Rothirschprojekt Aletsch-Goms : Abschlussbericht zum Forschungs- und Managementprojekt 2017–2021

Ab etwa Mitte des 20. Jahrhunderts kommt der Rothirsch im Wallis in nennenswerten Beständen vor. Trotz intensiver Bejagung nehmen die Bestände seither stetig zu und führen teilweise zu Konflikten, insbesondere im Wald und in der Region Aletsch-Goms. Über die Raumnutzung und das Wanderverhalten der Rothirsche in dieser Region lagen bislang einige Einschätzungen und Vermutungen, jedoch kaum gesicherte Fakten vor. Mit dem im Jahr 2017 initiierten Rothirschprojekt Aletsch-Goms wurden bedeutende Wissenslücken für einen fachlich fundierten Umgang mit dieser anspruchsvollen Wildtierart nun geschlossen

Green-up selection by red deer in heterogeneous, human-dominated landscapes of Central Europe

The forage maturation hypothesis (FMH) assumes that herbivores cope with the trade-off between digestibility and biomass in forage by selecting vegetation at intermediate growth. The green wave hypothesis (GWH) extends the FMH to suggest how spatiotemporal heterogeneity in plant quality shapes migratory movements of herbivores. Growing empirical support for these hypotheses mainly comes from studies in vast landscapes with large-scale habitat heterogeneity. It is unclear, however, to what extent ungulates surf green waves in human-altered landscapes with small-scale heterogeneity in terms of land use and topography. We used plant phenological proxies derived from Sentinel 2 satellite data to analyze the habitat selection of 93 collared red deer (Cervus elaphus) in montane and alpine habitats. Using a step selection analysis, we investigated how plant phenology, that is, the instantaneous rate of green-up (IRG) and normalized difference vegetation index (NDVI), and a set of variables describing topography and human presence influenced red deer resource selection in open habitats. We learned that red deer selected areas with high biomass at green-up and avoided habitats with possible exposure to human activity. Additionally, landscape structure and topography strongly influenced spatial behavior of red deer. We further compared cumulative access to high-quality forage across migrant strategies and found migrants gained better access than residents. Many migratory individuals surfed the green wave, and their surfing behavior, however, became less pronounced with decreasing distance to settlements. Within the constraints of topography and human land use, red deer track spring green-up on a fine spatiotemporal scale and follow the green wave across landscapes in migration movements. Thus, they benefit from high-quality forage even in human-dominated landscapes with small-scale heterogeneity and vegetation emerging in a heterogenic, dynamic mosaic

Mitigating the negative impacts of tall wind turbines on bats: Vertical activity profiles and relationships to wind speed

<div><p>Wind turbines represent a source of hazard for bats, especially through collision with rotor blades. With increasing technical development, tall turbines (rotor-swept zone 50–150 m above ground level) are becoming widespread, yet we lack quantitative information about species active at these heights, which impedes proposing targeted mitigation recommendations for bat-friendly turbine operation. We investigated vertical activity profiles of a bat assemblage, and their relationships to wind speed, within a major valley of the European Alps where tall wind turbines are being deployed. To monitor bat activity we installed automatic recorders at sequentially increasing heights from ground level up to 65 m, with the goal to determine species-specific vertical activity profiles and to link them to wind speed. Bat call sequences were analysed with an automatic algorithm, paying particular attention to mouse-eared bats (<i>Myotis myotis and Myotis blythii</i>) and the European free-tailed bat (<i>Tadarida teniotis</i>), three locally rare species. The most often recorded bats were the Common pipistrelle (<i>Pipistrellus pipistrellus</i>) and Savi’s pipistrelle (<i>Hypsugo savii</i>). Mouse-eared bats were rarely recorded, and mostly just above ground, appearing out of risk of collision. <i>T</i>. <i>teniotis</i> had a more evenly distributed vertical activity profile, often being active at rotor level, but its activity at that height ceased above 5 ms^-1 wind speed. Overall bat activity in the rotor-swept zone declined with increasing wind speed, dropping below 5% above 5.4 ms^-1. Collision risk could be drastically reduced if nocturnal operation of tall wind turbines would be restricted to wind speeds above 5 ms^-1. Such measure should be implemented year-round because <i>T</i>. <i>teniotis</i> remains active in winter. This operational restriction is likely to cause only small energy production losses at these tall wind turbines, although further analyses are needed to assess these losses precisely.</p></div

Cumulative number of bat passes per hour in relation to mean hourly wind speed at the truck-mounted crane.

<p>a) all species pooled, b) <i>Pipistrellus pipistrellus</i>, c) <i>Hypsugo savii</i>, d) <i>Myotis myotis/Myotis blythii</i> and e) <i>Tadarida teniotis</i>. The black line indicates 95% of the asymptote.</p

Observed (up to 65 m a.g.l.) and projected (>65 m a.g.l.) vertical bat activity profiles (nightly average + SE–the latter expressing between night variation–with 95% confidence intervals of projections shaded in grey) constructed from the hourly number of bat passes recorded at different heights.

<p>a) all species pooled, b) <i>Pipistrellus pipistrellus</i>, c) <i>Hypsugo savii</i>, d) <i>Myotis myotis/Myotis blythii</i> and e) <i>Tadarida teniotis</i>. For more realistic representation the response variable is on the X axis, height a.g.l. being the vertical (Y) axis. The red dashed line represents the lower limit (50 m) of the rotor-swept zone as depicted by the rotor icon (not represented in 1e for enhacing clarity).</p

Probability of hourly bat activity occurrence in relation to mean hourly wind speed (mean ± 95% confidence intervals) at the truck-mounted crane for all species pooled.

<p>a) all heights; b) heights > 50 m a.g.l., i.e. in the dangerous rotor-swept zone. The black solid lines indicate the wind speed at which the probability of activity occurrence drops below 5%.</p