THREE-DIMENSIONAL DIVING BEHAVIORS OF RINGED SEALS (PHOCA HISPIDA)

Dives of five freely diving ringed seals were classified into three-dimentional movement types. Horizontally convoluted dives, defined as dives with angular velocity > 15°/sec, appeared to be foraging or social dives. Simple dives that did not include convoluted movements (angular velocity < 10°/sec) were considered to be exploration dives. Directional dives with nearly linear horizontal travel (horizontal directionality >0.6, on a scale of 0–1) were presumed to be travel dives. Each three-dimensional dive type was observed with similar frequency in dives with two distinct time-depth profiles: V-shaped profiles in which ascent immediately followed descent, and U-shaped profiles in which >7 sec were spent at depth between descent and ascent. The lack of behavioral differences between dives with distinct time-depth profiles suggested that time-depth profiles are not a reliable means of inferring dive behaviors for ringed seals.     

COUNTS OF GROWTH LAYER GROUPS IN CEMENTUM AND DENTINE IN RINGED SEALS (PHOCA HISPIDA)

We compared counts of growth layer groups (GLGs) in the dentine of un-decalcified, unstained cross-sections and in the cementum of decalcified, stained longitudinal sections of canine teeth from 144 ringed seals ( Phoca hispida ). Although there was a statistically significant correlation until approximately 10 GLGs, about 75% of paired readings at ≤ 10 cementum GLGs disagreed. After 10 GLGs, the number of GLGs in the cementum usually was greater. The maximum GLG count in cementum was 33, compared to a maximum in dentine of only 19. Interobserver differences in median counts were not statistically significant using cementum or dentine counts. Regression analysis revealed that for cementum in female seals, readers differed at higher counts (P < 0.05), and for dentine, there was a constant difference of about 0.6 GLGs ( P < 0.05) for male seals and 1.1 GLGs ( P < 0.05) for female seals. Counting GLGs in the cementum of decalcified and stained longitudinal sections provided higher counts and more agreement between readers, and it was the better of the methods examined for ageing ringed seals.     

HAUL-OUT ACTIVITY OF RINGED SEALS (PHOCA HISPIDA) DETERMINED FROM SATELLITE TELEMETRY

The haul-out activity of 15 ringed seals ( Phoca hispida ) equipped with satellite-linked radio transmitters was studied in NW Greenland ( ca. 73°-78°N). Between 19 June 1997 and 30 June 1999, telemetry data on haulout activity were obtained by the "Land-Sea-Reporter" (LSR), "Time-at-Depth" (TAD), and "Timelines" (TIM) systems housed within the satellite transmitters. The haul-out activity (% of total time hauled out) reported by the TIM system, which is specifically designed for collecting haul-out data, was about 1.4 times higher than that inferred from the LSR, but only about 0.7 of that inferred from TAD data. The TIM were used to describe haul-out activity. A total of 1,011 d with TIM were obtained (64.5% of a total of 1,568 "seal-days" monitored) representing data from nearly an entire annual cycle. No differences were found in percentage of time hauled out per month among various age categories. At all seasons the haul-out time showed considerable individual variation. There were no trends in percentage of time hauled out per month during late summer, fall, and winter (August-February). During the High Arctic winter darkness (November-January) the percentage of haul-out per month ranged between 3.9% in an adult (SD = 2.44, range: 1.1%-5.7%, n = 3 mo) and 15.7% in a subadult (SD = 1.95, range: 13.7%-17.6%, n = 3 mo). From late March there was a significant increase in haul-out time. Between 1 and 30 June, when aerial surveys of basking ringed seals usually are conducted, the haul-out time (% per day) increased from about 25% to about 57%. No tendencies in diel haul-out activity were revealed.     

