, with no opportunity for browsing. Browsing leaves was the most important part of the browsing activity. During the cool season, browsing height was the same (1.0 m) for cattle and goats, but lower for sheep (0.6 m) (P < 0.05). In the dry and cool season, sheep and goats walked shorter distances than cattle.

The plant species with the highest frequency of consumption were Acacia dudgeoni Craib, Ficus gnaphalocarpa (Miq.) A. Rich, Dioscorea togoensis Knuth, Cordia myxa L., and Manguifera indica L. for sheep and goats and Afzelia africana Sm., Kaya senegalensis (Desv.) A. Juss, Pterocarpus erinaceus Poir. and Dicrostachys cinerea (L.) Wight and Arn. for cattle. Species with a high frequency of citation by farmers were A. africana (92%), K. senegalensis (88%), P. erinaceus (86%), Faidherbia albida A. Chevalier (80%), A. dudgeoni (70%) and F. gnaphalocarpa (69%).

In conclusion, browse species make an important contribution to the diet of ruminant animals in the sub-humid zone and farmers are familiar with the species consumed by ruminant animals.