Small rodents, their habitats, and the effects of flooding at Wicken Fen, Cambridgeshire

The habitat preferences of small rodents were studied by live trapping methods at Wicken Fen, Cambridgeshire, a relict area of East Anglian fenland. The study sites were chosen to cover areas of managed fields, dominated by sedge ( Cladium mwiscus ) or by litter (grasses with sedges); the adjacent fen carr "bush growth"; and an area of unmanaged sedge. Clethrionomys glareolus is the commonest rodent species, occurring at relatively high densities, and closely associated with sedge growth. It is ubiquitous in unmanaged sedge but in managed sedge and litter field areas there is a marked preference for the field/fen carr transition where sedge growth is not cut. Thick sedge seems to afford the optimum habitat for this species probably because of the three-dimensional vegetation structure which provides dense ground cover with a natural thatch of dead leaves; this decays only slowly, even in succeeding fen carr. Sedge fields provide a less stable habitat and recolonization of a harvested field by Clethrionomys only began after eight months of sedge regrowth. Micromys minutus are caught only in sedge and litter. Apodemus sylvaticus seem to show no marked habitat preference but there are some data which suggest that high Clethrionomys densities can affect Apodemus distributions locally. Microtus agrestis prefers grassy patches within sedge fields; trap success points tending to be associated with the presence of Calamagrostis canescens. Microtus avoids fen carr and unmanaged sedge and is generally caught more often in litter fields than in sedge fields; however, this preference seems to disappear at the end of the Clethrionomys breeding season. During flooding, Clethrionomys found refuge in the dense sedge and sedge/carr transition habitats; prolonged flooding caused a decline in numbers of Clethrionomys and the elimination of Microtus , while the distribution of Apodemus was apparently unaffected.     

Presence in the eastern part of the Spanish Pyrenees of Amphipsylla sibirica sepifera Jordan and Rothschild, 1920 (Siphonaptera: Ceratophyllidae: Amphipsyllinae)

The detection of two males and one female of Amphipsylla sibirica sepifera on three Clethrionomys glareolus is pointed out. The rodents were taken in Alt Aneu and Espot, two towns of Lerida (a Spanish Province). The finding of this flea species on Spanish Pyrenees increases to the west its geographical distribution and adds one new species to the Iberian flea fauna.     

Spatial and temporal patterns of seed predation on three tree species in an oak-pine forest

We experimentally examined spatial and temporal patterns of seed predation on three tree species in an oak-pine forest in southern Maine. USA, Rodents were the principal seed predators. Rates of seed loss varied with tree species and exposure to three different suites of potential seed predators (all vertebrate seed predators, medium-sized rodents [primarily squirrels] and small rodents [primarily mice and voles]), Acer rubrum seeds were removed more slowly (mean of 17.7% within 2 d across all habitats and treatments in 1991) than seeds of either Quereus rubra or Pinus strobus (e,g., > 99% removed within 2 d across all habitats and treatments for each species in 1991), Levels of final removal (cumulative removal at final census) varied with year but not with microhabitat; i.e., seed predation in four types of forest gap was not significantly different than in intact forest. Both field data and experimental feeding trials with captive Peromyscus leucopus and Clethrionomys gapperi suggest that a significant proportion of while pine seeds is eaten at time of detection, while red oak acorns are more likely to be cached. Captive Peromyscus leueopus cached and ate significantly more red oak acorns than Clethrionomys gapperi. These results suggest that red oak mast may be more important in overwintering success in Feromyscus than in Clethrionomys. Nevertheless, both species did consume red oak acorns, suggesting that in southern Maine these species are not substantially inhibited by high tannin levels in red oak acorns, as has been suggested by researchers elsewhere.     

Eimeviu (Protozoa: Coccidia) in wild populations of some British rodents

Four species of wild rodents from the British Isles, Myocustor coypus (the Coypu), Apodemus sylvaticus (the Wood mouse). Mus musculus (the House mouse) and Clethrionomys glureolus (the Bank vole) were examined during 1918 and 1919 for the presence of coccidian parasites of the genus Eimeriu. From an examination of 852 faecal samples a total of 14 species of Eimeriu was found. Species identification was based mainly on the morphology of the sporulated oocyst. The number of host species examined and the overall prevalence of infection were as follows: 252 M. coypus (45·6% infected), 471 A. sylvaticus 56·5%), 59 M. musculus (42·4%) and 70 C. glureolus (22·9%). The results are compared with previous surveys and discussed in the light of the general knowledge concerning coccidial infections. The present work showed that prevalence of infection in the wild rodents studied may be influenced by the age, weight and sex of the host, and by season.     

