A taste of space: Remote animal observations and discrete-choice models provide new insights into foraging and density dynamics for a large subarctic herbivore.

Competition for resources and space can drive forage selection of large herbivores from the bite through the landscape scale. Animal behaviour and foraging patterns are also influenced by abiotic and biotic factors. Fine-scale mechanisms of density-dependent foraging at the bite scale are likely consistent with density-dependent behavioural patterns observed at broader scales, but few studies have directly tested this assertion. Here, we tested if space use intensity, a proxy of spatiotemporal density, affects foraging mechanisms at fine spatial scales similarly to density-dependent effects observed at broader scales in caribou. We specifically assessed how behavioural choices are affected by space use intensity and environmental processes using behavioural state and forage selection data from caribou (Rangifer tarandus granti) observed from GPS video-camera collars using a multivariate discrete-choice modelling framework. We found that the probability of eating shrubs increased with increasing caribou space use intensity and cover of Salix spp. shrubs, whereas the probability of eating lichen decreased. Insects also affected fine-scale foraging behaviour by reducing the overall probability of eating. Strong eastward winds mitigated negative effects of insects and resulted in higher probabilities of eating lichen. At last, caribou exhibited foraging functional responses wherein their probability of selecting each food type increased as the availability (% cover) of that food increased. Space use intensity signals of fine-scale foraging were consistent with density-dependent responses observed at larger scales and with recent evidence suggesting declining reproductive rates in the same caribou population. Our results highlight potential risks of overgrazing on sensitive forage species such as lichen. Remote investigation of the functional responses of foraging behaviours provides exciting future applications where spatial models can identify high-quality habitats for conservation.

[Mortality in nuclear workers of the French electricity company: period 1968-2003]. / Cohorte des travailleurs du nucléaire à Electricité de France: mortalité des agents statutaires sur la période 1968-2003.

BACKGROUND: We conducted a mortality study on a cohort of French nuclear workers employed at Electricité de France (EDF). A first cancer mortality analysis had covered the period 1968-1994. This paper presents results from a mortality analysis including nine additional years of follow-up to cover workers employed from 1968 to 2003. METHODS: The cohort includes 22393 workers, 97% of whom are males. Employment data were updated using the EDF personnel file. Vital status was ascertained using the French National Registry of Population, and further completed using EDF personnel and pension files. Causes of death were obtained from the National registry of causes of death. Standardised Mortality Ratios (SMR) were computed using national rates as references. Variations of all causes and all cancers SMRs were studied according to demographic and occupational characteristics. RESULTS: At the study end point (31/12/2003), 74% of workers are still in active employment. Only 0.3% of workers are lost to follow-up. The median duration of follow-up is 20 years. Causes are ascertained for 96% of deaths. The total number of deaths is 874, 307 of which are cancer deaths. SMRs for all causes and cancers show a significant deficit compared to the French national mortality. No significant excess was observed for any of the cancer sites studied. Non-significant excesses are observed for pancreatic, pleural, kidney and brain cancer. Significant variations of all causes SMRs according to age at study entry and attained age are observed. Significant variations of all causes and all cancers SMRs according to diploma at employment are observed, with a reduced SMR for a higher level of diploma. CONCLUSION: There is a significant deficit of mortality compared to the general population, reflecting a strong Healthy Worker Effect. Although nine years of follow-up were added, this cohort is made up of young workers, most of whom are still in active service. Regular updating of the follow up of this cohort is planned, aiming for an occupational health surveillance of workers occupationally exposed to ionizing radiation in France.

Using seasonal landscape models to predict space use and migratory patterns of an arctic ungulate.

BACKGROUND: Caribou in the Western Arctic Herd undertake one of the longest, remaining intact migrations of terrestrial mammals in the world. They are also the most important subsistence resource for many northern rural residents, who rely on the caribou's migratory movements to bring them near for harvest. Migratory geography has never been static, but subsistence harvesters have reported recent shifts in migration away from areas where they traditionally occurred. The reasons behind these changes are not well-understood, but may be related to rapid climate change and anthropogenic disturbances. METHODS: To predict changes in distribution and shifting migratory areas over the past decade, we used GPS telemetry data from adult females to develop predictive ecological niche models of caribou across northwestern Alaska. We employed the machine-learning algorithm, TreeNet, to analyze interactive, multivariate relationships between telemetry locations and 37 spatial environmental layers and to predict the distributions of caribou during spring, calving season, insect-harassment season, late summer, fall, and winter from 2009 to 2017. Model results were analyzed to identify regions of repeated predicted use, quantify mean longitude, predict land cover selection, and track migratory changes over time. RESULTS: Distribution models accurately predicted caribou at a spatially-explicit, 500-m scale. Model analyses identified migratory areas that shifted annually across the region, but which predicted 4 main areas of repeated use. Niche models were defined largely by non-linear relationships with coastally-influenced, climatic variables, especially snow-free date, potential evapo-transpiration, growing season length, proximity to sea ice, winter precipitation and fall temperature. Proximity to roads and communities were also important and we predicted caribou to generally occur more than 20-100 km from these features. CONCLUSIONS: Western Arctic Herd caribou were predicted to occur in warmer, snow-free and treeless areas that may provide conditions conducive for efficient travel and foraging. Rapidly changing seasonal climates and coastal influences that determine forage availability, and human impediments that slow or divert movements are related to geographically and phenologically dynamic migration patterns that may periodically shift caribou away from traditional harvest areas. An enhanced understanding of the geographic behavior of caribou over time could inform traditional harvests and help conserve important Western Arctic caribou migratory areas.

The effect of murine B16F10 melanoma on the biodistribution of 99mTc-MDP in male C57BL/6J mice.

The biodistribution of radiopharmaceuticals used in diagnostic imaging can be altered by a wide variety of factors. We studied the effect of murine B16F10 melanoma on the biodistribution in mice of 99mTechnetium-methylenediphosphonic acid (99mTc-MDP). Viable B16-F10 cell lines (1 x 10(5)) were inoculated subcutaneously in the dorsal region of 8-12 week-old male isogenic C57BV/6j mice. 14-16 days after inoculation, 99mTc-MDP was injected in the ocular plexus and after 0.5 hr the animals were rapidly sacrificed. The organs and tumor were isolated, the mass determined and the percentage per gram of injected activity (%ATI/g) calculated. The results shown that the %ATI/g:i/ has not been altered in inguinal lymph nodes, prostate, pancreas, testis, seminal vesicle, bladder, kidney, stomach, small intestine, spleen, thymus, heart, lung, brain and muscle; but ii/ significantly decreased in thyroid, bone, blood and liver. In conclusion, the B16F10 melanoma can alter the 99mTc-MDP uptakes in some organs.