We measured stable carbon ( 13 C/ 12 C) and nitrogen ( 15 N/ 14 N) isotope ratios in nail, whiskers, skin, hair, and blood of captive harp seals (Pagophilus groenlandicus), harbour seals (Phoca vitulina), and ringed seals (Phoca hispida) held on a constant diet of herring (Clupea harengus) for at least 2 years. In addition, isotope ratios were measured in the muscle and liver of two harp seals, and in the lung, kidney, heart, and spleen of a single harp seal that had died in captivity. Isotopic fractionation values between dietary herring (δ 13 C: -20.3 ± 0.7‰; δ 15 N: 13.0 ± 0.4‰, n = 33) and these tissues ranged for nitrogen from +1.7 to +3.1‰ for blood and liver, respectively, and for carbon from +0.6 to +3.2‰ for liver and whiskers, respectively. No differences in isotopic fractionation values among species or age groups were detected. These values will permit more accurate dietary reconstructions on the basis of isotopic analysis of the tissues of seals and other marine mammals. For two captive harp seals, carbon and nitrogen isotope values showed small variation along the length of six whiskers (range of standard deviations for δ 13 C: 0.21 to 0.57‰, for δ 15 N: 0.27 to 0.45‰) but showed some evidence of being inversely correlated.Résumé : Nous avons mesuré des rapports d'isotopes stables pour le carbone ( 13 C/ 12 C) et l'azote ( 15 N/ 14 N) dans les griffes, les moustaches, la peau, le poil et le sang de phoques captifs, soit des phoques du Groenland (Pagophilus groenlandicus), des phoques communs (Phoca vitulina) et des phoques annelé (Phoca hispida), soumis à un régime alimentaire constant de hareng (Clupea harengus) pendant au moins 2 ans. De plus, on a mesuré les rapports isotopiques dans le muscle et le foie de deux phoques du Groenland, ainsi que dans les poumons, les reins, le coeur et la rate d'un phoque du Groenland mort en captivité. Les plages des valeurs de séparation isotopique observées pour le hareng du régime alimentaire (δ 13 C : -20,3 ± 0,7‰; δ 15 N : 13,0 ± 0,4‰, n = 33) et pour ces tissus étaient comprises entre +1,7 et 3,1‰ (sang et foie, respectivement), dans le cas de l'azote, et dans celui du carbone, ces plages étaient comprises entre +0,6 et +3,2‰ (foie et moustaches, respectivement). On n'a décelé aucune différence, pour ce qui est des valeurs de séparation isotopique, entre des espèces ou groupes d'âges. Ces valeurs permettront une reconstruction plus précise du régime alimentaire, basées sur l'analyse isotopique des tissus des phoques et d'autres mammifères marins. Pour deux phoques du Groenland captifs, les valeurs du carbone et de l'azote présentaient de petites variations dans le sens de la longueur sur six moustaches (plage des écarts-types pour δ 13 C : 0,21 à 0,57‰; pour δ 15 N : 0,25 à 0,45‰), mais on pouvait aussi y voir certains signes de corrélation inverse. [Traduit par la Rédaction]

Calls of harbour seal (Phoca vitulina) pups, propagated simultaneously in air and underwater while the pups' heads were above the surface of the water, were recorded to examine in detail the differences between them and to determine if both versions are individually distinct. Although the airborne and underwater versions of the calls were different from one another, they were distinct for each pup on the basis of several physical parameters, primarily the frequency of the major harmonic. Interactions between the mothers and pups at the time of calling were observed to assess the role of the cries in maintaining mother–pup contact. Analysis of the variations in vocalizations and contextual data supported the hypothesis that the mothers use these vocalizations for individual recognition of their offspring and for ensuring that contact with them is maintained. It is postulated that differences between the aerial and underwater versions of calls increase the accuracy with which the mothers can locate their pups.

The Tasmanian devil, Sarcophilus harrisii, the largest extant carnivorous marsupial, is normally solitary, but it congregates when feeding on carcasses. In this study, observations of behaviour during group feeding were used to document the communication and social organisation of these little-known animals. Their communication repertoire involved visual (20 postures), vocal (11 sound forms) and probably chemical signalling via urination and ano-genital drag. While some animals had conspicuous markings, 13% had none, suggesting that markings were not necessary for individual recognition. Agonistic interactions seldom resulted in physical clashes, but a few led to damage to the muzzle and rump, as supported by heavy scarring in these regions. Adult males were the most frequently and seriously scarred, probably related to agonistic encounters from longer feeding bouts and copulatory aggression. Devils gorged themselves, eating approximately 40% of their body mass. There was no apparent hierarchical structure to the sequence in which individuals fed. Feeding duration seemed to be determined by the extent to which an animal feeding on the carcass was sated.

