Microtus Montanus Research Articles

Sciurus aberti and Microtus montanus on Foothills of the Culebra Range in Southern Colorado

Sciurus aberti and Microtus montanus on Foothills of the Culebra Range in Southern Colorado

Experimental Trypanosoma (Nannomonas) congolense infection in Microtus montanus.

Seventy-two voles (Microtus montanus) were infected with a strain of Trypanosoma congolense of low virulence in mice to study their susceptibility and value as a tool for testing chemotherapeutic agents. The infection in Microtus was highly virulent. Parasitaemia was low to moderate. Significant spleen and body weight changes were observed. Blood capillaries of the heart, brain, kidneys and lungs were markedly dilated and numerous parasites were present in the dilatations, particularly in the heart. There was a generalized serous inflammation, often associated with histiocytic interstitial lesions (except in the brain), particularly in the heart. Treatment of voles with diamidines on cumulative mortality day 60% gave a complete cure.

Effects of Environmental Variables on Some Physiological Responses of Microtus montanus under Natural Conditions

Cyclic fluctuations in the population density of microtine rodents have been known since antiquity. However, factors responsible for this phenomenon are not known. The objectives of this long term study are essentially threefold. First, to characterize those environmental variables that might affect Microtus montanus in different seasons of the year. Second, to record the growth, maturation and reproductive activity of the voles under natural conditions. Third, to determine the maturational as well as the seasonal pelage changes of these rodents. The data resulting from the execution of the above objectives would be correlated in an attempt to determine the causes underlying the multiannual fluctuations in the population density of these microtine rodents in Grand Teton National Park.

Increased urinary excretion of aromatic amino acid catabolites by Microtus montanus chronically infected with Trypanosoma brucei gambiense.

Microtus montanus infected with Trypanosoma brucei gambiense for 16 and 21 days excreted significantly greater quantities of several aromatic amino acid catabolites when compared to uninfected control animals. Very large quantities of three aromatic alpha-keto acids (alpha-oxocarboxylic acids), phenylpyruvic acid, 4- hydroxyphenylpyruvic acid and indole-3-pyruvic acid, were excreted by infected animals. Increased excretion of indole-3-lactic acid and indole-3-acetic acid was also detected. Gas chromatographic-mass spectral analysis of the trimethylsilyl derivatives of phenylpyruvic acid, 4- hydroxyphenylpyruvic acid and indole-3-pyruvic acid confirms the identity of the aromatic alpha-keto acids elevated during infection. The marked alpha-keto aciduria indicates that a large disturbance exists in aromatic amino acid metabolism in this chronic animal model of African trypanosomiasis. The disturbance may contribute to the pathogenesis of the disease. The increased catabolite concentrations may also prove to be useful diagnostically and prognostically.

Copulatory behavior of voles (Microtus montanus and M. ochrogaster) in multiple-female test situations.

Copulatory behavior of voles (Microtus montanus and M. ochrogaster) in multiple-female test situations.

Copulatory behavior of voles (Microtus montanus and M. ochrogaster) in multiple-female test situations.

Copulatory behavior of voles (Microtus montanus and M. ochrogaster) in multiple-female test situations.

Life History Strategies of the Montane Vole, Microtus montanus

Emphasis in microtine rodent biology has historically been placed on population regulation and the population cycle. Until recently, little attention has been directed to behavior and sociality in microtine rodents, but work on the sociobiology of the montane vole (Jannett, 1978, 1980, 1981, 1982, 1984) is serving to integrate various aspects of the biology of this species so that its life history characteristics can be interpreted in an evolutionary framework. Work undertaken in 1984 continues previously initiated surveys of various topics, such as synchrony of population events in different populations, survivorship, scent gland development, patterns of cranial and dental variation, population trends in a sympatric species of vole ( M. longicaudus), and reproduction in a primary predator, the shorttail weasel (Mustela erminea). In addition, work in 1984 was initiated with C. Welsh on age variation in the chemical composition of male M. montanus preputial glands.

Factors determining the abundance and distribution of rodents in a shrub-steppe ecosystem: the role of shrubs.

This study addressed the relative importances of shrub "resources" on a rodent community in a sagebrush dominated shrub-steppe ecosystem in southwestern Wyoming. Direct effects of shrubs (i.e., providing rodents with "food and cover") were assessed by removing shrubs from a 1.25 ha study plot and monitoring both rodent populations and their food resources. Shrub architecture and shrub-related food resources were found to be unimportant to deermice (Peromyscus maniculatus), Great Basin pocket mice (Perognathus parvus) northern grasshopper mice (Onychomys leucogaster) and Uinta ground squirrels (Spermophilus armatus), as shrub removal caused no significant changes in population sizes, sex ratios or age structure. Least chipmunks (Eutamias minimus) responded to shrub removal by leaving the plot and moving into adjacent shrubland. The montane vole (Microtus montanus) population showed a slight increase following shrub removal. Shrub removal did not alter the abundance of major rodent food resources on the plot (percent cover of herbaceous vegetation, soil seed reserves and ground-dwelling arthropods). Micrometeorological data suggested that shrubs did not significantly ameliorate a nocturnal rodent's micro-climate, but may have affected diurnal rodents' thermal loading rates by removing shade. While shrub architecture and food resources do not directly affect most of the rodents in this shrub-steppe ecosystem, shrubs may be important to rodents in a long-term time frame. Shrubs provide "safe sites" for germination and growth of herbaceous vegetation, thereby enhancing the diversity of the potential rodent food resources.

