Oaks can live to over 1,000 years old. That means they can sustain wildlife for centuries. Even as a sapling, the oak gets straight to work providing food and homes for wildlife. As it grows and ages, it becomes more valuable, developing cavities, crevices, dead wood and other features that plants and animals love. Once oaks reach 400 years old, they are considered ancient trees. They make perfect wildlife havens and support the greatest number of species.