Temporal dynamics of carrion fly communities at carrion bait in the South African Highveld

Calliphoridae, Sarcophagidae and Muscidae are important components of invertebrates involved in decomposition and nutrient cycling and dispersal. These carrion flies are vectors of gastroenteric pathogens, pollinators, and are valuable as evidence in medicolegal investigations. Despite their importance, carrion fly surveying methods applied in the published literature are inconsistent, varying in bait type, mass, and exposure period, making it difficult to compare results and be certain that representative samples of target communities were captured. This study aimed to determine how species of Calliphoridae, Sarcophagidae and Muscidae are attracted to chicken liver-baited traps decaying over time and, therefore, the time required to catch representative samples of carrion flies in the Highveld ecoregion of South Africa. Modified Redtop® bag traps were used and baited with 120g of food-grade chicken liver. Grassland, shrubland and woodland habitats were surveyed with the traps exposed for three, six, nine and twelve days in the spring and winter of 2024. In total, 28 species were trapped. The flies arrived at the traps at different rates between habitat types and seasons. In spring, Chrysomya chloropyga was the most abundant species at traps while in winter, Sarcophaga spp. were most abundant at traps. Species accumulation curves indicated that more than 12 days of bait exposure are required for a representative sample to be obtained across all habitats and seasons sampled thus far. The patterns of arrival of members of Calliphoridae, Muscidae and Sarcophagidae at traps align with studies using other baiting methods. However, this method caught fewer species than studies in the same region using large animal carcasses and fewer Sarcophagidae species compared to using fish carrion.