Although carrion ecology has received a great deal of scientific attention in recent years, carrion supply is still poorly described in most ecosystems. Animals die from many causes and their carcasses are exploited by a wide array of scavengers and decomposers. In terrestrial ecosystems, carrion is produced naturally at an annual rate of tens to hundreds of kg/km², although this figure may increase by several orders of magnitude in areas where living animals are concentrated, such as coastal ecosystems with important marine mammal colonies and the breeding grounds of semelparous fish. Mortality rates, cause of death, and species and individual identity of carcasses greatly influence how much carrion is available to scavengers. For instance, in populations characterized by a stationary age distribution, terrestrial megaherbivores, marine mammals, and other large animals contribute substantially to the total carrion biomass production in their ecosystems. After carcasses are produced, other factors such as carcass location, weather conditions, and biotic interactions may influence their availability to scavengers. Overall, the spatiotemporal variation in carrion availability is inevitably linked to the distribution of animals and the places and periods where they are more vulnerable to mortality. Also, although carcasses in terrestrial ecosystems are rarely moved during their consumption, carcasses in aquatic ecosystems frequently sink, float, or follow the currents. In relation to time, carrion production may experience strong fluctuations both within and between years. The growing field of carrion ecology, including the evolution of scavenging behaviour and carrion management, would benefit greatly from a better understanding of how much, where, and when carrion is produced and becomes available to scavengers.