Scavenging in the Anthropocene: Human impact drives vertebrate scavenger species richness at a global scale

Abstract

© 2019 John Wiley & Sons Ltd Understanding the distribution of biodiversity across the Earth is one of the most challenging questions in biology. Much research has been directed at explaining the species latitudinal pattern showing that communities are richer in tropical areas; however, despite decades of research, a general consensus has not yet emerged. In addition, global biodiversity patterns are being rapidly altered by human activities. Here, we aim to describe large-scale patterns of species richness and diversity in terrestrial vertebrate scavenger (carrion-consuming) assemblages, which provide key ecosystem functions and services. We used a worldwide dataset comprising 43 sites, where vertebrate scavenger assemblages were identified using 2,485 carcasses monitored between 1991 and 2018. First, we evaluated how scavenger richness (number of species) and diversity (Shannon diversity index) varied among seasons (cold vs. warm, wet vs. dry). Then, we studied the potential effects of human impact and a set of macroecological variables related to climatic conditions on the scavenger assemblages. Vertebrate scavenger richness ranged from species-poor to species rich assemblages (4–30 species). Both scavenger richness and diversity also showed some seasonal variation. However, in general, climatic variables did not drive latitudinal patterns, as scavenger richness and diversity were not affected by temperature or rainfall. Rainfall seasonality slightly increased the number of species in the community, but its effect was weak. Instead, the human impact index included in our study was the main predictor of scavenger richness. Scavenger assemblages in highly human-impacted areas sustained the smallest number of scavenger species, suggesting human activity may be overriding other macroecological processes in shaping scavenger communities. Our results highlight the effect of human impact at a global scale. As species-rich assemblages tend to be more functional, we warn about possible reductions in ecosystem functions and the services provided by scavengers in human-dominated landscapes in the Anthropocene.

Uncovering the vertebrate scavenger guild composition and functioning in the Cerrado biodiversity hotspot

“…This community is among the most diverse scavenger communities described worldwide, with 15 of the 19 of the species detected here being exclusive to the Neotropics (IUCN, 2020;Sebastián-González et al, 2019). We find few scavenging communities with higher species richness in the literature, like the Polish temperate forests, with…”

“…This is the first time the Cerrado scavenging community is described, and our findings emphasize the importance of the functions and ecosystem services provided by the scavenger guild in this Neotropical region. Several factors have been shown to influence the composition of scavenger communities, such as habitat, topography, and climate (Mateo-Tomás et al, 2017;Sebastián-González et al, 2019Turner et al, 2017). Nevertheless, it has been concluded that human disturbance is the factor that most affects the richness of scavengers (Sebastián-González et al, 2019) and also influences the way scavenger assemblages are structured and their efficiency at the global scale (Sebastián-González et al, 2020).…”

Directed endozoochorous dispersal by scavengers facilitate sexual reproduction in otherwise clonal plants at cadaver sites

“…This could be particularly detrimental to long-term plant population resilience when, as we show, some plant species may benefit from the endozoochorous dispersal service provided by facultative scavengers to facilitate recruitment and so completion of their life cycle (Traveset et al, 2012). Our study area had a relatively intact scavenger guild, but anthropogenic pressures are significantly affecting scavenger richness and abundance on a global scale (Sebastián-González et al, 2019. Humans can affect scavenger species directly through persecution (Swenson et al, 1995) but also indirectly through cadaver removal (Margalida et al, 2010), habitat fragmentation and destruction (Sebastián-González et al, 2019).…”

“…Moreover, the assembly of scavenger guilds (i.e., disperser species) utilizing cadavers (Selva et al, 2005;Turner et al, 2017) and the interactions between a cadaver, scavengers and surrounding habitat may have a considerable impact on whether CDIs, directed dispersal, or seedlings occur. For example, a cadaver deposited in winter might be either completely consumed or scattered over the landscape by scavengers within a relatively short time (Towne, 2000;Turner et al, 2017) Tomás et al, 2017;Sebastián-González et al, 2019. This could be particularly detrimental to long-term plant population resilience when, as we show, some plant species may benefit from the endozoochorous dispersal service provided by facultative scavengers to facilitate recruitment and so completion of their life cycle (Traveset et al, 2012).…”

“…Our study area had a relatively intact scavenger guild, but anthropogenic pressures are significantly affecting scavenger richness and abundance on a global scale (Sebastián-González et al, 2019. Humans can affect scavenger species directly through persecution (Swenson et al, 1995) but also indirectly through cadaver removal (Margalida et al, 2010), habitat fragmentation and destruction (Sebastián-González et al, 2019). Furthermore, a reduction in cadaver availability would also decrease the frequency of CDIs, that is, reduce microsite availability.…”