Beheer van dierpopulaties ter preventie van tekenbeten

Het aantal mensen dat naar de huisarts gaat met een tekenbeet is in de afgelopen decennia enorm toegenomen. Dit is waarschijnlijk een combinatie van betere bekendheid van teken bij recreanten en huisartsen, en een toename van het aantal teken in Nederland. De grote vraag is of natuurbeheerders iets kunnen doen aan het tekenprobleem. Dit was een van de centrale vraagstukken binnen het project ‘Shooting the messenger’ van het Rijksinstituut voor Volksgezondheid en Milieu (RIVM) en Wageningen University & Research wat plaatsvond van 2012 t/m 2016. Beide auteurs verrichtten binnen dit project onderzoek naar de rol van verschillende diersoorten in de levenscyclus van de schapenteek (Ixodes ricinus) om te kijken waar er ingegrepen kon worden om het aantal teken in het landschap te verminderen

Behaviour of horses and cattle at two stocking densities in a coastal salt marsh

Livestock grazing has been practiced in salt marshes in the Wadden Sea area since 600 B.C. Currently livestock grazing is also applied for conservation management. However, effects of such grazing management on salt marshes are likely to vary depending on the species of livestock and stocking density due to differences in the behaviour of the animals. Yet, little is known about the behaviour of different livestock species and stocking densities grazing in salt marshes. We studied the grazing behaviour of horses and cattle by focal observation in an experiment with four different grazing treatments on a coastal salt marsh. In all treatments we recorded diet choice, movement and grazing activity, and spatial distribution. Livestock species shared an overlap in diet choice. Yet, horses more often foraged on the short grass Puccinellia maritima, while the cattle diet contained a higher amount of Aster tripolium. Horses travelled longer distances per day and spent more time grazing than cattle. Spatial distribution of cattle was significantly clustered, while horses showed a random distribution utilizing the whole area. Animal behaviour differs between livestock species and stocking densities with respect to diet choice, activity and spatial distribution

Beheer van dierpopulaties ter preventie van tekenbeten

Het aantal mensen dat naar de huisarts gaat met een tekenbeet is in de afgelopen decennia enorm toegenomen. Dit is waarschijnlijk een combinatie van betere bekendheid van teken bij recreanten en huisartsen, en een toename van het aantal teken in Nederland. De grote vraag is of natuurbeheerders iets kunnen doen aan het tekenprobleem. Dit was een van de centrale vraagstukken binnen het project ‘Shooting the messenger’ van het Rijksinstituut voor Volksgezondheid en Milieu (RIVM) en Wageningen University & Research wat plaatsvond van 2012 t/m 2016. Beide auteurs verrichtten binnen dit project onderzoek naar de rol van verschillende diersoorten in de levenscyclus van de schapenteek (Ixodes ricinus) om te kijken waar er ingegrepen kon worden om het aantal teken in het landschap te verminderen

Estimation of Vegetation LAI from Hyperspectral Reflectance Data: Effects of Soil Type and Plant Architecture

The retrieval of canopy biophysical variables is known to be affected by confounding factors such as plant type and background reflectance. The effects of soil type and plant architecture on the retrieval of vegetation leaf area index (LAI) from hyperspectral data were assessed in this study. In situ measurements of LAI were related to reflectances in the red and near-infrared and also to five widely used spectral vegetation indices (VIs). The study confirmed that the spectral contrast between leaves and soil background determines the strength of the LAI¿reflectance relationship. It was shown that within a given vegetation species, the optimum spectral regions for LAI estimation were similar across the investigated VIs, indicating that the various VIs are basically summarizing the same spectral information for a given vegetation species. Cross-validated results revealed that, narrow-band PVI was less influenced by soil background effects (0.15 = RMSEcv = 0.56). The results suggest that, when using remote sensing VIs for LAI estimation, not only is the choice of VI of importance but also prior knowledge of plant architecture and soil background. Hence, some kind of landscape stratification is required before using hyperspectral imagery for large-scale mapping of vegetation biophysical variables.JRC.G.3-Agricultur

Data_file_manuscript

This data file contains raw data collected at the plantation scale, within-plantation scale and the raw data from the number of pellet groups collected

Relationships of reproductive performance indicators in black rhinoceros (Diceros bicornis michaeli) with plant available moisture, plant available nutrients and woody cover

Plant available moisture and plant available nutrients in soils influence forage quality and availability and subsequently affect reproductive performance in herbivores. However, the relationship of soil moisture, soil nutrients and woody forage with reproductive performance indicators is not well understood in mega-browsers yet these three are important in selecting suitable areas for conservation of mega-browsers. Here, the eastern black rhinoceros (Diceros bicornis michaeli), a mega-browser, was studied in seven geographically distinct populations in Kenya to understand the relationships between its reproductive performance indicators and plant available moisture, plant available nutrients and woody cover. Reproductive parameters showed a complex relationship with plant available moisture and plant available nutrients. We found an increase in the predicted yearly percentage of females calving as plant available nutrients decreased in areas of high levels of plant available moisture but no relationship with plant available nutrients in areas of low plant available moisture. Age at first calving was earlier, inter-calving interval was longer and yearly percentage of females calving was higher at higher woody cover. Woody plant cover contributes positively to black rhino reproduction performance indicators, whereas plant available moisture and plant available nutrients add to the selection of conservation areas, in more subtle ways.</p

Data from: Does wolf presence reduce moose browsing intensity in young forest plantations?

