Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Animal Ecology


There is, at present, no unbiased, convenient, and economically feasible means available to determine the true prevalence of rabies in wildlife. Four projects were undertaken to test the feasibility of using the Common Crow as a reliable sentinel species of sylvatic rabies. In one project, captive crows contracted rabies orally when fed rabies infected mice brains. One-year-old crows developed an earlier humoral immune response with a greater mean antibody titer than did 2-year-old birds. Antibody levels persisted for about 2 weeks. No birds died or showed overt clinical signs of rabies disease during the experiment;In another project, rabies virus remained viable in striped skunk carcasses for about 2 weeks at 24(DEGREES)C and throughout the 22-day study period at 10(DEGREES)C. The skunks with experimentally induced furious rabies had a higher mean titer than did the other skunks;In order to determine the geographic area that a crow survey of rabies would monitor, information was collected on crow foraging areas and movement patterns. The mean foraging area around the nest site was 151 ha with the longest recorded flight from a nest of 4.8 km. During July and August, crow families continued to feed in their respective nest areas but joined other crows at nighttime roosts. Northern breeders migrated into central Iowa during November. Some crows were year-around residents. The mean foraging area for winter roosting crows was 110.8 km('2) and varied directly with the number of birds in the roost;In the fourth project, vertebrate foods occurred in more than 40% of the food samples collected from November to June. Fifty observations of crows scavenging on road-killed carcasses were recorded. On 8 of these occasions, crows were feeding on Striped Skunks. The prevalence of rabies antibodies in 332 wild adult crows and 70 crow broods was 18.3% and 31.4%, respectively. No statistical correlations were found between the prevalence of rabies antibodies in crows and rabies antigens in skunks. Sampling 4-week-old nestling crows is recommended as the best index of rabies prevalence in wildlife.



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Joseph Martin Schaefer



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85 pages