Fluctuating asymmetry of craniometric characters in rodents (Mammalia: Rodentia): interspecific and interpopulational comparisons

Ontogenetic instability was studied in four rodent species (Ellobius talpinus, Microtus arvalis, M. rossiaemeridionalis, Mus musculus). It was measured by fluctuating asymmetry (FA) of 21 craniometric characters. Each species was represented by two populations differing in average level of chromosomic instability and in degree of anthropogenic influence. Relation between FA and individual age was observed in none of the studied species. The level of cranial structure FA in rodents is probably formed during embryogeny or early postnatal ontogeny and is not changing significantly during the further development. The studied species showed distinct differences in the degree of ontogenetic instability of the axial skull, but not of the mandible. No connection was found between craniometric character FA and technogenic stress. The differences of cranial FA level among the studied species of rodents agree with their systematic position and the sequence of their evolutionary divergence.     

Experimental adiaspiromycosis of the common vole (Microtus arvalis) and other small wild mammals after intraperitoneal inoculation

After intraperitoneal inoculation ofE. crescens to nine species of wild small mammals, six species of rodents (Apodemus flavicollis, A. sylvaticus, Clethrionomys glareolus, Microtus agrestis, M. arvalis, Mus musculus) developed generalized adiaspiromycosis. The course of experimental infection corresponded to the infections of laboratory animals provoked in the same manner of inoculation. The authors studied the affliction of individual organs, the dynamics of growth of adiaspores in the organs of the abdominal cavity and in the lungs and followed up morphological changes in the adiaspores. In fresh cover glass preparations, the presence of manifestations was demonstrated justifying considerations on the capacity of multiplication of the adiaspiromycosis agent in the host organism.     

Densities of microtime rodents along a pollution gradient from a copper-nickel smelter

Population densities of microtine rodents were studied along an air pollution gradient in the Kola Peninsula, Russia, by long-term and short-term trapping. The study area is affected by high sulphur dioxide and heavy metal emissions from the Severonikel copper-nickel smelter in Monchegorsk. The density of Clethrionomys rufocanus, the most abundant vole species in the area, was lowest close to the smelter and increased with distance up to the farthest, less polluted trapping sites. Clethrionomys glareolus, C. rutilus and Lemmus lemmus were absent from the most severely damaged area and were also scarce at the moderately polluted area 28 km south of the smelter. Although the population of C. glareolus has previously been cyclic at the moderately polluted area, we were unable to demonstrate any regular cycle. The most likely explanation for the low number of microtine rodents in the damaged and moderately polluted areas in a decrease in the quantity of important food plants: epiphytic lichens for C. glareolus and possibly C. rutilus, mosses for L. lemmus and seed plants, especially Vaccinium myrtillus, for C. rufocanus. Close to the smelter, direct toxic effects of heavy metals may also reduce population densities. The results show that pollutants may change the relative proportions of microtine species.     

The reproductive potential of the bank vole (Clethrionomys glareolus Schreb) and of the tundra vole (Microtus oeconomus Pall.) under the conditions of the elevated radiation background of Bryansk Province]

The continuous irradiation (connected with the accident on the Chernobyl atomic power plant) by cesium-137 of the dominant species of rodents (Clethrionomys glareolus, Microtus oeconomus) in the forests of Bryansk Province had a deteriorating effect on the state of reproductive organs and on the course of embryogenesis, stimulated the reproduction cycle but inhibited the rate of sexual maturation and increased the death-rate of young animals. These effects resulted in significant ageing of the population. But all these phenomena provoked by radiation are within the limits of rodents adaptive capacities.     

