Energetics of hibernation in the Arctic ground squirrel (Spermophilus parryii kenicotti)

Thesis (M.S.) University of Alaska Fairbanks, 2002Arctic ground squirrels (Spermophilus parryii kenicotti) hibernate underground; experiencing burrows temperatures of -5 to -25C̊. Hibernation consists of 7-9 months of torpor interrupted every 2-3 weeks by 10-20 h arousal episodes with high body temperatures and metabolic rates. Metabolic rates and body temperatures were measured during arousal episodes under temperate and arctic conditions. No difference in cost of arousal episodes was detected. Yet, when the cost of thermogenesis during torpor was included, proportional cost of arousal episodes decreased from 86 to 27% comparing temperate to arctic conditions. The relationship between metabolic rate and body temperature was examined during the recooling phase of hibernation. As animals entered torpor, body temperature was allowed to either decrease naturally or was experimentally altered at different points along the recooling curve. The changes in metabolic rate can be explained by changes in body temperature and no sign of temperature-independent metabolic suppression was detected.Introduction -- Hibernation in Arctic ground squirrels -- Arousal episodes -- Recooling phase -- Ch. 1. Energetics of hibernation under Arctic conditions -- Ch. 2. Metabolic suppression during the recooling phase of hibernation in the Arctic ground squirrel -- Conclusions

Morphological characteristics of harbor seal (Phoca vitulina) whiskers and their use in dietary reconstruction using stable isotope ratios

We investigated whether inferences about harbor seal (Phoca vitulina Linnaeus, 1758) whisker shed status and growth rates based on whisker morphology could improve dietary time series from whisker isotopic profiles. We identified morphometric characteristics of Alaskan harbor seal whiskers, including a smooth root section (SRS) and a bumpy section. The SRS was longer for spring versus fall-collected whiskers and matched the length of fully-grown, shed whiskers. Thus, SRS length can differentiate whisker shed and growth status, and we used it to determine the sequence of whisker shedding by cohort in summer-captured seals. The mean inter-bump length (IBL) correlated with whisker length, potentially providing a proxy for whisker growth rate. We compared carbon isotope ratios (expressed as δ13C values) along the three longest whiskers from 10 harbor seals, using two approaches for converting whisker position to date: (1) a standard growth rate constant based on captive studies and (2) individually adjusted growth rates based on whisker morphology. Intra-individual patterns of whisker δ13C values became more synchronous when expressed by deposition date rather than by position, however, adjusting growth rates based on IBL did not improve synchrony further. These findings suggest that whisker morphology can contribute whisker growth rate and shedding information for dietary reconstruction.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Seasonal differences in foraging and isotopic niche width related to body size in Gulf of Alaska harbor seals

Harbor seals (Phoca vitulina Linnaeus, 1758) use different foraging strategies based on body size and sex, but this difference can be difficult to evaluate across seasons. We used stable isotope analysis of harbor seal whiskers from 32 individuals to assess seasonal foraging of seals inhabiting tidewater glacial habitat in Southeast Alaska. We analyzed stable isotope ratios from serial sections of whiskers, estimated deposition date for each section, and used mixed models to determine if sex and body size influence stable isotope ratios. Seals were grouped by size (>1.4 m or ≤1.4 m curvilinear length) as a proxy for sexual maturity to describe isotopic differences between groups using standard ellipse corrected area. Mean carbon and nitrogen isotope ratios differed significantly between size classes (p < 0.005), with no effect of sex. Larger seals exhibited a broader isotopic niche in the fall, winter, and spring relative to smaller seals, but not in the summer. Our results suggest that seals using tidewater glacial habitat share common foraging behavior in the summer, while larger seals exhibit more diverse foraging throughout the rest of the year. These results highlight the importance of tidewater glacial habitat for this population of harbor seals during the summer.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author