Urbanization and Habitat Diversity Promote Endozoochorous Seed Dispersal by Raccoon Dogs Within Forest Fragments in Tokyo

TL;DR

Raccoon dogs in Tokyo's urban forests help disperse native plant seeds, with more seed diversity in areas with higher habitat diversity and built-up spaces.

Contribution

This study reveals the additive effect of urbanization and habitat diversity on seed dispersal by raccoon dogs in urban forest fragments.

Findings

Raccoon dogs dispersed 66 plant species, mostly native, with Morus australis and Aphananthe aspera being the most frequent.

Higher built-up areas and habitat diversity increased plant species richness in feces, enhancing seed dispersal.

Urban-adapted raccoon dogs play a key role in maintaining plant biodiversity in fragmented urban forests.

Abstract

Urbanization affects biodiversity and essential ecological functions, such as animal‐mediated seed dispersal. Novel urban habitats introduce environmental heterogeneity that alters the effectiveness of animal‐mediated seed dispersal. Despite growing urbanization, the additive effect of urban indicators on habitat diversity in shaping animal‐mediated seed dispersal by urban mammals remains poorly understood. Hence, this study examined the influence of urban indicators and habitat diversity on endozoochorous seed dispersal by urban‐adapted raccoon dogs within urban forest fragments of the Tokyo metropolitan area. We surveyed raccoon dog latrines across 19 urban green spaces and identified 66 plant species in their feces with most of them primarily native. The most frequently dispersed species were Morus australis and Aphananthe aspera. However, discrepancies between plant species found in the feces and those present in local vegetation suggest a broader foraging range beyond the study sites. The results showed that the presence of more built‐up area, significantly increased plant species richness in feces. The additive effect of built‐up areas and habitat diversity increased endozoochory at larger scales. This underscores the role of seed dispersers in maintaining plant diversity in urban forest fragments, where increasing habitat diversity at large scales supports more plant dispersal. Our findings highlight the importance of native plants in endozoochory, which supports their conservation by dispersing them. This study reinforces the ecological importance of urban‐adapted raccoon dogs in maintaining biodiversity and ecological processes despite the challenges posed by urbanization.

A study of raccoon dogs in Japan's urban forests revealed they are vital seed dispersers, primarily for native plant species. Notably, the dispersed plant species richness increased significantly with respect to habitat diversity and built‐up area compared to other urbanization indicators. This finding underscores the crucial ecological role of urban‐adapted wildlife in maintaining plant biodiversity within urban forest fragments.

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