Green wave tracking by large herbivores: an experimental approach

• Published in: Ecology (Durham) Vol. 97; no. 12; pp. 3547 - 3553
• Main Authors: Rivrud, Inger Maren, Heurich, Marco, Krupczynski, Philipp, Müller, Jörg, Mysterud, Atle
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-12-2016; Ecological Society of America
• Subjects: Animal Identification Systems; Animal Migration - physiology; animal movement; Animals; Cervus elaphus; Correlation analysis; Deer; Deer - physiology; Experiments; Female; Forage; Foraging behavior; Genotype & phenotype; global positioning system tracking; Herbivores; Herbivory - physiology; Maturation; migration; Motor task performance; Movement; normalized difference vegetation index; Phenology; Phenotypic plasticity; Seasons; Tracking; wildlife experiment; Germany; migration; normalized difference vegetation index; wildlife experiment; global positioning system tracking; animal movement
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1002/ecy.1596

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 socalled "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.