Shinsuke Koike’s research while affiliated with Tokyo University of Agriculture and Technology and other places

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Publications (145)


a Locations of the Ashio-nikko mountains (ASH), Abukuma highlands (ABU), Kanto mountains (KAN), b the rough topography around the study areas, and c characteristics of the study sites. Topography was obtained from the geospatial information authority of Japan (https://maps.gsi.go.jp/)
Number of dispersed seeds of Cerasus leveilleana and Padus grayana by (a) each mammal species and by (b) birds. Bears and macaques are extinct in ABU
Vertical seed dispersal distance by each mammal species and by birds in each study area. In x-axis, vertical seed dispersal distance of each dispersed seed is arranged in descending order. The dots indicate the mean vertical distance, and the vertical bars indicate the 95% credible interval of each dispersed seed. Those seeds for which the vertical distance = 0 lies within their 95% credible intervals are highlighted with a gray background. Dotted lines indicate the mean of simulated vertical seed dispersal distance assuming that frugivores move and disperse seeds randomly in their home range based on topography. Silhouette images of the bear, marten, and bird (by L. Shyamal) were obtained from PhyloPic (http://phylopic.org)
Frequency distribution of dispersed seeds of aCerasus leveilleana and bPadus grayana by each mammal species and by birds. Bears and macaques are extinct in ABU. Note that the number of dispersed seeds and vertical seed dispersal distance of each frugivore were multiplied to assess the contribution of each frugivore to whole vertical seed dispersal. Because one dispersed seed per faeces was analysed for the estimation of vertical seed dispersal distance, the vertical seed dispersal distance of remaining the non-analysed seeds in each faeces was assumed to be identical to that of the analysed seed in the same faeces (see Discussion for limitations associated with this)
Fruiting phenology affects the direction of vertical seed dispersal by mammals and birds across mountain ranges
  • Article
  • Publisher preview available

January 2025

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25 Reads

Oecologia

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Shinsuke Koike

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Shoji Naoe

Vertical seed dispersal towards higher or lower altitudes is an important process for plants’ adaptation to climate change. Although many plants depend on animals for seed dispersal, studies on vertical seed dispersal by animals, determined by complex animal behaviours, are scarce. Previous studies hypothesised that animals inhabiting temperate regions disperse seeds uphill in spring/summer and downhill in autumn/winter due to their seasonal movement following the altitudinal gradients in food phenology. However, this hypothesis has only been tested in seed dispersal by mammals on one mountain range. Vertical seed dispersal by birds might differ from that by mammals, and frugivorous megafauna extinction and mountain topography may affect seed dispersal patterns. Here we assessed the vertical seed dispersal of summer and summer-to-autumn fruiting cherries by mammals and birds across three Japanese mountain ranges, two of them with presence of a megafauna, the Asian black bear. We found strong uphill seed dispersal of summer fruiting cherry species and weak downhill seed dispersal of summer-to-autumn fruiting cherry species, irrespective of the frugivore community and mountain topography. These indicate that the fruiting phenology affects the direction of vertical seed dispersal by mammals and birds across mountains. Mammals and birds dispersed seeds over a similar vertical profile, although birds are likely to be low-quantity seed dispersers. The absence of bears, which dispersed the majority of the seeds, was not compensated by the remaining mammal species. The results suggest that the fruiting phenology and megafauna presence affect whether animal-dispersed temperate plants can migrate efficiently under climate change.

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Figure 4
Large terrestrial mammals resurging in a depopulating country

September 2024

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122 Reads

Large terrestrial mammals have generally declined due to human activity, but the recovery of some populations poses new issues for coexistence. Few studies to date have investigated drivers of this recovery and its impacts on human societies at the national scale. We assessed the process of range expansion of six species of large terrestrial mammals over approximately 40 years and its impacts on human society in Japan, one of the most rapidly depopulating countries. We found evidence that increased agricultural abandonment and decreased snowfall drove the range expansion of large terrestrial mammals. The range of all six species expanded from mountainous landscapes to those closer to human settlements, leading to an increase in conflicts that threaten people’s property and safety. We predict that accelerating depopulation and climate warming could lead to further range expansion of these species, and call for measures to mitigate conflicts and achieve coexistence with them.



