Investigating possible immunosuppression in wild Svalbard ptarmigan

Life at high latitudes is characterized by pronounced seasonal variation in ambient temperature, precipitation and light intensity. Year-round residency in such environments is challenging, especially for warm-blooded animals that maintain a high and stable body temperature that may be more than 60°C above the surroundings for prolonged periods. Consequently, these animals, such as the Svalbard ptarmigan (Lagopus muta hyperborea), must invest considerable amounts of energy in the development of cold defense mechanisms in preparation for winter. Because improved cold tolerance requires increased size of organs that supply muscles with nutrients and deal with metabolic waste products, winter acclimatization is often associated with a higher basal metabolic rate. As this occurs at a time of year when food is often scarce, allocation to other energy-demanding processes might be reduced to accommodate the higher cost of thermoregulation. Our previous work suggests that the immune defense system is a likely candidate to suffer reduced allocation: captive Svalbard ptarmigan seem to suffer pronounced immunosuppression in winter which is in sharp contrast to birds wintering under less severe conditions. These responses remain largely unaltered in ptarmigan in benign spring conditions of constant light and mild temperature, which suggests that (at least some) high latitude animals may have permanently downregulated immune function, perhaps as a result of having evolved in a pathogenically rather pristine environment. We are now interested to investigate the extent to which our preliminary data from captive Svalbard ptarmigan are mirrored by wild birds during different times of the year. As a first step in the project, we will undertake a pilot study on Prins Karls Forland and Forlandsøyene under, and in collaboration with, the umbrella project "Bridge Builder Expeditions Spitsbergen (Svalbard)" [RiS -id 10275], funded by the IK Foundation, London, United Kingdom. Project objectives will be achieved be live capture (using mist nets) and blood sampling (minuscule volumes, ca. 400 ul) of up to 16 adult Svalbard ptarmigan of both sexes, in September 2017 - a handling that is expected to have no adverse effects on the birds.Sample size is kept at what is assumed to be a minimum, based on previous experience on inter-individual variation in captive ptarmigan. Blood samples will be analyzed for several markers of baseline immune function, and will be put into context of the birds' body condition and stage of moult, and environmental parameters surrounding the time of capture. The immune assays applied in this project require only small plasma volumes. Yet, to further reduce the required volume, we optimize the assays applied in this project so that they require even less blood plasma. There are neither non-animal models nor non-invasive techniques available to achieve the goals of the current project.