Experimental chronic Trypanosoma brucei rhodesiense infection in Microtus montanus.

Adult Microtus montanus were inoculated with a recently isolated strain of Trypanosoma brucei rhodesiense of human origin. The animals developed subacute to chronic infection and low-grade parasitemia. Histopathological examination of the heart revealed a severe pancarditis resulting in pronounced weight loss, and survival times of 5-8 weeks, preventing development of meningoencephalitis. In the brain a moderate meningitis was found, usually associated with moderate numbers of parasites in the choroid plexus and leptomeninges; however, trypanosomes were also found without tissue inflammation. Meningoencephalitis was found after 7 weeks, with parasites in the cerebral parenchyma. Chronic inflammation was present in lungs and kidney, often associated with trypanosomes; in one animal glomerulonephritis was found. Spleen and lymph glands showed a variable degree of lymphoid hyperplasia but no extravascular parasites. In the liver of all animals plasmolymphoid infiltrates were observed in the periportal connective tissue; no extravascular parasites were observed. A variable degree of lymphoplasmohistiocytic infiltrate in the connective tissue and occasional rare trypanosomes were seen in mesenterium, pancreas, epididymis, striated muscle, and skin. Experimental infection in M. montanus appears to be a suitable model for study of the acute trypanosomiasis of T. b. rhodesiense, but not for chronic African sleeping sickness with cerebral involvement.

The relationship of hepatic monooxygenase activity to histological changes observed in Microtus montanus due to the inducers phenobarbital, β-naphthoflavone, and aroclor 1254

the relationship of hepatic monooxygenase activity to histological changes observed in Microtus montanus due to the inducers phenobarbital, β-naphthoflavone, and aroclor 1254

Diel plasma testosterone rhythms in male Microtus montanus, the montane vole, under long and short photoperiods

Diel plasma testosterone rhythms were examined in adult male Microtus montanus, a seasonal breeder which displays nocturnal locomotor activity under long photoperiod and diurnal activity under short photoperiod. Under 16 hr light: 8 hr dark (16L: 8D), plasma testosterone levels peak during the light at 11.8 ng/ml. Under 8L: 16D, plasma testosterone peaks during the dark at 5 ng/ml.

Ecological Characteristics of Small Mammals on a Radioactive Waste Disposal Area in Southeastern Idaho

Species composition, diversity, biomass and densities of small mammal populations were examined in crested wheatgrass (Agropyron cristatum) and Russian thistle (Salsola kali) habitats on a solid radioactive waste disposal area and in native sagebrush (Artemisia tridentala) habitat surrounding the disposal area. The 15-month live-trapping study resulted in the marketing of 2384 individuals representing 10 species of small mammals. The deer mouse (Peromyscus maniculatus) was the most common rodent in both disposal area habitats and the adjacent sagebrush habitat; Ord's kangaroo rat (Dipodomys ordii) was also an abundant rodent in all vegetation types. The montane vole (Microtus montanus) was common only in crested wheatgrass stands on the disposal area. Although the adjacent native sagebrush habitat had the highest species diversity and the Russian thistle habitat on the disposal area had the lowest, the total rodent density was not significantly different among the three vegetation types. Crested wheatgrass within the disposal area contained the largest rodent biomass throughout the study, in part due to an increasing M. montanus population. The peak small mammal biomass of 5000 g/ha in creasted wheatgrass and sagebrush habitats was considerably higher than previously reported for similar habitats. Differences in diversity and biomass between the disposal area andmore » surrounding native habitat are most likely related to differences in soil compaction and vegetation between these two areas.« less

Biphenyl hydroxylation and its induction differ between montane voles and Swiss Webster mice

