The economic loss caused by herbivore browsing in forest plantations is a concerning problem in many areas around the world. Information on the spatial distribution of browsing damage is important for forest owners when selecting locations for new plantations, because planting trees in areas of high browsing pressure increases economic losses. Although it is difficult to survey browsing damage across large areas, sporadic sampling data on browsing damage are often collected by foresters, governments, and researchers. Thus, in this study, we applied a generalized additive model (GAM) for analysis of sporadic data to reveal large-scale spatial variation in deer (Cervus nippon) browsing damage. A map of browsing pressure produced by a GAM that used years after planting (plantation age) and location as independent factors showed a few areas of high browsing pressure. In addition, browsing damage increased with increasing plantation age, and plantation stands aged 2+ years showed more browsing damage. Areas with high browsing damage estimated based on plantation stands aged 2+ years generally coincided with areas of high deer abundance, with some exceptions. Thus, this model reflects large-scale browsing damage relatively well and will help forest owners to avoid locating new plantations in areas of high browsing pressure.

Regional management of large herbivore populations is known to be effective in reducing local economic damages and conserving local endemic plants. However, herbivores often move across management areas, and the effect of population management on a large spatial scale is poorly understood, even though it is necessary to use a large-scale approach across multiple management units to implement appropriate management. In this study, to better understand large-scale management and improve management efficiency, we evaluated effects of large-scale management of a sika deer (Cervus nippon) population on Kyushu Island (approximately 36,750 km2) in Japan. We estimated the population dynamics and spatial distributions of the deer and evaluated the effects of harvests, density dependence, and climatic conditions on the population dynamics both across Kyushu Island and in smaller prefectural management units. Fecal pellet count surveys conducted from 1995 to 2019 and results from a vector autoregressive spatio-temporal model showed relatively stable population dynamics and four high-density core areas. No increasing or decreasing trends were observed in the population dynamics, even though harvesting increased annually until it reached about 110,000 in 2014, indicating that harvesting was not related to the population dynamics. In addition, although no effects of density dependence were confirmed, maximum snow depth during winter decreased deer density at the management unit scale. Harvesting represents a major source of mortality in the Kyushu Island population because of the absence of predators. Although, approximately 110,000 sika deer were harvested annually after 2014, it is surprising that the effect of harvesting on population dynamics was not significant. A main cause of no reduction of the population was that the population used to determine the harvest number was underestimated. In addition, it was indicated that multi-management units need to manage the core areas because the high-density core areas were located across a few management units. This study highlights the difficulties involved with wide-area management of large herbivores and points out the importance of accurate stock assessment, reduction of the risk of management failure, and cooperation among management units. Our research is an important contribution to the study of the effects of large-scale harvesting in a large geographic area.

Sika deer (Cervus nippon) populations have damaged habitats, agricultural crops, and commercial forests in many parts of the world, including Asia, Europe, northern America, and New Zealand. Population management of sika deer is an important task in those areas. To better understand large-scale management and improve management efficiency, the authors estimated spatio-temporal changes of density distribution and population dynamics of a managed population of sika deer on Kyushu Island (approximately 36,750 km2), Japan. The authors estimated these changes by using fecal pellet count surveys conducted from 1995 to 2019 and results from a vector autoregressive spatio-temporal model. No decreasing trend of populations were observed at the island and prefectural scales, even though the management goal has been to reduce the population by half, and harvesting on the island increased annually until it reached about 110,000 sika deer in 2014. A possible explanation for the stable population dynamics is that the population used to determine the harvest number under the prefectural management plan was originally underestimated. This study highlights not only the difficulties of wide-area management of sika deer but also three important factors for successful management: reducing the risk of management failure, using an adaptive management approach, and appropriate management scale.

Increasing populations of large herbivores have caused environmental damage around the world, and it is necessary to improve population management strategies. Culling is a traditional management method. Antlerless deer proportions, consisting of adult female deer and fawn in Cervidae in wildlife statistics, are directly related to population increases; thus, the culling-based removal of individuals from habitats and the removal of these antlerless individuals by game hunting and nuisance control might be effective approaches for reducing population sizes. We evaluated the effectiveness of antlerless culling on 17-year density trends in the sika deer (Cervus nippon) population across an area of 1175 km2 in Fukuoka Prefecture (Japan). In 11 out of 47 grids (area measuring 5 by 5 km), the densities of sika deer tended to decline; meanwhile, in the remaining 36 grids, the densities increased. These density trends were explained by changes in the proportion of antlerless culling, as the densities declined with increasing proportions of antlerless deer. The results affirm the theory that antlerless culling is effective in population management; it is posited that antlerless-biased culling could be a crucial measure in managing overabundant populations of herbivores, contributing to more effective conservation of forest environments.

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