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I evaluated rates of marrow fat deposition and skeletal growth of caribou (Ranifer tarandus granti) calves through 20 days of age at Denali National Park, Alaska, USA. Both were negatively correlated with late winter snowfall, indicating the prolonged effects of maternal undernutrition following severe winters. Using regression analyses, I found that the rates of marrow fat deposition and hindfoot growth during the 20 days following birth declined 46% and 68%, respectively, over the range of winter severity during this study. These measures of development may indicate a broader array of effects of maternal undernutrition, influencing the vulnerability of caribou calves to predation.

We examined the reproductive performance of female caribou (Rangifer tarandus granti) in relation to age, physical condition, and reproductive experience for 9 consecutive years (1987-95) at Denali National Park, Alaska, during a period of wide variation in winter snowfall. Caribou in Denali differed from other cervid populations where reproductive performance has been investigated, because they occur at low densities (≤0.3/km 2 ) and experience high losses of young to predation. Females first gave birth at 2-6 years old; 56% of these females were 3 years old. Average annual natality rates increased from 27% for 2-year-olds to 100% for 7-year-olds, remained high for 7-13-year-olds (98%), and then declined for females ≥14 years old. Females ≥2 years old that failed to reproduce were primarily sexually immature (76%). Reproductive pauses of sexually mature females occurred predominantly in young (3-6 yr old) and old (≥14 yr old) females. Natality increased witl body mass for 10-month-old females weighed 6 months prior to the autumn breeding season (P = 0.007), and for females >1 year old and weighed during autumn (late Sep-early Nov; P = 0.003). Natality for 2-, 3-, 4-, and 6-year-olds declined with increasing late-winter snowfall (Feb-May; P ≤ 0.039) during the winter prior to breeding In most years, a high percentage of sexually mature females reproduced, and lactation status at the time of breeding did not influence productivity the following year. However, following particularly high snowfall during February-September 1992, productivity was reduced in 1993 for cows successfully rearing calves to autumn the previous year. High losses of calves to predators in 1992 may have increased productivity in 1993. Losses of young-of-the-year to predation prior to the annual breeding season can be an important influence on subsequent productivity for ungulate populations where productivity varies with lactation status of females at the time of breeding.

To investigate relations between body condition and fecundity, we determined pregnancy status of arctic caribou (Rangifer tarandus granti) from presence or absence of pregnancy-specific protein B (PSPB) and progesterone concentration in blood sera or plasma. We drew peripheral blood samples from female caribou 3-5 (n = 142) and 20-23 (n = 44) weeks after the breeding season. We then weighed and estimated the fat content of each caribou, and we radiocollared 115 of 184 individuals. We verified parturition status for 96 of these radiocollared females in June. In addition, we determined presence of PSPB for captive caribou in autumn and early winter. Progesterone concentration was superior to PSPB as a predictor of pregnancy during early gestation, and a threshold value of 1.5 ng/mL was used to separate pregnant from nonpregnant females in autumn and winter. Pregnancy status was strongly related to body condition in both autumn and winter, and fatter or heavier caribou were more likely to be pregnant. Use of both PSPB and progesterone concentration allowed detection of early embryonic mortality among lactating caribou that were in poor condition.

Body condition scores provide a subjective measure of body fatness. We scored the condition of 64 barren-ground caribou (Rangifer tarandus granti) and 10 reindeer (R. t. tarandus) that were later killed and analyzed for chemical composition. A body reserve index (product of body condition score and body mass) was superior to either body mass or body condition score as a predictor of fatness for older calves and adults. The probability of pregnancy for adult female caribou was significantly related to both body condition score (n = 107, P = 0.017) and body reserve index (n = 103, P < 0.001).

Estimates of the relative effects of demographic parameters on population rates of change, and of the level of natural variation in these parameters, are necessary to address potential effects of perturbations on populations. We used a stochastic model, based on survival and reproduction estimates of the Porcupine Caribou (Rangifer tarandus granti) Herd (PCH), during 1983-89 and 1989-92 to obtain distributions potential population rates of change (r). The distribution of r produced by 1,000 trajectories of our simulation model (1983-89, r = 0.013; 1989-92, r = 0.003) encompassed the rate of increase calculated from an independent series of photo-survey data over the same years (1983-89, r = 0.048; 1989-92, r = −0.035). Changes in adult female survival had the largest effect on r, followed by changes in calf survival. We hypothesized that petroleum development on calving grounds, or changes in calving and post-calving habitats due to global climate change, would affect model input parameters. A decline in annual adult female survival from 0.871 to 0.847, or a decline in annual calf survival from 0.518 to 0.472, would be sufficient to cause a declining population, if all other input estimates remained the same. We then used these lower survival rates, in conjunction with our estimated amount of among-year variation, to determine a range of resulting population trajectories. Stochastic models can be used to better understand dynamics of populations, optimize sampling investment, and evaluate potential effects of various factors on population growth

