There is an excellent handbook put out by Colorado State Parks called "Planning Trails with Wildlife in Mind". This handbook or similar guidelines should be mandatory for all trail planners who are constructing trails through habitat used by wildlife. It says that "any trail will have some negative impact on wildlife and the impact must be weighed against the benefits of the trail." It offers many practical suggestions for planning such trails. The handbook can be ordered by sending a stamped (requires six first class stamps), self-addressed 9"x12" envelope to Trails Program, 1313 Sherman St., Rm. 618, Denver, CO 80203 or fax 303-866-3206. It is also available from their website at http://dnr.state.co.us/parks/