Sika Deer Population Research Articles

Increased brown bear predation on sika deer fawns following a deer population irruption in eastern Hokkaido, Japan

AbstractBy the 1970s, brown bears (Ursus arctos) in Hokkaido, northern Japan, were opportunistic omnivores that mainly depended on plant materials. Because the sika deer (Cervus nippon) population irrupted in eastern Hokkaido in the 1990s, we expected that brown bears might prey on sika deer fawns. First, we developed a simple and cost‐effective method of monitoring possible bear predation on deer fawns by analyzing the widths of deer hairs remained in bear scats. Based on hair thickness standards, we distinguished the brown bear consumption of deer fawns from adults by analyzing bear scats (n = 108) collected during the deer birthing season (late May–late July) in 1999–2008. To evaluate the importance of fawns to bears, we compared the occurrence of fawn and adult deer hairs in bear scats among three periods (I, 1999–2000; II, 2003–2005; III, 2006–2008) in eastern Hokkaido. The occurrence of fawn hairs in bear scats increased from 12.5 to 27.3 % in volume and from 6.3 to 33.6 % in frequency from period I to period III, whereas adult hairs in scats decreased from 42.8 to 26.1 % in volume and from 34.4 to 22.7 % in frequency during the same time. These data suggest that bears increasingly preyed on deer fawns after the deer population irruption and decreasingly used adult carcasses because of the enforcement of deer carcass treatment by the Hokkaido government.

Optimizing the Conditions for In Vitro Maturation and Artificial Activation of Sika Deer (Cervus nippon hortulorum) Oocytes

With the goal of establishing experimental protocols for cloning sika deer, various conditions for in vitro maturation (IVM) and artificial activation of sika deer oocytes were examined. In vitro maturation was evaluated in seven different culture media. The highest rate of oocyte maturation was 75.4% in 10 μg/ml follicle-stimulating hormone (FSH), 1 μg/ml LH, 0.2 mm cysteamine and 50 ng/ml epidermal growth factor (EGF) after 24 h of IVM. The efficiency after 24 h of IVM did not differ significantly (p > 0.05) from that observed after 20 h. Cysteamine (0.2 mm) significantly increased the maturation rates after 20 h (from 59.1% to 67.2%, p < 0.05) and after 24 h (from 63.2% to 71.6%, p < 0.05) of IVM. The IVM rates of oocytes collected during the oestrous season (75.4%) and the anoestrous season (23.3%) were significantly different at 24 h. The 20 μg/ml FSH, 2 μg/ml LH, 0.4 mm cysteamine and 100 ng/ml EGF significantly increased the maturation rates (from 23.3% to 54.2%, p < 0.01) at 24 h during the anoestrous season. For the activation experiments, the most effective method was chemical activation [ionomycin + 6-dimethylaminopurine (6-DMAP)], which promoted the development of sika deer oocytes to the blastocyst stage (32.4%). Our results indicate that in vitro matured sika deer oocytes are good candidates for parthenogenetic activation and that chemical treatment is needed for relatively efficient activation of the oocytes. These optimized conditions for IVM and parthenogenetic activation may be useful for efforts to restore populations of the endangered sika deer using the somatic cell nuclear transfer technique.

Correlation between Genetic Diversity and Neonatal Weight of Sika Deer (Cervus nippon) Fawns

Abstract. Genetic variations and their relationships to individual fitness have been the major topics in studies of ecology and evolution. The concept that a reduction in genetic variations leads to lower fecundity termed “inbreeding depression” has been predominantly supported by studies involving laboratory organisms, but has rarely been tested in wild populations. We therefore examined whether the individual genetic diversity among a population of wild sika deer (Cervus nippon) on Kinkazan Island, northern Japan, affected neonatal weight that is often considered as a fitness-related trait. First, the neonatal weights of fawns born during 1994–2004 were recorded, and 11 microsatellite loci were genotyped to obtain 5 different estimates of an individual's genetic diversity. To test whether the genetic diversities of fawns correlated with their neonatal weights, multivariate analyses using a generalized linear mixed model were performed. The neonatal weights were significantly affected by standardized mul...

