Takashi Saitoh

Takashi Saitoh
Hokkaido University | Hokudai · Field Science Center for Northern Biosphere

Doctor of Philosophy

About

169
Publications
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Introduction

Publications

Publications (169)
Article
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The effective gene number (the number of genes that can be inherited) of mitochondrial DNA (mtDNA) is one‐fourth of that of nuclear DNA (ncDNA) in idealized populations. Therefore, mtDNA haplotype diversity (h) is predicted to be lower than ncDNA heterozygosity (HE) because of the higher effect of genetic drift on mtDNA. This prediction has not yet...
Article
Taylor's law (TL) is an empirical rule that describes an approximate relationship between the variance and mean of population density: log10(variance) ≈ log10(a) + b × log10(mean). Population synchrony is another prevailing feature observed in empirical populations. This study investigated the effects of environmental synchrony and density‐dependen...
Article
Full-text available
1).Decadal changes in masting behaviour—directional changes in seed production with fluctuations on a decadal time scale—are attracting widespread attention in the context of global climate change. However, our mechanistic understanding of the effects of climate on seed production on a decadal scale is unsatisfactory, partly because of insufficient...
Article
Taylor's law (TL) is an empirical rule describing the approximate relationship between the variance and the mean of population density: log10(variance) ≈ log10(a) + b × log10(mean). Although TL has been verified in various ecological systems, essential questions remain unanswered. Why is TL so widely observed? What mechanisms or processes generate...
Article
Plant diets of 2 sympatric species of wood mice in Japan (Apodemus argenteus and A. speciosus) were determined by DNA meta-barcoding analyses of feces using the nucleotide sequences of the chloroplast trnL P6 loop intron region as a molecular marker. The 2 species showed a relatively large degree of niche overlap in plant dietary profiles, feeding...
Article
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Transplant and common garden experiments have been used in studies on local adaptation, but are difficult to be conducted for large animals with long life span. A previous study on the southern Japanese islands demonstrated that relative limb lengths of sika deer (Cervus nippon) were short on islands with steep slopes. We hypothesized that this mor...
Article
The assignment test is believed to have the potential to estimate the contemporary rate of immigration and is considered as an alternative to ecological methods (e.g., mark-recapture and radio/GPS tracking). However, the conventional assignment test provides different results from those of the mark-recapture method, when it is applied to population...
Article
Rodent population dynamics are predicted to respond positively to the masting of acorns, but diverging results have been published. This study tested the hypothesis that population responses to acorn masting vary depending on differences in the tolerance to tannins of different rodent species. The effects of acorn abundance on the rodent population...
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Taylor's law (TL) asserts that the variance in a species’ population density is a power-law function of its mean population density: log(variance) = a + b × log(mean). TL is widely verified. We show here that empirical time series of density of the Hokkaido gray-sided vole, Myodes rufocanus, sampled 1962-1992 at 85 locations, satisfied temporal and...
Book
This is the second edition of a reference book about wild mammals in Japan, including both terrestrial and marine species. (I CAN NOT send you a pdf of this book, if requested.)
Article
Full-text available
INTRODUCTION One hundred and one native terrestrial mammalian species, excluding Sirenia, Cetacea, Phocidae, and Otariidae, inhabit or inhabited Japan, and 51.5 % of them are endemic, most being forest dwellers. Four species, the wolf, the Okinawa flying fox, the Bonin Pipistrelle, and the Japanese river otter went extinct during the modern age. Th...
Article
We reconstructed a red fox population through a cohort analysis based on age-specific numbers of culled individuals between 1987 and 2008, a timeframe that covers the pre-mange and mange periods, and analyzed the impact of sarcoptic mange on the fox population in Nemuro, Japan. In the process of the reconstruction, we estimated annual mortality (ca...
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The terrestrial mammalian fauna of the North Japanese island, Hokkaido, is more similar to that of Southern Siberia than to the main island of Japan, Honshu. Three species of the genus Myodes (Muridae, Rodentia) are found on Hokkaido, but not on Honshu. While Myodes rufocanus and M. rutilus are widely distributed across Hokkaido as well as the Eura...
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The genetic structure of gray-sided voles was investigated at a spatial scale of 2 km using mtDNA sequences. The control region (674bp) of 162 voles was sequenced and 18 haplotypes were identified. Within 0.5-ha trapping plots (n = 8), the number of haplotypes and gene diversity was significantly greater in males than in females. The fixation index...
Article
Full-text available
Since the 1980s, the sika deer (Cervus nippon Temminck, 1838) population of Hokkaido, Japan, has grown, resulting in range expansion. To assess the effects of this range expansion on the spatial genetic structure of the population, we compared subpopulation structures during 2 different periods (168 samples for 1991–1996, and 169 samples for 2008–2...
Article
Previous studies on patterns in ungulate size variations have emphasized the effect of a particular environmental factor such as Bergmann's rule and the island rule. However, although multiple environmental factors may influence the body size, these studies focused on a single factor, and various measurements that may be influenced by different env...
Article
Full-text available
Mammalian herbivores adopt various countermeasures against dietary tannins, which are among the most widespread plant secondary metabolites. The large Japanese wood mouse Apodemus speciosus produces proline-rich salivary tannin-binding proteins in response to tannins. Proline-rich proteins (PRPs) react with tannins to form stable complexes that are...
