Effect of abrasive properties of sedges on intestinal absorptive surface and Resting Metabolic Rate of the root voles

Recent studies on grasses and sedges suggested that the induction of a mechanism reducing digestibility of plant tissues in response to herbivore damage may drive rodent population cycles. This defence mechanism seems to rely on the abrasive properties of ingested plants. However, the underlying mechanism has not been demonstrated in small wild herbivores. Therefore, we carried out an experiment in which we determined the joint effect of abrasive sedge components on histological structure of small intestine as well as Resting Metabolic Rates (RMR) of the root voles (Microtus oeconomus). The histological examination revealed that voles fed with a sedge-dominated diet had shorter villi composed from narrower enterocytes in duodenum, jejunum and ileum. Reduction in the height of villi decreased along the small intestine. Activity of the mucus secretion increased along the small intestine and was significantly higher in ileum. The intestinal abrasion exceeded compensatory capabilities of voles, which responded to sedge-dominated diet by the reduction of body mass and a concomitant decrease in whole body RMR. These results explain an inverse association between body mass and the probability of winter survival observed in voles inhabiting homogenous sedge wetlands.