GASTROINTESTINAL NEMATODES DEPRESS FOOD-INTAKE IN NATURALLY INFECTED REINDEER

Models have predicted that directly transmitted macroparasites may inf luence the abundance of forage plants in herbivore grazing systems by reducing the food intake of their host. Evidence of parasite-induced a lterations in host food intake is, however, limited mainly to sheep, c attle and laboratory rodents. We estimated the effect of naturally acq uired parasite infections on the appetite of reindeer. Food intake was significantly lower in infected reindeer compared to animals in which the parasites had been experimentally removed. Among the infected ani mals there was a significant negative relationship between intensity o f the directly transmitted macroparasites (i.e. gastrointestinal nemat odes) and mean food intake, indicating that the lower food intake was caused by these parasites. The time-specific onset of depression in fo od intake is also consistent with seasonality in the pathogenic effect from gastrointestinal nematodes. This shows that parasite-induced cha nges in herbivore food intake is not restricted to agricultural system s, and implies that parasites may have impact on the dynamics of a wid e range of herbivore plant communities.