Do you need location releases for national parks and model releases for Pets to use in picture books?
Many U.S. National Parks have permit systems in place for commercial photographers, but typically they allow unrestricted or less restricted amateur photography (1, 2,3,4,5,6). Restrictions that sometimes apply include forbidding use of tripods or use of flash or use of anything. For example, link 3 says,
Generally, photography in National Parks that is intended to produce commercial photographs must be permitted in advance. Here is an excerpt from link 4 for the Great Sand Dunes National Park and Preserve, in the San Luis Valley of Colorado, that is typical of the language used for several different parks:
You can publish without restriction pictures you take yourself in the parks, if they do not include persons who are recognizable. If persons are recognizable a model release is needed. For pictures taken by other people, copyright remains with the photographer unless other arrangements have been made (7).