BOLD MRI provides noninvasive estimates of regional renal oxygen content and our study demonstrates that this technique may provide a useful tool in UUO which is associated with altered renal oxygen consumption.

SummaryClimate change may influence the phenology of organisms unequally across trophic levels and thus lead to phenological mismatches between predators and prey. In cases where prey availability peaks before reproducing predators reach maximal prey demand, any negative fitness consequences would selectively favor resynchronization by earlier starts of the reproductive activities of the predators. At a study site in northeast Greenland, over a period of 17 years, the median emergence of the invertebrate prey of Sanderling Calidris alba advanced with 1.27 days per year. Yet, over the same period Sanderling did not advance hatching date. Thus, Sanderlings increasingly hatched after their prey was maximally abundant. Surprisingly, the phenological mismatches did not affect chick growth, but the interaction of the annual width and height of the peak in food abundance did. Chicks grew especially better in years when the food peak was broad. Sanderling clutches were most likely to be depredated early in the season, which should delay reproduction. We propose that high early clutch predation may favor a later reproductive timing. Additionally, our data suggest that in most years food was still abundant after the median date of emergence, which may explain why Sanderlings did not advance breeding along with the advances in arthropod phenology.

Alpine and arctic lemming populations appear to be highly sensitive to climate change, and when faced with warmer and shorter winters, their well-known high-amplitude population cycles may collapse. Being keystone species in tundra ecosystems, changed lemming dynamics may convey significant knock-on effects on trophically linked species. Here, we analyse long-term , community-wide monitoring data from two sites in high-arctic Greenland and document how a collapse in collared lemming cyclicity affects the population dynamics of the predator guild. Dramatic changes were observed in two highly specialized lemming predators: snowy owl and stoat. Following the lemming cycle collapse, snowy owl fledgling production declined by 98 per cent, and there was indication of a severe population decline of stoats at one site. The less specialized long-tailed skua and the generalist arctic fox were more loosely coupled to the lemming dynamics. Still, the lemming collapse had noticeable effects on their reproductive performance. Predator responses differed somewhat between sites in all species and could arise from sitespecific differences in lemming dynamics, intra-guild interactions or subsidies from other resources. Nevertheless, population extinctions and community restructuring of this arctic endemic predator guild are likely if the lemming dynamics are maintained at the current non-cyclic, low-density state.

Animal abundance is a key measure in conservation and management and tightly linked to population demographics. Demographic data from remote regions, however, are often scarce. Here, we present long-term (1996-2013) demographics on the muskox Ovibos moschatus population at Zackenberg in northeast Greenland. We examine both the inter-and intra-annual patterns in demographic parameters and relate these to environmental conditions. The sex and age composition of muskox groups changed during the study period, and changes were particularly evident in the increasing versus the decreasing phase of muskox abundance. The seasonal pattern of muskox density and group size was a parallel increase from late winter to autumn, which peaked at high densities (approximately seven individuals per km 2 ) in the autumn. The composition of muskox groups also changed between seasons. Across years, the muskox population dynamics was mainly driven by spring snow cover (an indicator of winter conditions), which primarily impacted the calf and yearling recruitments. This relationship, however, appeared to have a temporary decoupling, which may be attributable to pathogens. Our study provides rare insight into the longterm demographics of a remote ungulate population in relation to drivers of change and thus aids the development of adequate monitoring and management plans for muskoxen in a changing Arctic.

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.