Developmental instability of the organism as a result of pessimization of environment under anthropogenic transformation of natural landscapes

The value of fluctuating asymmetry is considered to be an indicator of the developmental instability of the organism. The consequences of activities of the mining industry facilities, which are characterized by alienation and transformation of large areas of natural landscapes, are analyzed as an anthropogenic factor. The objects of study were small mammals (northern red-backed (Clethrionomys rutilus) and gray red-backed (Clethrionomys rufocanus) voles, tundra vole (Microtus oeconomus), Laxmann’s (Sorex caecutiens) and tundra (S. tundrensis) shrews) and trees (Japanese white birch (Betula platyphylla), Betula divaricate, Betula exilis, Duschekia fruticosa, and busket willow (Salix viminalis)). In total, 3500 skulls and approximately 30000 leaves collected in the taiga zone of Yakutia were studied. The index of fluctuating asymmetry, as well as population parameters and composition of small mammal communities, were analyzed. The data on the value of the fluctuating asymmetry in the studied species in natural habitats are given. It is shown that, in natural conditions, this parameter can rise with deterioration in living conditions, particularly at the ecological periphery of the range. Anthropogenic transformation of natural landscapes creates an “anthropogenic periphery” and causes changes similar to the adaptive responses at the northern limit of the distribution of species. It was found that, through pollution and disruption of ecosystems, the mining industry affects all levels of organization of the living matter, but the population and cenotic parameters give an unambiguous response only at macroanthropogenic transformations. Increase in the level of fluctuating asymmetry is the most sensitive indicator of anthropogenic impact and it should also be taken into account that disruptions in the developmental stability of an organism reflect the destructive processes occurring in the population and community.     

Mechanical advantage of area of origin for the external pterygoid muscle in two murid rodents, Apodemus speciosus and Clethrionomys rufocanus

The actions of masticatory muscles in relation to transverse grinding, associated with forward masticatory movement of the mandible, were investigated by using a mechanical model in the two murid rodents, the Japanese field mouse (Apodemus speciosus: subfamily Murinae) and the gray red-backed vole (Clethrionomys rufocanus: subfamily Arvicolinae). Furthermore, statics of the masticatory system on a sagittal plane while chewing is taking place were also analyzed in these rodents. The inward grinding movements of hemimandibles are generated by the posterior temporalis and internal and external pterygoids in both species. In addition to these muscles, the anterior temporalis also moves the hemimandibles lingually in Apodemus speciosus. The area of origin of the external pterygoid seems more advantageous for transverse grinding in A. speciosus than in Clethrionomys rufocanus. On the basis of the static analysis, the anterodorsal area of origin of the external pterygoid to the upper second and third molars in Clethrionomys rufocanus appears to be an adaptive character to prevent the jaw joints from dislocation during occlusion at a posterior point on the elongated row of cheek teeth.     

A study of the internal parasites of small rodents from woodland areas in Surrey

The occurrence of helminth parasites and leptospires from the Long-tailed field mouse, Apodemus sylvaticus , the Bank vole, Clethrionomys giareolus and the Short-tailed vole, Microtus agrestis has been studied from four woodland areas in Surrey. The composition of the helminth fauna of these rodents, particularly A. sylvaticus and C. giareolus , differs from that of previous studies carried out in the British Isles in consisting largely of cestodes and fewer species of digeneans and nematodes. On the other hand the degree of infection of the rodents with nematodes as in the case of A. sylvaticus infected with the trichostrongylid Nematospiroides dubius and theoxyurid Syphacia stroma and of C. giareolus with thecap-illarid Capillaria muris sylvatici is greater than the cestode and digenean infections and is probably linked with the monoxenous nature of the nematode life cycles.
Differences in the number, incidence and degree of infection of mice and voles with species of helminths is undoubtedly linked with differences in the feeding habits of the respective hosts but the present study has also confirmed that infection levels in both leptospires and helminths are influenced by the age/sex relationships of the host together with season and habitat. The relationship between the distribution of rodents infected with leptospires and some helminths suggests similarities in the mode of their transmission.     

The use of arboreal runways by the woodland rodents, Apodemus sylvaticus (L.), A. flavicollis (Melchior) and Clethrionomys glareolus (Schreber)

The use of arboreal runways by the rodents, Apodemus sylvaticus, A. flavicollis and Clethrionomys glareolus , was investigated in the deciduous woodland of Woodchester Park, Gloucestershire, England. Longworth live traps were tied to horizontal and inclining branches of trees and shrubs up to 3 m. Arboreality was extensive in all three species, although less in C. glareolus than in either Apodemus species. There was no indication that A. flavicollis consistently used arboreal runways more than A. sylvaticus but the data suggest that the peak of arboreal activity of these congeners occurred in different seasons. In A. sylvaticus , males were more arboreal than females and adults were more arboreal than juveniles. In, 4. flavicollis , juveniles were trapped significantly more often on arboreal runways than adults. The reasons for, and the consequences of, arboreality in small rodents are discussed.     

