Oral rabies vaccination (ORV) baiting programs for control of raccoon (Procyorl lotor) rabies in the USA have been conducted or are in progress in eight states east of the Mississippi River. However, data specific to the relationship between raccoon population density and the minimum density of baits necessary to significantly elevate rabies im~nunity are few. We used the 22-km2 US National Aeror~autics and Space Administration Plum Brook Station (PBS) in Erie County, Ohio, USA, to evaluate the period of exposure for placebo vaccine baits placed at a density of 75 baits/km2 relative to raccoon population density. Our objectives were to 1) estimate raccoon population density within the fragmented forest, old-field, and industrial landscape at PBS; and 2) quantify the time that placebo, Merial HABORAL V-RG" vaccine baits were available to raccoons. Froin August through November 2002 we surveyed raccoon use of PBS along 19.3 km of paved-road transects by using a forward-looking infrared camera rnol~r~ted inside a vehicle. We used Distance 3.5 software to calc~~late a probaljility of detection function by whit11 we estimated raccoon pop~ilation density from transect data. Estimated population density on PBS decreased from August (33.4 raccoons/km2) through November (13.6 raccoons/krn2), yielding a monthly rnean of 24.5 raccoons/km2. We also quantified exposure time for ORV baits placed by hand on five 1-km2 grids on PBS from September through October. An average 82.7% (SD=4.6) of baits were removed within 1 wk of placement. Given raccoon population density, estimates of bait removal and sachet condition, and assllming 22.9% nontarget take, the baiting density of 75/ km' yielded an average of 3.3 baits consurned per raccoon anti the sachet perforated.
Selection may act on the weakest link in fitness to change how a species adapts to an environmental stress. For many species, this limitation may be reproduction. After adult Drosophila melanogaster, Drosophila simulans, and Drosophila mojavensis males were exposed to varying levels of thermal stress well below those that endanger life, courtship and mating frequency declined. The regression coefficients of both courtship and mating success did not differ significantly between D. melanogaster and D. simulans males. In contrast, significant differences were present between the two cosmopolitan species and D. mojavensis. Courtship frequency decreased at a much slower rate in D. mojavensis than in D. melanogaster and D. simulans, and while heat-stressed D. mojavensis males continued to court, many did not mate. In the cosmopolitan species, courting males almost always mated successfully. Courtship behaviors, including wing waving, were observed in D. mojavensis at temperatures that prohibited flight, while flight, courtship, and mating were knocked out simultaneously in D. melanogaster. One possible explanation for decreased flight ability and courtship success may be the reduced heat shock response in the flight muscle tissue because Hsp70 expression was lowest in the thoracic tissue of both D. melanogaster and D. mojavensis.
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