Concerns have been raised that displacement from traditional calving and postcalving areas by petroleum exploration may cause increased calf mortality in the Porcupine Caribou (Rangifer tarandus) Herd. Consequently, we determined productivity and early calf survival by frequently locating 23-53 radio-collared cows and 59-61 radio-collared calves from 1983 to 1985. Seventy-nine to 87% of the adult females gave birth each year, and 68-90% of calves were born within, or adjacent to, a coastal plain area proposed for petroleum leasing and development. Sixteen to 35% of the calves died by 25 June. Fifty-nine to 74% of calf mortality occurred within 48 hours of birth and involved a number of causes in addition to predation. Predation was the major cause of death after the first 48 hours, and mortality increased toward higher terrain away from the coastal plain

(1) This paper incorporates empirical, derived, and theoretical values of diet digestibility, dry matter intake requirements (DMI), diet nutrient content, and nitrogen (N) and phosphorus (P) balance in a summary of the nutrient regime of well-nourished adult female caribou (Rangifer tarandus granti) of the Denali herd. This study provides a baseline framework for comparisons with other herds, and discusses the utility and advantages of estimating intake requirements when investigating caribou-range relationships. (2) Estimated apparent dry matter digestibility (ADMD) of seasonal forages weighted by diet composition indicated that the ADMD of diets was high and varied little (60-70%) by season. A technique for predicting ADMD of seasonal diets was demonstrated assuming cell contents were 98% digestible, hemicelluloses were 35-61 0/o digestible and the remaining small fractions of cells were indigestible. (3) Derived DMI requirements (ME required . ME of the diet) were 86, 104, 104, and 74 g kg-0 75 day-' during spring, summer, autumn and winter, respectively. Spring and summer derived intake rates were similar to spring and summer intake rates of oesophageal-fistulated reindeer. Proposed changes in the energy model (Boertje 1985a), diet composition (Boertje 1984), and ADMD of individual forages (Boertje 1981) can easily be reflected in DMI requirements. (4) Derived values predict that caribou consuming a lichen-dominated diet are in a negative phosphorus balance and probably a negative nitrogen balance. Pregnancy and survival rates indicate caribou are well adapted to this winter diet. Dietary Ca, K, and Mg are likely to be adequate all the year round. Caribou of the Denali herd frequented mineral licks in spring and summer, probably to supplement Na-deficient forage. (5) Future comparisons of DMI requirements with empirical measurements of nutritional status and related demography are recommended as the most appropriate and practical approach to developing reliable predictors of caribou nutrition limitation. Conventional appraisals of caribou nutritional status, based on lichen abundance, are deemed inadequate.

In some line transect surveys, the population of interest consists of groups or clusters of individuals rather than single items. If group size influences the probability of detecting a group, then the observed group size data are size-biased. This can lead to overestimation of the true mean group size and hence could lead to overestimation of the density of individuals. Our method of line transect sampling incorporates group size as a covariate in line transect detection functions. We applied our method to shipboard surveys of sea otter (Enhydra lutris) and to surveys of pellet groups from barren ground caribou (Rangifer tarandus granti). Group size influence varied in the sea otter surveys. Our method of estimation adequately adjusted for size bias when it was present. Estimates of pellet group density were unaffected by significant size bias. J. WILDL. MANAGE. 54(3):511-514 Many factors can influence the detectability of items in line transect and other surveys of biological populations (e.g., Caughley 1974, Bayliss and Giles 1985, Gasaway et al. 1985). A particular problem occurs when the population consists of groups of items, and the size of the group influences its chance of detection (Quinn 1979, Rao et al. 1981, Drummer and McDonald 1987). We illustrate the procedure proposed by Drummer and McDonald (1987) in which group size is used as a covariate in existing line transect detection functions. Note that our method can also be used more generally to adjust estimates of the mean and total of any auxiliary variable that influences detectability in line transect sur

