DOI: 10.5061/dryad.1vhhmgqw9
title: Green-up selection by red deer in heterogeneous, human-dominated landscapes of Central Europe

description: 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 analyse 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, i.e. the instantaneous rate of green-up [IRG] and
 normalised 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 behaviour 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, their surfing behaviour, 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. --
description: We used
 spatial relocation data for female [58] and male [35] red deer that were
 captured and marked in a period from 2015 to 2018. Individuals were darted
 and immobilized at night in order to collar them [GPS telemetry collars;
 Vectronic Aerospace GmbH]. They were then monitored over a period of 1-2
 years, except for early drop-offs due to fatalities or technical issues.
 Capturing, marking and collaring was performed in the winter home ranges
 by authorities and game wardens of the respective cantons and was in line
 with Swiss animal welfare laws and approved by the appropriate authorities
 [permissions SG13-12, GR2014-07F, GR2015-09,
 VS07-17]. We used
 plant phenological proxies derived from Sentinel 2 open satellite data to
 analyse the habitat selection of the 93 red deer in montane and alpine
 habitats based on the Greenwave hypothesis (GWH). With a step selection analysis, we investigated how
 plant phenology, i.e. the instantaneous rate of green-up (IRG), normalised
 difference vegetation index (NDVI) and a set of variables describing
 topography and human presence contributed to explaining red deer resource
 selection in open
 habitats. Additionally, we assessed the animals’ migration strategies and
 investigated which strategy might be more beneficial in terms of access to
 high quality forage.  
description: ArcGIS [version 10.5, ESRI], R version 3.5.1 (R Core Team, 2018)