**Preface to "Ecology of Predation and Scavenging and the Interface"**

Imagine the rise of animals on our planet. Around 650 million years ago, certain multicellular organisms began to thrive in the waters and on seabed of the primitive ocean. These earliest animals primarily fed on non-animal organisms, either living or dead. However, these animals themselves represented an additional food resource, one that was particularly nutritional. Straight away, we can also envisage how some of those tiny animals promptly started to exploit this emergent resource, thus leading to the first carnivory events ever on Earth. In those rudimentary aquatic ecosystems, the earliest carnivorous species very likely exploited animals—possibly transported by currents or resting on the seabed—that could not escape from being consumed, because of their lack of mobility or simply because they were dead. During the Cambrian explosion, around 100 million years later, some of these creatures, perhaps in an attempt to avoid predators, forged their way onto land, under a low-oxygen atmosphere. Amongst the ancient arthropods that ventured into this newly occupied and challenging environment, there were carnivorous species that undoubtedly made use of other live and dead animals. Thus, carnivory surely displayed its predation–scavenging duality from the very first moment of animal history. Since then, many species in most faunal groups have adopted a carnivorous diet, either strict or opportunistic.

When the first naturalists and scientists, in their initial efforts to unravel nature, engaged in the arduous task of disentangling and naming its basic components, they usually considered predators (and predation) to be neatly different from scavengers (and scavenging). This distinction has pervaded the ecological and evolutionary research of carnivorous animals until very recently, which, admittedly, still causes me some surprise. At the beginning of the 21st century, the pioneer work of Travis L. DeVault and his colleagues, in North America, and Nuria Selva and her colleagues, in Europe, called broad attention to the fact that both processes, predation and scavenging, were indeed intimately linked. These and other studies widely showed that there are not pure predators and pure scavengers, but that different individuals, populations and species are positioned somewhere in the predation–scavenging gradient. For a carnivorous animal, including hominins, the decision of hunting prey or scavenging its carcass is merely the result of the balance between the costs in accessing the food and its energetic reward, plus some aspect of chance—exactly like that which characterizes many other biological phenomena.

By that time, I was facing a new, largely uncertain, though decisive, stage in my life. Like many other young researchers, once I finished by PhD thesis on predator–prey interactions, I was eagerly struggling to find my place in the postdoctoral universe. The mentioned pioneer works became a real stimulus in guiding my research scheme onwards. The stimulating, enthusiastic, informal, and always funny conversations with my good friend Jose A. S ´ anchez-Zapata, along with inspiration from ´ other researchers that I also profoundly admired, such as Jose A. Don ´ azar, Fernando Hiraldo, and ´ Norman Owen-Smith, greatly motivated me to begin the basis of a project to explore the interactions between predators and scavengers. Not surprisingly, the first steps of this novel research line for me were done in Africa. This continent meets all the ideal conditions for this purpose, as it still maintains (unfortunately, in an increasingly restricted number of areas) complex assemblages of carnivorous species, including large predators and vultures, as well as a varied offer of prey and carrion, including megaherbivores. In Africa, moreover, one can feel himself, probably like in no other place, as an integral part of nature, which aids the process of thinking about the ecological interactions that take place within food webs—and that shaped our origin and evolution as humans.

Today, we know well that full recognition of the dual facet of carnivorous species has profound implications at different levels of life organization. However, most of them still remain largely unexplored. Some of these relevant questions include: What is the proportion of predated versus scavenged prey in the diet of carnivorous animals? Which are the factors that make some individuals more prone to scavenging, and some others more prone to hunting? To what extent do predators and scavengers compete for shared resources? Can predators benefit scavengers, and vice versa? How may these interactions between predators and scavengers indirectly affect prey populations? What is the role of carcasses as information centers and predator and parasite risk sites for scavengers, predators and their prey? How may the interaction between predation and scavenging challenge established principles in food web and community structure and function? Are there new methodological tools to help advance our understanding of the interface between predation and scavenging?

This book is the result of a Diversity's Special Issue, of which I was honored to guest edit, which was an exciting opportunity to deal with some of these and other questions. The book's main goal is to consolidate our awareness of the close connection that exists between predation and scavenging. Through its six chapters, I hope this compendium of science may help to inspire ecologists, evolutionary biologists, paleontologists, anthropologists, epidemiologists, forensic scientists, anatomists, and, of course, conservation biologists in their stimulating and promising endeavor of achieving a more comprehensive understanding of carnivory in this rapidly changing world.

> **Marcos Mole ´on** *Editor*
