Little impact of over-winter parasitism on a free-ranging ungulate in the high Arctic

1.Macroparasites have a central place in wildlife ecology because they have the potential to regulate host populations through effects on reproduction and/or survival. However, there remains a paucity of studies that have demonstrated the regulatory role of these parasites in free-ranging animals.

2.Previous work on Svalbard reindeer demonstrated that the experimental removal of the parasitic gastrointestinal nematode Ostertagia gruehneri transmitted in summer, improved reindeer fecundity, and that the species was capable of mediating a density-dependent reduction in fecundity.

3.The main coexisting parasitic nematode in the system, Marshallagia marshalli, exhibits a contrasting life-history with low abundances in summer and an increase during the winter. Here, we examine the impact of this over-winter infection on fitness of female reindeer in the same population.

4.Worm burdens were removed at the start of the winter in October using a novel delayed-release anthelmintic bolus...