GRAZING PATTERNS OF SAMBAR DEER (CERVUS-UNICOLOR) AND RED DEER (CERVUS-ELAPHUS) IN CAPTIVITY

Grazing behaviour was recorded in sambar deer and red deer for 24-h co ntinuous periods, at 2-monthly intervals, over 12 months from March 19 90 to March 1991. Scan-sampling was used, with observations made every 12 min. Both groups of deer grazed separate but adjoining areas of th e same pasture for the duration of the study. Sambar deer grazed most actively during the night (0100-0500 h), late afternoon, and evening ( 1700-2100 h), whereas red deer grazed most intensely during early morn ing (0500-0700 h), afternoon, and early evening (1500-2000 h). This sp ecies difference in grazing pattern was not altered by season or month . Total grazing time was similar for sambar and red deer (9.1 versus 9 .4 h/24 h), but sambar deer spent more time grazing during the night ( 6.2 versus 4.9 h/24 h; P < 0.01) and less time grazing during the day (2.9 versus 4.5 h/24 h; P < 0.01) than red deer. The ratio night grazi ng:daytime grazing was much greater for sambar deer (2.3: 1.0) than fo r red deer (1.1:1.0;P< 0.001). During the day, sambar deer spent more time resting than red deer (6.4 versus 5.1 h P < 0.001), but time spen t ruminating was similar (2.1 versus 1.9 h) for the two species. Rate of prehending biting was greater for sambar deer than for red deer (65 versus 48 bites/min; P < 0.001). It is suggested that longer night gr azing by sambar deer may have evolved to reduce thermoregulatory stres s in tropical environments and as a defensive strategy against attack by predators. Pasture mass/ha and surface height changed with season o f the year, but areas grazed by both species of deer were always of si milar height and mass, indicating that grazing pressures were similar. However, herbage in areas grazed by sambar deer had higher total N co ntent and organic matter digestibility during winter, the period of lo west pasture mass/height, indicating that relative to areas grazed by red deer, grazing by sambar deer had modified forage nutritive value a t this time.