The interaction of food availability and endogenous physiological cycles on the grazing ecology of red deer hinds (Cervus elaphus)

The objective of the study was to establish the role of endogenous circannual physiological cycles in regulating the grazing behaviour of red deer. This was investigated by manipulating the timing of seasonal cycles in red deer hinds by administration of melatonin between July and October and comparing the subsequent grazing responses to either a low or high herbage biomass at the times of previously observed seasonal decline (autumn) and rise (spring) in voluntary food intake of enhoused animals. Food intake was determined using the n-alkane marker technique. Melatonin treatment resulted in respective 15- and 10-day advances in the timing of the onset and termination of the breeding season of non-pregnant hinds, indicating a phase-shift in the underlying circannual rhythm of reproduction