Apodemus Speciosus Research Articles

Walnut foraging and hoarding behaviors by squirrels (Sciurus vulgaris orientis) and wood mice (Apodemus speciosus)

Walnut foraging and hoarding behaviors by squirrels (Sciurus vulgaris orientis) and wood mice (Apodemus speciosus)

CLIMATE CHANGE AND SIZE EVOLUTION IN AN ISLAND RODENT SPECIES: NEW PERSPECTIVES ON THE ISLAND RULE

As stated by the island rule, small mammals evolve toward gigantism on islands. In addition they are known to evolve faster than their mainland counterparts. Body size in island mammals may also be influenced by geographical climatic gradients or climatic change through time. We tested the relative effects of climate change and isolation on the size of the Japanese rodent Apodemus speciosus and calculated evolutionary rates of body size change since the last glacial maximum (LGM). Currently A. speciosus populations conform both to Bergmann's rule, with an increase in body size with latitude, and to the island rule, with larger body sizes on small islands. We also found that fossil representatives of A. speciosus are larger than their extant relatives. Our estimated evolutionary rates since the LGM show that body size evolution on the smaller islands has been less than half as rapid as on Honshu, the mainland-type large island of Japan. We conclude that island populations exhibit larger body sizes today not because they have evolved toward gigantism, but because their evolution toward a smaller size, due to climate warming since the LGM, has been decelerated by the island effect. These combined results suggest that evolution in Quaternary island small mammals may not have been as fast as expected by the island effect because of the counteracting effect of climate change during this period.

Negative effects of acorns on the wood mouse Apodemus speciosus

AbstractAntinutritional effects of acorns and tannic acid on the Japanese wood mouse Apodemus speciosus were examined in the laboratory. The first feeding experiment was conducted for 15 days using three types of diet: control diet (laboratory chow for mice), acorns of Quercus serrata (QS), and acorns of Q. mongolica var. grosseserrata (QM), which differ in tannin content (control, tannin free; QS, 2.7% tannic acid equivalent; QM, 8.5%). Six and one of eight mice died in the QM and QS groups, respectively, whereas all mice survived in good health in the control group. Body weight in the QM and QS groups decreased as much as 23.6% and 16.8% in the first 5 days, respectively, whereas that in the control group did not change significantly. Dry matter intake in the QM group was 50.0% and 38.7% less than that in the control and QS, respectively. Apparent dry matter digestibility was not different among the diets, but apparent nitrogen digestibility did differ between the two acorn groups (QM, −17.5%; QS, 12.0%). The logistic regression analyses revealed that the survival of mice was synergistically influenced by both dry matter intake and apparent nitrogen digestibility. In the second experiment, wood mice fed the tannin‐free formula diet, which is nutritionally matched to QS and QM acorns except for the tannin, did not suffer antinutritional effects, whereas mice fed the tannin‐supplemented formula diets suffered body weight loss and negative nitrogen digestibility. These results indicate that the tannins in acorns could cause serious damage to the wood mouse, which may rely on acorns as a usual diet. Plausible hypotheses explaining how the wood mice could overcome the deleterious effects of the acorns are discussed.

愛媛県で越冬したトラフズクのペリットから見つかった餌動物

Sixty seven pellets of Long-eared Owls, Asio otus, were collected in a village, Ehime Prefecture, during 19February 2001to 6 April 2001. The bones of 164 Mus musculus, ten Micromys minutus, two Apodemus speciosus, two Rattus sp., seventeen Pipistrellus abramus, two Myotis macrodactylus, twelve Crocidura dsinezumi and a bird were found in the pellets. M. minutus, P. abramus, M. macrodactylus and C. dsinezumi were new records in diet of the Long-eared owls.

Distribution of Apodemus speciosus and Mogera wogura on islands in the inland sea

Distribution of Apodemus speciosus and Mogera wogura on islands in the inland sea

Survey on wild rodents for endoparasites in Iwate Prefecture, Japan.

