Effect of seasonal differences in dietary meat intake on changes in body mass and composition in wild and captive brown bears

The influence of seasonal dietary meat intake on changes in body mass and c omposition in wild and captive brown bears (Ursus arctos) was investigated because the importance and availability of meat to brown bear populations i s currently an important management consideration in several North American ecosystems. Adult female brown bears on the Kenai Peninsula, Alaska, utili zed meat heavily in both spring and fall. Meat accounted for 76.2 +/- 26.0% (mean +/- 1 SD; primarily moose carrion and calves) of assimilated carbon and nitrogen in the spring and 80.4 +/- 22.2% (primarily salmon) in the fal l. Mass increases in the spring (71.8 +/- 28.2%) were mostly lean body mass , but increases in the fall (81.0 +/- 19.5%) were primarily fat. Daily inta ke by captive brown bears fed meat ad libitum during 12-day trials was posi tively related to body mass. Mass change was positively related to intake i n both seasons, but the composition of the gain varied by season, with spri ng gains primarily lean body mass (64.2 +/- 9.4%), while fall gains were 78 .8 +/- 19.6% lipid. Absolute rates of gain by wild bears occasionally equal ed, but were usually much less than, those of captive bears. This was likel y due to a combination of factors, which included the time required to loca te and handle meat resources, the limited availability of or access to meat resources, and (or) the duration of meat resource availability. Estimated intake by bears not feeding selectively on high-energy components of moose and salmon were 8.5 +/- 1.5 kg/day and 541 +/- 156 kg/year and 10.8 +/- 4.6 kg/day and 1003 +/- 489 kg/year, respectively. Intake would drop by as muc h as 58% for bears feeding exclusively on salmon roe. Management strategies for areas with brown bears that consume significant amounts of meat should address the perpetuation and availability of these meat resources.