A Preliminary Study of Pig Carcass Decomposition and Necrophagous Fly Community Dynamics on Hainan Island, China

Carcass decomposition and necrophagous fly activity provide important forensic evidence for postmortem interval estimation, yet data from tropical island environments remain limited. This study investigated decomposition characteristics, the relationship between total body score (TBS) and accumulated degree days (ADD), and changes in necrophagous fly communities on Hainan Island. In May 2025, 10 pig carcasses were placed simultaneously at five sites. Decomposition was recorded continuously using a pig-specific TBS system, environmental temperature and relative humidity were monitored, and adult flies were collected with Malaise traps and identified morphologically. All carcasses passed through the fresh, bloated, active decay, advanced decay, and skeletonization stages. Decomposition proceeded rapidly overall, although some variation occurred among regions and individuals. TBS showed a strong relationship with accumulated thermal input, and the log10(ADD) model provided a better fit than the raw ADD model. A total of 15,054 necrophagous flies representing 24 species from 13 genera and 5 families were collected. Calliphoridae was the dominant family, and Chrysomya nigripes Aubertin, 1932, was the absolute dominant species. This study provides reference data for forensic entomology under tropical conditions on Hainan Island.