Lactation in the Ringed Seal (Phoca hispida)

1991 ◽  
Vol 48 (12) ◽  
pp. 2471-2476 ◽  
Author(s):  
M. O. Hammill ◽  
C. Lydersen ◽  
M. Ryg ◽  
T. G. Smith

Length of lactation, pup growth rate, and female weight loss in ringed seals (Phoca hispida) were estimated using cross-sectional data from the Canadian and Norwegian Arctic. At birth the pups had a standard length of 63.4 cm (SE = 1.3, N = 11) and weighed 5.4 kg (SE = 0.4, N = 6). Weaning occurred approximately 39 d (range 36–41 d) after birth at an estimated length of 88.4 cm (SE = 0.65, N = 96) and an estimated weight of 22.1 kg, resulting in an increase in length of 0.64 cm∙d−1 and a weight change of 0.43 kg∙d−1. Regression of female weight on the number of days after the nominal date of birth for each region indicated that the postpartum female weighed 81.2 kg and lost 0.64 kg∙d−1 (95% CI = ±0.20). During lactation, female weight declined by an estimated 32%, with much of the loss occurring from the blubber. Analyses of stomachs indicated that ringed seals supplemented stored energy reserves by feeding during lactation.

1987 ◽  
Vol 65 (4) ◽  
pp. 1021-1027 ◽  
Author(s):  
Christian Lydersen ◽  
Ian Gjertz

Samples were taken from 284 ringed seals (Phoca hispida) in the Svalbard area during April–July 1981 and March–April 1982. The age of 283 seals was determined by reading annuli in the cementum of the canine teeth. The mean age of the males was 11.3 years, and of the females, 14.9 years. Females were found to be significantly older than males. The mean length of sexually mature ringed seals was 128.9 cm for both sexes. The mean weight of adult males and females was 53.5 and 61.4 kg, respectively. Females were found to be significantly heavier than males. The sex ratio was 47.8% males and 52.2% females. Studies of microscopic sections of testis and epididymis from ringed seal males showed that 63, 75, and 80% of 5-, 6-, and 7-year-old animals, respectively, were sexually mature. The weights of testis and epididymis, diameters of tubuli, and the size of testis all showed a marked increase in the 5-year age-class. Macroscopic sections of ovaries from ringed seal females showed that 20, 60, and 80% of 3-, 4-, and 5-year-old animals, respectively, were sexually mature. The size of the ovaries showed a marked increase in the 5-year age-class. The ovulation rate of ringed seals from Svalbard was calculated to be 0.91.


1996 ◽  
Vol 74 (5) ◽  
pp. 858-874 ◽  
Author(s):  
C. M. Furgal ◽  
K. M. Kovacs ◽  
S. Innes

Characteristics of ringed seal (Phoca hispida) subnivean structures and breeding habitat were quantified and their potential influence on predation success by polar bears (Ursus maritimus), arctic foxes (Alopex lagopus), and humans on ringed seals was investigated in Admiralty Inlet and Strathcona Sound, Northwest Territories. A total of 237 ringed seal structures were located between April and June 1991–1993 using trained dogs. Ringed seal lairs and breathing holes were concentrated in areas of deep snow, and were associated with large, thick ice ridges. Only a small percentage of the available fast-ice habitat had sufficient snow depth for lair construction each year. A discriminant function analysis used to classify structures located in 1992, using a combination of structural and habitat measurements, correctly classified 70% of structures located in 1991 and 1993 into functional groups. The length, width, internal height, and level of "tiggak," the odour of rutting male ringed seals, associated with structures were the most important descriptors separating structure types. Seventy-three percent of structures located in the study were undisturbed by predators. The mean length and width of structures entered by predators were significantly greater than those of undisturbed structures. Polar bear success decreased as snow depth and the thickness of the roof covering the structures increased. The conditions necessary for successful arctic fox predation are unclear. Inuit hunters attacked structures close to ice ridges, and ridge height and snow depth influenced their success. All predators attacked lairs having the odour of rutting male ringed seals less often than structures with no male odour.


