Tapeworms in caribou and plastic worms in wolves are two examples of parasites that inhabit in a host's intestinal system. These worms act as parasites because they take away vital nutrients needed by their hosts and then use them for their own survival. Caribou and wolves can live long lives with these parasites, depending on the amount of food they are able to obtain. If food is limited, because they are being forced to share their nutrients with these internal parasites, these situations can be fatal.