The rate of energy expenditure by caribou (Rangifer tarandus granti) digging in snow for lichens was determined by heart rate telemetry and an analysis of cratering mechanics. Based on a significant linear relationship between energy expenditure and heart rate, the mean cost per digging stroke in light, uncrusted snow was 118 J, whereas in denser (0.36 g/cm3) snow with a thin, hard crust the mean cost was 219 J/stroke. The cost of cratering through snow compacted by a snowmobile was 481 J/stroke. A comparison of metabolic and mechanical energy required for cratering suggested that caribou have evolved an energetically-efficient mechanism for obtaining food from beneath the snow layer. J. WILDL. MANAGE. 49(4):987-993 The ability of caribou to obtain lichens and other forages from beneath the snow by digging is well known. The amount of time caribou and reindeer (R. t. tarandus) reportedly spend digging for food in winter varies from only a few minutes per day in areas of shallow or patchy snow (Boertje 1981, Duquette 1984) to approximately 2 hours/day where snow is deep and continuous (Segal 1962, Thing 1977). During the winter months, caribou often obtain energy by catabolizing body fat and protein (McEwan and Whitehead 1970, Dauphine 1976), and thus it is important to the body condition and survival of the animal that the energy cost of obtaining food be low or be compensated for by the energy derived from the forage. Previous estimates of the energy expenditure associated with digging in snow by caribou and reindeer (Makarova and Segal 1958, Thing 1977) did not include the energy costs of digging in different snow types and at different rates. The most frequently used field method for measuring energy expenditure, using a gastight muzzle mask to measure oxygen consumption (White and Yousef 1978), cannot easily be used to measure digging costs because the mask restricts the animal's ability to smell and/or eat the forage. In addition, the valves in the mask may freeze or become clogged with snow, thereby affecting energy cost determinations. Heart rate telemetry has been used successfully with several domestic and wild ungulate species to predict energy expenditure (e.g., Webster 1967, Yamamoto et al. 1979, Renecker and Hudson 1983, Nilssen et al. 1984, Richards and Lawrence 1984) and appeared to be suitable for measuring cratering costs under various conditions. This study was supported by State of Alaska funds for organized research through the Inst. of Arct. Biol. and by a Graduate Fellowship in Resource Problems from the Univ. of Alaska to the senior author. The heart rate transmitters were implanted by R. A. Dieterich. We thank B. C. Anderson, S. L. Zeylmaker, N. J. Ferron, and D. R. Ashby for assisting with data collection and training and handling of captive caribou. R. D. Cameron and D. R. Klein provided helpful comments on the manuscript. We also thank E. A. Sturm and D. A. Borchert for pre