Ecological correlates and determinants in the geographical variation of deer morphology

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 environmental factors (at least partly) were used as indices of body size. In this study, we used several skull and limb measurements to examine size variations among island populations of sika deer (Cervus nippon) in southern Japan considering the effects of multiple environmental factors. We found that all measurements differed markedly between populations. We focused on the skull and limb condylobasal length (CBL) and metacarpal length because they had the most important variations among the populations and the largest sample sizes. The common environmental factors influencing CBL and metacarpal length were island area and precipitation. Since these environmental factors reflect the availability of food resources, the causal factor of body size variation may be food resources. Interpopulation variation in metacarpal length was greater than that of CBL, indicating that metacarpal length may be affected by additional factors besides the common factors shared with CBL. Specific environmental factors influencing relative (CBL adjusted) metacarpal length were precipitation and slope. A common direct cause of those environmental factors was discussed in relation to topography. Analyses of phenotypic variation using multiple measurements with multiple environmental factors are useful to gain insight into underlying causes and can lead to identification of a measurement-specific variation with a specific driving force.

Management techniques for effective control of overabundant sika deer populations in Kyushu

Management techniques for effective control of overabundant sika deer populations in Kyushu

Compensatory response of molar eruption for environment-mediated tooth wear in sika deer

Teeth move continuously in the occlusal direction after they have approached the occlusal plane, which is considered a compensatory mechanism for loss of tooth crown by wear, although quantitative data have been inadequate. To clarify phenotypic correlation of tooth eruption and wear 10 populations of wild sika deer (Cervus nippon) in Japan were investigated. Mandibles, with ages assigned by cementum annuli of incisor roots, were used to estimate molar wear rate and eruption timing. Molar eruption status was assessed by observation of the buccal side of molars and coded as 3 ordinal levels according to the appearance of a cervical line (a boundary between molar crown and root). Logistic regression of the eruption status revealed that eruption timing of the lower 3rd molar (m3) was significantly different among populations (P < 0.0001) and correlated with m3 wear rate; faster molar wear resulted in faster molar eruption (P < 0.01). Eruption timing of lower 1st (m1) and 2nd (m2) molars did not show significant correlation with wear rate, possibly due to less variation in eruption timing in m1 and m2 than for m3. These findings indicate that the compensatory response of molar eruption occurs for m3 in accordance with wear mediated by environments.

How Low Quality Foods Sustain High Density Sika Deer (Cervus nippon) Population in Heavily Grazed Habitat?: Comparison of Intake, Digestibility and Feeding Activities between the Deer Fed High and Low Quality Food

Abstract. Sika deer (Cervus nippon) populations continue to survive at a relatively high density in heavily grazed habitats, where preferable plants have been decreased. To clarify the contradiction concerning the relation between food quality and carrying capacity, we compared the nutrition contents of original food and remaining available food, and experimentally tested the prediction that the low quality foods may increase carrying capacity through a reduction of food intake. High quality foods have been decreasing, and the remaining available foods were low quality foods with low crude protein. We quantified the amount of intake and digestibility of alfalfa as a high quality food and timothy as a low quality food, and measured the feeding activities. The dry matter intake and digestibility of timothy were lower than those of alfalfa. Additionally, the deer fed timothy ruminated a longer time than the deer fed alfalfa. Our results indicate that low quality food restricted the amount of intake. The low ...

Mortality profiles of late Pleistocene deer remains of Okinawa Island: evidence from the Hananda-Gama cave and Yamashita-cho cave I sites

In the present study, we estimated age at death of extinct deer (Cervus astylodon) excavated from two Late Pleistocene sites in Okinawa Island (the Hananda-Gama Cave and Yamashita-cho Cave I sites) from degree of molar wear. This was done using a regression equation of extant sika deer of known age, and deriving an age estimation equation based on M3 crown height applicable to fossil specimens. We then reconstructed mortality profiles using 45 and 88 individuals of the Hananda-Gama and Yamashita-cho assemblages, respectively, and compared the profiles with those of extant and archaeological (Jomon period) sika deer (C. nippon) populations. The reconstructed age profiles of both sites were strikingly different from the living and hunted Jomon period profiles in relative abundance of old adults. They were more similar to the attritional mortality profiles of the extant sika deer that died by natural causes (i.e. not by human or animal predation), but showed a further shift towards older age. Combined with the fact that there is no fossil evidence of medium- to large-sized carnivores on Okinawa Island during the Late Pleistocene, our results suggest that C. astylodon populations had extended longevity because of low predatory pressure, including that by Paleolithic human hunters.

