Use of Artificial Enclosures to Determine the Survival of Rana pipiens Larvae in Upper Midwestern Agricultural Ponds

Amphibians in the upper Midwest use agricultural ponds for breeding. Unfortunately, the risks (both direct and indirect) associated with using these ponds are poorly understood in both amphibian adults and larvae. In order to quantify these risks, we performed a comparison of larval survival rates between agricultural and natural ponds in southeastern Minnesota during the spring and summer of 2001. During this time, larval survival was observed in Rana pipiens tadpoles raised through metamorphosis in enclosures placed in agricultural and natural ponds. In addition, we measured the levels of nutrients commonly linked with agricultural ponds (i.e., ammonia, total phosphorous, and total nitrogen), and whether or not nutrient concentration was associated with larval survival. No differences were detected in nutrient levels or survival of larvae reared in agricultural and natural ponds. Furthermore, neither nutrient levels nor pond type significantly predicted larval survival. Our data were highly variable, making the interpretation of our results difficult. The enclosures used to rear tadpoles were highly effective and can be easily incorporated into future studies

Lack of Response to Olfactory Lures Among Mammals in Riparian Habitat in Southern Wisconsin

Non-invasive mammal surveys often employ olfactory stimuli on the assumption that they will attract mammals and increase the success of monitoring projects. However, information on the effectiveness of scent lures is variable and often relies on data generated from mammal tracks or sign, which can be challenging to quantify. Therefore, we sought to determine whether certain olfactory stimuli are more effective than others at eliciting a response from mammals along riparian corridors in Southern Wisconsin, using camera traps to monitor response to four scents and a control of de-ionized water. We recorded the number of times each species responded as well as the length of time spent investigating scents (Muskrat gland, mink gland, Red fox urine, crayfish oil) and the control. We recorded 2812 passes by 16 mammal species during our 12-month study, with Virginia Opossum (Didelphis virginiana), Woodchuck (Marmota monax), Eastern Gray Squirrel (Sciurus carolinensis), Eastern Fox Squirrel (Sciurus niger), Raccoon (Procyon lotor), Coyote (Canis latrans), and White-tailed Deer (Odocoileus virginianus)observed on cameras most frequently. However, 72% of observations involved mammals passing through without investigating any scents or the control, and among the 28% of observations where mammals did investigate, we found no significant differences in their response to specific scents or the control or in response by season. Further analysis revealed no significant differences in the time mammals spent investigating individual scents or the control. The lack of response suggests that factors other than scent may have attracted wildlife to our stations. Although under some circumstances olfactory attractants may increase the level of response to monitoring stations, we suggest that attraction to our stations was largely a behavioural response to novel stimuli in the environment