Hepatic microsomes from female montane voles, Microtus montanus, metabolized biphenyl to 4-hydroxybiphenyl (359 ng/mg microsomal protein/min), 3-hydroxybiphenyl (49 ng/mg/min), and 2-hydroxybiphenyl (29 ng/mg/min). Phenobarbital treatment of the voles (ip) induced in vitro biphenyl hydroxylations by about 324, 865, and 445% for 4-, 3- and 2-hydroxylation, respectively. Comparable studies were made of female, white Swiss Webster mice. The major microsomal metabolite was 4-hydroxybiphenyl (1010 ng/mg/min) but more 2-hydroxybiphenyl (118 ng/mg/min) was formed than 3-hydroxybiphenyl (92 ng/mg/min). Phenobarbital treatment of the mice barely changed biphenyl 2-hydroxylation (−1.3%) but did raise 3- and 4-hydroxylation (55 and 211%, respectively). Treatment of voles with 3-methylcholanthrene raised biphenyl 2-, 3-, and 4-hydroxylation by about 81, 50, and 47%, respectively, whereas in mice the increases were 176, 41, and 31%, respectively. β-Naphthoflavone treatment had similar effects. The vole liver microsomes were dependent upon NADPH for biphenyl hydroxylation. The carbon monoxide difference spectra of reduced cytochrome in the microsomes show a peak at 450.4 nm. This was unchanged by phenobarbital and only slightly shifted (−0.8 nm) by 3-methylcholanthrene or β-naphthoflavone treatment. Voles and mice represent different families of the order Rodentia. The results obtained with voles more closely resemble those reported for hamsters which are in the same family but a different subfamily than voles. Comparative consideration of the taxonomic relations of the rodents, therefore, may be useful in interpreting their comparative toxicology.

Effects of Environmental Variables on Some Physiological Responses of Microtus montanus under Natural Conditions

Cyclic fluctuations in the population density of microtine rodents have been known since antiquity. However, factors responsible for this phenomenon are not known. The objectives of this long term study are essentially threefold. First, to characterize those environmental variables that might affect Microtus montanus in different seasons of the year. Second, to record the growth, maturation and reproductive activity of the voles under natural conditions. Third, to determine the maturational, as well as the seasonal pelage changes of these rodents. The data resulting from the execution of the above objectives would be correlated in an attempt to determine the causes underlying the multi-annual fluctuations in the population density of these microtine rodents in Grand Teton National Park.

Hyperthermic reactions of voles to novel and repetitive psychogenic stimuli

Montane voles (Microtus montanus) respond to brief conspecific encounters with strange voles by adrenergic reactions which result in elevations of their core temperatures by approximately 1.0 degrees C. Elevations of body temperatures and agonistic behaviors decrease in intensity with sequential encounters between the same conspecific challengers but are restored when one of the challengers is replaced by a new "strange" vole. The rates of habituation of agonistic behaviors and of hyperthermic response are a function of the number of encounters permitted, rather than time between encounters. Levels of hyperthermic responses resulting from contact between previously habituated animals are higher than those elicited by non-specific stimuli such as noise or handling. Radiotelemetry of feral animal temperature homeostasis may provide a useful measure of low-frequency social encounters between conspecific voles.

Life History Strategies of the Montane Vole, Microtus montanus

Emphasis in microtine rodent biology has historically been placed on population regulation and the population cycle. Until recently, little attention has been directed to behavior and sociality in microtine rodents, but work on the sociobiology of the montane vole (Jannett., 1978, 1980, 1981, 1982) is serving to integrate various aspects of the biology of this species so that its life history characteristics can be interpreted in an evolutionary framework. Work undertaken in 1983 continues previously initiated surveys of various topics, such as synchrony of population events in different populations, survivorship, scent gland development, patterns of cranial and dental variation, population trends in a sympatric species of vole (M. longicaudus), and reproduction in a primary predator, the shorttail weasel (Mustela erminea). In addition, work in 1983 was initiated on genic substructuring of populations as indicated by electrophoretic analyses of tissues.

CONSPICUOUS ALGAL COLONIZATION OF THE ASH FROM MOUNT ST. HELENS1

ABSTRACTConspicuous growth of green and yellow‐green algae developed in arid steppe communities in eastern Washington on the silt‐sized ash from the 18 May 1980 eruption of Mount St. Helens. In a veneer on the ash, cell numbers per gram dry ash of these aerial immigrants equaled or exceeded the highest reported values for terrestrial chlorophytes (108 cells · g−1 dry soil). Such pronounced growth was restricted largely to three microsites (under the canopy of Artemisia tridentata, along the runways of the vole, Microtus montanus, and surrounding emergent agarics), apparently in response to water‐holding properties of the ash, localized nutrient input and possible reduction of predation by nematodes. Highest algal counts were in Microtus runways where daily water and urea‐N input per adult animal may be 8 mL and 23 mg, respectively. Cyanophytes, commonly considered early colonizers of volcanic ash, were extremely rare. The role of blue‐green algae in succession on volcanic materials may be more restricted geographically than previously recognized.

Photoperiodic induction of diurnal locomotor activity in Microtus montanus, the montane vole

Some microtine species are nocturnal in the summer and diurnal in the winter. This activity shift has been induced in Microtus montanus in the laboratory using photoperiod alone as a cue. The shift from nocturnal to diurnal activity involves modifying the intensity and timing of short activity bouts. This phenomenon may be a mechanism for avoiding harsh microclimates.

Nesting Patterns of Adult Voles, Microtus montanus, in Field Populations

Nesting Patterns of Adult Voles, Microtus montanus, in Field Populations

Female regulation and choice in the copulatory behavior of montane voles (Microtus montanus).

Female regulation and choice in the copulatory behavior of montane voles (Microtus montanus).