OPTIMAL GRAZING OF WAPITI (CERVUS-ELAPHUS) ON GRASSLAND - PATCH AND FEEDING STATION DEPARTURE RULES

We studied factors which may shape giving-up decisions of wapiti grazi ng grassland patches (area where a wapiti initiates and terminates a f eeding sequence) and feeding stations (area within a patch that a wapi ti can reach without moving its forelegs). In grassland patches, cropp ing rate decreased after a critical period, whereas at feeding station s cropping rate increased with cumulative bites consumed. The number o f feeding stations grazed, number of bites taken and grazing time did not dictate the termination of grazing in a patch. Wapiti gave up a pa tch only after the cropping rate at a feeding station dropped below th e seasonal expectation during trials on lush pasture in May, but gave up after the cropping rate dropped below the seasonal expectation at t wo consecutive feeding stations in March/April and August when foragin g conditions were less favourable. This confirmed a prediction of the marginal value theorem. Wapiti did not give up a feeding station accor ding to bites taken, grazing time or cropping rate, but they left feed ing stations when their lateral neck angle reached a critical point su ggesting a biokinetic explanation. Leaving feeding stations when ungra zed forage can no longer be reached and patches when intake rate drops both appeared to be rules used by wapiti grazing grasslands of the bo real mixed wood forest.