Fauna Series No. 1 Cover Contents Foreword Approach Methods Analysis Conspectus Suggested Policy

Fauna of the National Parks of the United States PROBLEMS OF GEOGRAPHICAL ORIGIN CONDITIONS CAUSED BY EXTERNAL INFLUENCES The extent to which the fauna of any particular park suffers from adverse external influences depends upon three factors, namely: (a) How much the fauna in the surrounding territory has been altered from its primitive condition. (b) How adequate the area of the park is. (c) How nearly the park boundaries follow natural barriers. Every park is surrounded by territory in which the wild life has been greatly changed, but in some cases the aridity of the faunal life in such regions has become so great that the vitality of the park fauna is sapped at every boundary. Inasmuch as the external factor itself can not be generally controlled, resort must be had to improving the other two conditions. Increasing the size of the area and bounding it by natural barriers will help in many cases, but some encroachments, such as the spread of certain exotic plants or animals into a park, can not be stopped by any of these methods. Management measures to counteract these influences may be worked out in some instances, but there will be others where nothing that can be done is likely to correct matters. FIGURE 19. – River otter is one of the fur-bearers that can only be perpetuated in parks of large area. There are few places where the otter trusts man enough to play in the waters of a small lake while people watch from shore. Photograph taken July 10, 1931, at Bear Paw Lake, Grand Teton, by B. H. Thompson. Wild Life Survey No. 2424 NEXT> CARNIVORES DRAINED FROM PARK BECAUSE BLACKLISTED OUTSIDE (6)

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