Hiroyuki Uno

Seasonal migration patterns of female sika deer in eastern Hokkaido, Japan

Fifty-seven female sika deer (Cervus nippon yesoensis), captured at the wintering area in the Shiranuka Hills in eastern Hokkaido, Japan, were radio-tracked during 1997–2001 to examine the factors affecting seasonal migration at the individual-landscape level. Ten of the 57 deers migrated between low-altitude summer home ranges and intermediate-altitude winter home ranges (the upward migrants). Twenty-nine migrated between high-altitude summer home ranges and intermediate-altitude winter home ranges (the downward migrants). Twelve used the intermediate-altitude home ranges all year round (the non-migrants). The remaining six were unknown. The summer home ranges of deer were widely scattered over an area of 5734 km2. Migration distances ranged between 7.2 and 101.7 km. Deer showed high site fidelities to their seasonal home ranges. The upward migrants wintered in areas of less snow, higher quality of bamboo grass, and more coniferous cover than their summer home ranges. The downward migrants wintered in areas of less snow, higher quality of bamboo grass, higher winter temperature, and more southern slopes, but less coniferous cover than their summer home ranges. The non-migrants used year-round ranges with little snow, high quality of bamboo grass, and sufficient coniferous cover. We suggest that snow cover and bamboo grass are the factors affecting seasonal migration of the population and that coniferous cover is another factor for the upward migration.

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

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 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.

A management policy for sika deer based on sex-specific hunting

We consider here a management policy for a sika deer (Cervus nippon) population in the eastern part of Hokkaido. Deer populations are characterized by a large intrinsic rate of population increase, no significant density effects on population growth before population crash, and a relatively simple life history. Our goals of management for the deer population are (1) to avoid irruption with severe damage to agriculture and forestry, (2) to avoid the risk of extinction of the deer population, and (3) to maintain a sustainable yield of deer. To make a robust program on the basis of uncertain information about the deer population, we consider three levels of relative population size and four levels of hunting pressures. We also take into consideration a critical level for extinction, an optimal level, and an irruption level. The hunting pressure for females is set to increase with the population size. We also recommend catching males if the population size is between the critical and optimal levels and catching females and males if the population size is larger than the optimal level. We must avoid cases of irruption or threatened population under various sets of uncertain parameter values. The simulation results suggest that management based on sex-specific hunting is effective to diminish the annual variation in hunting yield.

Harvest-based Bayesian estimation of sika deer populations using state-space models

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 survey. A generalized linear mixed model (GLMM) with corner point constraints is used in this estimation. We then estimate the population from the index by evaluating the response of index to the known amount of harvest, including hunting. A stage-structured model is used in this harvest-based estimation. It is well-known that estimates of indices suffer from large observation errors when the probability of the observation fluctuates widely; therefore, we apply state-space modeling to the harvest-based estimation to remove the observation errors. We propose the use of Bayesian estimation with uniform prior-distributions as an approximation of the maximum likelihood estimation, without permitting an arbitrary assumption that the parameters fluctuate following prior-distributions. We are able to demonstrate that the harvest-based Bayesian estimation is effective in reducing the observation errors in sika deer populations, but the stage-structured model requires many demographic parameters to be known prior to running the analyses. These parameters cannot be estimated from the observed time-series of the index if there is insufficient data. We then construct a univariate model by simplifying the stage-structured model and show that the simplified model yields estimates that are nearly identical to those obtained from the stage-structured model. This simplification of the model simultaneously clarifies which parameter is important in estimating the population.

Evaluation of relative density indices for sika deer in eastern Hokkaido, Japan

We evaluated relative density indices of sika deer (Cervus nippon) to aid in population management. We monitored sika deer population trends from 1992 to 2002 in the eastern part of Hokkaido Island, northern Japan, using spotlight surveys, aerial surveys, catch per unit effort (CPUE), sighting per unit effort (SPUE), and cost of damage to agriculture and forestry. We assumed that the artificial bias in the spotlight index would be lower than in other indices, and compared temporal patterns of other indices to those produced using spotlight surveys using model II regression. There was a significant correlation between the damage cost index and the spotlight index, and both indices indicated consistent population trends. Managers used CPUE as a tool to determine hunting quota efficiency. The SPUE index had the smallest standard error among the indices, and the spotlight survey index had the second smallest standard error. Overall, the spotlight survey was the most useful index because its estimate error was small and it was precise in showing population trends; however, spotlight surveys did lead to underestimation once in 1994. The SPUE index seems to be effective in checking the validity of the spotlight index, but there are so many environmental and demographic uncertainties that several independent indices should be used and crosschecked for accurate evaluation of population trends.

