The dietary habits of most small mammals are not well documented, and stable isotope measurements can provide information on when and how diets change. Here we document the discrimination and turnover times for carbon and nitrogen isotopes in blood, liver, muscle, hair, and milk from deer mice ( Peromyscus maniculatus (Wagner, 1845)) fed a controlled diet. Nonbreeding adults and pregnant females were livetrapped, maintained on a commercial laboratory chow, and had tissues sampled on a regular schedule. After adjusting to the laboratory diet, most tissues of nonbreeding adults were slightly depleted of 13C and enriched in 15N relative to diet (Δ13Ctissue–diet range = 0.3‰ to –1.1 ‰; Δ15Ntissue–diet range = 1.9‰ to 3.4‰). Liver (half-lives of 2.8 and 3.6 days for C and N, respectively) turned over more rapidly than blood (22.4 and 19.8 days for C and N, respectively) and muscle (18.7 and 24.8 days for C and N, respectively). The isotopic compositions of nonbreeding and breeding adults indicated tissue turnover at approximately the same rate, but juvenile tissues reflected the laboratory diet much more quickly than adult tissues.

[1] The prairie pothole physiographic region of North America is likely to be affected by climate change, and it is important to establish its baseline global warming potential as a basis for assessing global change effects. This study estimated the hydrologic effects on soil greenhouse gas efflux during the growing season along hydrologic profiles within natural prairie potholes ranging from the southern to northern limits of the prairie pothole region within central Canada. Soil moisture was found to be an important driver of differences in soil efflux along the hydrologic profiles and along the south-to-north gradient. The position of peak cumulative soil efflux varied along the hydrologic profile, with the N 2 O peak occurring at the backslope, the CO 2 peaks at footslope and toeslope, and the CH 4 peaks at toeslope and surface waters. When cumulative soil efflux was converted to global warming potential (Mg CO 2 eq), the largest values were restricted to the narrow land-water interface in the south but expanded to a broader area of the hillslope in the north. CO 2 was the major (> 95%) contributor to global warming potential. Omitting hydrologic controls on greenhouse gas fluxes from estimates of global warming potential led to substantial underestimates of the contributions of N 2 O and CH 4 . Arid regions in the south had smaller global warming potential than wetter regions in the north. If future climate projections for a warmer, drier climate in this region are realized, global warming potential from soil greenhouse gas fluxes will be smaller in this landscape, because the changing hydrologic conditions should result in a reduction of global warming potential from land surfaces, even as global warming potential from surface waters increases.

a b s t r a c tWe investigated the stable nitrogen-and carbon-isotope compositions of blood, liver, muscle and hair of income breeding deer mice (Peromyscus maniculatus) to determine the extent to which stable isotope compositions of mothers and offspring differed. We found small differences between the ␦ 15 N and ␦ 13 C values of dependent offspring and adult tissues (by a magnitude of −0.8‰ to 1.1‰ for 15 N and 0.3-0.9‰ for 13 C), and limited 15 N discrimination between juvenile tissues and milk, which explains the small mother-offspring trophic effects in isotopic composition. Discrimination of 15 N between offspring and adults was greater than expected but smaller than known for capital breeding mammals, suggesting that different biochemical pathways for milk production and processing may affect the discrimination of 15 N in these systems.

extubation. We have observed only a moderate incidence of POUR and a low incidence of urinary infections. In addition, no correlation between POUR and worse outcome has been shown. Our data suggests that thoracic epidural analgesia is not an absolute indication of urinary drainage.

We report the first record of Hairy-tailed Moles (Parascalops breweri) moving above ground during the day and suggest that the four individuals observed were young-of-the-year dispersing from their natal territories. Extreme drought conditions may also have driven these animals to move above ground.