Responses of a bird community to sporadic outbreaks of woody herbivorous insects in a temperate beech forest in Japan

May 2024

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36 Reads

Forest Ecology and Management

Sporadic large outbreaks of herbivorous insects alter forest ecosystems via a top-down effect, and a high frequency of outbreaks led to the death of the trees on which the insects fed. The top-down effect of predators, such as other insects and birds, often regulates the outbreaks. Predator insects exert effective top-down control on outbreaks of herbivorous insects, but the effect of bird predation varies because birds have a broader diet range and higher mobility than insects. It was hypothesized that when large insect outbreaks occur during the breeding season of birds, most bird species would not respond owing to a fixed home range during this season and would, therefore, not exert top-down effects. To test this hypothesis, the relationship between bird and beech sawfly abundance was investigated for over nine years in the Tanzawa Mountains of central Japan, where temperate beech forests and large sporadic outbreaks of woody herbivorous insects occur. In this study, 28 649 female beech sawfly adults were captured, and 2515 individuals were identified from 50 bird species. The abundance of most bird species foraging on beech sawfly larvae, except Sitta europaea, did not increase proportionally with the number of beech sawfly adults. Many bird species did not respond to the unpredictable and temporary abundance of food resources in a way that would enhance their density, supporting the hypothesis. These results can be explained by examining the nesting and foraging guilds of the birds. S. europaea is less restricted in nesting sites and nests earlier in the season than other species; therefore, they could select nests in areas where beech sawfly larvae were abundant. Regarding foraging, S. europaea has a unique foot shape that allows it to move down the tree trunk freely and respond rapidly to fluctuations in beech sawfly abundance. Bird species that exert top-down effects on insects show promise for use in an integrated pest management approach to manage sporadic outbreaks of herbivorous insects in forest ecosystems.




Drastic changes in ground-dwelling beetle communities following high-intensity deer culling: insights from an island ecosystem

February 2024

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62 Reads

Environmental Entomology

The overabundance of large herbivores can have detrimental effects on the local environment due to overgrazing. Culling is a common management practice implemented globally that can effectively control herbivore populations and allow vegetation communities to recover. However, the broader indirect effects of culling large herbivores remain relatively unknown, particularly on insect species such as ground-dwelling beetles that perform key ecosystem processes such as decomposition. Here we undertook a preliminary investigation to determine how culling sika deer on an island in North Japan impacted ground-beetle community dynamics. We conducted pitfall trapping in July and September in 2012 (before culling) and again in 2019 (after culling). We compared beetle abundance and community composition within 4 beetle families (Carabidae, Scarabaeidae, Geotrupidae, and Silphidae), across seasons and culling treatments. We found each family responded differently to deer culling. Scarabaeidae displayed the greatest decline in abundance after culling. Silphidae also had reduced abundance but to a lesser extent compared to Scarabaeidae. Carabidae had both higher and lower abundance after culling, depending on the season. We found beetle community composition differed between culling and season, but seasonal variability was reduced after culling. Overall, the culling of large herbivores resulted in a reduction of ground-dwelling beetle populations, particularly necrophagous species dependent on dung and carrion for survival. Our preliminary research highlights the need for long-term and large-scale experiments to understand the indirect ecological implications of culling programs on ecosystem processes.


Citations (68)


... Closed canopy, prethinned stands are characterized by greater tree densities, including more competing vegetation in the underand mid-story, along with a closed canopy that hinders bat flight and foraging ability. As for nocturnal insect communities, previous research found species richness and abundance of multiple orders were lower in unthinned forest stands compared to thinned stands (e.g., Maleque et al., 2007a, b;Taki et al., 2010;Taniwaki et al., 2024). However, we found a positive association between closed canopy pre-thinned stands and catches of Coleoptera. ...

Reference:

Modeling winter foraging ecology of bats on working forest lands in the southeastern U.S. Coastal Plain
Indirect effects of low-impact thinning on insect communities in forest floor of coniferous plantations
  • Citing Article
  • March 2024

Journal of Forest Research

... Moreover, the absence of hyenas could have allowed the cave bear U. praekudarensis to occupy the scavenger niche seasonally, during the hyperphagia period, in a way to further supplement its diet. Being the largest specimen with facultative scavenger behaviour (Rabal-Garcés et al., 2012), U. praekudarensis could have potentially outcompeted smaller mesocarnivores like canids and the smaller Asian black bear in carcass scavenging (Allen et al., 2015;Inagaki et al., 2023). The partitioning of scavenger niches seasonally by different species while coexisting could be possible as observed in other ecosystems (Selva et al., 2005). ...

Evidence for interspecific modulation of carcass consumption among facultative scavengers in Asian temperate forest
  • Citing Article
  • October 2023

Food Webs

... In Hyogo Prefecture, Japan, »50% of female bears captured were accompanied by cubs in 2004 and 2006 (Hyogo Prefecture 2009). Additionally, it has been reported that more than half of the female bears reproduce biennially in the Echigo-Mikuni population in Japan (Tochigi et al. 2023). It is likely that the RAI values for females with unweaned offspring in our study were lower than expected, based on the birth rates observed in the Hyogo and Echigo-Mikuni populations. ...

