Feeding facilitation, the hidden interaction in mammalian herbivore assemblages?: a case-study on rabbits (Oryctolagus cuniculus L.) and large grazers

This thesis focuses on the positive interaction ‘feeding facilitation’ which is predicted to occur in assemblages of large and small(er) herbivore species. The main hypothesis of the research is that introduced large herbivores facilitate rabbits (medium-sized herbivores) by modification of the vegetation. This modification involves creating short swards, creating denser (more productive) swards, creating swards that have a high food quality for rabbits and influencing vegetation composition. By conducting field observation, semi-controlled field experiments up to entirely controlled feeding experiments, we tried to test several aspects of the main hypothesis. From our results, we conclude that the main hypothesis could not be affirmed, although some causal mechanisms of feeding facilitation have been affirmed. We suggest that feeding facilitation is not necessarily absent, but is hard to detect or is not present under particular conditions. Experimental research is needed for further unravelling causal mechanisms about feeding facilitation and alternative approaches, while field observations remain necessary to gain insight into other variables (e.g. habitat productivity, predators, food accessibility, seasonality) that may shift the balance between the occurrence and absence of feeding facilitation.