Seasonal foraging behavioural compensation in reproductive wapiti hinds (Cervus elaphus canadensis)

Captive wapiti hinds were observed during seven periods between June 1996 and November 1997. We investigated their activity and foraging behaviour on two pastures, heavily and lightly grazed, during four phases of the reproductive cycle (early gestation, late gestation, peak lactation, and late lactation). Within season, differences in forage availability between pastures had little apparent effect on wapiti feeding behaviour (p0.05). However, within each pasture, hinds tended to select locations of higher phytomass than the pasture average. Among seasons, effects of forage availability on feeding behaviour were pronounced. Hinds grazed longest in late lactation (12.8 h/day), when they spent 94% of their active time foraging, whereas during early gestation they foraged fewer hours (8.2 h/day) and less intensively (66% of active time). The longest foraging bouts also occurred in late lactation (100 min) and decreased linearly as the number of bouts per day increased (R(2)=0.88). The annual peak bite rate (BR) was in late lactation (62 bites/min), whereas the annual nadir occurred in early gestation (37 bites/min). Smallest bite sizes (BS) (mg) were recorded in late gestation (127 mg), and increased linearly with forage availability (R(2)=0.46), with largest BS occurring during peak lactation (280 mg). This study demonstrated how seasonal modifications in activity and foraging behaviour enabled gestating and lactating wapiti hinds to satisfy their changing nutritional requirements on seasonal pastures. Knowledge of behavioural compensation in response to nutritional demand and pasture conditions will be useful in designing supplementation program for farmed wapiti.