Density-dependent switches in diet:a likely mechanism for negative feedbacks on goose population increase?

Goose grazing on arctic tundra vegetation has shown both positive and negative effects on subsequent foraging conditions. To understand the potential of a density-dependent feedback on herbivore population size, the relation between grazing pressure and future foraging conditions is essential. We studied the effect of increasing grazing pressure of barnacle geese (Branta leucopsis) on Spitsbergen. During the establishment of a breeding colony in the period 1992-2004, the proportion of graminoids decreased in the diet of wild geese, while the percentage of mosses increased. Grazing trials with captive geese in an unexploited area showed a similar shift in diet composition. High-quality food plants were depleted within years and over years. Intake rate declined too and as consequence, metabolisable energy intake rate (MEIR) decreased rapidly with increasing grazing pressure. During three successive years of experimental grazing, MEIR decreased at all levels of grazing pressure and declined below minimal energetic requirements when grazing exceeded natural levels of grazing pressure. This suggests that foraging conditions rapidly decline with increasing grazing pressure in these low-productive habitats. The potential for density-dependent feedbacks on local population increase is discussed

The connectivity of spring stopover sites for geese heading to arctic breeding grounds

During the spring migration arctic-breeding geese pause in temperate and sub-arctic staging areas in order to deposit body reserves for breeding. Focusing on a single arctic stopover site in West-Spitsbergen, Svalbard, Norway (Varsol-bukta, 77 degrees 45'N, 14 degrees 24'E), behavioural strategies of Barnacle Geese Branta leucopsis were investigated and body condition and presence of individually marked birds recorded. Individuals using different staging areas earlier along the migration route (Helgeland and Vesteralen on the Norwegian mainland) and heading to different breeding colonies (the close-by Nordenskioldkysten, and the distant Kongsfjorden) were compared during springs 2003-05. Birds in Vesteralen left the staging area earlier than those in Helgeland, and arrived earlier in Varsolbukta as well. In Varsolbukta, females gained body condition at a similar rate regardless of their colony affiliation, whereas males from Nordenskioldkysten exhibited a smaller overall increase in condition compared to males from Kongsfjorden. The Kongsfjorden birds stayed for a shorter period (average 2.8 days) than those from Nordenskioldkysten (average 4.0 days). Nordenskioldkysten birds frequently left Varsolbukta for short periods presumably visiting the breeding area in order to optimise nest initiation with respect to prevailing snow conditions. The date of final departure was also correlated with nest initiation date at Nordenskioldkysten. No such relationship for the Kongsfjorden birds was found. We suggest that the geese adopt a 'hopping' strategy, using a network of stopover sites in Svalbard during spring with a last stopover at a buffer area in the proximity to the breeding area. For this vulnerable population it is important to identify the sites forming the links in this chain, and to establish their function and utilisation by geese during the vital prebreeding period

Potential of Svalbard reindeer winter droppings for emission/absorption of methane and nitrous oxide during summer

Droppings of Svalbard reindeer (Rangifer tarandus platyrhynchus) could affect the carbon and nitrogen cycles in tundra ecosystems. The aim of this study was to evaluate the potential of reindeer droppings originating from the winter diet for emission and/or absorption of methane (CH4) and nitrous oxide (N2O) in summer. An incubation experiment was conducted over 14 days using reindeer droppings and mineral subsoil collected from a mound near Ny-Ålesund, Svalbard, to determine the potential exchanges of CH4 and N2O for combinations of two factors, reindeer droppings (presence or absence) and soil moisture (dry, moderate, or wet). A line transect survey was conducted to determine the distribution density of winter droppings at the study site. The incubation experiment showed a weak absorption of CH4 and a weak emission of N2O. Reindeer droppings originating from the winter diet had a negligible effect on the exchange fluxes of both CH4 and N2O. Although the presence of droppings resulted in a short-lasting increase in N2O emissions on day 1 (24 h from the start) for moderate and wet conditions, the emission rates were still very small, up to 3 μg N2O m−2 h−1

Contrasting consequences of climate change for migratory geese:Predation, density dependence and carryover effects offset benefits of high-arctic warming

Climate change is most rapid in the Arctic, posing both benefits and challenges for migratory herbivores. However, population-dynamic responses to climate change are generally difficult to predict, due to concurrent changes in other trophic levels. Migratory species are also exposed to contrasting climate trends and density regimes over the annual cycle. Thus, determining how climate change impacts their population dynamics requires an understanding of how weather directly or indirectly (through trophic interactions and carryover effects) affects reproduction and survival across migratory stages, while accounting for density dependence. Here, we analyse the overall implications of climate change for a local non-hunted population of high-arctic Svalbard barnacle geese, Branta leucopsis, using 28 years of individual-based data. By identifying the main drivers of reproductive stages (egg production, hatching and fledging) and age-specific survival rates, we quantify their impact on population growth. Recent climate change in Svalbard enhanced egg production and hatching success through positive effects of advanced spring onset (snow melt) and warmer summers (i.e. earlier vegetation green-up) respectively. Contrastingly, there was a strong temporal decline in fledging probability due to increased local abundance of the Arctic fox, the main predator. While weather during the non-breeding season influenced geese through a positive effect of temperature (UK wintering grounds) on adult survival and a positive carryover effect of rainfall (spring stopover site in Norway) on egg production, these covariates showed no temporal trends. However, density-dependent effects occurred throughout the annual cycle, and the steadily increasing total flyway population size caused negative trends in overwinter survival and carryover effects on egg production. The combination of density-dependent processes and direct and indirect climate change effects across life history stages appeared to stabilize local population size. Our study emphasizes the need for holistic approaches when studying population-dynamic responses to global change in migratory species.</p

The predictive value of the 'VMS frail older patients' for adverse outcomes in geriatric inpatients

Background/Objective: The Dutch Safety Management system (VMS) screening for frail older patients is used as a predictor for adverse outcomes. We aimed to determine the predictive value of the VMS for adverse outcomes in geriatric inpatients. Design: Retrospective cohort study in geriatric inpatients. Outcomes were institutionalization, readmission and mortality (3- and 12-months). Logistic regression analysis was performed to assess the predictive value of the number of positive VMS domains, a VMS score >= 1, and individual domains for adverse outcomes. Results: We included 477 patients. Median age was 85 years (54-99) and 37% were male. Eighty-seven % scored positive on delirium risk, 57% on fall risk, 39% on malnutrition and 64% on physical impairment. One-hundredthirty-five patients (28%) were institutionalized, 78 patients (16%) were readmitted and mortality rate was 127 (27%) at 3 months and 184 (39%) at one year. The VMS was not predictive for readmission (OR 1.6; 95%-CI 0.213.7) and mortality, (OR 0.6 95%-CI 0.2-2.0 and OR 1.1; 95%-CI 0.3-3.7). For institutionalization, delirium risk (OR 2.2; 95%-CI 1.1-4.4), physical impairment (OR 1.8; 95%-CI 1.1-2.9) and a positive score on all four domains were predictive (OR 12.1 95%-CI-1.4-101.7). Malnutrition was predictive for readmission (OR 1.74; 95%-CI 1.05-2.91) and three-month mortality (OR 1.69; 95%-CI 1.11-2.57), delirium risk for one -year mortality (OR 2.0; 95%-CI 1.0-4.0) . Conclusions: Almost all geriatric inpatients scored positive on at least one domain of the VMS. The number of positive VMS domains had some predictive value for institutionalization. Individual domains were able to predict adverse outcomes