Human-Mediated Carrion: Effects on Ecological Processes

Abstract

Humans play an essential role as modulators of energy flow within food webs in terrestrial and marine ecosystems. This is especially relevant given their capacity to generate large amounts of carrion as a result of anthropogenic activities. These trophic subsidies have increased since the twentieth century due to uses related to livestock management, hunting, waste disposal and sea fishing, changing the way in which food resources are available for scavenging species. Knowledge about the management of anthropogenic carrion is key to understanding the supply and demand mechanisms of this resource for necrophagous animals and the associated effects. Thus, changes in carrion occurrence patterns are happening at a global scale. Carrion has shifted from a pulsed random resource from carcasses of wild animals, to a more predictable resource in its appearance at certain times and locations depending on human activities. These changes have occurred in a short period of time, mainly in industrialized countries with large human populations. As a result, some wild scavengers have been forced to adapt their diet and their manner of obtaining food, modulating their biological fitness, including fertility, survival, morphology, and space use. To these individual effects, different population implications have been added, including demographic (increases or decreases in population size and density-dependence phenomena), behavioral (intra- and interspecific competition and migration), and chorological (modulation of distribution range). At the community level, anthropogenic carrion subsidies have also produced alterations, especially in food web performance, in predator-prey relationships, in aspects like species richness and even in characteristics of the landscape. This determinant influence of humans on carrion-related ecological processes also requires an analysis from the point of view of conservation biology. In this sense, it is necessary to avoid negative effects leading to the extinction of certain species or populations as well as to ensure that carrion provisions in the wild is provided following natural patterns.