Lichen Intake Estimates for Reindeer and Caribou during Winter

Abstract

Lichen intakes by reindeer and caribou (Rangifer tarandus) during winter were estimated using penned reindeer, esophageal fistulated reindeer, and by the application of the fallout radiocesium method to free-grazing caribou. Estimated mean values for lichen intake as determined by the 3 methods were 16.4, 31.6, and 61.3 g/day of dry lichen per kg body weight or approximately 1.3, 2.5, and 4.9 kg/day dry lichen for an 80-kg reindeer or caribou. The 4-fold range in lichen intake estimates may be attributed to differences in environmental exposures inherent in the methods. Penned reindeer were necessarily sedentary without the stresses and activities normally associated with free-grazing animals. Esophageal fistulated reindeer were required to obtain forage for themselves. However, they were tethered or protected and therefore not subjected to influences such as migration or harassment by predators. The fallout radiocesium method is unique in that it does not affect the normal activity of the animal and thus has the potential for determining the most realistic estimate of lichen intake for an animal in the natural system. The forage intake rates in terms of metabolizable energy available to reindeer and caribou are compared to the probable energy requirements of the animals. J. WILDL. MANAGE. 43(1):192-201 The food habits of free-ranging reindeer and caribou are similar throughout the northern arctic (Kelsall 1968). In late spring as the snow begins to melt, reindeer and caribou actively seek out fresh green vegetation as the new forages appear. During the summer months forage is abundant and the diet consists of a wide variety of plants including shrubs, sedges, heaths, grasses, and lichens. As the deciduous forages mature and become fibrous, reindeer and caribou select increasing amounts of lichen. This transition continues through late fall when lichens become the predominate forage. Throughout winter and early spring when forage is often in short supply, lichens are consumed extensively. Winterkilled nonlichen vegetation is consumed, but to a lesser extent. Extreme cold temperatures during winter suggest greater energy demands for thermoregulation, a situation that is exacerbated whenever reindeer or caribou are required to excavate lichens and other forages from deep or ice-encrusted snow. Therefore, survival of reindeer or caribou is highly dependent upon an adequate forage intake during this critical p riod. Although there is considerable information concerning forage selection by reindeer and caribou (Skoog 1956, Courtwright 1959, Kelsall 1968), little quantitative data on forage intake exist. Forage intakes as calculated from metabolic and nutrient requirements (Brody 1945:470, Kelsall 1968:81) seem inadequate for reindeer or caribou subsisting in their winter environment. This paper reports estimates of lichen intakes based on feeding trials with pe ned and esophageal fistulated reindeer as well as lichen intake estimates derived from application of a fallout radiocesium method. The radiocesium method was first proposed by Holleman et al. (1971), and some preliminary lichen intake estimates for caribou were made. Hanson et al. (1975) applied the radiocesium method to data collected in northern Alaska during 1963-70 and esimated lichen intake by free-grazing car192 J. Wildl. Manage. 43(1):1979 This content downloaded from 157.55.39.217 on Tue, 06 Sep 2016 05:42:33 UTC All use subject to http://about.jstor.org/terms LICHEN INTAKE BY REINDEER AND CARIBOU. Holleman et al. 193 Table 1. Meterological summary for each study period. Temperature C Mean snow depth Study Dates Mean Max. Min. (cm) Pen feeding trial 1 Nov-Dec 1969 -16.7 -11.7 -22.0 15.9 Pen feeding trial 2 Mar-Apr 1974 -6.0 0.3 -12.8 33.0 Pen feeding trial 3 Nov-Dec 1975 -17.4 -13.9 -20.9 23.5 Esophageal fistula trial Mar, Apr 1973 -6.6 -2.1 -11.1 49.9 Radiocesium trial Jan, Feb, Mar 1976 -17.9 -13.5 -22.2 19.2 ibou. Alldredge et al. (1974) used the fallout radiocesium method to determine forage intake rates of mule deer (Odocoileus hemionus). We now report lichen intake estimates for reindeer and caribou from November through March in interior and northern Alaska. This study was part of a continuing study of the nutrition and metabolism of reindeer and caribou in Alaska (Luick 1967-74, Luick 1977). Lichen intake estimates in winter were obtained at the Institute of Arctic Biology, Fairbanks, Alaska; the Reindeer Research Station, Cantwell, Alaska; and Old John Lake in northern Alaska. Only studies involving penned reindeer were conducted at the Institute of Arctic Biology, whereas both penned reindeer and esophageal fistulated reindeer studies were conducted at the Reindeer Research Station. Estimates of lichen intake using the radiocesium method were made on caribou collected at Old John Lake. The study was supported by U.S. A.E.C. contract AT (45-1)2229 and U.S. E.R.D.A. contract EY-76-