VARIABILITY IN THE BLUBBER FATTY ACID COMPOSITION OF RINGED SEALS (PHOCA HISPIDA) ACROSS THE CANADIAN ARCTIC

We determined the blubber fatty acid (FA) composition of 281 ringed seals ( Phoca hispida ) across the Canadian Arctic to make inferences about spatial, temporal, and demographic patterns of foraging. Seals were sampled in nine locations between 1992 and 2004. Regional differences in FA signatures were related to the distance between groups, with the greatest similarity occurring among seals sampled in three locations within the Beaufort Sea-Amundsen Gulf. Seals in the western and southeastern portions of Hudson Bay also had similar FA signatures. Discriminant analysis on seventeen FAs classified ringed seals to their correct geographic region with 95% accuracy. Although location accounted for most of the variability in FA signatures, adult and juvenile ringed seals in Frobisher Bay-Labrador Sea and Jones Sound showed significant FA differences, as did male and female ringed seals in Jones Sound and Qaanaaq. Demographic differences were not detected among ringed seals in the Beaufort Sea-Amundsen Gulf or in western Hudson Bay. Seals off the coast of Labrador showed significant seasonal variability in FA signatures. Overall, seasonal, regional, and demographic patterns in FA signatures were consistent with differences in ringed seal diets, as inferred from stomach content and stable isotope analyses.     

SPRING HAUL-OUT BEHAVIOR OF RINGED SEALS (PUSA HISPIDA) IN KONGSFJORDEN, SVALBARD

Haul‐out behavior of ringed seals (Pusa hispida) was investigated during the spring molting period of 2003 (May–July) in Kongsfjorden, Svalbard, Norway. Hourly counts were conducted on the land‐fast ice in six spatially defined sectors in the inner fjord, from an elevated land‐based vantage point from early May through until the ice began to break up in June, from 0600 to 2200 daily (total counts n= 478). Concomitantly, measurements were made of a variety of weather parameters. Multiple regression analyses revealed that time of day (P < 0.001) and date (P < 0.001) significantly affected the number of ringed seals hauled out on the ice surface. Other factors influencing the number of seals counted on the ice were air temperature (P= 0.011) and wind speed (P < 0.001). Daily peaks occurred in the early afternoon between 1300 and 1400 and the seasonal high (n= 385) was registered during the first week in June, after which the number of seals on the ice in the fjord declined. In addition to the visual counts, 24 ringed seals were equipped with VHF transmitters, and the haul‐out behavior of individuals was monitored from May through July via an automatic recording station. The VHF‐tagged seals exhibited the same diurnal pattern seen in the total counts, with haul‐out most frequent from 1300 to 1400. Pups exhibited short and frequent haul‐outs, whereas longer haul‐out periods were seen in the older age classes; adult females had the greatest number of haul‐out periods that exceeded 24 h. The seasonal peak of haul‐out for the tagged seals preceded the peak seasonal counts by approximately 3 wk. This may reflect significant out‐ and influx of seals from and to the area, a phenomenon warranting further attention because of its implications for assessment studies.     

DIVING BEHAVIOR OF THE SAIMAA RINGED SEAL (PHOCA HISPIDA SAIMENSIS NORDQ.)

The activity and diving patterns of four adult Saimaa ringed seals ( Phoca hispida saimensis , a landlocked subspecies living in Lake Saimaa, Finland) were examined during spring, summer, and autumn by the use of VHF-transmitters. Over 17,000 dives were registered. The duration of the dives and diving patterns differed among individuals. The mean duration of dives increased from spring to autumn; e.g. , in one individual the mean dive duration increased from 6 min in June to 10.5 min in October. The haul-out periods of one individual in May to early June made up 46.2% of its total activity budget, but in another individual in July to August the haul-out periods made up only 11% of the budget and the seal was submerged for 80% of the time. Periods of successive long duration dives (>10 min) were observed in three individuals in summer and autumn. The longest dive measured was 23 min. The duration of the periods containing long dives was often over three hours (maximum six hours) and the mean duration of the dives about 15 min. These long duration dives are assumed to be aerobic resting dives. Generally, the dives of the Saimaa ringed seal appear to be of longer duration than previously assumed.     

