Observational Study of Small-Clawed Otters (Aonyx cinereus) as a Bio-indicator in the Mangrove Habitats of Mayiladuthurai District of Tamil Nadu, India

The small-clawed otter (Aonyx cinereus) serves as an essential component of mangrove ecosystems, yet its role as a bio-indicator remains largely understudied, particularly in the Mayiladuthurai District of Tamil Nadu, India. In this observational study, we aimed to assess the ecological significance of small-clawed otters and their potential as bio-indicators of mangrove habitat health. Field surveys were conducted between March 2023 and August 2024 in various mangrove habitats across the Mayiladuthurai District, as the study period was strategically selected to encompass key behavioural phases of Aonyx cinereus spanning two monsoon cycles and multiple ecological phases. The duration ensured robust assessment of otters as bio-indicators of mangrove habitat health while accommodating field accessibility and research feasibility. We employed direct observation techniques supplemented with community spotting to document otter presence, behavior, and habitat preferences. Additionally, environmental parameters, including water quality, vegetation density, and prey availability, were assessed to understand their influence on otter distribution. Preliminary findings revealed a notable presence of small-clawed otters in the mangrove habitats of Mayiladuthurai District. Otters were predominantly observed in areas with higher mangrove tree density and proximity to freshwater sources. Behavioral observations suggest a preference for specific microhabitats within the mangroves, such as dense root networks and tidal channels. Furthermore, our study indicates a potential correlation between otter presence and overall mangrove ecosystem health. Analysis of water quality parameters revealed higher levels of dissolved oxygen and lower pollutants in areas frequented by otters, suggesting their role as indicators of habitat quality. This study underscores the importance of small-clawed otters in mangrove ecosystems and highlights their potential as bio-indicators for monitoring environmental changes.