Stress Effects on Natural Ecosystems

Author Institution: Institute of Environmental Sciences and Department of Zoology, Miami Universit

Comparison of Food Resource Removal by Animals in Forest, Old-Field, and Ecotone Habitats

Author Institution: Department of Zoology, Miami UniversityThis study was conducted at the Miami University Ecology Research Center from mid-July through late September, 1980. A 1-ha plot of forest, an adjacent 1-ha second-year old-field, an ecotone interface, and a nearby wooded fence-row ecotone served as the study site. Ten fleshy fruits of each species, red mulberry (Morus rubra), blackberry (Rubus frondosus), and wild black cherry (Prunus serotina) were situated on 0.5-m-high log feeding sites (3/habitat). Each trial lasted for 5 days and was replicated. Sites were observed each morning and the number of remaining fruits recorded. Visual observation for avian consumers and live-trapping for small mammal consumers were conducted to estimate their role in resource removal. Morus trials showed no significant differences (p > 0.05) in fruit removal rates from each site; Rubus removal from the woods ecotone was significantly less (p ^ 0.05) than from the fence-row ecotone or the forest on day 1; Prunus removal from the old-field was significantly less (p ^ 0.05) than from the fence-row ecotone or the forest on day 1. Small mammals (Peromyscus spp.) appeared to play a major role in fruit removal. Removal rate differences appeared to be a function of habitat structure

Brief Note Caloric Ingestion Rate and Assimilation Efficiency of the Short-Tailed Shrew, Blarina Brevicauda

Author Institution: Department of Zoology, Miami Universit

Species Importance within a Virgin and a Timbered Beech-Maple Forest Ecosystem

Author Institution: Department of Zoology, Miami UniversityA virgin forest, Hueston Woods in southwestern Ohio, and a selectivelycut forest, Lewis Woods in east central Indiana, were sampled by a modified pointquarter method in order to evaluate the impact of timbering on community structure. Timbering occurred in Lewis Woods in 1910, 1935, and 1955. Importance values were computed for each species encountered (> 1 inch diameter breast height) within each study area in order to determine the timbering impact on community structure. Hueston Woods was clearly dominated by sugar maple (Acer saccharum) and American beech (Fagus grandifolia) with importance values of 132.6 and 117.3, respectively. Lewis Woods was characterized by a more even importance distribution patterns, although sugar maple and American beech were still found to be of greatest importance with values of 120.8 and 76.8, respectively. Sixteen species were encountered in Lewis Woods as compared to 13 species for Hueston Woods. The significance of these differences is discussed

Prey Selection and Bioenergetics of Captive Screech Owls

Author Institution: Department of Zoology and Institute of Environmental Sciences, Miami UniversityScreech owls appeared to select meadow voles {Microtus pennsylvanicus) as a primary food source, although deer mice (Peromyscus maniculatus) were apparently equally abundant and vulnerable. This feeding behavior resulted in a larger energy reward. A mean ingestion rate of 0.37 kcal/g live wt/day was derived from average values of 29-3 g live wt/day for Microtus as prey and only 11.3 g live wt/day for Peromyscus. Assimilation energy (ingestion-pellets-feces) was 0.28 kcal/g live wt/day; the mean assimilation efficiency (ingested energy-pellet energy-fecal energy/ingested energy x 100) was 76%. These findings support the hypothesis that a large energy reward is a prime factor in prey selection

Golden Mouse (Ochrotomys nuttalli) and White-Footed Mouse (Peromyscus leucopus) Dietary Resource Partitioning Under Experimental Field Conditions

Ochrotomys nuttalli and Peromyscus leucopus are two small-mammal species that have similar life histories. This results in a relationship with a high degree of sociality between the two species, including extreme niche overlap. We investigated differences in diet preference and daily caloric intake under experimental field conditions in order to clarify this close relationship. Diets were based on reported food preferences in their natural environment. Five food resources were provided to 20 adult individuals (10 male, 10 female) of each species for three consecutive days. Individuals were contained in separate covered mesocosm tanks located in a riparian forest ecosystem. White-footed mice consumed more energy per day than golden mice (0.89 and 0.70 kcal • g live wt-1, respectively), which is considerably less (2.38 and 1.48 kcal • g live wt-1, respectively) than those reported by Gibbes and Barrett (1) when fed identical diets under controlled, laboratory conditions (22°C). This study also suggests that nest cavities and soundscape assist in mitigating environmental perturbations, such as food scarcity and predation, in their natural habitat

Effects of DDT on the Density and Diversity of Tardigrades

Twenty lichen-bearing tree bark samples were collected from DDT sprayed American elm trees (Ulmus Americana L.) in central Iowa. Twenty comparable samples were collected from an adjacent nontreated habitat. A tardigrade density of 4 individuals collected from the treated habitat was found to differ significantly (P \u3c .01) from a density of 97 individuals collected from the non-treated area. Margalef\u27s diversity index (D=S-1/1n N) determinations were found to be 0.00 and 0.44 for the treated and non-treated habitats, respectively. Tardigrade species organization within the nontreated habitat did not differ significantly from that as predicted by MacArthur\u27s broken-stick model, suggesting that tardigrade species occupy contiguous, non-overlapping niches within a lichen-bearing tree bark ecosystem. It is suggested that measurements depicting microfauna-lichen-tree bark relationships might serve as useful criteria in evaluating pesticide stress effects on total forest ecosystems

Prey Coat Color Selection and Bioenergetics of Captive Screech Owls

Author Institution: The Institute of Environmental Sciences and Department of Zoology, Miami Universit