Large carnivores can be a key factor in shaping their ungulate prey’s behavior, which may affect lower trophic levels. While most studies on trade-offs between food acquisition and risk avoidance by ungulate prey species have been conducted in areas with limited human impact, carnivores are now increasingly returning to highly anthropogenic landscapes. Many of these landscapes are dominated by forestry, and ungulate-forestry conflicts are an increasing issue. The aim of this study was to test if the indirect effects of a re-colonizing large predator, the wolf (Canis lupus), results in a change in browsing intensity by moose (Alces alces) in young forest plantations in a boreal forest in Sweden. We selected 24 different forest plantations, with 12 located in low-wolf and 12 in high-wolf utilization areas. In each plantation, we measured browsing intensity, tree height, tree density, distance to the closest forest edge and we counted the number of moose pellet groups. In contrast to our predictions, wolf utilization was not the main driver of moose browsing patterns. Instead, moose browsing intensity declined with tree density and height. Separate analyses on the main tree species showed that wolf utilization had an influence, but browsing intensity was in fact higher in the high-wolf utilization areas for three out of five tree species. This pattern seemed to be driven by a strong confounding relationship between wolf utilization, tree density and height, which were both lower in the high-wolf utilization areas. We argue that this confounding effect is due to wolves being pushed towards the less productive parts of the landscape away from human activity centers. Therefore, we concluded that in order to better understand carnivore driven risk- mediated effects on herbivore behavior in anthropogenic landscapes we need to better understand the complexity of human-carnivore-prey-ecosystem interactions

Cascading effects of predator activity on tick-borne disease risk.

Predators and competitors of vertebrates can in theory reduce the density of infected nymphs (DIN)-an often-used measure of tick-borne disease risk-by lowering the density of reservoir-competent hosts and/or the tick burden on reservoir-competent hosts. We investigated this possible indirect effect of predators by comparing data from 20 forest plots across the Netherlands that varied in predator abundance. In each plot, we measured the density of questing Ixodes ricinus nymphs (DON), DIN for three pathogens, rodent density, the tick burden on rodents and the activity of mammalian predators. We analysed whether rodent density and tick burden on rodents were correlated with predator activity, and how rodent density and tick burden predicted DON and DIN for the three pathogens. We found that larval burden on two rodent species decreased with activity of two predator species, while DON and DIN for all three pathogens increased with larval burden on rodents, as predicted. Path analyses supported an indirect negative correlation of activity of both predator species with DON and DIN. Our results suggest that predators can indeed lower the number of ticks feeding on reservoir-competent hosts, which implies that changes in predator abundance may have cascading effects on tick-borne disease risk

Pathogen communities of songbird-derived ticks in Europe's low countries

Background: Birds play a major role in the maintenance of enzootic cycles of pathogens transmitted by ticks. Due to their mobility, they affect the spatial distribution and abundance of both ticks and pathogens. In the present study, we aim to identify members of a pathogen community [Borrelia burgdorferi (s.l.), B. miyamotoi, 'Ca. Neoehrlichia mikurensis', Anaplasma phagocytophilum and Rickettsia helvetica] in songbird-derived ticks from 11 locations in the Netherlands and Belgium (2012-2014). Results: Overall, 375 infested songbird individuals were captured, belonging to 35 species. Thrushes (Turdus iliacus, T. merula and T. philomelos) were trapped most often and had the highest mean infestation intensity for both Ixodes ricinus and I. frontalis. Of the 671 bird-derived ticks, 51% contained DNA of at least one pathogenic agent and 13% showed co-infections with two or more pathogens. Borrelia burgdorferi (s.l.) DNA was found in 34% of the ticks of which majority belong to so-called avian Borrelia species (distribution in Borrelia-infected ticks: 47% B. garinii, 34% B. valaisiana, 3% B. turdi), but also the mammal-associated B. afzelii (16%) was detected. The occurrence of B. miyamotoi was low (1%). Prevalence of R. helvetica in ticks was high (22%), while A. phagocytophilum and 'Ca. N. mikurensis' prevalences were 5% and 4%, respectively. The occurrence of B. burgdorferi (s.l.) was positively correlated with the occurrence of 'Ca. N. mikurensis', reflecting variation in susceptibility among birds and/or suggesting transmission facilitation due to interactions between pathogens. Conclusions: Our findings highlight the contribution of European songbirds to co-infections in tick individuals and consequently to the exposure of humans to multiple pathogens during a tick bite. Although poorly studied, exposure to and possibly also infection with multiple tick-borne pathogens in humans seems to be the rule rather than the exception