Article
The gray-sided vole, Myodes rufocanus (= Clethrionomys rufocanus) is a widespread species in Hokkaido, Japan. We applied an integrative approach to determine adaptive and neutral genetic variation in the gray-sided vole populations to identify full or partial Evolutionarily Significant Units. We surveyed 38 mainland populations and six island popul...
Article
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Wildlife managers often manipulate hunting regulations to control deer populations. However, few empirical studies have examined the level of hunting effort (hunter-days) required to limit population growth and demographic effects through harvesting of females. Moreover, the relative importance of density effects on population growth has not been q...
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Eighty-four specimens (34 females and 50 males) of the feral mink (Mustela vison) were collected in Hokkaido. It was at first confirmed that the annual layer in a canine was formed from autumn to winter in Hokkaido, and then the age of specimen (n=76) was determined by the annual layer. The proportion of 0⁺ year animals was 63.2% of the total sampl...
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Three one-hectare grids (A, B, and C) were set in broad-leaved natural woods in the suburbs of Sapporo, Hokkaido and the role of arboreal habitat space for forest rodents was measured by means of the following manipulations of the habitat. Rodent populations were censused six times during five months from June to October, 1985; three species, Apode...
Article
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We investigated the utility of adaptive management (AM) in wildlife management, reviewing our experiences in applying AM to overabundant sika deer (Cervus nippon) populations in Hokkaido, Japan. The management goals of our program were: (1) to maintain the population at moderate density levels preventing population irruption, (2) to reduce damage t...
Article
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Cohort analysis (also known as virtual population analysis) is a method of population reconstruction from age-specific harvest data. Because cohort analysis requires data over a whole life span to reconstruct a population for a single year, this method is impracticable for longer-lived animals. Three models are routinely combined by fisheries scien...
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Nest construction is a daily habit of independent orangutans for sleeping or resting. Data on their nests have been used in various ecological studies (e.g., density estimation, ranging behavior, evolution of material culture) because they are the most observable field signs. We investigated nest size and nest site features of Bornean orangutans in...
Article
The number of families in the urban fox population of Sapporo, Japan, was estimated from two sets of data reported by the public to government: records of road-killed foxes (information-A) and records of complaints about foxes (information-B). We assumed that fox populations consist of families that have exclusive home ranges, i.e., territories, du...
Book
This is a reference book about wild mammals in Japan, including both terrestrial and marine species. (Because this is a "book", I cannot send a copy of this if requested.)
Article
Effects of male-biased dispersal on inbreeding avoidance were investigated in a semi-natural population of Myodes (formerly Clethrionomys) rufocanus using a large outdoor enclosure (3 ha). Parentage of 918 voles weaned from 215 litters and relatedness of mates were analysed using microsatellite loci, and dispersal distances were obtained from mark-...
Article
Full-text available
We have estimated the number of sika deer, Cervus nippon, in Hokkaido, Japan, with the aim of developing a management program that will reduce the level of agricultural damage caused by these deer. A population index that is defined by the population divided by the population of 1993 is first estimated from the data obtained during a spotlight surv...
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Multiple paternity may vary in frequency within populations because of changes in density. We investigated the occurrence of multiple paternity in an enclosed population of gray-sided voles (Myodes [formerly Clethrionomys] rufocanus) while focusing on the effect of density. We determined parentage from microsatellite DNA loci and mark–recapture liv...
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Full-text available
We analysed the effects of Quercus crispula acorn abundance on the density dependence of the large Japanese wood mouse Apodemus speciosus using time series data (1992-2007). The data were obtained in a forest in northern Hokkaido, Japan, by live-trapping rodents and directly counting acorns on the ground. Acorn abundance in one year clearly influen...
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Effects of cold stress on immune function and energy demand were experimentally investigated in the grey-sided vole. Laboratory-born and wild voles were divided into two groups: one maintained at 5°C (low temperature) and the control at 23°C (room temperature). The voles exposed to low temperature showed a weaker immune response to the challenge an...
Article
Full-text available
International Symposium, "The Origin and Evolution of Natural Diversity". 1–5 October 2007. Sapporo, Japan. Based on their skull morphology voles found on Daikoku Island have been regarded as a distinct form of Clethrionomys rufocanus (Sundevall, 1846) but their taxonomic status has been controversial: the vole population on this island was once id...
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Populations of the Asian black bear (Ursus thibetanus) are relatively large and continuous in central Honshu, the main island of Japan, but they are isolated in western Honshu. To clarify the degree of genetic isolation of the populations in western Honshu, we compared the genetic diversities of four populations in western Honshu with that of one o...
Article
The Evolutionarily Significant Unit (ESU) was conceptualized in 1986 as a conservation unit below the species level, theoretically applicable to a wide range of taxa. The concept has gained support, and various definitions or criteria, some of which are inconsistent with each other, have since been proposed. Recent critiques of the ESU have pointed...