Multidimensional niche partitioning allows coexistence of multiple snake species

Abstract

Investigations on resource use by predators are important for understanding the mechanisms of biological coexistence. Although time, habitat, and diet are considered the three major dimensions for niche partitioning, studies that comprehensively investigate these dimensions in predator guilds are limited. Snakes are one of the predators whose populations have been reported to be declining worldwide. While diet has been considered as a fundamental variable that allows snakes to coexist, the importance of spatiotemporal resources has also been noted especially in temperate regions. To clarify the coexistence mechanisms of terrestrial snakes, we assessed the niche partitioning patterns of snakes on Sado Island, a Japanese island rich in snake species, from the perspectives of spatiotemporal and dietary resources. Specifically, we investigated the daily and seasonal occurrences as temporal niches, landscape-level distribution as a spatial niche, and stomach content as a dietary niche. We found that niche partitioning in all three major resources occurred among snake species on the island. Daily occurrence was partitioned into three groups: completely diurnal, nocturnal, and active during both periods. Seasonal occurrence was partitioned into three groups: widely active from spring to autumn, mainly active in summer, and mainly active in autumn. Distribution was partitioned into two groups: mainly distributed in lowlands and distributed even in mountainous areas. Food habits were partitioned into three groups: rodents, frogs, and earthworms as main prey, respectively. Our results provide empirical evidence that snakes can coexist through multidimensional niche partitioning, and that spatiotemporal resources are also an important force in terrestrial snake coexistence. Furthermore, we suggest that snakes on the island coexist through subtle differences along the three major niche axes, and that conservation of a variety of niches, rather than a single niche, will increase the species diversity of local snakes.