Spatial Movement Patterns and Local Co-Occurrence of Nutria Individuals in Association with Habitats Using Geo-Self-Organizing Map (Geo-SOM)

초록

Simple Summary Nutrias (Myocastor coypus) escaped captivity in the 1990s in Korea; these individuals rapidly established wild populations, causing substantial environmental issues, including biodiversity loss, local habitat disturbance, and agricultural damage. The South Korean government initiated the Nutria Eradication Project in 2014 to control nutrias on a national scale. The aim of this research was to support the eradication efforts by improving our understanding of nutria movements based on biological and environmental factors. In this study, the geo-self-organizing map software was applied to radio-tracking data from individuals, and it was determined that males dominate nutria movement. Movement patterns were seasonal and varied with vegetation types between sexes and within each sex. Tall grassland was mainly associated with interactions between individuals of opposite sexes (possibly related to mating), whereas floating-leaved hydrophytes were related to same-sex interactions (possible feeding grounds). Data from this large-scale monitoring provide initial results for a more targeted and effective eradication program. Further large-scale population dynamics research is needed for a successful eradication program in the future. Nutrias (Myocastor coypus) were imported to South Korea for farming in 1985; individuals escaped captivity and established wild populations in natural ecosystems in the late 1990s. Numerous studies have focused on their monitoring and management; however, information on the continuous movement of individuals is not available. In this study, telemetry data from field conditions were used to identify the nearest-neighbor distances of individuals in association with environmental factors, including plant type, land cover, and biological parameters. The minimum nearest-neighbor distances for the different sexes were, overall, according to the minimum distances for the same sex. Local co-occurrences of individuals, either of the same or different sex, were seasonal. Tall grasslands, followed by herbaceous vegetation, were associated with the co-occurrence of different sexes. Conversely, floating-leaved hydrophytes, followed by xeric herbaceous vegetation, were correlated with the co-occurrence of the same sex. Local female-male co-occurrences were negatively associated with male-male co-occurrences but not with female-female co-occurrences, suggesting male dominance in group formations. Movement and co-occurrence information extracted using Geo-self-organizing maps furthers our understanding of population dispersal and helps formulate management strategies for nutria populations.

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