Seasonal and annual fluctuations of deer populations estimated by a Bayesian state–space model

Abstract

Deer overabundance is a contributing factor in the degradation of plant communities and ecosystems worldwide. The management and conservation of the deer-affected ecosystems requires us to urgently grasp deer population trends and to identify the factors that affect them. In this study, we developed a Bayesian state-space model to estimate the population dynamics of sika deer (Cervus nippon) in a cool-temperate forest in Japan, where wolves (Canis lupus hodophilax) are extinct. The model was based on field data collected from block count surveys, road count surveys by vehicles, mortality surveys during the winter, and nuisance control for 12 years (2007-2018). We clarified the seasonal and annual fluctuation of the deer population. We found a peak of deer abundance (2010) over 12 years. In 2011 the estimated deer abundance decreased drastically and has remained at a low level then. The deer abundance gradually increased from April to December during 2013-2018. The seasonal fluctuation we detected could reflect the seasonal migration pattern of deer and the population recruitment through fawn births in early summer. In our model, snowfall accumulation, which can be a lethal factor for deer, may have slightly affected their mortality during the winter. Although we could not detect a direct effect of snow on population dynamics, snowfall decrease due to global warming may decelerate the winter migration of deer; subsequently, deer staying on-site may intensively forage evergreen perennial plants during the winter season. The nuisance control affected population dynamics. Even in wildlife protection areas and national parks where hunting is regulated, nuisance control could be effective in buffering the effect of deer browsing on forest ecosystems.

A 25-years population dynamics of sika deer in Kyushu Island, Japan: Estimation using vector autoregressive spatiotemporal model and evaluation of a large-scale management

“…Although this movement can be a limiting factor for appropriate management (Iijima et al, 2015;Bengsen et al, 2020), it is often not considered (Yamamura et al, 2008). Although no effects of harvesting on DDI were shown in this study, localized management is known to be effective in large herbivores (Kilpatrick and Walter, 1999;Hagen et al, 2018), including sika deer (Mizuki et al, 2020).…”

eDNA metabarcoding analysis reveals the consequence of creating ecosystem‐scale refugia from deer grazing for the soil microbial communities

“…radicans ) in the upper to middle part of the slope, Japanese beech ( Fagus crenata ) in the lower part of the slope, and Aesculus turbinata and Pterocarya rhoifolia in the valley area (Sakaguchi et al., 2008, 2012). In the study area, sika deer ( Cervus nippon ) density drastically increased in the 2000s and peaked in 2010 (Mizuki et al., 2020). Since the end of the 1990s, the degradation of vegetation by deer browsing has become extensive and profound, resulting in the significant loss of understory vegetation (Fujiki & Takayanagi, 2008; Fukuda & Takayanagi, 2008).…”

“…The large‐scale fence experiment was initiated in 2006 when the urgent need to defend vegetation from deer overabundance was unfolding (Mizuki et al., 2020; Sakaguchi et al., 2012). In the experiment, a large deer fence encompassing the entire catchment (13 ha) was established and maintained to observe ecosystem recovery, and an unfenced, adjacent catchment (19 ha) was set as a control site accessible to the deer population.…”

Regional‐scale effects of deer‐induced forest degradation on river ecosystem dynamics

“…Deer overabundance has become a worldwide problem, resulting in forest degradation that impacts not only terrestrial ecosystems (Côté et al, 2004; Kaji et al, 2022), but also aquatic ecosystems (Sakai et al, 2022). For instance, in the catchment forest of a Japanese mountain stream, noticeable damage to forest‐floor vegetation caused by deer overbrowsing has been observed since the late 1990s, with significant denudation of the forest floor occurring by the late 2000s (Mizuki et al, 2020). The denuded slopes have increased the input of fine sediments into nearby headstreams (Sakai et al, 2013).…”