The tight linkage between mineral status and health and demographics in animals is well documented. Mineral deficiencies have been coupled to population declines in wildlife. Current practices typically rely on liver, kidney and/or serum samples to assess mineral levels. Such destructive sampling strategies are, however, not feasible for remote or endangered populations. Hair may constitute an alternative tissue, sampled through non-invasive means, to investigate mineral levels in wildlife. In the pilot study presented here, we examine whether mineral levels in hair samples from a well-studied muskox (Ovibos moschatus) population in High-Arctic Greenland are associated with a vital rate and may, therefore, serve as indicators of wildlife population demographics. We show that inter-annual variations in levels of three minerals—copper, selenium and molybdenum—are associated with fluctuations in annual calf recruitment, with poor recruitment in years of low mineral levels in hair. Local environmental conditions also varied with calf recruitment but appeared to be less robust predictors of calf recruitment than hair mineral levels. Our results suggest that hair mineral levels may serve as an indicator of vital demographic rates and, ultimately, of wildlife population trends.
Seabirds in cold biomes sometimes aggregate near glacier fronts and at sea-ice edges to forage. In this note, we report on large aggregations of black guillemots (Cepphus grylle) at the edge of sea ice in front of the tidewater glacier Kongsbreen (Kongsfjorden, Svalbard). During several days in the second half of June 2011, we observed 49–155 individuals of black guillemots at this ice edge. They foraged actively, and many of the dives were directed underneath the sea ice. The outflow of glacial meltwater and resulting upwelling generated opportunities for the black guillemots to feed, likely on zooplankton or fish. The black guillemots used the sea ice as a resting platform between dives or diving sessions, and whilst on the ice, they interacted socially. On our last visit, the sea ice was gone, and the black guillemots had left the bay. At the neighbouring tidewater glacier Kronebreen, there was no sea ice connected to the glacier. Surface-feeding seabirds, particularly black-legged kittiwakes (Rissa tridactyla), were numerous at the plumes generated by meltwater from Kronebreen. Black guillemots were not seen at these plumes, but some individuals were seen scattered in the fjord system. Our observations add to the natural history of black guillemots and enhance our knowledge of ecological interactions and seabird habitat use shaped by tidewater glaciers.
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