K. Ronald

Mammalian hibernation and the oxygen consumption of a denning black bear (Ursus americanas)

Abstract 1. 1. Definitive criteria for mammalian hibernation are reviewed and a new definition based upon specialized metabolic reductions is developed. 2. 2. Results of indirect calorimetry, heart rates and deep body temperature measurements on a denning black bear are discussed with respect to the proposed definition.

Apparent specific dynamic action in the harp seal (Phoca groenlandica)

Abstract 1. 1. SDA increased the metabolic rate of a female harp seal up to 1.67 times, and the metabolic rate was increased for at least 7 hr. 2. 2. The magnitude and duration of the increase in metabolic rate were dependent upon the ration size. 3. 3. The apparent SDA was approx. 17% of the gross energy of the diet.

Weight loss and catabolic adaptations to starvation in grey seal pups

Five grey seal pups lost from 18 to 32% of their initial body weight during a 21 day starvation period. Blubber fat mass density was 0.93 +/- 0.03 g/cm3. A considerable loss of blubber fat was recorded, but analysis of the weight loss and body size data indicated that blubber fat was retained for thermoregulatory reasons, particularly in the lean, smaller seals. It is possible that phocid seals during periods of negative energy balance have a higher rate of protein catabolism than normal for terrestrial mammals.

Pinniped visual pigments

Abstract 1. 1. Harp ( Pagophilus groenlandicus ) and harbour ( Phoca vitulina ) seals had rod visual pigments with λ max of 496–497 nm. Grey seals ( Halichoerus grypus ) had a similar, if not identical visual pigment. 2. 2. The visual pigment from the northern fur seal ( Callorhinus ursinus ) appeared to have a λ max near 500 nm. 3. 3. Limited evidence available to date suggests that seal visual pigments, like those of fish and whales, are probably adapted for vision in their respective photic environments.

Blood levels of thyroid hormones and certain metabolites in relation to moult in the harp seal (Phoca groenlandica)

1. Changes in blood levels of thyroxine (T4), triiodothyronine (T3), free fatty acids (FFA), glucose, pyruvic acid and lactic acid in the harp seal during moult, were studied. 2. Serum levels of both T4 and T3 showed significant increase in the moult phase from that in the pre-moult phase. While T4 level continued to remain high during the early and late post-moult phases, T3 level dropped in the latter two phases to the same low pre-moult level. 3. The T3/T4 ratio was significantly higher during the pre-moult phase than that in all the other phases. It is suggested that the high pre-moult T3/T4 ratio marks the initiation of moult. 4. There were no significant changes in the levels of the metabolites studied except that of FFA which was highest in the moult phase indicating the hormonal basis of lipid mobilization.

Radiative surface temperatures of harp seals

Abstract 1. 1. Ambient air temperature rather than wind speed or heat flow exerted the greatest effect on radiative heat loss from harp seal pup fur. 2. 2. Fur conductance was higher when calculated using radiative temperature rather than air temperature as representative of ambient temperatures. 3. ]3. An equation was derived from data on thermal properties of fur samples and adjusted to fit the expected in vivo heat loss to predict the radiative temperatures of harp seal pups on the ice.

Physiological indices of activity and metabolism in the polar bear

Abstract 1. 1. Respiratory frequency, core temperature, cardiac and stride frequencies, were evaluated as indirect indices of activity and metabolism in the polar bear ( Ursus maritimus ). 2. 2. Respiratory frequency was found inadequate as an index due to its role as a thermoregulatory effector and its “resonant” nature. 3. 3. The core temperature of the bears was highly correlated with activity or metabolic rate. 4. 4. The relationship was however curvilinear, resulting in only a 0.5°C change in core temperature over a five-fold metabolic range. 5. 5. It was impossible to accurately define different levels of activity. 6. 6. The cardiac frequencies of resting bears were extremely variable and not, as a result, good indices of these activities. 7. 7. In the active or walking animal, however, cardiac frequency is an accurate index of activity or metabolic rate. 8. 8. Stride frequency may also be used to accurately predict walking speed and, thus, metabolic rate in the polar bear.

Plasma concentrations of thyroid hormones in a captive and feral polar bear (Ursus maritimus)

Abstract 1. 1. Adult male polar bears (Ursus maritimus) collected from Fort Churchill, Manitoba, during October to December had lower plasma L-thyroxine (T4) and triiodo-L-thyronine (T3) levels than adult females collected at the same time and place. The reverse appeared to be true in juveniles, although the sample size was too small to permit statistical evaluation. 2. 2. Plasma T4 and T3 values in two male cubs were similar to those in the juveniles. 3. 3. Plasma T3:T4 ratios were consistent throughout the age-sex classes. 4. 4. Plasma T4 and T3 concentrations and T3:T4 ratios in a captive adult male polar bear showed peak values during the winter months.

The phospholipid and fatty acid compositions of seal platelets: a comparison with human platelets.

1. Platelet phospholipid compositions were studied in four species of phocid seals consuming herring or herring and shrimp and in human subjects consuming a normal mixed diet. 2. There were no major differences in platelet phospholipid, cholesterol and protein levels between different species of seal nor between seals and human subjects, nor in the relative abundance of the individual types of phospholipid. 3. The seal platelet phospholipids (phosphatidylcholine (PC) and phosphatidylethanolamine (PE), were greatly enriched in the omega 3 fatty acid, eicosapentaenoic acid (EPA) and depressed in arachidonic acid (AA) relative to the corresponding human platelet phospholipids. 4. Much less accumulation of EPA in phosphatidylserine (PS) and phosphatidylinositol (PI) was found. 5. The EPA contents of the individual seal platelet phospholipids exhibited considerable differences (including EPA discrimination from PI) but gave patterns which were generally similar to those reported for human volunteers consuming fish/fish oils enriched in EPA. 6. These results suggest that the seal platelet may be a useful model for studying the metabolism and function of the omega 3 fatty acids, such as EPA, in relation to platelet reactivity, phospholipid turnover and the formation of AA- and EPA-derived eicosanoids.

The spectral sensitivity of a polar bear

Abstract 1. 1. The visual sensitivity of a polar bear was examined by standard operant techniques. Scotopic and photopic functions were determined. 2. 2. Scotopic peak sensitivity occurred at 525 nm while the photopic function was bimodal with peaks at 450 nm and 525 nm. 3. 3. The photopic peak sensitivity indicated a 75 nm shift from the scotopic maxima.