In the wild, keeping family of lions or whatever you consider have to consume food within the territory. So enough food has to grow or to be produced for prey animals, whereas in zoos, the animal keeper is bringing the food. And, therefore, the quantity of space can be much smaller, if the quality is correct. And this gives us the right to keep animals. And this is never, ever understood by animal rights person, which usually have no scientific background. Dr. Hediger has written these important books, but yet, at least in the United States, many younger curators, zoologists, animal keepers, are not aware of his writings. And they seem to be a foundation for good zoo management.