Wild rodents (58 Apodemus speciosus, 29 A. argenteus and 7 Microtus montebelli) were surveyed for endoparasites in Iwate Prefecture, Japan, from October to December 1995 and from April to October 1996. Two trematodes (Echinostoma macrorchis, Plagiorchis muris), 4 or more cestodes (Hymenolepis diminuta, Raillietina coreensis, Cladothyridium spp., Cysticercus fasciolaris), 12 nematodes (Carolinensis minutus, Eucoleus sp., Heligmosomoides kurilensis, H. protobullosus, H. speciosus, Heterakis spumosa, Rhabditis (Pelodera) orbitalis, Rictularia cristata, Syphacia emileromani, S. frederici, S. montana, Trichuris sp.) and 3 protozoans (Giardia sp., Trichomonas sp., Trypanosoma sp.) were identified. The two species of Apodemus were similar to each other, but they were extremely different from M. montebelli in parasite fauna.

Hoarding of acorns by granivorous mice and its role in the population processes of Pasania edulis (Makino) Makino

In order to evaluate the role of granivorous mice, Apodemus speciosus Temminck and Apodemus argenteus Temminck, in the regeneration of Pasania edulis (Makino) Makino, an evergreen tree, we conducted field studies examining acorn crops, the population dynamics and hoarding behavior of mice and pre‐ and postdispersal acorn predation in an evergreen broad‐leaved forest dominated by P. edulis in Kagoshima, southern Japan. The study was conducted from 1994 to 2000. Apodemus mice selected sound acorns and hoarded them in the soil after transporting them for distances ranging from 5.4 to 19.9 m. This behavior appeared to be beneficial to the establishment of seedlings of P. edulis. However, the positive effects were negated by a high rate of recovery of the acorns hoarded by the mice. A life‐table analysis of five cohorts of P. edulis indicated that postdispersal predation of acorns by Apodemus mice was a major contributor to annual variation in the number of new seedlings. A considerable number of acorns germinated only in years with a good acorn crop and a low level of resident mice. These results suggest that Apodemus mice are serious acorn predators rather than important dispersers. After germination, acorns were attacked by the acorn borer at a high rate. From these results, we can conclude that acorn production probably makes a smaller contribution to the regeneration of P. edulis than coppice shoot production at the study site.

Effect of rodents on acorn dispersal and survival of the Liaodong oak ( Quercus liaotungensis Koidz.)

We used a new method of labeling seeds with small pieces of coded tin-tags to investigate the effect of rodent on the seed fate of Liaodong oak ( Quercus liaotungensis) in a mountainous area (40°00′N, 115°30′E) of Beijing, China. In the fall of 1999 and 2000, a total of 1994 and 660 acorns were released and then seed loss was checked. Both sides of the 50 m wide transect were extensively checked to locate the tagged seeds or their fragments. The results indicated that Apodemus speciosus, Rattus confucianus and A. agrarius were potential Liaodong oak acorn predators. Nearly all acorns were consumed by small rodents within 10 days after acorn placement, demonstrating that seed predation was very heavy and that rodent predation contributes to the poor seed regeneration of the oak. The dispersal distances of most seeds were within 20 m. The dispersal distance of the buried seeds was the longest and it was in favor of seed survival and seedling recruitment. Rodents preferred to eat tagged seeds under dense shrub. This is mostly related to predation risk in different micro-environments. Rodents tended to bury the tagged seeds under dense shrub. This burial place of rodent does not favor the seedling recruitment of the oak. The rodents preferred to move seeds to the horizontal and down directions of a slope and this tendency would save energy for rodents. The seeding regeneration rate of tagged acorns were very low in 2 years. Rodent predation is the causative factor of low regeneration of Liaodong oak in the study region.

The specialist seed predator Bruchidius dorsalis (Coleoptera: Bruchidae) plays a crucial role in the seed germination of its host plant, Gleditsia japonica (Leguminosae)

Summary This paper describes the germination mechanism of hard seeds of a species of honey locust, Gleditsia japonica, which can germinate only when externally damaged, in relation to four germinating factors: feeding damage by two specialist seed predators, a bean weevil (Bruchidius dorsalis) and a cydid bug (Adrisa magna); feeding damage by a generalist seed predator, a wild mouse (Apodemus speciosus); and physical damage. In laboratory experiments, both the bean weevil and physical damage facilitated germination, while damage by the cydid bug and wild mouse did not. In contrast to laboratory findings, field censuses of G. japonica seed survival revealed that more than 99% were damaged either by B. dorsalis or A. magna. Therefore, less than 0·5% of the seeds remained intact, preventing formation of a seed bank. In addition, all germinating seeds found in the field contained B. dorsalis larvae. These results strongly suggest that damage by B. dorsalis is a prerequisite for G. japonica germination, in contrast to the conventional view that physical disturbance, possibly flooding, is the primary germinating factor for hard seeds.

