Seasonal variation of dung-associated arthropods in cattle pastures of Terceira Island (Azores): a year-round, event-based dataset.

Background: Dung-associated arthropods, particularly dung beetles (Scarabaeidae), together with rove beetles (Staphylinidae) and water scavenger beetles (Hydrophilidae), support key ecosystem functions in cattle-grazed landscapes, including dung removal, nutrient cycling, soil aeration and pest suppression. Their activity is strongly seasonal in temperate systems, driven by temperature and moisture and can be further reshaped by pasture management (e.g. changes in grazing regimes and dung availability). Oceanic islands add an important perspective because species pools are typically smaller and often dominated by introduced taxa, potentially altering phenology and dominance patterns across the year. However, year-round, standardised, event-based datasets for dung-associated arthropod assemblages remain scarce for oceanic islands, limiting robust comparisons amongst guilds, sites and management regimes and reducing our ability to benchmark seasonal windows of activity under climate variability and land-use change. New information: We provide a one-year, monthly, standardised dataset of dung-associated arthropods from two cattle pastures on Terceira Island (Azores, Portugal), spanning October 2022 to September 2023. Sampling used dung-baited pitfall traps (four traps per site per month, deployed for 2-4 days) at a low-elevation pasture ("University of Azores Campus", 41 m) with seasonal cessation of grazing during summer maize cultivation and a mid-elevation pasture ("University of Azores Granja", 380 m) grazed year-round. The published Darwin Core Archive includes an Event core (96 sampling events) and an Occurrence extension (1,701 occurrence records), with associated metadata including minimum and maximum temperatures per event. In total, 13,882 individuals, belonging to four classes, 16 orders and 61 families, were assigned to 175 morphospecies; 143 morphospecies (12,865 specimens) were identified to full scientific name.The annual series documents contrasting seasonal dynamics amongst focal dung-associated beetle groups: Scarabaeidae show a short May-July peak at Granja, but a longer, irregular activity period at Campus; Staphylinidae remain active most of the year with site-specific peaks; and Hydrophilidae display a strong late spring-summer pulse at Granja, but a weaker, more prolonged pattern at Campus.