Nest Site Preference and Fidelity of Chinese Alligator (Alligator sinensis)

Oviparous female reptiles select nesting sites with optimal ecological factors that contribute to egg development. Chinese alligator (Alligator sinensis), an oviparous reptile, is a critically endangered crocodilian with temperature-dependent sex determination. Research on its nesting behavior may facilitate the protection of this species. In this study, we monitored nesting behavior over eight years. We compared selected frequency of nest sites, distance from nest site to water, height from nest site top to the water surface, distance from nest site to human activity region, and canopy density between nest sites on the island and bank. The results showed that 45 nest sites were used by female alligators over eight years and each site was selected from one to 10 times. The selected frequency of nest site occurrence on the island was higher than that on the bank (P < 0.001). We observed that 88% of the individual alligators (15/17) showed different degrees of nest site fidelity. However, Chinese alligators might not always be loyal to only one nest site because of environmental changes or interspecific competition at nest sites. Our findings suggest that female alligators prefer to nest at island, which might be because of the nests on the island had a higher canopy density (P = 0.010) and were further from the human activity region (P < 0.001) than those on the bank did. It would be beneficial to reduce human activities during the breeding season and protect the vegetation of Chinese alligator habitats in the future.