"Nature's Cleanup Crew" describes the busy scavengers that live in our cities, recycling mountains of waste consumers leave behind. To us, it's garbage. To them, it's dinner. With the help of thoughtful and passionate scientists, we find out what makes scavengers tick.  Urban ecologists and entomologists are studying the interactions and behaviours of various ant species living in underground colonies in New York City. The most mature ants forage for food dropped by humans, competing with rats. On the planet, ants outnumber humans by a billion to one and are important in the ecosystem.   Toronto psychologist and biologist, Suzanne MacDonald, studies urban nocturnal animal behavior, including raccoons, skunks and - last in line - Virginia opossums, North America's only marsupial. Climate change has extended their habitat north and these harmless animals provide a service in urban areas by eating ticks, slugs, snails, snakes and even digesting bones and carcasses left by other scavengers.  In Berlin, foxes have adapted to scavenge in the urban environment as human settlements encroached on their habitat. And in Ethiopia, the city of Addis Ababa is teeming with vultures, one of the most recognizable scavengers of all. These striking birds are protecting people from deadly disease, but their populations are in decline due to poisoning. Researchers are on a mission to reverse the fortunes of Africa's vultures. Vultures, ants, foxes, opossums and others offer us many benefits, simply by sharing our space. Nature's Cleanup Crew is a cast of vital creatures, each beautiful in their own right. Without them, our waste would be piling up and we would be dealing with many deadly diseases. A 'Nature of Things' video.