Raymond D. Cameron

Estimating fat content of caribou from body condition scores

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).

Reproductive pauses by female caribou

Parturition status of 53 radiocollared, female caribou ( Rangifer tarandus granti ) of the central Arctic herd was determined through repeated observations by fixed-wing aircraft during 2–5 periods of parturition. The overall frequency of reproductive pauses for females that were initially parturient, or previously confirmed to be parturient, was 24% (ca. once every 4 years). Most pauses preceded (78%) and followed (87%) parturition events. Periodic infertility, as a response to nutritional stress, may enhance long-term reproductive performance in caribou and other ungulates.

Abundance and movements of caribou in the oilfield complex near Prudhoe Bay, Alaska

We examined the distribution and movements of 141 radiocollared female caribou (Rangifer tarandus granti) of the Central Arctic Herd during summer, 1980-1993. Numbers of caribou locations within each of 5 quadrats along the arctic coast were totalled separately for days during which insects were active and inactive, and numbers of east-west and west-east crossings of each quadrat mid-line were determined from sequential observations. Both abundance and lateral movements of radiocollared females in the quadrat encompassing the intensively-developed Prudhoe Bay oilfield complex were significantly lower than in other quadrats (P < 0.001 and P < 0.00001, respectively). Avoidance of, and fewer movements within, the complex by female caribou are ostensibly in response to the dense network of production and support facilities, roads, above-ground pipelines, and the associated vehicular and human activity. Impaired access to this area constitutes a functional loss of habitat.

Summer range fidelity of radio-collared caribou in Alaska's Central Arctic Herd

Sixty-four adult (2 + years) female caribou (Rangifer tarandus grand), radio-collared in April or May 1975 - 82, were relocated during the following June and/or July within the summer range of the Central Arctic Herd (CAH). Relocations made during the following three summers were used to assess range fidelity. Cumulative relocations of radio-collared females in the Central Arctic region were equivalent to 91% of the projected availability based on transmitter life. A chronological analysis indicates that 98%, 91%, and 82% of radio-collared females were found there one, two, and three years later; most of the progressively lower relocation success is probably attributable to transitter malfunctions rather than emigration. These observations suggest that summer range fidelity of adult females in the CAH is at least 90%, and may approach 100%.

Advancing the match-mismatch framework for large herbivores in the Arctic: Evaluating the evidence for a trophic mismatch in caribou

Climate-induced shifts in plant phenology may adversely affect animals that cannot or do not shift the timing of their reproductive cycle. The realized effect of potential trophic “mismatches” between a consumer and its food varies with the degree to which species rely on dietary income and stored capital. Large Arctic herbivores rely heavily on maternal capital to reproduce and give birth near the onset of the growing season but are they vulnerable to trophic mismatch? We evaluated the long-term changes in the temperatures and characteristics of the growing seasons (1970–2013), and compared growing conditions and dynamics of forage quality for caribou at peak parturition, peak lactation, and peak forage biomass, and plant senescence between two distinct time periods over 36 years (1977 and 2011–13). Despite advanced thaw dates (7−12 days earlier), increased growing season lengths (15−21 days longer), and consistent parturition dates, we found no decline in forage quality and therefore no evidence within this dataset for a trophic mismatch at peak parturition or peak lactation from 1977 to 2011–13. In Arctic ungulates that use stored capital for reproduction, reproductive demands are largely met by body stores deposited in the previous summer and autumn, which reduces potential adverse effects of any mismatch between food availability and timing of parturition. Climate-induced effects on forages growing in the summer and autumn ranges, however, do correspond with the demands of female caribou and their offspring to gain mass for the next reproductive cycle and winter. Therefore, we suggest the window of time to examine the match-mismatch framework in Arctic ungulates is not at parturition but in late summer-autumn, where the multiplier effects of small changes in forage quality are amplified by forage abundance, peak forage intake, and resultant mass gains in mother-offspring pairs.

