Foraging behaviour and habitat use of large herbivores in a coastal dune landscape

Forage resources in the natural landscape are distributed in a mosaic of patches of variable size and shape with a fluctuating quantity and quality of food. Free-ranging herbivores have to make many foraging decisions at different resolution levels, resulting in a foraging behaviour that meets the large herbivores’ nutrient and energy requirements. Habitat use is an outcome of the foraging behaviour of the herbivores. The relation between the animal and its food supply, and thus its foraging behaviour and habitat use, are determined by the characteristics of the environment on the one hand and the characteristics of the herbivore on the other. It is evident that the foraging animal has to make more foraging decisions in a heterogeneous than in a homogeneous environment. Different animal species, animal breeds as well as individuals may show considerable variation in their nutritional demands, due to intrinsic as well as extrinsic factors. Digestive system, digestive efficiency, metabolic rate, body size, age, reproductive state, health condition, origin are some of the intrinsic factors lying on the basis of differences in nutritional demands. Different species and breeds of large ungulates have been introduced into several dune reserves along the Belgian coast as a management measure. The nature conservation expectations of this grazing management are high. However, management results and the predictability of them still carry a high level of uncertainty since little is known about the possible impact of the herbivores on such a relatively low-productive, heterogeneous ecosystem. This research does not aim to evaluate the grazing management in the first place, but aims to gain better insights into the (foraging) behaviour and the habitat use of the large herbivores in such a low-productive environment, with a considerable amount of spatial and temporal heterogeneity. We focus on different herbivore species and breeds, since we expect differences in their foraging behaviour and habitat use, due to their morphological and physiological differences. In the end, the results of the study are expected to contribute directly to the understanding of the herbivore impact. The central hypothesis is that foraging behaviour reflects the nutritional ecology of the herbivores and provides a mean to gain insight in the mechanisms determining herbivore impact at the landscape scale. The (foraging) behaviour and habitat use of Highland cattle, Haflinger horses, Shetland ponies and donkeys, free-ranging in several coastal dune reserves, is described at different hierarchical ecological levels. Foraging behaviour and habitat use of Highland cattle and Shetland ponies, foraging in the same area, showed significant differences, although they had a high habitat use overlap. Indications are found that foraging behaviour may be dissimilar among equid groups, especially when comparing the donkey (Equus asinus) with horse breeds (Equus caballus). We found that equids free-ranging in large heterogeneous areas do not perform latrine behaviour, but defecate where they graze; this is in contrast with horses grazing in pastures. Possible mechanisms of foraging behaviour have been put forward and we were able to formulate some predictions on herbivore impact. Within the investigated topics many new hypotheses are proposed, hence continuation of this research is desirable.