Present distribution of a sika deer population and its impact on vegetation around Mt. Hyonosen, Hyogo Prefecture

Present distribution of a sika deer population and its impact on vegetation around Mt. Hyonosen, Hyogo Prefecture

Age Structure in Mass Mortality in the Sika Deer (Cervus nippon) Population on Kinkazan Island, Northern Japan

Age Structure in Mass Mortality in the Sika Deer (Cervus nippon) Population on Kinkazan Island, Northern Japan

Adaptive management of sika deer populations in Hokkaido, Japan: theory and practice

AbstractWe 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 to crops and forests, and (3) to sustain a moderate yield of hunting without endangering the population. Because of significant uncertainty in biological and environmental parameters, we designed a “feedback” management program based on controlling hunting pressure. Three threshold levels of relative population size and four levels of hunting pressure were configured, with a choice of four corresponding management actions. Under this program, the Hokkaido Government has been promoting aggressive female culling to reduce the sika deer population since 1998. We devised a harvest‐based estimation for population size using relative population size and the number of deer harvested, and found that the 1993 population size (originally estimated by extrapolation of aerial surveys) had been underestimated. To reduce observation errors, a harvest‐based Bayesian estimation was developed and the 1993 population estimate was again revised. Analyses of population trends and harvest data demonstrate that hunting is an important large‐scale experiment to obtain reliable estimation of population size. A serious side effect of hunting on sika deer was inadvertent lead poisoning of large birds of prey. The prohibition of the use of lead bullets by the Hokkaido Government was successful in reducing the lead poisoning, but the problem still remains. Two case studies on sika population irruption show that the densities set by maximum sustainable yield may be too high to prevent damage to agriculture, forestry, and/or ecosystems. Threshold management based on feedback control is better for ecosystem management. Since volunteer hunters favor higher hunting efficiency in resource management (e.g., venison), it is necessary to support the development of professional hunters for culling operations for ecosystem management, where lower densities of deer should be set for target areas. Hunting as resource management and culling for ecosystem management should be synergistically combined under AM.

Irreversible microevolutionary changes in genotypic composition of sika deer Cervus nippon populations in response to vegetation degradation and food shortage

The present study deals with changes in important skull characteristics of the sika deer Cervus nippon Temminck, 1838 in response to changes in food supply. Moderate food shortage results mainly in a linear reduction in skull size, while severe food shortage results in changes in skull shape. In the deer that returned to habitats with sufficient food supply, some skull parameters recovered to, or even exceeded, normal values, whereas other parameters remained stressed resulting in retention or enhancement of skull distortions. Differences in skull parameters among the populations studied were comparable to those between some cervid species, eg, the Siberian roe deer Capreolus pigargus Pallas, 1771 and European roe deer Capreolus capreolus Linnaeus, 1758 and other deer subspecies. In the introduced sika deer populations, skull distortions were apparently caused by interspecific hybridization. Descendants of the escaped deer have not reverted to the normal phenotype, even over several generations, providing a recent case of true evolutionary changes. This occurred by a change in the ratio of different morphotypical groups, probably due to their different responses to food shortage. Thus sufficient food supply may account for changes in a population’s genotypic composition through selection of characteristics that favour passing on genetic material when food is limited.

Altitudinal variation in the diet of sika deer on the Izu Peninsula: patterns in the transitional zone of geographic variation along the Japanese archipelago

Geographical variation in the diet of sika deer Cervus nippon Temminck, 1838 has been well characterised: northern populations are grazers, whereas southern deer are browsers. This variation largely reflects genetic-based differences in morphology. However, environmental factors would be also important. If a same genetic population live in different habitats, we can check altitudinal shifts in sika deer food consumption. We hypothesised that changes in the diet of the sika deer population on the Izu Peninsula, which is located within the transitional zone of resource (vegetation) variation and encompasses a broad altitudinal range, would mirror shifts in the composition of vegetation. Analyses of the rumen contents of the deer population indicated that dwarf bamboo accounted for 10.5, 46.2, and 74.3% of the deer diet in the low ( 1000 m) altitudinal zones, respectively. In contrast, evergreen broad-leaved species accounted for 35.7, 23.1, and 5.9%, respectively. These results suggest that the diet of sika deer is more strongly affected by environmental factors, such as plant community composition, than by genetic factors.