Optimal diet models and rodent food consumption

Generalizations derived from simple optimal diet models were field-tested at forest feeding stations where a choice of two foods was offered. The relationship between food availability and consumption by three species of rodents (Peromyscus maniculatus, Clethrionomys gapperi and Napaeozapus insignis) was examined in five separate experiments. In all five cases rodents preferred the food which yielded the highest caloric gain per unit handling time, as predicted by the simple models. However, in all five cases, less preferred items were sampled even when they were not part of the optimal diet. In three cases the consumption of the non-preferred food type varied with its abundance and in one case food preference changed with its availability. The latter three results indicate that these rodents do not use simple optimal diet strategies.     

Preliminary molecular characterization of Cryptosporidium parvum isolates of wildlife rodents from Poland

Isolates of Cryptosporidium were collected from 3 species of woodland and field rodents (Clethrionomys glareolus, Microtus arvalis, and Apodemus flavicollis) and were characterized by polymerase chain reaction amplification and sequencing of fragments of the oocyst wall protein (COWP) gene and of the 18S ribosomal RNA gene. Sequence analysis of these markers revealed that the animals were infected with C. parvum, and that the genotype involved was almost identical to the mouse genotype previously described from Mus musculus. Thus, small rodents should be considered as an important reservoir of C. parvum genotypes closely related to the zoonotic genotype 2 and potentially hazardous to humans.     

Responses of small mammals to Red fox (Vulpes vulpes) odour

This paper describes the responses of three species of rodents (Apodemus sylvaticus, Microtus agrestis and Clethrionomys glareolus) and a shrew (Sore.x araneus) to traps tainted with the faecal odour of a predator, the Red fox. The rodents generally avoided traps bearing fox odour, but readily entered traps marked with rodent odour, whereas shrews entered all traps equally. Among the rodents, avoidance of fox odour was strongest in male A. sylvaticus and C. glareolus and least in M. agrestis and female A. sylvaticus . Fox droppings were found principally along paths and in open habitats where, of the rodents mentioned, they were most likely to be encountered by A. sylvaticus . It was suggested that avoidance of fox faecal and urinary odours in this species, especially by the active males, would reduce the time spent in areas frequented by foxes, and hence reduce the chance of encountering the predator itself. In contrast, M. agresis would seldom encounter fox droppings in its sub-surface runways, so avoidance of fox faecal odour would do little to reduce its chance of encountering the predator. Avoidance by the rodents of the faecal odour of badger, a predator not present in the study areas, was only slightly less marked than their avoidance of fox faecal odour. It was postulated that similar chemicals eliciting avoidance in rodents may commonly occur in the faeces and urine of carnivores.     

Ecological characterization of murine gammaherpesvirus 68 and it’s epidemiological implications

Murine gammaherpesvirus 68 (MHV-68) is a natural pathogen of free-living murid rodents, isolated from a bank vole (Clethrionomys glareolus) in Slovakia. It belongs to the family Herpesviridae, the genus Rhadinovirus, the species Murid herpesvirus 4. Neutralizing serum MHV-68 antibodies were found in animals of other species living with infected rodents in the same biotope (fallow deer, wild boars, deer, sheep, foxes, and mouflons) as well as in humans (laboratory personnel working with MHV-68 or wild rodents, hunters, general population). In this study, the shedding of MHV-68 in the nature was investigated on the model of laboratory mice experimentally infected with the virus. The virus was first detected in breast milk and lactic glands at day 4, in urine and salivary glands at day 9, and in saliva and tear glands at day 14 p.i. Out of intranasal, peroral, intramuscular, intraperitoneal, and subcutaneous routes of infection the first two proved most effective.     

