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Effects of predator treatments, individual traits, and environment on moose survival in Alaska
Author(s) -
Keech Mark A.,
Lindberg Mark S.,
Boertje Rodney D.,
Valkenburg Patrick,
Taras Brian D.,
Boudreau Toby A.,
Beckmen Kimberlee B.
Publication year - 2011
Publication title -
the journal of wildlife management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.94
H-Index - 111
eISSN - 1937-2817
pISSN - 0022-541X
DOI - 10.1002/jwmg.188
Subject(s) - ursus , predator , predation , biology , population , canis , ecology , zoology , relative survival , demography , sociology , cancer registry
Abstract We studied moose ( Alces alces ) survival, physical condition, and abundance in a 3‐predator system in western Interior Alaska, USA, during 2001–2007. Our objective was to quantify the effects of predator treatments on moose population dynamics by investigating changes in survival while evaluating the contribution of potentially confounding covariates. In May 2003 and 2004, we reduced black bear ( Ursus americanus ) and brown bear ( U. arctos ) numbers by translocating bears ≥240 km from the study area. Aircraft‐assisted take reduced wolf ( Canis lupus ) numbers markedly in the study area during 2004–2007. We estimated black bears were reduced by approximately 96% by June 2004 and recovered to within 27% of untreated numbers by May 2007. Brown bears were reduced approximately 50% by June 2004. Late‐winter wolf numbers were reduced by 75% by 2005 and likely remained at these levels through 2007. In addition to predator treatments, moose hunting closures during 2004–2007 reduced harvests of male moose by 60% in the study area. Predator treatments resulted in increased calf survival rates during summer (primarily from reduced black bear predation) and autumn (primarily from reduced wolf predation). Predator treatments had little influence on survival of moose calves during winter; instead, calf survival was influenced by snow depth and possibly temperature. Increased survival of moose calves during summer and autumn combined with relatively constant winter survival in most years led to a corresponding increase in annual survival of calves following predator treatments. Nonpredation mortalities of calves increased following predator treatments; however, this increase provided little compensation to the decrease in predation mortalities resulting from treatments. Thus, predator‐induced calf mortality was primarily additive. Summer survival of moose calves was positively related to calf mass ( β > 0.07, SE = 0.073) during treated years and lower ( β = −0.82, SE = 0.247) for twins than singletons during all years. Following predator treatments, survival of yearling moose increased 8.7% for females and 21.4% for males during summer and 2.2% for females and 15.6% for males during autumn. Annual survival of adult (≥2 yr old) female moose also increased in treated years and was negatively ( β = −0.21, SE = 0.078) related to age. Moose density increased 45%, from 0.38 moose/km 2 in 2001 to 0.55 moose/km 2 in 2007, which resulted from annual increases in overall survival of moose, not increases in reproductive rates. Indices of nutritional status remained constant throughout our study despite increased moose density. This information can be used by wildlife managers and policymakers to better understand the outcomes of predator treatments in Alaska and similar environments. © 2011 The Wildlife Society.