Investigating temporal changes in hybridization and introgression in a predominantly bimodal hybridizing population of invasive sika (Cervus nippon) and native red deer (C. elaphus) on the Kintyre Peninsula, Scotland

We investigated temporal changes in hybridization and introgression between native red deer (Cervus elaphus) and invasive Japanese sika (Cervus nippon) on the Kintyre Peninsula, Scotland, over 15 years, through analysis of 1513 samples of deer at 20 microsatellite loci and a mtDNA marker. We found no evidence that either the proportion of recent hybrids, or the levels of introgression had changed over the study period. Nevertheless, in one population where the two species have been in contact since approximately 1970, 44% of individuals sampled during the study were hybrids. This suggests that hybridization between these species can proceed fairly rapidly. By analysing the number of alleles that have introgressed from polymorphic red deer into the genetically homogenous sika population, we reconstructed the haplotypes of red deer alleles introduced by backcrossing. Five separate hybridization events could account for all the recently hybridized sika-like individuals found across a large section of the Peninsula. Although we demonstrate that low rates of F1 hybridization can lead to substantial introgression, the progress of hybridization and introgression appears to be unpredictable over the short timescales.

The relationship between food habits, molar wear and life expectancy in wild sika deer populations

Functionality of cheek teeth is essential for ruminants to masticate plant materials thoroughly and promote microbial degradation in their rumens. Thus, an excessive rate of tooth wear is expected to lead to premature loss of tooth functionality, and hence to reduced longevity. So far, however, the relationships between food habits, molar wear and longevity have not been investigated. We first compared molar wear rates among nine sika deer Cervus nippon populations with different food habits. We then investigated correlations between molar wear rate and two ecological factors, percentage of graminoids in diet and annual precipitation, relating to intrinsic and extrinsic abrasiveness of the ingested food, respectively. Secondly, we estimated ‘retained molar durability’ (molar height at a given age divided by wear rate) at successive ages for each population, and tested for correlation between molar durability and life expectancy among populations. The M1 and M3 wear rates differed among the populations and showed a positive correlation with graminoid consumption and a negative correlation with precipitation, suggesting that both ecological factors influence molar wear rates in the Japanese sika deer. M3 durability had a stronger correlation with life expectancy than M1 durability, especially at the older age stages. This implies that the influence of M3 durability on life expectancy becomes stronger at the time when the M1 is severely worn and loses its functionality, and is therefore more important for life span elongation than the M1. These results are concordant with the fact that the M3 is the most hypsodont molar in many ungulates. In the Japanese sika deer, microevolutionary acquisition of hypsodonty appears to be the case in a northern population (the Kinkazan Island), whose molar wear rates are extremely rapid due to their food habits.

Evidence for Cryptic Genetic Discontinuity in a Recently Expanded Sika Deer Population on the Boso Peninsula, Central Japan

The genetic structure of populations is not necessarily reflected in the geographical proximity of individuals, because environmental gradients such as those of vegetation or climate can function as cryptic barriers to gene flow. We examined polymorphisms at nine microsatellite loci to determine and discuss whether a distinctive genetic structure was detectable in a spatially continuous population of the sika deer (Cervus nippon) on the Boso Peninsula of central Japan. Spatially explicit Bayesian analysis revealed that two genetically distinctive clusters exist in the Boso population. The spatial boundary of the two clusters approximately conformed to the border defined previously from a mitochondrial DNA dataset. By combining information on the geomorphic features surrounding the boundary and that on the lineage of 1970s population, we propose a schematic scenario for characterizing the population genetic structure to the present. The current population consists of genetically different lineages, and spatially discontinuous clusters have come into contact in the vicinity of a local road running along a steep-walled ravine that could act as principal barrier to gene flow. Biological factors such as distribution of vegetation and philopatric behavior might also have helped strengthen the cryptic genetic structure of the Boso population.

