Vulture dominance in a scavenger assemblage in the Neotropical dry forest

Scientific knowledge of vertebrate scavenging communities has increased over the last decades. However, there is a lack of information on the Neotropics. We aimed to describe the vertebrate scavenger community of the tropical dry forest of western Ecuador and to identify the factors influencing carcass consumption patterns by this guild. Between November 2022 and May 2023, we placed 64 experimental carcasses of different sizes in eight camera-trapping stations (32 carcasses for each category). At each station, we simultaneously placed two carcasses at least 100 m apart: one small-sized (chicken) and one medium-sized (goats or pigs) carcass. We fitted Generalized Linear Mixed Models to assess the effects of carcass size and season (rainy and dry) on the scavenger species richness and abundance, considering all scavenger species and by species group. We also fitted Linear Mixed Models to assess differences in carcass detection time, total consumption time and rate, using the carcass size, vulture abundance, and percentage of canopy cover as predictors. The scavenger community was dominated by obligate scavengers (i.e., vultures), and the species detected were the Black Vulture (Coragyps atratus), the Turkey Vulture (Cathartes aura), and the King Vulture (Sarcoramphus papa). Facultative mammalian scavengers such as Ocelot (Leopardus pardalis), Tayra (Eira barbara), Crab-eating Raccoon (Procyon cancrivorus) and domestic dog (Canis lupus familiaris) were recorded in a smaller number of carcasses. No facultative avian scavenger species were detected. Carcass size influenced all the variables analyzed, except the scavenger species richness. While the season influenced the vulture abundance, especially of S. papa. Facultative scavenger richness and abundance did not show significant differences. Carcass total consumption time was not explained by any of the variables included in the models. Both carcass detection time and consumption rates were influenced by carcass size, particularly in the case of consumption rates, where larger carcasses exhibited higher consumption rates than smaller ones. The dominance of vulture species in the scavenger community suggests that their ecological role is indispensable for the dry forest of western Ecuador. The loss of obligate scavengers could have important implications for ecosystem services and human well-being.