Impact of site‐induced mouse caching and transport behaviour on regeneration in Castanea crenata

Abstract. Dispersal and retrieval site selection by mice, transport distance, cache depth, and emergence and survival of seedlings of Castanea crenata (Japanese chestnut) were investigated by a magnet‐locating experiment in two habitat conditions (gap vs. forest understorey). Magnets were inserted into nuts (n= 450) and the nuts placed in the edge of forest gaps. Although wood mice (Apodemus speciosus and A. argenteus) initially buried nuts singly in shallow surface caches near the nut source, by the following spring these cached nuts were retrieved and re‐cached in larger, deeper caches farther from the source, particularly in forest understories, probably to reduce the threat of pilferage. All the nuts cached in the forest understories were consumed, but 4 seedlings emerged in gaps, apparently because of lower foraging activity in the gaps by the mice. Seed size was not correlated with cache depth or cache site selection. With increasing seed size, transport distance increased, particularly in gaps, possibly due to a greater potential energy gain (relative to handling cost to the cacher), or to attempts to prevent density‐ or mass‐dependent loss of caches by other foragers. Variable seed dispersal behaviour based on variation in seed size may influence the chances of colonization and distribution of the light‐demanding Castanea trees in mosaic landscapes and may play an important role in community organization and dynamics.

Changes in Foraging Behavior of Two Species of Field Mice, Apodemus speciosus Temminck and A. argenteus Temminck (Rodentia: Muridae), in the Response to Artificial Illumination

Predation hazard is one of the most important factors that affect foraging behavior. Light intensity is an indirect measure of a predation hazard for nocturnal rodents. In 1988 and 1989, I conducted laboratory experiments to reveal the effects of the predation hazard on foraging behavior of two species of field mice, Apodemus speciosus Temminck and A. argenteus Temminck (Rodentia: Muridae), which co-exist in many areas in Japan. I released a mouse into the experimental arena, where I set one nest box and two food stations (one near and the other far from the nest box), and recorded the foraging behavior for six A. speciosus and six A. argenteus mice. I planned to illuminate the experimental arena when the mouse left the nest box to mimic a predation hazard during excursion. The light treatment decreased the time the mouse spend outside the nest box, the duration of an excursion, the number of visits to the food station far from the nest box, and the number of peanuts handled at the food station far away. Mice handled food more intensely at the food station near to the nest box and tended to carry more foods back to the nest box and eat them there during the light treatment period than the control period. These behavioral changes, which seemed to be adaptive to avoid the predation hazard in the field, were more apparent in smaller mice, A. argenteus, than larger mice, A. speciosus.

Ecological network map of Sciurus lis and Apodemus speciosus as indicators of forest habitats

Ecological network map of Sciurus lis and Apodemus speciosus as indicators of forest habitats

Impact of site-induced mouse caching and transport behaviour on regeneration in Castanea crenata

Abstract Dispersal and retrieval site selection by mice, transport distance, cache depth, and emergence and survival of seedlings of Castanea crenata (Japanese chestnut) were investigated by a magnet-locating experiment in two habitat conditions (gap vs. forest understorey). Magnets were inserted into nuts (n = 450) and the nuts placed in the edge of forest gaps. Although wood mice (Apodemus speciosus and A. argenteus) initially buried nuts singly in shallow surface caches near the nut source, by the following spring these cached nuts were retrieved and re-cached in larger, deeper caches farther from the source, particularly in forest understories, probably to reduce the threat of pilferage. All the nuts cached in the forest understories were consumed, but 4 seedlings emerged in gaps, apparently because of lower foraging activity in the gaps by the mice. Seed size was not correlated with cache depth or cache site selection. With increasing seed size, transport distance increased, particularly in gaps, pos...

Complex structure of B-chromosomes in two mammalian species: Apodemus peninsulae (Rodentia) and Nyctereutes procyonoides (Carnivora).

