Naha Nature Conservation Office

Naha-shi, Japan

Naha Nature Conservation Office

Naha-shi, Japan

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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.


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.


Komine H.,Tokyo University of Agriculture and Technology | Takeshita K.,Tokyo University of Agriculture and Technology | Abe S.,Naha Nature Conservation Office | Ishikawa T.,Naha Nature Conservation Office | And 6 more authors.
Biological Invasions | Year: 2016

We used a generalized linear model (GLM) to investigate environmental characteristics of capture sites of the invasive small Indian mongoose (Herpestes auropunctatus) on Amami Island, Japan. Data were collected from 2002 to 2011, from an area with the lowest mongoose density. Data on capture levels and environmental factors were obtained within 1 × 1 km grid cells. In addition, we developed an evaluation map that predicts the occurrence of mongooses throughout the island by extrapolating the 2011 results, in which the last mongoose appearance was confirmed. We found that environmental characteristics of capture sites drastically changed during the final stage of the eradication project. From 2002 to 2010, mongooses were captured in grid cells with many gentle ridges. In 2011, when mongoose density became exceedingly low, mongooses seem to have survived in the grid cells with abundant steep ridges, where it was difficult to establish traps. Therefore, environmental factors affected capture levels and the density of the mongoose population. The evaluation map predicts that mongooses could survive on the southwest and southeast island peninsulas. This evaluation map will be helpful in allocating limited labor and financial resources toward the most effective capture strategies. This study suggests that an analysis of pest management data is an important step in the eradication of mongooses. Our results can contribute to long-term projects in invasive pest management not only for the mongoose population on Amami Island, but also for other invasive species globally. © 2015, Springer International Publishing Switzerland.


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.


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.


Fukasawa K.,Japan National Institute of Environmental Studies | Miyashita T.,University of Tokyo | Hashimoto T.,Japan Wildlife Research Center | Abe S.,Naha Nature Conservation Office
Proceedings of the Royal Society B: Biological Sciences | Year: 2013

Invasive species and anthropogenic habitat alteration are major drivers of biodiversity loss. When multiple invasive species occupy different trophic levels, removing an invasive predator might cause unexpected outcomes owing to complex interactions among native and non-native prey. Moreover, external factors such as habitat alteration and resource availability can affect such dynamics. We hypothesized that native and non-native prey respond differently to an invasive predator, habitat alteration and bottom-up effects. To test the hypothesis, we used Bayesian state-space modelling to analyse 8-year data on the spatio-temporal patterns of two endemic rat species and the non-native black rat in response to the continual removal of the invasive small Indian mongoose on Amami Island, Japan. Despite low reproductive potentials, the endemic rats recovered better after mongoose removal than did the black rat. The endemic species appeared to be vulnerable to predation by mongooses, whose eradication increased the abundances of the endemic rats, but not of the black rat. Habitat alteration increased the black rat's carrying capacity, but decreased those of the endemic species. We propose that spatio-temporal monitoring data from eradication programmes will clarify the underlying ecological impacts of land-use change and invasive species, and will be useful for future habitat management. © 2013 The Author(s) Published by the Royal Society.


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.


Yamada F.,Japan Forestry and Forest Products Research Institute | Kawauchi N.,Island Ecology Institute | Kawauchi N.,Yachiyo Engineering Co. | Nakata K.,Yambaru Wildlife Conservation Center | And 5 more authors.
Mammal Study | Year: 2010

The Okinawa spiny rat, Tokudaia muenninki, is a critically endangered species endemic to the northern part of Okinawa Island and may be extinct in the wild as there have been no recent sightings of the animal in its natural habitat. We initiated the present search to determine whether the spiny rat still exists in the northern part of Okinawa Island. Sensor cameras and traps were distributed across areas in which past studies had identified the location of occurrence of spiny rats. From a total of 1,276 camera-nights and 2,096 trap-nights from 2007 to 2009, we captured 24 spiny rats; however, we were only successful in identifying spiny rats in the northernmost of the areas sampled, with no indications of the spiny rat in the more southerly areas. The area in which the spiny rats were still present was estimated to be only 13 km 2 and is comprised of forest dominated by Castanopsis sieboldii, Lithocarpus edulis, Distylium racemosum and Schima wallichii. The trees range in age from about 30 to more than 100 years old, and have an average height of 12 m (range 7 m16 m). Our rediscovery of the spiny rat in 2008 comes after an interval of 30 years since the previous trapping study in 1978 and seven years since indirect survey evidence from analysis of feral cat feces 2001. Measures for conservation of the location of the spiny rats are urgently required. © 2010 the Mammalogical Society of Japan.


Kuroiwa A.,Hokkaido University | Handa S.,Hokkaido University | Nishiyama C.,Hokkaido University | Chiba E.,Hokkaido University | And 3 more authors.
Chromosome Research | Year: 2011

Tokudaia osimensis (the Amami spiny rat) and Tokudaia tokunoshimensis (the Tokunoshima spiny rat) have a sex chromosome composition of XO/XO, no Y chromosome. The mammalian sex-determining gene, SRY, is also absent in these species, which indicates that these spiny rats exhibit a novel sex-determining mechanism that is independent of SRY. To identify a candidate gene that controls this mechanism, the copy numbers and chromosomal locations of 10 genes with important functions in gonadal differentiation were determined: ATRX, CBX2 (M33), DMRT1, FGF9, NR0B1 (DAX1), NR5A1 (Ad4BP/SF1), RSPO1, SOX9, WNT4, and WT1. Multiple bands were detected for NR0B1 in Southern blot analysis, which suggested the presence of multiple copies of the gene in the genomes of these two species. CBX2 was localized to two loci in both sexes of the two species by fluorescence in situ hybridization mapping: 3q24 and 6p11.2 in T. osimensis and 10q25-q26 and 14q12-q13.1 in T. tokunoshimensis. Quantification of copy numbers in the two species by quantitative real-time PCR indicated that there were two or three more copies of CBX2 per haploid genome in males (T. osimensis, n∈=∈3; T. tokunoshimensis, n∈=∈2) than in females (T. osimensis, n∈=∈4; T. tokunoshimensis, n∈=∈2), whereas NR0B1 was present as a single copy in both. The results suggest that additional copies of CBX2 in males might be involved in a novel sex-determining mechanism in species that lack SRY. © 2011 Springer Science+Business Media B.V.


PubMed | Japan Forestry and Forest Products Research Institute, Chiyoda Corporation, Naha Nature Conservation Office and University of Tokyo
Type: Journal Article | Journal: 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 Ishikawas 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.

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