Island Biogeography and Guidelines for the Selection of Conservation Units for Large Mammals.
Bekele, Ermias
1980
Abstract
The proposals for applying island biogeography in the design of nature reserves are evaluated and general guidelines for the selection and management of conservation units are made. A total of 46 Ethiopian, 26 Indian and 16 United States large mammal species and subspecies distributed in 42 presently existing nature reserves of the three countries is considered in this evaluation. The relationships of number of species of ungulates, carnivores and total mammals to size and shape of conservation units, distance between conservation units, diversity of habitat, mean annual precipitation, mean annual temperature and mean elevation is determined. Step-wise multiple regressions are used to factor out the independent variable that contributed most to the respective number of mammals. Arithmetic and logarithmic models are also employed to predict number of species of mammals found in reserves. Finally, general guidelines for selection of conservation units are formulated. Overall, results show that the principles of island biogeography are not necessarily applicable in designing reserves for large mammals. Rather, diversity of habitat is found to be the single best criterion for selecting reserves containing large mammals. Specifically, relationships between size of reserve and the respective number of species of Ethiopian and Indian ungulates, carnivores and total mammals are not significant under an arithmetic model. Use of a logarithmic model produces significant increases in numbers of Ethiopian ungulates, Indian carnivores and total mammals, with increases in size of unit. Relationships between size of United States units and the respective number of species of mammals are significant and positive under both models; however, size of unit, in turn, is very highly and positively correlated with habitat diversity. With few exceptions, relationships between isolation and the respective Ethiopian and Indian mammals are not significant with either model. On the other h and , increases in distance between United States reserves show significant increases in numbers of carnivores and total mammals. The relationships between shape of conservation units and number of mammals found in the three countries are not significant under either model. Mean annual precipitation, mean annual temperature and mean elevation alone does not significantly influence number of mammals found in the conservation units examined. However, diversity of habitat shows significantly positive influences on large mammals. In fact, it is by far the single best predictor of mammals of all seven independent variables considered. The strategy in reserve selection should be to opt for sites that contain species that are representative, unique and endangered. In designing reserves, the primary objective should be to meet the habitat requirements of the target species. Size and shape of unit, isolation and conventional abiotic factors should be considered important only within the context of their indirect effect on habitat diversity. Thus, the island biogeographic considerations of area, shape and distance between colonizing source are of little or no benefit in designing reserves for generally non-mobile species as the large mammals. Instead, habitat diversity together with socio-economic factors should be considerations that guide the selection and management of conservation units for large mammals.Types
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