B-chromosomes (Bs) of two mammalian species, raccoon dog (Nyctereutesprocyonoides, Carnivora) and Asian wood mouse (Apodemus peninsulae, Rodentia) were investigated using chromosome segment microdissection and double-colour FISH. In the raccoon dog, all B-chromosomes showed homology with each other but not with the A-chromosomes. Two segment-specific probes (from proximal and distal parts of B) have been localized in corresponding chromosome parts, with significant variation in their sizes. In Asian wood mice, two types of B-specific chromatin were revealed--B1 and B2. Most Bs were either B1 or B2 specific; furthermore, some Bs were found to be composed of both types of chromatin. B-chromosome-specific libraries of A. peninsulae contain sequences homologous to the heterochromatic regions of sex and some A-chromosomes and dispersed repeated sequences. B1-specific probes gave signals on sex chromosomes of Apodemus speciosus and Apodemus agrarius. The origin and evolution of B-chromosomes in mammals are discussed.

Detection of Babesia microti-like parasite in filter paper-absorbed blood of wild rodents.

The first case of human babesiosis was reported in Japan. The epidemiology of this disease in Japanese nature remains unclear. In this study, 97 common field mice captured in Hokkaido, Japan, were examined. Blood specimens absorbed onto filter papers were eluted and tested by nested PCR using specific primers for the B. microti nuclear small subunit rRNA genome. Twenty-three percent (11/47) of Apodemus speciosus and four percent (2/50) of Clethrionomys rufocanus were positive. The 159-bp primary sequences of PCR products tested exhibited 97.5% and 96.8% homology with those of the human isolate in Japan and of U.S. strains of B. microti, respectively.

Human babesiosis in Japan: epizootiologic survey of rodent reservoir and isolation of new type of Babesia microti-like parasite.

We have carried out epizootiologic surveys at various sites in Japan to investigate wild animals that serve as reservoirs for the agents of human babesiosis in the country. Small mammals comprising six species, Apodemus speciosus, Apodemus argenteus, Clethrionomys rufocanus, Eothenomys smithii, Crocidura dsinezumi, and Sorex unguiculatus, were trapped at various places, including Hokkaido, Chiba, Shiga, Hyogo, Shimane, and Tokushima Prefectures. Animals harboring Babesia microti-like parasites were detected in all six prefectures. Inoculation of their blood samples into hamsters gave rise to a total of 20 parasite isolates; 19 were from A. speciosus, and the other 1 was from C. rufocanus. Sequencing of the parasite small-subunit rRNA gene (rDNA) sequence revealed that 2 of the 20 isolates were classified as Kobe type because their rDNAs were identical to that of the Kobe strain (the strain from the Japanese index case). The other 18 isolates were classified as a new type, designated the Hobetsu type, because they all shared an identical rDNA sequence which differed significantly from both that of Kobe-type isolates and that of northeastern United States B. microti (U.S. type). The parasites with Kobe-, Hobetsu- and U.S.-type rDNAs were phylogenetically closely related to each other but clearly different from each other antigenically. The isolates from rodents were demonstrated to be infective for human erythrocytes by inoculation into SCID mice whose erythrocytes had been replaced with human erythrocytes. The results suggest that a new type of B. microti-like parasite, namely, the Hobetsu type, is the major one which is prevalent among Japanese wild rodents, that A. speciosus serves as a major reservoir for both Kobe- and Hobetsu-type B. microti-like parasites, and that C. rufocanus may also be an additional reservoir on Hokkaido Island.