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This study tested the hypothesis that seasonal variation in resting metabolic rate (RMR) was more closely related to changes in total energy use than to energy intake. It also quantified the extent to which variation in metabolism contributed to changes in total energy expenditure. RMR, gross energy intake, and body mass and composition were measured in six captive Atlantic harbour seals (Phoca vitulina concolor) over 16 months. Gross energy intake during the year (across all seals) averaged 25.4 ± 4.1 MJ/d (mean ± SD). The energy used by the seals (E used ; a composite measure of energy expenditure from ingested energy and tissue catabolism) averaged 19.2 ± 3.4 MJ/d. RMR averaged 11.2 ± 1.5 MJ/d during the year, while mass-corrected metabolism declined with age. The seals displayed significant changes in both absolute and mass-corrected metabolism during the year. Overall, E used was a stronger predictor of changes in metabolism than either gross energy intake or body mass. Mass-corrected metabolic rate was more closely related to E used than was absolute metabolism. Energy changes in metabolism during the year (range = 6.9 ± 1.9 MJ/d) were minor compared with those in E used (27.8 ± 7.3 MJ/d). These results suggest that seasonal changes in metabolism were a response to, or facilitated by, concurrent changes in E used but were not the cause of variation in E used . Rather, variation in both RMR and E used was the result of changes in other bioenergetic components of the seals' energy budget, such as activity.Résumé : Nous avons éprouvé l'hypothèse selon laquelle la variation saisonnière du métabolisme au repos (RMR) est plus étroitement reliée aux changements dans l'utilisation de l'énergie totale que dans l'absorption de l'énergie. Nous avons également quantifié l'influence de la variation du métabolisme sur les fluctuations de la dépense énergétique totale. RMR, l'absorption brute d'énergie, la masse totale et la composition corporelle ont été mesurés chez six Phoques communs (Phoca vitulina concolor) en captivité pendant une période de 16 mois. L'absorption brute d'énergie au cours de l'année (calculée chez tous les phoques) a été évaluée à 25,4 ± 4,1 MJ/jour (moyenne ± erreur type). L'énergie utilisée par les phoques (E utilisée ; une mesure combinant la dépense énergétique tirée de l'énergie ingérée et le catabolisme tissulaire) a été estimée à 19,2 ± 3,4 MJ/jour. RMR était de 11,2 ± 1,5 MJ/jour au cours d'une année, mais le métabolisme corrigé en fonction de la masse diminuait avec l'âge. Les phoques ont subi des changements significatifs de leur métabolisme absolu et de leur métabolisme corrigé pour tenir compte de leur masse au cours de l'année. Dans l'ensemble, la valeur E utilisée constituait un meilleur indice des changements métaboliques que l'absorption brute d'énergie ou que la masse totale. Le taux de métabolisme corrigé pour tenir compte de la masse était plus étroitement relié à la variable E utilisée que le métabolisme absolu. Les variations énergétiques du métabolisme au cours d'une année (éte...

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Among its functions, the hypodermal blubber layer of pinnipeds serves as both an energy reserve and insulation. This study examined seasonal changes in blubber distribution and body morphology in a group of captive changesharbor seals to test whether these changes were designed to maximize insulative effectiveness. Seasonal changes were found in girth, blubber volume, mean blubber depth, and the ratio of blubber depth to body radius (d/r ratio). These changes were more evident in older seals. The d/r ratio demonstrated a smaller relative annual change than mean blubber depth. The d/r ratio also exhibited less variation along the length of the seal than blubber depth at any given time. Similar to reports for ringed seals, and contrary to those for southern elephant seals, the harbor seals preferentially lost blubber from overinsulated areas of the body. These results suggest that core tissue and blubber mass are lost in a manner that maximizes insulative effectiveness.

Bioelectrical impedance analysis (BIA) measures resistance and reactance of a current as it passes through an organism. The validity of using BIA as a tool to measure body water content, and hence body composition and condition, was tested on harp and ringed seals. The resistance and reactance readings from BIA were compared to estimates of total body water (TBW) determined via tritiated water dilution. The relationship between resistance and TBW (% of body mass) was linear after logarithmic transformation and the two variables were highly correlated. We describe the electrode configuration and placements which provide reliable results in these seals. Our findings indicate that BIA has considerable potential as an inexpensive, rapid, and reliable technique for estimating body composition of phocid seals.