Small Mammal Populations on Islands
1965
Webb, William L.
Small mammal populations on three islands in Adirondack lakes were studied by trap removal, and results compared with trap removal data from three similar mainland areas. Number of species present on islands was less than on the mainland, but island size did not affect faunal diversity. Microtus were much more prevalent on islands and occurred in forested habitats. Total population density of small mammals on the islands was determined by extended removal trapping. Total density and density by species are given. Short periods of removal trapping do not indicate species composition of the community because some abundant species are seldom captured in the early part of the trapping period. Species differences in initial attraction to the traps or changes in behavior following extensive removal of "social dominants" may be involved. Probability of capture is variable, and not consistently related to population density. Several census methods are evaluated and shown to provide an inaccurate estimate of population. Comparison of capture rates on mainland areas with that on islands suggests that invasion may not be a major factor until after 10 to 15 days of trapping. Long—continued trapping on mainland areas produces periods of high catch which may exceed capture rates of the initial period. The reasons for these periods of high catch are not known.
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