Marrow Fat in Alaskan Moose Femurs in Relation to Mortality Factors

Abstract

Fat content in femur marrow was analyzed by the dry-weight method from 181 Alaskan moose (Alces alces). Samples were classified as adults or calves, cause of death, and month sampled. Marrow fat values from adults killed by wolves (Canis lupus) or by various accidental means (road-kill, shot, and drug) were not significantly different from each other, but both were significantly higher than those from suspected starved moose. Marrow fat values from wolf-killed calves were not significantly different from those of calves dying accidentally; however they were significantly higher than those of suspected winter-killed (starved) calves. Marrow fat values from suspected winter-killed adults and calves were not significantly different. Only 3 of 97 marrow fat values from suspected winter-kills were above 10 percent. Wolves were not selective for moose with marrow fat values below 10 percent, but took both cows and calves with marrow fat means not significantly different from accidental mortalities. The effect of severity of winter on fat values is discussed. Femur marrow fat values provide a method for comparing mortality factors and a means of identifying winter-killed (starved) moose. J. WILDL. MANAGE. 40(2):336-339 Femur marrow fat content as determined by alcohol-ether extraction has been correlated with condition in white-tailed deer (Odocoileus virginianus) (Cheatum 1949). Color and consistency of marrow were used by Riney (1955) to estimate marrow fat content in red deer (Cervus elaphus). Bischoff (1954) indicated marrow characteristics have limitations in assessing conditions of black-tailed deer (0. hemionus columbianus), and consistency of marrow was the only adequate measure of its condition. Greer (1968) reported a compression method as an index of fat content in elk (C. canadensis) femur marrows. Neiland (1970) reported the dry-weight method for determining fat in barrenground caribou (Rangifer tarandus) femurs, and Verme and Holland (1973) utilized a reagent-dry assay of marrow fat in white-tailed deer. The marrow fat indices utilizing color and consistency as a basis for evaluation have subjective error potential. Extraction procedures are relatively accurate but timeconsuming. All methods may be subject to variation based upon handling of femurs prior to analysis. Femur marrows frozen for extended periods of time may have 5 to 10 percent higher fat content than a fresh sample (Greer 1968:750). With consistency in collection, handling, and procedure each method has validity for comparative purposes. The Alaska Department of Fish and Game has utilized Neiland's (1970) dry-weight method for several years. This paper reports the use of the method for moose on the Kenai Peninsula, Alaska. Sampling was done to document the level of marrow fat ordinarily associated with various types of mortality in Alaskan moose. We are grateful to J. Davis, D. Johnson, R. LeResche, and P. LeRoux, who collected many of the femurs, and to C. Lucier and his staff at the Game Division Laboratory in Anchorage for the analyses. J. Coady, K. Neiland, D. McKnight, and K. Schneider read the manuscript and provided helpful suggestions. J. Oldemeyer 1 This work was supported, in part, by Federal Aid in Wildlife Restoration Project W-17-R. 336 J. Wildl. Manage. 40 (2) :1976 This content downloaded from 157.55.39.147 on Wed, 21 Sep 2016 05:46:34 UTC All use subject to http://about.jstor.org/terms MARROW FAT IN MOOSE FEMURS ? Franzmann and Arneson 337 provided assistance with statistical analyses. The Kenai Moose Research Center is a cooperative project of the Alaska Department of Fish and Game and the U.S. Fish and Wildlife Service, Kenai National Moose Range.