We used linear regression to examine the relationship between femur marrow fat and marrow fat of the other 5 long leg bones (tibia, metatarsus, humerus, radius, and metacarpus) and mandibles using paired bones from individual caribou (Rangifer tarandus granti) in Alaska. Correlations were high in all regressions (range of r = 0.90-0.98) and suggested that all bones were useful as gross indices to relative body condition. However, when interpreting fat content of bones other than femurs and making between-bone comparisons, there is merit in indexing fat values to a "femur standard." The percent marrow fat in all leg bones of individual caribou was more uniform than in moose (Alces alces). The sequence of fat depletion in caribou long bones was closer to that of moose than other wild ungulates. Fat depletion in both moose and caribou advances more rapidly in proximal long bones than in more distal ones. Mandible marrow fat can be used as a relative condition index if limitations are recognized. J. WILDL. MANAGE. 51(2):365-371 Field biologists are frequently faced with assessing the cause of death in large mammals when only skeletal parts remain. This situation is particularly common in predator-prey studies. Inferences about the physical condition of prey selected by predators have major implications, particularly when the condition of the prey population is known. Mech and DelGiudice (1985) have discussed potential limitations of using marrow fat in ungulate long bones as an index of relative body condition. For a number of reasons (Cheatum 1949) marrow fat in the femur has emerged as the relative condition index of choice to estimate relative body condition at death in many ungulate species. The substantial interest in femur marrow fat as a relative condition index has stimulated much investigation and refinement of techniques for femur marrow fat determinations since Harris (1945) reported that advancing malnutrition changed the bone marrow fat content in white-tailed (Odocoileus virginianus) and mule (0. hemionus) deer. Femur marrow fat has been estimated by ?6 general approaches: (1) ether extraction (AOAC method in Horwitz [1965:346], cited by Greer [1968]), (2) visual estimation (Harris 1945, Cheatum 1949), (3) compression (Greer 1968), (4) oven drying (Neiland 1970), (5) reagent-dry assay (Verme and Holland 1973), and (6) freeze drying (Hunt 1979). Ether extraction techniques yield reliable quantitative data but are tedious, expensive, and potentially dangerous. Consequently, they are used infrequently in wildlife studies. Subjectivity of the visual estimation technique limits its usefulness. The compression method is only quasiquantitative. The several drying techniques are relatively fast, inexpensive, and sufficiently accurate for most wildlife work (Hunt 1979). A logical extension of the femur relative condition index has been the use of marrow from other leg bones (Ballard et al. 1981, Fong 1981, Peterson et al. 1982) and from mandibles (Baker and Leuth 1966, Purol et al. 1977, Snider 1980, Ballard et al. 1981). Use of these additional bones as relative condition indices is appealing for many reasons. On frozen, intact carcasses femurs are much more difficult to extract than other bones. Large carnivores often consume all or portions of the femurs but frequently leave distal bones and mandibles intact. Mandibles, in particular, are often available in large numbers from hunterkilled animals. While investigating natural mortality in Alaska's western Arctic caribou herd, we found many caribou carcasses that were missing femurs, but contained other long bones or mandibles. To determine if these other bones were useful as indices of relative body condition, we tested the correlation between paired marrow values for femurs vs. other leg bones and mandibles. Those correlations and fat depletion patterns of those bones are the subject of this paper. Many Alaska Dep. Fish and Game employees

Estimates of the energy costs of resting, activity, and productive processes from the literature were applied to caribou activity budgets and movements documented during 1978-80 to estimate seasonal and annual energy requirements of adult female caribou (Rangifer tarandus granti) in Denali National Park and Preserve. Energy requirements were 45% lower in winter than summer, primarily because of a 21% reduction in resting metabolic rate and benefits of fat catabolism in winter, and high summer costs of lactation, fat deposition, and activity. Estimated energy requirements totaled 38.2 MJ . day-' during the insect season, 36.7 during summer migration, 34.2 during fall migration, 31.9 during prerut and rut, 29.3 during calving and postcalving, 23.7 during early and late winter migrations, 21.6 during early winter, 20.9 during late winter, and 20.5 during midwinter. Annual energy requirements, including costs of pregnancy (368.6 MJ) and lactation (560.3), totaled 9,870 MJ, excluding costs of cratering through snow and apparently minor costs of physiological stress. Compared to studies of food energy requirements of penned caribou, the model gives accurate predictions of total metabolizable energy requirements when allowances are made for the relative inactivity of penned animals. Modeling the energy requirements of an ungulate population is a prerequisite to estimating nutritional carrying capacities (Moen 1973, Robbins 1973, Wallmo et al. 1977, Mautz 1978). Measurements of the energy requirements of Rangifer have received emphasis in several studies (Makarova and Segal 1958, Hammel et al. 1961, Segal 1962, McEwan 1970, Luick et al. 1974, Young and McEwan 1975, White and Yousef 1978), but these measurements have not previously been used to model seasonal energy requirements of a caribou/ reindeer (Rangifer tarandus) population. Author is game research biologist, Alaska Department of Fish and Game, 1300 College Road, Fairbanks, Alaska 99701. At the time of the research, author was graduate student, Alaska Cooperative Wildlife Research Unit, University of Alaska, Fairbanks. Financial and logistical support was provided by the U.S. National Park Service (contract CX-9000-7-E080). Manuscript accepted May 28, 1985. Thomson (1977) attempted to model the year-round energy expenditure of wild reindeer in Norway using estimates of energy expenditure from the literature. However, Thomson's applications of energy costs differed in several ways from those presented here, making comparisons difficult. The most significant deviations included Thomson's exclusion of estimates for the calorigenic effect of food and his extremely high estimate for the energy cost of trotting. Gaare et al. (1975) also estimated seasonal energy requirements of wild reindeer in Norway. However, their estimates are about 45% of those reported here. Since they did not present energy-cost estimates of the various activities, it is impossible to account for the difference. White et al. (1975) estimated the summer energy requirements for caribou activity as simply 2 X basal metabolic rate (BMR). However, they used a winter-BMR value, so their summer energy estimates are substantially lower than presented here. I studied the Denali (formerly McKinley) caribou herd in Denali National Park and Preserve, Alaska during 1978-80. A model of the nutritional ecology of the herd was developed to assess the energetic/ nutritional status of this extremely reduced population (Boertje 1981). This paper demonstrates the applicability of measurements of energy costs by modeling metabolizable energy requirements of adult female caribou in the Denali herd.

