BITE CHARACTERISTICS OF WAPITI (CERVUS-ELAPHUS) IN SEASONAL BROMUS-POA SWARDS

We used a cubic sampling quadrat to study the 3-dimensional structure of volunteer Bromus-Poa swards, and explored the relationship of bite depth and sward height as a determinant of bite sizes of wapiti (Cervu s elaphus) in the mixed-wood parklands of central Alberta, Canada. The vertical biomass distribution of the sward was pyramidal with leaves dominating the top stratum. Bite depths of yearling and adult wapiti w ere not significantly different but both were influenced by sward heig ht and season. Wapiti selected bites in both vertical and horizontal d imensions. In spring, wapiti selected vertically, taking green leaves in the top layer of the sward. They selected forbs horizontally in sum mer and selected leaves vertically in mature autumn swards. Based on t he relationships among bite depth and sward height, biomass and sward height, as well as vertical biomass distribution, we calculated expect ed bite sizes of wapiti on seasonal pasture. We also predicted changes of dietary protein and neutral detergent fiber with increasing bite d epth. On spring swards, calculated dietary protein decreased and fiber increased as animals grazed deeper into the swards. In summer and aut umn, dietary protein peaked as wapiti cropped about half of the height of the sward whereas dietary fiber was relatively constant. Wapiti ad justed their bite depth to select forage containing at least 14% prote in in spring, summer, and autumn. The sacrifice of bite size in tall s ummer and autumn swards was compensated by diet quality.