Functional traits driving species role in the structure of terrestrial vertebrate scavenger networks

Species assemblages often have a non-random nested organization, which in vertebrate scavenger (carrion-consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the “role” of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species “normalized degree”), and the role of that species in the nested structure of the assemblage (i.e., the species “paired nested degree”), therefore identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages.

ESG, ZMR, JMB and LNA were supported by Generalitat Valenciana (SEJI/2018/024, APOSTD/2019/016, CIDEGENT/2020/030 and ACIF/2019/056, respectively), JMB, JMPG and CGC by Juan de la Cierva contracts (MEC; IJCI‐2017‐32149, FJCI‐2015‐25632 and IJC2018‐036642‐I, respectively), ACA by the Govern de les Illes Balears (PD/039/2017) and ESG and MM by Ramón y Cajal contracts (MEC; RYC‐2019‐027216‐I, RYC‐2015‐19231). EA was supported by La Caixa‐Severo Ochoa International PhD Program 2015. NS was partly supported by the National Science Centre in Poland (2013/08/M/NZ9/00469 and 2016/22/Z/NZ8/00). MK and KJ were supported by the Slovenian Research Agency (P4‐0059). Contributions of HG, KLT, EFA, OER, TLD, and JCB were partially supported through funding from U.S. Department of Agriculture and the U.S. Department of Energy under (DE‐EM0004391) to the University of Georgia Research Foundation. HG was also supported by the Institute of Environmental Radioactivity at Fukushima University. ALB and JDA were partially supported by Queens College and the Graduate Center at the City University of New York. JDA is currently supported by a Ramón y Cajal contract (RYC‐2017‐22783). ERB and EF were supported by the USA National Science Foundation Graduate Research Fellowship (1256065). CK completed study with support from Hawk Mountain Sanctuary, The Peregrine Fund, and via Pompeo M. Maresi Memorial Fund via Princeton University. JAS and CCW were supported by the USA National Science Foundation #1255913, the American Association for University Women, and the Gordon and Betty Moore Foundation. HUW acknowledges funding from the California Department of Fish & Wildlife (P0880013). PLP was supported by the Rufford Foundation and University of Wisconsin‐Madison. JB and JdT thank the Percy Sladen Memorial Fund and Mr Rodney Fuhr. Several authors were funded by funds from the MEC (CGL2012‐40013‐C02‐01/02, CGL2015‐66966‐C2‐1‐R, CGL2015‐66966‐C2‐1‐R2, CGL2017‐89905‐R, RTI2018‐099609‐B‐C21 and RTI2018‐099609‐B‐C22) and from the Junta de Andalucía (RNM‐1925). POV was supported by a research contract by the University of Lleida. EES and TMN were funded and supported by Australian Geographic, Bush Heritage Australia, Australian Academy of Sciences, Ecological Society of Australia, NSW Office of Environment and Heritage, NESP Threatened Species Recovery Hub, Emirates Wolgan Valley One and Only Resort. EP, YA, MS and UY completed study under research permit by The Republic of Turkey Ministry of Agriculture and Forestry. SAL thanks PICT (BID) 0725/2014, and IAATE. ALB and JDA would like to thank the Edmund Niles Huyck Preserve, Lyme Adirondack Forest Company, and LandVest Timberland