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University of Colorado Museum. A total of 71 trap deaths were recorded, out of nearly
<br /> 1650 individual small mammals captured over the course of the field season, an overall
<br /> mortality of about 4.3 percent Percentage of individuals captured which died varied
<br /> widely from one species to another, as follows: Sorex cinereus (1009,61), Chaetodipus
<br /> hispidus (0.0%), Reithrodontomys mega/ods (4.8%), Peromyscus maniculatus (2.3%),
<br /> P. nasutus (0.0%), Neotoma mexicana (0.0%), Mus musculus (3.2%), Rattus
<br /> norvegicus (0.0%), Microtus ochrogaster(20.4%), M. pennsy/vanicus (3.4%), Microtus
<br /> sp. (30.8%), Zapus hudsonius (3.7%). Note that trap mortality of meadow jumping mice
<br /> was below average for the 11 species recorded.
<br /> Species Diversity.—Species diversity is widely recognized as an important characteristic
<br /> of biotic communities, although there is no agreement on such fundamental issues as
<br /> how best to measure diversity or just what diversity means with regard to the history,
<br /> structure, function, health, or prospects of a particularly biotic community. Magurran
<br /> (1988) presented a cogent review of principles and methods. Habitat diversity as a
<br /> possible predictor of the presence of the meadow jumping mouse is explored in the
<br /> section on habitat, beyond. Focus in this section is on species diversity of small
<br /> mammals.
<br /> The simplest meaning of"species diversity" is species richness, the number of species
<br /> per area. Richness per site (see Appendix 1) ranged from three species on each of
<br /> three parcels (Gebhard, Kenosha Ponds, Dawson/Doniphan, Tracy Collins, week 6) to
<br /> six species (Hedgecock-Neuhauser, Lindsey, Culver/Ertl 11, East Varra). Mean species
<br /> richness was 4.5.
<br /> Of course, simple richness is a very crude measure of diversity. For one thing, it does not
<br /> express the relative abundance or dominance of species. For another, exotic species (Mus
<br /> musculus, Rattus norvegicus) contribute to richness equally with native species, although
<br /> they surely cannot be argued to contribute to habitat quality. By the way, presence of house
<br /> mice in study area does not appear to indicate habitat degraded to the extent that meadow
<br /> jumping mice cannot occupy a site. Z. hudsonius was taken with M. musculus on the
<br /> VanVleet Parcel (transect A in May, transects D and F in September). House mice were not
<br /> captured on the Gebhard Parcel, however.
<br /> Evenness usually is a more interesting measure of species diversity than is richness.
<br /> There are numerous ways to describe evenness (Magurran, 1988), none of which is
<br /> demonstrably superior to the others. Simpson's Index (Simpson, 1949) has the distinct
<br /> advantage of being fairly simple to calculate.
<br /> Table 5 indicates species diversity (evenness) by transect. The index is reported as the
<br /> reciprocal of Simpson's D, so that the index increases with increasing evenness. For
<br /> calculation of species diversity, captures identified only as "Microtus sp."were ignored
<br /> as those animals should not contribute to evaluation of either richness or evenness.
<br /> Such captures occurred on five study sites (see Appendix 1) as follows: VanVleet
<br /> (Week 2), 3.6%; Gebhard, 3.3%; Kenosha Ponds, 0.5%; Hedgecock-Neuhauser,
<br /> 1.7%; Culver/Ertl 11, 0.5%. Of course, per transact the influence of such unidentified
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