Foraging behaviour and habitat use of large herbivores in coastal dune landscape = Foerageergedrag en habitatgebruik van grote herbivoren in een kustduinlandschap

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

Large herbivores in coastal dune management: do grazers do what they are supposed to do?

After some decades of rather sparse and more or less ad-hoc nature management (e.g. local shrub-cutting, sod-cutting, mowing), the manager of the Flemish coastal nature reserves [Nature Department (Coastal Zone Management Cell) of AMINAL, Ministry of the Flemish Community] decided to introduce a more coherent and relatively large-scale nature management approach. Since the mid-nineties, several large areas were cleared from scrubs and in the larger nature reserves different herbivore species were introduced. On historical grounds and based on general management expectations, several ungulate species were introduced (sheep, donkeys and different horse and cattle breeds). Since the herbivore introductions from 1997 onwards, research has been done on the foraging behaviour and habitat use, diet selection and preference of some of the introduced herbivores and on their potential contribution to seed dispersal. Above that, several monitoring research programmes were carried out, following the impact of the ungulates on flora, vegetation and different faunal groups in order to evaluate the effectiveness of grazing in realizing the predefined management goals. Here we summarize some results of the research focussing on the driving forces in grazing management and try to conclude on the impact they will have through their habitat use, foraging behaviour, diet selection and other behavioural aspects. We formulate generalized conclusions on the suitability and usefulness of year round grazing by domestic animals in these rather low productive, spatially and temporally heterogeneous dune ecosystems

Donkeys as mobile links for plant seed dispersal in coastal dune ecosystems

Long-distance seed dispersal is a key factor in vegetation dynamics, especially in highly dynamic ecosystems such as dune landscapes. To assess the role of large herbivores in long-distance seed dispersal in dunes, we examined epi- and endozoochory by free-ranging donkeys, released for grazing in a Flemish dune nature reserve. At least 29, respectively 53, plant species were dispersed epi- and endozoochorously by the donkeys. Comparison of the species with the local vegetation using dispersal-relevant plant traits, showed that epi- and endozoochory are additive and complementary dispersal mechanisms, epizoochory being restricted to a narrower range of dispersal-functional plant types. To estimate potential dispersal distances of the seeds, we used empirical studies of the movement and behaviour of the donkeys, in combination with experimental epi- and endozoochorous seed retention times of selected plant species in the dune reserve. The mean potential dispersal distances indicated that the donkeys disperse seeds over the entire 100ha nature reserve, hereby providing a mobile link function between fragmented dune habitats for at least 20% of the local plant species. The influence of large herbivores on dune vegetation dynamics through seed dispersal should be considered in nature management decisions

Grazing behaviour of free-ranging donkeys and Shetland ponies in different reproductive states

We investigated how free-ranging mares of two species of equids (donkeys and Shetland ponies) modify their foraging behaviour to meet the increased nutritional requirements induced by lactation. We initially hypothesised that lactating mares would graze for a longer time and/or graze faster than non-lactating (dry) mares. The grazing behaviour of free-ranging animals. foraging in two low-productive dune areas, was recorded during I year. Results show that in both species lactating animals did. not spend more time grazing than non-lactating mares. However, lactating animals took more bites, and therefore achieved a higher bite rate than dry mares. Several factors affected the differences between lactating and non-lactating animals, Lactating mares took more bites only in grassy and rough vegetations and they did this only in patches with a short sward height. In addition, lactating mares took more bites of grasses only and not of forbs or woody plants. We con- clude that the extra grazing effort of the lactating animals was not distributed randomly. Lactating mares invested their extra grazing effort principally towards those items that are the most grazed by the equids in general. We propose some hypotheses to explain why lactating mares increase their bite rate instead of augmenting the time spent grazing

Endozoochorous seed dispersal by cattle and horse in a spatially heterogeneous landscape