Demographic Parameters of Asian Black Bears in Central Japan
  • Citing Article
  • July 2023

Mammal Study

... In fact, it has been reported that dwarf bamboo and conifers are the staple food of serows in the subalpine zone of Mt. Fuji, which is part of our study area (Hiruma et al. 2023). Therefore, the population density of serows may have been high in coniferous forests with abundant conifers and areas with an abundant supply of dwarf bamboos. ...

Dietary partitioning and competition between sika deer and Japanese serows in high elevation habitats
  • Citing Article
  • March 2023

Mammal Research

... This observed fidelity may be due to philopatry, on-ice spatial fidelity, and a tendency to travel a similar distance in-land once returning to shore. Spatial fidelity of female ursids to the general area of their birth site is in part associated with higher levels of philopatry in females than in males (Manchi & Swenson, 2005;Roy et al., 2012;Takayama et al., 2023). Similarly, philopatry in polar bears appears common across both sexes (Derocher & Stirling, 1990;Paetkau et al., 1999;Zeyl et al., 2010) but may be lower in males that move across subpopulations more often . ...

Timing and distance of natal dispersal in Asian black bears

Journal of Mammalogy

... In the fall of 2019, 98.9% of raccoon dog visits to cultivated Ginkgo trees took place at night, while in the fall of 2020, that figure dropped to 71.1% (Osugi et al., 2022). They also observed the Japanese badger (Meles anakuma, Mustelidae) visiting the same Ginkgo trees as the raccoon dogs, but much less frequently-only 30 times over the 2-year study period versus 640 raccoon dog visits-and that their daytime activity also increased during the pandemic. ...

The effect of decreasing human activity from COVID‐19 on the foraging of fallen fruit by omnivores

... Asiatic black bears traditionally have been thought to not regularly prey on adult deer (Hashimoto and Takatsuki 1997), but previous experiments and studies have suggested that Asiatic black bears consume carcass remains of culled deer Inagaki et al. 2020Inagaki et al. , 2023Naganuma et al. 2022;Tezuka et al. 2023). The scavenging indicates that culled remains are a food source with nutritional value for bears, but little is known about the instances of predation by bears on deer captured by traps. ...

Comparing information derived on food habits of a terrestrial carnivore between animal-borne video systems and fecal analyses methods

Journal of Mammalogy

... It also should be noted that the use of paved roads in ASH and ABU as census routes might influence what animal species we collected seeds from. Notably, seed deposition site differs amongst target mammal species in KAN (Tochigi et al. 2022). Badgers and raccoon dogs prefer to excrete on soils and thus the number of badger-and raccoon dog-dispersed seeds might be underestimated in ASH and ABU. ...

Differentiation and seasonality in suitable microsites of seed dispersal by an assemblage of omnivorous mammals
  • Citing Article
  • November 2022

Global Ecology and Conservation

... Asiatic black bears traditionally have been thought to not regularly prey on adult deer (Hashimoto and Takatsuki 1997), but previous experiments and studies have suggested that Asiatic black bears consume carcass remains of culled deer Inagaki et al. 2020Inagaki et al. , 2023Naganuma et al. 2022;Tezuka et al. 2023). The scavenging indicates that culled remains are a food source with nutritional value for bears, but little is known about the instances of predation by bears on deer captured by traps. ...

Carcass detection and consumption by facultative scavengers in forest ecosystem highlights the value of their ecosystem services

... The Japanese serow (Capricornis crispus) is endemic to Japan and primarily inhabits lower montane to subalpine forests on the islands of Honshu, Shikoku, and Kyushu. Long-term dietary investigations of Japanese serows in forested areas of northern and central Japan have been conducted (e.g., Ochiai 1999;Jiang et al. 2008;Takatsuki et al. 2010;Kobayashi and Takatsuki 2012;Hiruma et al. 2022). In the last decade, studies on the species' feeding behaviors in previously unstudied environments or areas (e.g., alpine meadows and the island of Shikoku; Asakura et al. 2014;Takada and Minami 2019;Yamashiro et al. 2019;Hiruma et al. 2023;Takada et al. 2024) have revealed that, although the Japanese serow generally feeds on nutritious dicotyledonous plants, such as deciduous broad-leaved trees and broad-leaved herbs, their feeding habits differ by region. ...

Long-term stability in the winter diet of the Japanese serow (Artiodactyla, Caprinae)