Japanese Field Vole Microtus Montebelli Research Articles

Unique population dynamics of Japanese field vole: Winter breeding and summer population decline

AbstractIt is common knowledge that winter temperatures influence the life history of small mammals. Cold temperatures necessitate increased energy requirements for survival, and recent studies indicate that snow cover can have both negative and positive influences. With each new observation, we develop a more comprehensive understanding of the mechanisms that influence small mammal populations. Here we report on our recent study on Japanese field vole Microtus montebelli, which reaches its peak in population during the early spring and its low during the autumn. To understand the population dynamics of these voles, we conducted a capture‐mark‐recapture survey, then estimated the seasonal abundance, recruit, capture probabilities, and survival probabilities using the Bayesian hierarchical model. We also analyzed the impact of mammalian generalist predator visits on the survival probabilities. Our data indicates that the early spring peak in population is due to intensive winter breeding and the highest survival probabilities during the periods of deep snow cover. When snow cover reaches a certain depth, the circumstances can combine to raise survival probability and favor breeding. During the breeding season in May and June, on the contrary, the survival probability reached its lowest, resulting in a decrease in population despite breeding. The low survival probability between spring and autumn could be attributed to the impact of generalist predators, and low vegetation may have amplified the effect. In summary, the deep snow cover and generalist predators were considered to be the key factors shaping this unique population dynamics in this orchard area.

Complete mitochondrial genome of the Japanese field vole microtus montebelli (Milne-Edwards, 1872) (Rodentia: Arvicolinae)

The complete mitochondrial DNA sequence of the Japanese field vole Microtus montebelli was determined using Illumina MiSeq platform. The assembled genome was 16,307 bp in length and contained 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes. According to phylogenetic analysis of 13 protein-coding genes, M. montebelli and other Microtus species consist of paraphyletic clades and M. montebelli is most closely related to M. kikuchii, a species endemic to Taiwan.

Effectiveness of vole control by owls in apple orchards

Abstract Biological pest control is gaining greater acceptance as an important part of integrated pest management for sustainable agriculture. However, knowledge regarding biological control of rodent pests is limited, and its effectiveness in temperate areas has not been quantified. In traditional Japanese apple orchards, the Ural owl Strix uralensis breeds in tree hollows and preys on the Japanese field vole Microtus montebelli, a native pest species that can harm fruit production. In this study, we hypothesised that the Ural owl, a generalist predator, can act as a biological control agent by reducing vole densities in temperate orchards. To quantify the pest control effects of breeding Ural owls, we first analysed the diet of individual owls nesting in apple tree hollows. Second, we installed nest boxes in orchards to attract breeding owl pairs and collected data on vole population changes around owl nests to compare with control areas. The population changes were analysed using a generalised linear mixed model to assess the effect of breeding owls within their breeding territory. The model considered seasonal fluctuations in vole population size as well as surrounding land‐use. We also examined vole populations around the owl nests in April, and the distance between nests and forested areas, to determine if these variables influenced nest site selection. Voles were the primary prey of Ural owls breeding in orchards and the owls reduced vole populations within their estimated breeding territories by 63% (±SE: 53%–70%) compared with the predicted density without owls. Owls preferred to nest in orchards with higher vole population densities in April. Our findings also indicate that higher occupancy rates are possible by distributing nest boxes based on Ural owl breeding territory size (306 m radius circle in our study). Synthesis and applications. As breeding Ural owls provide significant pest control effects within their breeding territories, the reintroduction of breeding Ural owl pairs within orchards would contribute to rodent pest control. Promoting the reproduction of native raptors in agricultural areas can be an option for developing integrated pest management while simultaneously maintaining regional biodiversity.

Effects of a soft diet and hypothyroidism on the oxidative capacity of the masseter muscle fibers of the young Japanese field vole Microtus montebelli.