DIET OF RINGED SEALS (PHOCA HISPIDA) ON THE EAST AND WEST SIDES OF THE NORTH WATER POLYNYA, NORTHERN BAFFIN BAY

In conjunction with the International North Water Polynya Study (NOW) in northern Baffin Bay, we examined the diets of ringed seals ( Phoca hispida )¹ on the west (Grise Fiord, Nunavut) and east (Qaanaaq, Greenland) sides of the polynya, using conventional stomach content analysis, as well as inferences from stable isotope ratios in seal muscle. Between May and July 1998, stomach and muscle tissue samples were collected from 99 ringed seals taken near Grise Fiord and 100 taken near Qaanaaq. The amphipod Themisto libellula was the dominant prey type in the diet of immature ringed seals from Grise Fiord, whereas arctic cod ( Boreogadus saida ) and polar cod ( Arctogadus glacialis ) predominated in the diet of adults. Both immature and adult seals collected near Qaanaaq fed predominantly on arctic cod. Overall, seals collected near Grise Fiord had significantly higher δ¹³C values than those collected near Qaanaaq ( P < 0.001), but there was no statistical separation in δ¹⁵N values between the two samples ( P = 0.06). Differences in diets of ringed seals from the east and west sides of the North Water Polynya may be due to differences in prey distribution and/or differences in biological productivity and fish biomass within the polynya.     

EFFECTS OF AN OFFSHORE OIL DEVELOPMENT ON LOCAL ABUNDANCE AND DISTRIBUTION OF RINGED SEALS (PHOCA HISPIDA) OF THE ALASKAN BEAUFORT SEA1

This study investigates how densities of ringed seals were affected by construction and oil production activities at Northstar, an artificial island built in the nearshore Alaskan Beaufort Sea. Intensive and replicated aerial surveys of seals on landfast ice were conducted during six spring seasons: for three seasons before island construction began (1997–1999); after a winter of intensive island construction (2000); and after more limited construction plus drilling (2001) and drilling plus oil production (2002). A Poisson regression model was used to examine seal densities relative to distance from Northstar after allowance for environmental covariates. Post hoc power analysis indicated that the study design and Poisson regression approach had high power to detect small‐scale changes in seal densities near Northstar if such changes had occurred. However, seal densities during spring were not significantly affected by proximity to Northstar in 2000–2002. Habitat, temporal, and weather factors did have significant effects on seal densities. This study shows that effects of the Northstar oil development on local distribution of basking ringed seals are no more than slight, and are small relative to the effects of natural environmental factors. An understanding of environmental effects is essential when assessing potential impacts of industrial activity on ringed seals.     

ABUNDANCE OF RINGED SEALS (PUSA HISPIDA) IN THE FJORDS OF SPITSBERGEN, SVALBARD, DURING THE PEAK MOLTING PERIOD

Ringed seal (Pusa hispida) abundance in Spitsbergen, Svalbard, was estimated during the peak molting period via aerial, digital photographic surveys. A total of 9,145 images, covering 41.7%–100% of the total fast‐ice cover (1,496 km²) of 18 different fjords and bays, were inspected for the presence of ringed seals. A total of 1,708 seals were counted, and when accounting for ice areas that were not covered by images, a total of 3,254 (95% CI: 3,071–3,449) ringed seals were estimated to be hauled out during the surveys. Extensive behavioral data from radio‐tagged ringed seals (collected in a companion study) from one of the highest density fjords during the molting period were used to create a model that predicts the proportion of seals hauled out on any given date, time of day, and under various meteorological conditions. Applying this model to the count data from each fjord, we estimated that a total of 7,585 (95% CI: 6,332–9,085) ringed seals were present in the surveyed area during the peak molting period. Data on interannual variability in ringed seal abundance suggested higher numbers of seals in Van Keulenfjorden in 2002 compared to 2003, while other fjords with very stable ice cover showed no statistical differences. Poor ice conditions in general in 2002 probably resulted in seals from a wide area coming to Van Keulenfjorden (a large fjord with stable ice in 2002). The total estimated number of ringed seals present in the study area at the time of the survey must be regarded as a population index, or at least a minimum estimate for the area, because it does not account for individuals leaving and arriving, which might account for a considerable number of animals. The same situation is likely the case for many other studies reporting aerial census data for ringed seals. To achieve accurate estimates of population sizes from aerial surveys, more extensive knowledge of ringed seal behavior will be required.     