Walnut Hoarding by the Japanese Wood Mouse, Apodemus speciosus Temminck

Walnuts, Juglans ailantifolia Carriere, are large and the shell is difficult to open. Thus, seed predators in Japan are restricted mainly to the Japanese squirrel (Sciurus lis Temminck) and the wood mouse (Apodemus speciosus Temminck), which can shave away the hard shells with their sharp incisors. Previous work indicated that the squirrels are not only predators, but also disperse walnuts. In this study, 95 walnuts in Period1 (September 1996–February 1997) and 80 walnuts in Period 2 (September 1999–February 2000) each attached to a miniature radio transmitter, were placed in a feeding box, and 93 and 53 of them were transported by free-living wood mice in the respective periods. Most of the walnuts provided from September to November were scatter-hoarded in the litter layer, while from December to February, the mice fed immediately and seldom scatter-hoarded on the ground surface. In all, 66 walnuts were hoarded and 80 were eaten soon after discovery, although walnuts were eaten more frequently in Period 1 than in Period 2, which may be related to annual differences in seed crop size in the study site. The mean transport distance of hoarded seeds was 6.2 ± 5.0 m (mean ± SD, n=66). The fate of hoarded walnuts was followed from September 1996 to May 1997; 21 (75%) of the scatter-hoarded walnuts were recovered, but 7 (25%) were left uneaten. Consequently, the Japanese wood mouse also plays a role in seed-dispersion of the walnut, but the transport distance for mice was shorter than that for squirrels.

Human babesiosis in Japan: isolation of Babesia microti-like parasites from an asymptomatic transfusion donor and from a rodent from an area where babesiosis is endemic.

To determine the source of infection for the Japanese index case of human babesiosis, we analyzed blood samples from an asymptomatic individual whose blood had been transfused into the patient. In addition, we surveyed rodents collected from near the donor's residence. Examination by microscopy and PCR failed to detect the parasite in the donor's blood obtained 8 months after the donation of the blood that was transfused. However, we were able to isolate Babesia parasites by inoculating the blood sample into SCID mice whose circulating red blood cells (RBCs) had been replaced with human RBCs. A Babesia parasite capable of propagating in human RBCs was also isolated from a field mouse (Apodemus speciosus) captured near the donor's residential area. Follow-up surveys over a 1-year period revealed that the donor continued to be asymptomatic but had consistently high immunoglobulin G (IgG) titers in serum and low levels of parasitemia which were microscopically undetectable yet which were repeatedly demonstrable by inoculation into animals. The index case patient's sera contained high titers of IgM and, subsequently, rising titers of IgG antibodies, both of which gradually diminished with the disappearance of the parasitemia. Analysis of the parasite's rRNA gene (rDNA) sequence and immunodominant antigens revealed the similarity between donor and patient isolates. The rodent isolate also had an rDNA sequence that was identical to that of the human isolates but that differed slightly from that of the human isolates by Western blot analysis. We conclude that the index case patient acquired infection by transfusion from a donor who became infected in Japan, that parasitemia in an asymptomatic carrier can persist for more than a year, and that A. speciosus serves as a reservoir of an agent of human babesiosis in Japan.

Hoarding behaviors of two wood mouse species: Different preference for acorns of two Fagaceae species

Two species of wood mouse, Apodemus argenteus and A. speciosus, were observed consuming and hoarding acorns of Quercus serrata and Castanopsis cuspidata. When each species of acorn was supplied individually, both species of mice used each species of acorn for eating and hoarding. When both species of acorn were supplied, A. argenteus consumed or hoarded only C. cuspidata, whereas A. speciosus tended to eat C. cuspidata acorns at the feeding site, and disperse or hoard Q. serrata acorns. Apodemus speciosus is unlikely to disperse C. cuspidata acorns (their utilization was biased towards consumption) when Q. serrata acorns are also available. Apodemus argenteus will make almost no contribution to the dispersal of Q. serrata when the two acorn species coexist.

神奈川, 山梨, 静岡, 長野各県および東京都に生息する野生動物の寄生虫調査

From 1997 to 1999, epidemiological surveys of helminths in such wild mammals as foxes and rodents were conducted in Kanagawa, Yamanashi, Shizuoka, and Nagano Prefectures and in Tokyo. Each infected fox harbored two or more of the following helminth species: six species of nematodes (Taxocara canis, Trichuris vulpis, Anclystoma kushimaense, Arthrostoma miyazakiense, Strongyloides planiceps, and Molineus patens); two species of trematodes (Metagonimus takahashii and Concinnum ten); and one species of cestode (Taenia pisiformis). In total, nine different helminths were detected in 25 (78.1%) of 32 animals examined. The crysticerci T. taeniaeformis and T. crassiceps were found in Rattus rattus and in Apodemus speciosus. The pleroceroide of Spirometra erinaceieuropaei was detected for the first time in Urotrichus talpoides, heretofore never considered a host. No Echinococcus adults or larvae, however, were detected in the animals examined.