Scavenger assemblages are structured by complex competition and facilitation processes among vultures

Abstract

Understanding the factors that allow multiple species to coexist and share resources is an outstanding question in community ecology. Animals that share resources tend to use different strategies to decrease potential competition, through morphological adaptations, establishment of hierarchies, behavioral adaptations or spatial or temporal segregation. The main objective of this study was to infer interspecific processes of competition and facilitation through the study of species co-occurrence patterns in a vertebrate scavenger guild in de Brazilian cerrado. We analyzed patterns of spatial and temporal co-occurrence between species pairs, both qualitatively and quantitatively, and determined the activity patterns of the different scavenger species. For this purpose, we placed and monitored 11 large (i.e. goat) and 45 small (i.e. chicken) carcasses by camera-trapping, obtaining a total of 27 448 images. Our results show complex competitive and facilitative relationships among scavenging species in the Brazilian cerrado that are influenced by carcass size and change depending on the spatial and temporal scale at which they are analyzed. The scavenger assemblages that consumed large and small carcasses were different, evidencing resource partitioning between obligate and facultative scavengers. Furthermore, as an alternative to reduce competition levels, most species showed differences in their scavenging patterns, in addition to a strong temporal segregation during carcass consumption. Regarding New World vultures, our results suggest a strong interference competition between species with clear differences in their ecological traits (e.g. size, social behavior). However, we also found evidence of facilitation processes between vulture species in the location and access to the interior of the carcasses. Our findings highlight the role of obligate scavengers both in competition and facilitation processes in this vertebrate scavenger community. Future research should focus on investigating which species play the most important role in the structure and dynamics of this community, also considering intraspecific and behavioral patterns.

Scavenging in the realm of senses: smell and vision drive recruitment at carcasses in Neotropical ecosystems

“…All the raw data and analysis code used during the current study are available in the electronic supplementary material [54].…”

Behavioral interactions are modulated by facilitation along a heterotrophic succession

“…Carcass opening has already been established as a facilitative process in vertebrate scavenger communities in other ecosystems, although it has only been described with time‐static measurements (Alvarez et al, 1976; Naves‐Alegre, Morales‐Reyes, Sánchez‐Zapata, & Sebastián‐González, 2022; Orr et al, 2019; Selva et al, 2003). The time of carcass opening was highly variable between carcasses, as it relied on the arrival of the only species strong enough to slit the skin, that is, the king vulture.…”

“…The process of carcass opening refers to tearing apart the hard ungulate skin, which can only be done by a few scavenger species (e.g., those with the largest body size, or with powerful beaks), and thus giving access to the inside of the carcass for all scavengers. But this event has only been studied with time‐static measurements, relating it to the total time of carrion consumption (Orr et al, 2019; Selva et al, 2003), association patterns between species with different skin‐opening abilities (Kendall, 2013; Naves‐Alegre, Morales‐Reyes, Sánchez‐Zapata, & Sebastián‐González, 2022) or the relationship between the number of skin apertures and the frequency of feeding of a given species (Alvarez et al, 1976). Therefore, carrion is an ideal system to study temporal changes in the competition and facilitative processes that occur within vertebrate organisms during a heterotrophic succession because the community changes rapidly over time and carcasses could be easily monitored.…”

“…Carrion of a certain size allows the consumption of multiple individuals of different species at the same time (Moleón et al, 2015), which implies very high levels of competition, occurring among both conspecific and heterospecific individuals (Moreno‐Opo et al, 2020; Naves‐Alegre, Morales‐Reyes, Sánchez‐Zapata, & Sebastián‐González, 2022; Ruxton & Houston, 2004). Furthermore, different facilitative processes have also been described in scavenger communities, in the provision of carrion by carnivores (Allen et al, 2014), in the location of the carcass (Kane et al, 2014; Kane & Kendall, 2017; Naves‐Alegre, Morales‐Reyes, Sanchez‐Zapata, et al, 2022) and for carcass opening (Naves‐Alegre, Morales‐Reyes, Sánchez‐Zapata, & Sebastián‐González, 2022; Orr et al, 2019; Selva et al, 2003). The process of carcass opening refers to tearing apart the hard ungulate skin, which can only be done by a few scavenger species (e.g., those with the largest body size, or with powerful beaks), and thus giving access to the inside of the carcass for all scavengers.…”

Condors scavenge on fish at the land–water interface in the Andean foothill of southern Bolivia

“…A fish, unlike larger carrion (e.g. an ungulate carcass), can be consumed directly by any scavenger as it does not need to be opened or dismembered (a role that generally falls to condors due to their size and strength; Houston et al., 2020); so it is expected that the consumption of fish carrion often involves more competitive interactions than facilitative interactions between scavengers (Naves‐Alegre et al., 2022). Thus, for condors to decide to feed on fish, a series of factors (i.e.…”