title: Green wave tracking by large herbivores: an experimental approach.
abstract: The forage maturation hypothesis (FMH) states that herbivores should follow the onset of growth in spring to obtain access to forage of higher quality and quantity, the so-called "green wave surfing." Several studies have found correlative evidence in support of this by associating animal movement with plant phenology. However, experimental manipulation of vast natural systems determining causes of large herbivore movement is usually beyond reach. The unique management system involving winter enclosures for wild red deer (Cervus elaphus) in Germany facilitated an opportunity for an experimental approach. We manipulated release dates of red deer into free-ranging conditions in spring, predicting increased overall access to high quality forage if released early (1 April), and more rapid initial movement speed towards higher elevation if released late (15 May). The latter had lower access to high quality forage than individuals released early, as they missed parts of the green wave. In strong support of the FMH, individuals released late moved at faster initial speed than early released individuals which tracked the green wave more closely, both settling when reaching similar elevations. This shows that red deer were flexible in their movements, and they can adapt to new patterns of phenology by phenotypic plasticity.
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, Oslo, 0316, Norway.
authors.forename: Inger Maren
authors.initials: IM
authors.lastname: Rivrud
authors.affiliation: Department of Conservation and Research, Bavarian Forest National Park, Freyunger Str. 2, Grafenau, 94481, Germany.|Chair of Wildlife Ecology and Management, Freiburg University, Tennenbacherstr. 4, Freiburg, 79106, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Heurich
authors.affiliation: Department of Conservation and Research, Bavarian Forest National Park, Freyunger Str. 2, Grafenau, 94481, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Krupczynski
authors.affiliation: Department of Conservation and Research, Bavarian Forest National Park, Freyunger Str. 2, Grafenau, 94481, Germany.|Chair for Terrestrial Ecology, Department of Ecology and Ecosystem Management, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, 85354, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Müller
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, Oslo, 0316, Norway.
authors.forename: Atle
authors.initials: A
authors.lastname: Mysterud
mesh_terms: D000823:Animal Identification Systems; D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D003670:Deer / Q000502:physiology*; D005260:Female; D060434:Herbivory / Q000502:physiology*; D012621:Seasons
keywords: animal movement; global positioning system tracking; migration; normalized difference vegetation index; wildlife experiment