Seed dispersal has become an important issue in plant ecology and restoration management. In this paper we examined dung germinating seed content and seed deposition patterns of horses (Shetland and Konik breeds) and Scottish Highland cattle grazing two coastal dune nature reserves. Two times 2.5 l of fresh dung from each type of herbivore were collected during seven sessions in the main fruiting season. Dung samples were placed under greenhouse conditions after drying and cooling. Animal defecation patterns were derived from a study of herbivore activities during 6 h observation sessions 8 times a month. One hundred and seventeen plant species i.e. 27% of all species occurring in the study area, were recorded as seedlings emerging from the dung samples. The most abundantly and frequently recorded plant species were Urtica dioica, Juncus spp. and different species of Poaceae and Caryophyllaceae. In general seedling density is high (1158 seedlings/dung sample). Seedling density and species richness were further analysed in order to detect temporal variability and possible animal and site related characteristics. Dung deposition patterns reflect a non-random use of habitats and hence a non-random seed deposition among habitats. Calculated seed deposition per square meter ranged from a few (<10 germinating seeds) to more than 100 in the most frequently selected habitats. From the herbivores’ selective habitat use and their estimated mean retention time we can further assume their ability for inter-habitat endozoochorous seed dispersal. This characteristic of large herbivores is further discussed in the light of nature management and restoration

Dimensioning of automated regenerative cooling: Setting of high-end experiment

International audienceRegenerative cooling is a hot topic as it contributes to energy saving and energy conversion, for example within high speed propulsion or chemical plants frameworks. Considering the use of this technology in fuel-cooled hypersonic structures, the propellant duality in terms of functions (coolant and fuel) makes the thermal and combustion management to be quite challenging. Dynamics of the system must be studied in order to develop regulation and control strategies which should be performed with a response time lower than the lowest characteristic time found in supersonic combustion ramjet, i.e. about 1 ms. The present work aims at setting experiments at lab scale by simplifying the additional difficulty of supersonic flow. A combustion chamber is dimensioned with similitude rules in terms of heat flux density, conversion rate, chemical compositions, dynamics. Computational Fluid Dynamics and analytical calculations are developed to dimension the experimental bench. Instead of using trial-error approach when setting up an experiment, this prediction work ensures having appropriate regulation dynamics for latter model and control developments. It has been found that a pyrolysis rate up to 100% can be obtained using ethylene as fuel at 50 bar and 1200 K and with a residence time of about 100 s. Combustion with air (adiabatic flame temperature up to 2400 K) will provide the required heat flux density. The operating range in terms of fuel pressure (10-50 bar), of fuel mass flow rates (50-100 mg s-1) and of equivalence ratio (0.8 to 1.0) have been certified

Eliminative behaviour of free-ranging horses: do they show latrine behaviour or do they defecate where they graze?

In contrast to horses in pastures, it is thought that free-ranging horses do not perform latrine behaviour, i.e. a behavioural pattern whereby the animals graze and defecate in separate areas. However, few studies deal with this particular subject, reporting contrasting conclusions. We hypothesize that horses free-ranging in large heterogeneous areas do not perform latrine behaviour. Thus, we believe that grazing and elimination behaviour are spatially related: where horses graze, they will also defecate. Behavioural data were collected from Konik horses, Haflinger horses, Shetland ponies and donkeys, grazing in different nature reserves (54–80 ha). Data for the different equids were analyzed separately, as well as data for mares and stallions (Konik and donkey stallions only). We investigated the proportion of the number of defecations/urinations while grazing on the total number of defecations/urinations; furthermore, we searched for the sequence of behaviours representing latrine behaviour in the strict sense. Additionally, we analyzed the correlation between grazing behaviour and eliminative behaviour on both vegetation type level and patch level. All the female equids often continued grazing while defecating. During urination, grazing ceases in the majority of instances. Cases where a mare terminated grazing in a certain vegetation type and sward height to eliminate in another vegetation type or in another sward height within the same vegetation type were rarely observed. On the vegetation type level as well as on the patch level, there was a highly significant (Pr ranges between 0.553 and 0.955; in case of the urination variables r ranges between 0.370 and 0.839) illustrate that the spatial distribution of the eliminative behaviour can be explained to a high degree by the spatial distribution of the grazing behaviour. Results in the case of the stallions are preliminary, but indicate the same pattern. Horses, free-ranging in large heterogeneous areas, do not perform latrine behaviour, but defecate where they graze. Possibly, animal density is of major importance to explain this behavioural difference with horses in pastures. We suggest that also spatial vegetation heterogeneity and plant productivity of the grazed area, as well as parasite status of the grazing animals could play a role