Genetic and morphological heterogeneity in small rodent whipworms in southwestern Europe: characterization of Trichuris muris and description of Trichuris arvicolae n. sp. (Nematoda: Trichuridae)

Genetic and morphological variability of whipworms Trichuris Roederer, 1761 (Nematoda: Trichuridae), parasites of small rodents in southwestern Europe, was studied. Isozyme patterns of natural populations of nematodes parasitizing rodent species of the Muridae (Apodemus sylvaticus, Apodemus flavicollis, Mus musculus) and Arvicolidae (Clethrionomys glareolus, Microtus agrestis, Microtus arvalis) were analyzed at 6 putative loci. Two diagnostic loci were found in T. muris from Muridae and from Arvicolidae. Thus, the existence of 2 species of Trichuris restricted to different host families was indicated. They included Trichuris muris Schrank, 1788, originally described as being from mice, and Trichuris arvicolae n. sp., parasitizing the above species of Arvicolidae. The morphological variability of both species was compared. Although ranges of all morphological characters of the new species overlapped with those of T. muris, stepwise discriminant analysis yielded a 100% accurate classification of females when using vagina length and egg size. Males of T. muris and T. arvicolae cannot be separated entirely. A set of 6 variables yielded 95.7% discrimination; the most discriminating variables were spicule size and body width.     

High Frequency Responsiveness in Rodents at the Level of the Inferior Colliculus

PREVIOUS work on the cochlear microphonic (CM) response of three species of rodents showed a second peak of sensitivity coinciding in frequency with the ultrasound emitted in each species¹. It was indicated that the microphonic response did not necessarily represent hearing, but Sewell's² finding that Apodemus can hear the ultrasonic cries of its young makes an investigation into the neural response to ultrasound seem necessary. The gross inferior collicular (IC) response of the same three species, Apodemus sylvaticus Linnaeus, Clethrionomys glareolus Schreber and Meriones shawi Rozet, has now been studied together with the CM response of the same individuals.     

Summer grazing by voles and lemmings upon subarctic snow-bed and tall herb meadow vegetation – an enclosure experiment

Ther hypothesis of the exploitation of ecosystems predicts that plant communities in productive habitats should experience a low grazing pressure, while communities in less productive habitats should be structured by intense grazing. Thus, if a high population density of rodents was to be established in these communities and they could graze without predation, the plant community in the productive habitat should be more affected than the community in the less productive habitat. This was tested by building enclosures for grey-sided voles Clethrionomys rufocanus and lemmings Lemmus lemmus in a productive tall herb meadow and a less productive snow-bed on Finnmarksvidda, northern Norway. The simulated rodent population densities varied from 150 to 750 ind. ha^-1, and the rodents were allowed to graze for 18 to 55 d. The shoot mortality of relatively abundant plant species were monitored together with plant community structure, and the above-ground biomass were harvested at the end of the experiment. The shoot mortality were generally low, the significantly grazed species were either known preferred species or species with a grazing-sensitive morphology. The community structure did not show any major changes. The aboveground biomass of woody plants was significantly lower in the enclosures on the snow-bed, but not in the tall herb meadow. The total biomass did not differ significantly. These results are somewhat ambiguous with reference to the predictions from the food chain hypothesis, and the conclusion were drawn that intense grazing by voles and lemmings during 18 to 55 d during the growing season does not seem to be sufficient to greatly influence shoot mortality and structure of the studied plant communities.     

Detection of the larva of Taenia multilocularis in 2 voles (Microtus arvalis and Clethrionomys glareolus) in a focus of alveolar echinococcosis in the Massif Central (France)

Small wild rodents were collected and examined during 1983-1984 to investigate parasite-host relationships of Echinococcus multilocularis in one habitat suitable for red foxes of Auvergne (France). The natural infestation of the liver of two different voles, Microtus arvalis and Clethrionomys glareolus, by the larval stage of the cestode is recorded for the first time. In the both cases, the larvae were fully developed and numerous protoscolices were present with some calcareous corpuscules; the expansion of the larvae involved several hepatic lobes in Microtus and was restricted to a single lobe in Clethrionomys. Epidemiological consequences of the receptivity of the two hosts are not yet investigated in the field. However several species of voles inhabiting the same endemic area and which are receptive to the larval stage of alveolar echinococcosis should be a favourable factor of durability for the cestodiasis of the foxes; so the parasite is able of surviving the cyclic and considerable but not simultaneous fluctuations of the three populations of voles which are locally implicated in the zoonosis: M. arvalis, C. glareolus and Arvicola terrestris, by changing from one species to the others.