INFRARED SENSING OF THE UNDER-SNOW LAIRS OF THE RINGED SEAL

Airborne sensing of emitted infrared (IR) was tested as a means of detecting under-snow lairs of the ringed seal ( Phoca hispida ) in study areas in Resolute Passage, N.W.T. Lairs and regularly used large breathing holes could in some cases be detected by emitted IR from altitudes of up to 180 m. Lairs were more easily detected if they had thin roofs, and detectability was higher before sunrise, and under conditions of low wind, low ambient temperature and high cloud cover.     

DIGESTIBILITY OF CRUSTACEANS and CAPELIN IN HARP SEALS (PHOCA GROENLANDICA)

Gross energy intake (GEI), apparent digestible efficiency (%DE), and body-mass change were studied both in recently weaned and in subadult harp seals fed capelin ( Mallotus villosus ) and crustaceans ( Parathemisto libellula and Thysanoessa sp.) ad lib. The median %DE of Parathemisto libellula (with a wet-weight energy density (ED) of 3.9 kJ/g) and Thysanoessa sp. (ED: 2.3 kJ/g) was 81% and 83%, respectively, while the median %DE of capelin (ED: 8.6 kJ/g) was 94% and 93% for subadult harp seals and one harp seal pup, respectively. No correlation between age and %DE was obtained (P > 0.05). Despite ad lib. access to the food, the harp seal pups were unable to maintain body mass while on a crustacean diet, and it is therefore suggested that harp seal pups most likely must supplement their crustacean diets with fish to maintain growth.     

CLIMATE CHANGE AND RINGED SEAL (PHOCA HISPIDA) RECRUITMENT IN WESTERN HUDSON BAY

Climate warming is predicted to reduce the extent of ice cover in the Arctic and, within the Hudson Bay region, the annual ice may be significantly decreased or entirely lost in the foreseeable future. The ringed seal ( Phoca hispida ), a key species that depends on sea ice, will likely be among the first marine mammals to show the negative effects of climatic warming. We used 639 ringed seals killed by Inuit hunters from western Hudson Bay (1991–1992, 1999–2001) to assess trends in recruitment relative to snow depth, snowfall, rainfall, temperature in April and May, North Atlantic Oscillation (NAO) from the previous winter, and timing of spring break-up. Snowfall and ringed seal recruitment varied from lower than average in the 1970s, to higher in 1980s and lower in 1990s. Prior to 1990, seal recruitment appeared to be related to timing of spring ice break-up which was correlated with the NAO. However, recent 1990–2001 environmental data indicate less snowfall, lower snow depth, and warmer temperatures in April and May when pups are born and nursed. Decreased snow depth, particularly below 32 cm, corresponded with a significant decrease in ringed seal recruitment as indicated by pups born and surviving to adults that were later harvested. Earlier spring break-up of sea ice together with snow trends suggest continued low pup survival in western Hudson Bay.     

A PREHISTORIC BREEDING POPULATION OF HARP SEALS (PHOCA GROENLANDICA) IN THE BALTIC SEA

The pelagic and gregarious, low Arctic harp seal ( Phoca groenlandica ) is the most common seal species in most refuse faunas from coastal hunter-gatherer sites dating from the late Atlantic to the early Subboreal period ( ca. 4000-2000 cal B. C.) in the Baltic Sea. Our main objective was to examine the migration contra breeding population hypotheses regarding the Baltic harp seals. Analyses of epiphyseal fusion data and osteometry of archeological harp seal remains from 25 dwelling-sites suggest that a local breeding population established itself in the early Subboreal period. In the Middle Neolithic the rookery possibly was situated in the Baltic proper, south of Aland and west of Gotland. The mean adult size of the Baltic harp seals decreased, suggesting minimal genetic exchange with the north Atlantic Ocean population. Genetic drift, interspecific competition, and over-hunting by humans are all factors likely to have contributed to the eventual extinction of harp seals in the Baltic Sea.     

