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Fukasawa K.,Japan National Institute of Environmental Studies | Hashimoto T.,Japan Wildlife Research Center | Abe S.,Naha Nature Conservation Office
Journal of Applied Ecology | Year: 2013

Summary: An understanding of the underlying processes and comprehensive history of invasive species is necessary to assess the long-term effectiveness of invasive species management. However, continuous, long-term labour-intensive population surveys on invasive species are often not feasible. Thus, it is important to learn about their dynamics through management action and its consequences.  Amami Island, Japan, has an ongoing large-scale and long-term eradication programme of invasive small Indian mongooses. To estimate the long-term pattern of population size and the parameters determining the dynamics, including anthropogenic removal, we applied a surplus-production model within a Bayesian state-space formulation incorporating the initial population size, number of captures and capture effort. Using the estimated process model directly, we conducted stochastic simulations to evaluate the feasibility of eradication.  Estimated 32-year annual capture probability of mongooses has increased since their introduction. The population size started to decline in 2001; mean population size in 2000 was 6141 (95% CI: 5415-6817), and declined to 169 (95% CI: 42-408) by 2011. Parameter estimates of a Weibull catchability model indicated that there was large individual heterogeneity in the probability of being captured, and per-effort capture probability declined with an increase in annual capture effort.  The simulation study indicated that the eradication feasibility in 2023 would be over 90% if the same annual capture effort is upheld as in 2010 (2 075 760 corrected trap-days). However, increasing annual capture effort would have little effect on shortening the time to eradication.  Synthesis and applications. A hierarchical model that incorporates multiple types of data to reveal long-term population dynamics has the potential to be updated with the outcomes of control efforts, and will enhance adaptive management of invasive species. This approach will offer valuable information about trade-offs between time to eradication success and effort per unit time in a long-term eradication project, and the length of time needed to continue management actions to achieve eradication success. A hierarchical model that incorporates multiple types of data to reveal long-term population dynamics has the potential to be updated with the outcomes of control efforts, and will enhance adaptive management of invasive species. This approach will offer valuable information about trade-offs between time to eradication success and effort per unit time in a long-term eradication project, and the length of time needed to continue management actions to achieve eradication success. © 2013 British Ecological Society. Source


Somiya K.,Naha Nature Conservation Office
Journal of Ecology and Environment | Year: 2015

The southwestern islands of Japan, especially southward from Amamioshima Island, have distinguished sets of nature and culture. However, various problems are arising on those islands. This report first introduces island characteristics as well as, their status briefly. Then it introduces conservation efforts. Since nature and culture are closely connected in the island system, conservation of the set of nature and culture is essentially important. From this point of view, this report focuses on two efforts. The first example is the effort for designation of a new national park with a new concept of “environmental culture type” and “ecosystem management type” in the Amami Gunto Islands. This effort is a new challenge to focus on the importance of cultural aspects. The second example is the unique effort of the national park visitor center to conserve as one set of integrated nature and culture with an alliance of all stakeholders in Taketomijima Island, Iriomote-Ishigaki National Park. The visitor center serves not only visitors, but also islanders. These two cases are good models that suggest hints for future conservation measures © 2015 The Ecological Society of Korea. All rights are reserved. Source


Watari Y.,Chiyoda Corporation | Nishijima S.,University of Tokyo | Fukasawa M.,University of Tokyo | Yamada F.,Japan Forestry and Forest Products Research Institute | And 2 more authors.
Ecology and Evolution | Year: 2013

For maintaining social and financial support for eradication programs of invasive species, quantitative assessment of recovery of native species or ecosystems is important because it provides a measurable parameter of success. However, setting a concrete goal for recovery is often difficult owing to lack of information prior to the introduction of invaders. Here, we present a novel approach to evaluate the achievement level of invasive predator management based on the carrying capacity of endangered species estimated using long-term monitoring data. In Amami-Oshima Island, Japan, where the eradication project of introduced small Indian mongoose is ongoing since 2000, we surveyed the population densities of four endangered species threatened by the mongoose (Amami rabbit, the Otton frog, Amami tip-nosed frog, and Amami Ishikawa's frog) at four time points ranging from 2003 to 2011. We estimated the carrying capacities of these species using the logistic growth model combined with the effects of mongoose predation and environmental heterogeneity. All species showed clear tendencies toward increasing their density in line with decreased mongoose density, and they exhibited density-dependent population growth. The estimated carrying capacities of three endangered species had small confidence intervals enough to measure recovery levels by the mongoose management. The population density of each endangered species has recovered to the level of the carrying capacity at about 20-40% of all sites, whereas no individuals were observed at more than 25% of all sites. We propose that the present approach involving appropriate monitoring data of native organism populations will be widely applicable to various eradication projects and provide unambiguous goals for management of invasive species. © 2013 The Authors. Source


Sugimura K.,CIFOR | Ishida K.,University of Tokyo | Abe S.,Naha Nature Conservation Office | Nagai Y.,Amami Ornithologists Club | And 5 more authors.
ORYX | Year: 2014

Wildlife populations on Amami Island, Japan, have been affected by forest clear-felling and the introduction of alien species, in particular the mongoose Herpestes auropunctatus. We used monitoring data collected over 24 years to track changes in the population sizes of five species of mammals and 20 species of birds. We assigned species to the following groups: indigenous, rare, insectivorous, negatively affected by forest clear-cutting, and negatively affected by mongoose invasion. We examined trends in each group at four time points between 1985 and 2010 using two methods: species abundance estimates and the Living Planet Index. We then assessed the usefulness of these methods as tools for conservation planning. Inspecting species individually we identified four main patterns of abundance change: (a) an increase from the first to the last census period, (b) an increase in all periods except 2009-2010, (c) a decrease from 1985-1986 to 2001-2002 but an increase in 2009-2010, and (d) a decrease in all census periods. We observed certain relationships between these patterns and the species groups assigned as above. According to the Living Planet Index the group negatively affected by forest clear-cutting did not show significant recovery and the groups of rare species and species negatively affected by mongoose recovered to c. 40% of the original level after a sharp decline during 1985-2002. The Living Planet Index is a more useful tool for assessing the urgency of particular conservation needs, although limited information on species abundance reduces its representativeness for some groups. © Fauna & Flora International 2013. Source


Kuroiwa A.,Hokkaido University | Ishiguchi Y.,Hokkaido University | Yamada F.,Japan Forestry and Forest Products Research Institute | Shintaro A.,Naha Nature Conservation Office | Matsuda Y.,Nagoya University
Chromosoma | Year: 2010

The Ryukyu spiny rat, Tokudaia osimensis, has an XO/XO sex chromosome constitution, lacking a Y chromosome and the mammalian sex-determining gene SRY. To investigate the Y-loss event, we traced three proto-Y-linked genes, RBMY1A1, EIF2S3Y, and KDM5D, in the genome. The original Y-linked RBMY1A1 was lost as well as SRY, and the remaining RBMY1A1 was a processed pseudogene on autosome. In contrast, EIF2S3Y and KDM5D were conserved in genomes of both sexes as a result of their translocation from the Y chromosome to the X chromosome and/or autosomes. Furthermore, these genes were expressed in gonads and brains of both sexes. Our study indicated a loss of Y-linked genes with important male functions to be necessary for the Y chromosome to disappear. These functions might have been retained through the acquisition of new genes, and therefore, the Y-loss has had no harmful effect on the maintenance of this species. © 2010 Springer-Verlag. Source

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