Effects of a soft diet (reduction in mastication activity: an exogenous factor) and hypothyroidism (endogenous factors) on the oxidative capacity of the masseter muscles in the young Japanese field vole Microtus montebelli, consisting only of fast-twitch oxidative (FO) fibers in the adult vole, was investigated histochemically and electron microscopically. Oxidative enzyme activity and mitochondrial development in the muscle fibers were not affected by a soft diet, while they were suppressed by doses of propylthiouracil (PTU) (hypothyroidism). Thus, it was suggested that acquisition of the sustained contraction ability in the masseter muscles of the young vole is induced by the endogenous factors rather than the exogenous factor.

Postnatal development of the masseter muscles in the Japanese field vole Microtus montebelli, with special attention to differentiation of the fast-twitch oxidative fiber.

Postnatal development and differentiation of the masseter muscles consisting only of fast-twitch oxidative (FO) fibers in the adult Japanese field vole Microtus montebelli were studied using histochemical and electron microscopic techniques. The masseter muscles were composed of myotubes and muscle fibers at day 0 (birth day). Most muscle cells showed the strong reaction for myosin ATPase after both alkaline and acid preincubations. For NADH-dehydrogenase (NADH-DH), small granular diformazan deposits were recognized in the sarcoplasm. Afterwards, the masseter muscles consisted of myofibers and satellite cells at day 5. For myosin ATPase, weakly-reactive fibers after acid preincubation (fast-twitch fibers) increased in number. For NADH-DH, granular diformazan deposits in all the myofibers increased in size. Since all the myofibers had numerous sarcoplasmic reticula, and they reacted strongly after alkaline preincubation and weakly after acid preincubation for myosin ATPase at day 10 when the young start to take solid food, it seems that the masseter muscles become contractive fast. At day 15 (before weaning), all the myofibers showed the adult-like strong reaction for NADH-DH and had numerous well-developed mitochondria, thus they acquired the ability of the fast and sustained contraction. It is accordingly considered that the masseter muscles of the vole mature in a short time after birth because of adaptation for herbivorous food habit.

Histochemical and Electron Microscopic Properties of the Masseter Muscle in the Japanese Field Vole Microtus montebelli

The masseter muscles of the Japanese field vole Microtus montebelli were studied histochemically and electron microscopically. The masseter muscles were composed of only fast-twitch oxidative (FO) fibers. As to ultrastructural features of the fibers, mitochondria, sarcoplasmic reticula and transverse tubules were well developed. It is concluded that the masseter muscles in M. montebelli have the structural characteristics that they can contract fast and enduringly. Thus, they appear to be highly adapted to herbivorous food habit.

Spatial segregation between the Japanese field vole Microtus montebelli and the Japanese wood mouse Apodemus speciosus on the Naka River flood plain, northern Kanto.

Spatial segregation between the Japanese field vole Microtus montebelli and the Japanese wood mouse Apodemus speciosus on the Naka River flood plain, northern Kanto.

Size and overlap of home range in a high density population of the Japanese Field vole Microtus montebelli

Relationships of size and overlap of home range with the population density in a flood plain population of Microtus montebelli (Milne-Edwards, 1872) with high density were examined from April to December 1993 using mark-recapture method. Population density in the study area was reached 280 males/ha nad 236 females/ha in summer. Although reproductively active voles were present throughout this study, more than half of females underwent reproductively resting period in summer. Main breeding seasons were spring and autumn when the density was relatively low. While the home range size of adult males did not decrease in summer when the population density was higher than in spring or autumn. In summer, males showed significantly larger degree of home range overlap than in spring or autumn, while home ranges of females overlapped little throughout this study. These results differed from those of the previous studies on this species, possibly due to much higher density in mountainous populations.

<b>Distribution of nerve growth factor activity in submandibular and prostate glands of various </b><b>mammals </b>

Nerve growth factor (NGF) activity is newly found in the submandibular gland of Horsfield’s shrew Crocidura horsfieldi, Japanese field vole Microtus montebelli and field mouse Mus caroli, and in the prostate gland of Crocidura horsfieldi, big-clawed shrew Sorex unguiculatus and Mus caroli. The total and specific activities of these NGFs are reported. Further, regularity and irregularity of the NGF distribution among the mammalian submandibular and prostate glands are discussed from the comparative morphological point of view.