Effects of winter-feeding on mule deer in northern Utah

During severe winters, mule deer (Odocoileus hemionus) concentrated on ranges in poor condition can experience high mortality. Winter-feeding programs have been implemented to mitigate this mortality. We studied effects on body condition, mortality, fawn production, and migration of mule deer following winter-feeding in the Cache-Wasatch Mountains of northern Utah, USA. Fed deer exhibited 12% higher live body-condition indices both years (main effect feed: F-1,F-7.32 = 5.39, P = 0.052), lower mortality (33 % vs. 55%: chi(2)(1) = 4.58, P < 0.05), and produced more fawns (19 fawns:18 fed F vs. 11 fawns:12 nonfed F; t(27.2) = 2.20, P < 0.036) than nonfed deer. Fed deer migrated later in spring 2004 ((x) over bar = 13 Apr) than nonfed deer ((x) over bar = 24 Mar; t(34) = 3.25, P=0.003). Fed deer spent more time on winter range in 2003-2004 ((x) over bar = 157 d) than nonfed deer ((x) over bar = 121 d; t(20) = 3.63, P = 0.002), and more time on winter range for both winters combined (fed deer (x) over bar = 321 d, nonfed deer (x) over bar = 257 d; t(27) = 3.29, P = 0.003). Concomitantly, wildlife managers need to recognize that any possible benefits accrued to mule deer populations in terms of increased nutritional status as a result of winter-feeding programs may be mitigated by altered timing of migration and increased duration of use of seasonal ranges by fed deer.