Estimating body composition of caribou and reindeer using bioelectrical impedance analysis and body condition scores

The use of non-destructive methods to assess body composit ion of w i l d cervids allows clarification of the dynamic influence of the environment on nutrient reserves w h i c h , in turn , affect reproductive success. Bo th bioelectrical impedance analysis (BIA) and body condit ion scores (BCS) have been used elsewhere to estimate in vivo body composit ion. B I A relies on the differential conductivity of lean and fatty tissues, while B C S are numerical indices of overall condit ion. This is a prel iminary report on the efficacy of B I A and B C S as predictors of fat content ( F A T ) and total body water ( T B W ) . N i n e captive male reindeer and 10 w i l d female caribou of the Central A r c t i c H e r d ( C A H ) were used in this analysis. A n additional 5 female caribou of the C A H were rated using B C S only . Each animal was weighed ( B W , nearest kg), and body measurements (body length, L , chest girth, G , metatarsal length, M T , all in cm) were taken. W h o l e body resistance (Z) was determined using a bioelectrical impedance analyzer (BIA-101A, R J L Systems, Inc., Detroi t MI) and 2 pairs of electrodes w h i c h were inserted under the skin at each of 2 sites (Fig. 1): on the legs w i t h the animal ly ing on its side (Z j J , and along the back w i t h the animal ly ing on its chest (Zt>). B C S was determined as the sum of numerical rating (1-5, 1 being low) of the amount of soft tissue covering bone at each of 3 sites: withers, ribs, and hips. A body reserve index (BRI) was computed as the product of B C S and body weight. A l l animals were k i l led and processed for chemical analysis (Huot and Picard 1988). Water content was determined by freeze drying; fat content was determined by petroleum ether extraction. Stepwise linear regression was used to examine relationships between dependent ( T B W , l i ters, and F A T , kg) and independent variables (BCS, B W , B R I , M T , L , G , 1 / Z B , 1 / Z L , ( M T or L ) 2 / Z L or Z ^ ) . Impedance values were expressed as ( l eng th )VZ, since body water volume is theoretically related to conductor length squared divided by resistance. Corre la t ion between T B W and body weight (eq. 1) was stronger than that between T B W and any impedance term. Impedance expressed as L V Z L was most strongly correlated w i t h T B W (eq. 2). T B W was not correlated w i t h Z ^ .

Efficacy of calf:cow ratios for estimating calf production of arctic caribou

Caribou (Rangifer tarandus granti) calf:cow ratios (CCR) computed from composition counts obtained on arctic calving grounds are biased estimators of net calf production (NCP, the product of parturition rate and early calf survival) for sexually-mature females. Sexually-immature 2-year-old females, which are indistinguishable from sexually-mature females without calves, are included in the denominator, thereby biasing the calculated ratio low. This underestimate increases with the proportion of 2-year-old females in the population. We estimated the magnitude of this error with deterministic simulations under three scenarios of calf and yearling annual survival (respectively: low, 60 and 70%; medium, 70 and 80%; high, 80 and 90%) for five levels of unbiased NCP: 20, 40, 60, 80, and 100%. We assumed a survival rate of 90% for both 2-year-old and mature females. For each NCP, we computed numbers of 2-year-old females surviving annually and increased the denominator of CCR accordingly. We then calculated a series of hypothetical “observed” CCRs, which stabilized during the last 6 years of the simulations, and documented the degree to which each 6-year mean CCR differed from the corresponding NCP. For the three calf and yearling survival scenarios, proportional underestimates of NCP by CCR ranged 0.046–0.156, 0.058–0.187, and 0.071–0.216, respectively. Unfortunately, because parturition and survival rates are typically variable (i.e., age distribution is unstable), the magnitude of the error is not predictable without substantial supporting information. We recommend maintaining a sufficient sample of known-age radiocollared females in each herd and implementing a regular relocation schedule during the calving period to obtain unbiased estimates of both parturition rate and NCP.

Growth and body composition of arctic caribou

Nutr i t ion and growth have been considered inseparable prior to puberty in mammals, and first summer growth is an important determinant of adult body size, l ikelihood of overwinter survival, and potential reproductive success. Knowledge of growth and its regulators is therefore critical to understanding and predicting changes in herd productivity. In addition, the relative importance of milk intake to growth rate changes wi th age (White, 1992), and the timing of nutritional independence may be affected by both regulatory (endogenous) and ecological components.