USE OF BIOELECTRICAL IMPEDANCE ANALYSIS TO ASSESS BODY COMPOSITION OF SEALS

Abstract: 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.     

PHOCINE DISTEMPER VIRUS INFECTION IN HARP SEALS (PHOCA GROENLANDICA)

Antibodies against phocine distemper virus were found in liver and serum specimens of harp seals from the Barents Sea and north of Jan Mayen (West Ice) in 1987 and 1989. By immunoperoxidase testing, antibodies against phocine distemper virus could be demonstrated in 34 of 74 liver specimens (46%) from 1987 and in 44 of 126 liver specimens (35%) from 1989. The prevalence of neutralizing serum antibodies against phocine distemper virus was found to be 98% in 1989. Both findings clearly demonstrate the presence of a widespread infection with phocine distemper virus or a closely related virus in harp seals. The significance of these findings to the recent outbreak of phocine distemper virus infection in harbor seals in Northwestern Europe is discussed and it is concluded that there may be an epizootiological link between this outbreak and the large migration of harp seals in 1987.     

CORRECTING AERIAL SURVEY COUNTS OF HARBOR SEALS (PHOCA VITULINA RICHARDSI) IN WASHINGTON AND OREGON

Aerial surveys of harbor seals on land produce only a minimum assessment of the population; a correction factor to account for the missing animals is necessary to estimate total abundance. In 1991 and 1992, VHF radio tags were deployed on harbor seals ( n = 124) at six sites in Washington and Oregon. During aerial surveys a correction factor to account for seals in the water was determined from the proportion of radio-tagged seals on shore during the pupping season. This proportion ranged from 0.54 to 0.74. Among the six sites there was no significant difference in the proportion of animals on shore nor was there a difference in age/sex categories of seals on shore between sites. The pooled correction factor for determining total population abundance was 1.53. An additional 32 seals were radio tagged in 1993 at one of the sites used in 1991. Comparing data from the two years, we found no interannual variation. Aerial surveys of all known harbor seal haul-out sites in Washington ( n = 319) and Oregon ( n = 68) were flown during the peak of the pupping season, 1991–1993. The Washington and Oregon harbor seal population was divided into two stocks based on pupping phenology, morphometics, and genetics. Mean counts for the Washington inland stock were 8,710 in 1991, 9,018 in 1992, and 10,092 in 1993. Oregon and Washington coastal stock mean counts were 18,363 in 1991, 18,556 in 1992, and 17,762 in 1993. Multiplying the annual count by the correction factor yielded estimates of harbor seal abundance in the Washington inland stock of 13,326 (95% CI = 11,637–15,259) for 1991, 13,798 (95% CI = 11,980–15,890) for 1992, and 15,440 (95% CI = 13,382–17,814) for 1993. In the Oregon and Washington coastal stock the corrected estimate of harbor seal abundance was 28,094 (95% CI = 24,697–31,960) in 1991, 28,391 (95% CI = 24,847–32,440) for 1992, and 27,175 (95% CI = 23,879–30,926) for 1993.     

INCREASED VIGILANCE TOWARD UNFAMILIAR HUMANS BY HARBOR (PHOCA VITULINA) AND GRAY (HALICHOERUS GRYPUS) SEALS

Two pairs of harbor ( Phoca vitulina ) and three pairs of gray ( Halicboeruls grypus ) seals were exposed to one of three human handlers for 15 min, twice a day, for a total of six sessions. Following habituation to the familiar handler, animals were then exposed to a novel human for 7 min, and then retested for 7 min with the familiar human. In all cases, animals responded to the unfamiliar human with increased vigilant behavior, i. e., they spent more time oriented towards the unfamiliar handler during the first 2 min of the test session than during the same interval of either the final habituation session or the retest with the familiar human ( P = 0.03 in all cases). There was also a tendency for seals to contact the familiar handler with their noses more rapidly than the novel human ( P = 0.06). These results support the hypothesis that phocid seals are capable of discriminating between individual humans in their environment, setting the stage for human-based Pavlovian conditioning.