Oxygen consumption (VO,, ml/g-hour) by caribou (Rangifer tarandus granti) calves trained to walk on a treadmill was measured using a headstall. Both the standing-resting VO, and the oxygen cost of locomotion (ml 02/g-km) decreased with increasing body weight. Net VO, (walking VO, minus VO, standing at rest) increased linearly with walking velocity, but an upward deflection was noted at velocities >3-5 km/ hour in the younger animals. In all caribou the stride frequency increased linearly with walking velocity between 2 and 7 km/hour. Evidence is presented that the oxygen cost of locomotion is different between Rangifer subspecies and an effect of leg length is implicated. J. WILDL. MANAGE. 50(1):148-152 Caribou usually are born in May-June (Kelsall 1968, Skoog 1968) and must grow to an adequate stature to meet the demands of summer movements, such as dispersal and assembly of nursery groups (Kelsall 1968, Skoog 1968, White et al. 1981). Summer movements are followed by fall migration, winter movements, and a 2nd long migration in spring (Duquette 1984). Consequently, the amount of energy required for locomotion may affect the growth and survival of caribou, especially those in their 1st year of life. The energy costs of movements in caribou are unknown; however, they could be estimated from interspecies prediction equations that show that the energy cost of locomotion/unit body weight declines markedly as body weight increases (Taylor et al. 1970, 1982; Robbins 1983; Parker et al. 1984). These studies suggest that the calf is of particular interest because its cost of locomotion/unit weight may be higher than that of its mother. The prediction of locomotory energy costs from interspecies comparisons must be made with caution since there are species-specific variations in the responses including nonlinear changes in the energy cost as velocity increases (Magaria et al. 1963, Yousef and Dill 1969, Cohen et al. 1978, Parker et al. 1984). The energy cost of locomotion in semidomestic reindeer (R. t. tarandus) walking on tundra surfaces (White and Yousef 1978) or on a treadmill (Nilssen et al. 1984) potentially could be applied to caribou. Yet, application of these data to caribou can be criticized because caribou have longer legs than reindeer and have been under continued selection for migration (Fancy and White 1985). The objective of this study was to determine the energy cost of walking in caribou; special emphasis was placed on calves of varying body size a d on verifying the linearity of the locomotory cost in relation to velocity. A preliminary report of this work was published elsewhere (Luick and White 1983). We acknowledge the assistance of J. L. Davis and P. Valkenburg from the Alaska Dep. Fish and Game for capture of caribou calves. Grants from the Inst. Arct. Biol. and the State of Alaska (Alaska Counc. Sci. and Technol., Grant 46-82) suppor ed equipment construction and testing and the healthcare and feeding of the caribou. We thank L. A. Harbo, K. M. Frisby, P. Line, L. L. Axtel, and S. Dier for their devoted care of animals through the critical period of bottle raising.

Analyses of 34 femur marrow samples from barren ground caribou, Rangifer tarandus granti, revealed that this tissue is a three-component system comprised of water, fat and non-fat residue. Both the water and fat, and residue and fat are linearly and inversely related. Because the residue amounts to only 24 percent of the net weight, the dry weight of the marrow, except at low fat levels, is essentially equal to the weight of fat in the marrow. For maximum accuracy at low fat levels, the dry weight:fat inequality can be corrected by subtracting the average residue value for that fat level from the dry weight. Such corrected dry weights adequately measure femur fat content at all fat levels for many studies concerned with marrow fat reserves. This content downloaded from 157.55.39.170 on Tue, 20 Sep 2016 04:31:31 UTC All use subject to http://about.jstor.org/terms DRIED MARROW WEIGHT AS FAT INDICATOR IN CARIBOU FEMURS * Neiland 905 + 1 s _ _ I AVERAGE CORRECTIOs FAC1OR