Application of fecal pellet group count to sika deer (Cervus nippon) population monitoring on Mt. Ohdaigahara, central Japan

ABSTRACT The relationship between the number of fecal pellet groups found in line transects and estimates of deer density based on block counts on Mt. Ohdaigahara in central Japan was examined and the validity of fecal pellet group counts for obtaining an index of sika deer population density was assessed. Sika deer population densities estimated by block count were 13.0/km2 in spring, 18.3/km2 in summer and 19.0/km2 in autumn. Fecal pellet group counts showed low positive correlations with deer density in spring and autumn (0.69 in spring and 0.68 in autumn), but not in summer, indicating that deer density may not be predictable then. We suggest that fecal pellet group count reflects deer density in spring or autumn, and might be feasible as an index of deer population density.

Effects of sika deer ( Cervus nippon yakushimae) population growth on saplings in an evergreen broad-leaved forest

An increase in size of sika deer populations has caused severe damage to forest vegetation in many regions of Japan. In a Natural World Heritage area on the western part of Yakushima Island, existing high densities of deer are thought to be increasing, but the impact of deer on forest vegetation has not been estimated. Roadside censuses of deer between 1988 and 2006 showed that encounter rates are continuing to increase. Long-term monitoring of individual tree saplings in a 0.13 ha area of the forest between 1992 and 2005 showed that many saplings still remain despite increases in sika deer density. However, differences in growth and mortality rates of preferred, neutral (neither preferred nor avoided) and avoided sika deer food species varied over time. As a group, preferred species continuously had a low growth rate, while their mortality rate increased through time. The growth rates of the neutral and avoided groups decreased especially in the second half of our study period at the same time that their mortality rates increased. These data suggest that in spite of food species preference, direct feeding pressures as well as indirect physical effects by increasing sika deer density are affecting growth and mortality of tree saplings. Clearly, it is difficult to predict how plant communities will respond to possible continued sika deer population growth, and it is therefore important to continue monitoring these forest communities in the interest of preserving the unique ecosystems on Yakushima Island.

Spatially heterogeneous distribution of mtDNA haplotypes in a sika deer (Cervus nippon) population on the Boso Peninsula, central Japan

We used variation in the mitochondrial DNA (mtDNA) control region (D-loop) to examine the genetic structure of the sika deer (Cervus nippon) population on the Boso Peninsula, central Japan. A total of four haplotypes was found. In order to examine whether or not artificial barriers such as roads, dams, and golf courses affect the spatial heterogeneity of mtDNA haplotypes, we implemented two exclusive spatial analyses (SAMOVA and network analysis based on Monmonier’s algorithm) for searching genetic discontinuities between artificial barriers. Prior to the analyses, the whole distribution area was divided into meaningful eight blocks. Analysis of molecular variance (AMOVA) detected significant spatial heterogeneity in the constitution of the haplotypes among the blocks. The subsequent spatial analyses detected some significant spatial discontinuities on borders of the blocks. In particular, the largest discontinuity was observed in the area including motorway Line 81, but the traffic density of Line 81 is generally not very heavy compared to other major roads. These findings suggest that roads could be one of major barriers to hamper migration of sika deer to some extent, but other potential factors such as the location of food resources and/or the history of bottleneck event are also likely to more or less contribute to configure the present patterns of haplotype distribution.

The biochemical systematics of red and sika deer (genus Cervus) in Ireland

Twenty enzyme loci were investigated using starch gel electrophoresis in managed populations of red deer (Cervus elaphus) and sika deer (C. nippon) from Ireland. The red deer, which originated from several European countries, were polymorphic (%P) at 25% of the loci examined and exhibited a mean heterozygosity (H) of 0.025. The sika, originally from Japan, were introduced to Ireland in very limited numbers. Here, %P was 5% and H was 0.006. Mean genetic distance (D) between these taxa was 0.160. Because Scottish red deer, the source of much of the Irish herd, had previously been investigated for 16 of the same enzyme loci, it was possible to merge the present data with results from that earlier study, which also included North American wapiti (C. elaphus canadensis). The resulting phenogram based on genetic distance demonstrates that sika are twice as distantly related to red deer and wapiti, than the latter are to each other and suggests that sika-like forms are ancestral. Also, the demonstration of absolute mobility differences in the products of two enzyme loci in red deer and sika has many practical applications.