Benefit of migration in a female sika deer population in eastern Hokkaido, Japan

The major factors affecting migration in large herbivores have been shown to be access to food resources and the risk of predation. Three migratory types of deer (resident, north migrant and east migrant) occur within a wintering female sika deer (Cervus nippon) population in eastern Hokkaido, Japan. We tested the hypothesis that north and east migrants feed on a higher quality diet than residents during summer, based on analyses of fecal nitrogen content. Fresh fecal pellets were collected in 18 summer ranges in the wintering area, northern area and eastern area between 1–5 August 2000. Fecal nitrogen content for all sampling sites was positively correlated with elevation, but was not correlated with distance from the wintering area. North migrants that inhabited higher (above 300 m elevation) summer ranges fed on a higher quality diet than residents. In contrast, the dietary quality of east migrants that migrated over a long distance and inhabited lower (below 300 m elevation) summer ranges was similar to that of residents. We conclude that east migrants may have gained significant benefit from the use of agricultural pastures with low population density conditions and without hunting; however, the recent population control program has reduced this benefit by avoiding the use of pasturelands.

Seasonal habitat selection of an expanding sika deer Cervus nippon population in eastern Hokkaido, Japan

Sika deer Cervus nippon in Hokkaido, Japan, have recovered from a population bottleneck about 120 years ago and their distribution has expanded rapidly in the last three decades. We tracked 53 radio-collared female sika deer, and obtained 4,430 locations during the 25-month study period from April 1997 to April 1999. We examined the seasonal distribution of female sika deer in relation to spatial landscape features (snow depth, vegetation, bamboo grass and roads) with a logistic regression model using a geographic information system database. We presented a population-landscape scale evaluation of sika deer habitat for summer and winter within the telemetry study area (TSA) using resource selection functions. We then extrapolated the model to the rest of eastern Hokkaido to discuss the seasonal migration for an expanding population. Most radio-collared sika deer (71%) moved between high-elevation summer and low-elevation winter ranges, whereas some (29%) moved between low-elevation summer and similar or high-elevation winter ranges. During winter, sika deer selected middle elevation habitats (200–400 m a.s.l.) with both a relatively low snow depth and the presence of coniferous and mixed forests. On the other hand, sika deer were widely distributed regardless of elevation during summer, although they were further from roads and less often in agricultural lands. Within the TSA, the suitable habitat was very limited during winter compared with during summer. Although migration from summer to winter ranges may depend on the abundance and distribution of suitable winter habitat at a landscape scale, migration from winter to summer ranges could not be explained from this study. Our approach is useful for understanding the relationships among seasonal habitat selection, seasonal migration and the expansion of the population.

Survival and cause-specific mortality rates of female sika deer in eastern Hokkaido, Japan

Survival and cause-specific mortality rates of female sika deer (Cervus nippon) were studied using radio telemetry in eastern Hokkaido, Japan. We captured and radio-collared 18 female deer, and monitored their survival from April 1993 to May 1996. Estimated annual survival rate for adult females was 0.779 (95% confidence interval was 0.609–0.997). The harvest mortality rate of adult females was higher than the natural mortality rate. Experimental female hunting during 1994–1996 contributed to an increase in the mortality rate for females and was useful in the control of the sika deer population.

Temporal change in the spatial genetic structure of a sika deer population with an expanding distribution range over a 15-year period

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 2008–2010), using mitochondrial DNA (mtDNA; D-loop) and microsatellites (9 loci). The number of gene-based subpopulations decreased across the 15-year period; specifically from four to three subpopulations based on mtDNA, and from two to one subpopulation based on microsatellite DNA. The fusion of the two northern subpopulations caused the change to the mtDNA-based structure, which might be explained by the dispersal of females from higher to lower density subpopulations. In comparison, the reason for the change in the microsatellite DNA-based structure was unclear, because no significant genetic differentiation was observed between the two study periods. A stable mtDNA-based structure was maintained in the north and central population separated by a west-to-east boundary, while a north-to-south boundary in eastern Hokkaido maintained stability in the eastern subpopulation versus all other subpopulations. The findings of this study demonstrate the importance of understanding gene flow within a structured population to implement effective management efforts; for instance, the culling of one subpopulation might not affect an adjacent subpopulation, because deer movement is limited between the subpopulations.

Seasonal Migration of Sika Deer on Hokkaido Island, Japan

We review the large-scale seasonal migration of sika deer on Hokkaido Island, Japan. A total of 57 female deer wintering in the Shiranuka Hills were radio- tracked between April 1997 and May 2002, yielding 7,765 relocations. Ten (18%) of the deer were upward migrants that had summer home ranges lower than or at similar elevation as their winter home ranges, 29 (51%) were downward migrants that had summer home ranges higher than their winter home ranges, and 12 (21%) were the nonmigrants that had overlapping seasonal home ranges. The summer home ranges of migrants were widely scattered over a total area of 5,734 km 2 . Migration distance of all migrants averaged 35.1 ± 3.6 km (mean ± SE, n = 39, range = 7.2-101.7 km). Deer showed strong site fidelity to their seasonal ranges. The results suggest that snow cover and bamboo grass are the factors affecting sea- sonal migration of sika deer in eastern Hokkaido. In addition, coniferous cover can be another important factor in the case of the reverse altitudinal migration by the upward migrants. We think the three migration types developed during the process of deer expanding their distribution after a population bottleneck 130 years ago.