Seasonal monopolization of small carrion by a scarab beetle in terra firme Amazonian rainforests

Abstract Small vertebrate carcasses represent an abundant resource in tropical rainforests, where scavengers play a key role in nutrient recycling, enhancing productivity in nutrient-poor habitats such as Amazonian terra firme forests. However, the contributions of vertebrate and invertebrate taxa to carrion decomposition in Amazonia remain understudied. Using motion-triggered and time-lapse cameras, we documented vertebrate species and arthropod groups interacting with 52 guinea pig carcasses in terra firme and floodplain forests in the Peruvian Amazon during dry and wet seasons. We quantified their contributions to carcass removal and examined variation across habitats and seasons, as well as temporal resource partitioning among insect taxa. A single dung beetle species, Coprophanaeus lancifer, removed 93% of carcasses in terra firme during the wet season, by burying them on-site. In contrast, 92% of floodplain carcasses in the wet season were removed by vertebrates. C. lancifer was absent in the dry season, when vertebrates removed most carcasses. Carcasses buried by C. lancifer lasted less than 24 h, reducing detectability for vertebrates and limiting access for other arthropods and necrophagous flies. To our knowledge, this is the first record of a rainforest invertebrate outcompeting vertebrates for carrion under natural conditions, highlighting C. lancifer as a keystone species shaping carrion trophic interactions.