2001 ◽  
Vol 79 (8) ◽  
pp. 1455-1464 ◽  
Author(s):  
Michael A Simpkins ◽  
Brendan P Kelly ◽  
Douglas Wartzok

We analyzed the three-dimensional movements within individual dives of five freely swimming ringed seals (Phoca hispida). We divided dives into a series of moves, each of which represented continuous movement in one direction, and evaluated several three-dimensional movement variables to distinguish between types of movement within dives. Horizontal directionality proved to be the most useful variable, and we distinguished convoluted and directional movements by fitting a mixture of two normal distributions to the observed horizontal-directionality values. Both convoluted and directional movements occurred within each phase of most dives, suggesting that ringed seals switched between behavioral modes within dive phases. Descent and ascent phases were not simply travel behavior, nor were bottom phases equivalent to patch time, complicating the formulation of optimal diving models for ringed seals. Most ringed seal dives appeared to consist of a series of patch times separated by travel times. Travel behavior accounted for the majority of dive times.


1977 ◽  
Vol 34 (8) ◽  
pp. 1143-1147 ◽  
Author(s):  
F. Rainer Engelhardt ◽  
Joseph R. Geraci ◽  
Thomas G. Smith

Ringed seals, Phoca hispida, showed rapid absorption of hydrocarbons from Norman Wells crude oil into body tissues and fluids when exposed by both immersion and ingestion. Relatively low but significant levels were found in tissue, blood, and plasma. Levels in bile and urine were high, indicating these to be routes of excretion. Key words: petroleum, hydrocarbons, benzene, ringed seal, immersion, ingestion, uptake, clearance


1998 ◽  
Vol 1 ◽  
pp. 63 ◽  
Author(s):  
Stanislav E Belikov ◽  
Andrei N Boltunov

This paper presents a review of available published and unpublished material on the ringed seal (Phoca hispida) in the western part of the Russian Arctic, including the White, Barents and Kara seas. The purpose of the review is to discuss the status of ringed seal stocks in relation to their primary habitat, the history of sealing, and a recent harvest of the species in the region. The known primary breeding habitats for this species are in the White Sea, the south-western part of the Barents Sea, and in the coastal waters of the Kara Sea, which are seasonally covered by shore-fast ice. The main sealing sites are situated in the same areas. Female ringed seals become mature by the age of 6, and males by the age of 7. In March-April a female gives birth to one pup in a breeding lair constructed in the shore-fast ice. The most important prey species for ringed seals in the western sector of the Russian Arctic are pelagic fish and crustaceans. The maximum annual sealing level for the region was registered in the first 70 years of the 20th century: the White Sea maximum (8,912 animals) was registered in 1912; the Barents Sea maximum (13,517 animals) was registered in 1962; the Kara Sea maximum (13,200 animals) was registered in 1933. Since the 1970s, the number of seals harvested has decreased considerably. There are no data available for the number of seals harvested annually by local residents for their subsistence.


1992 ◽  
Vol 70 (3) ◽  
pp. 458-461 ◽  
Author(s):  
Christian Lydersen ◽  
Morten Skrede Ryg ◽  
Mike Osborne Hammill ◽  
Peter James O'Brien

In this paper we measured total lung capacity, myoglobin content of muscle tissue, and hemoglobin content of the blood of ringed seals (Phoca hispida). Based on this information and body composition analysis we estimated the total available oxygen stores of a diving average adult ringed seal (standard length 129 cm, body mass 73.7 kg) to be 4.5 L. The aerobic dive limit for a ringed seal of this size was estimated to be 8.9 min. Diving data from previous studies show that less than 4% of the dives of adult free-living ringed seals exceed this aerobic dive limit. Based on information from the literature on maximum breathhold capacity and observed maximum dive times of ringed and Weddell seals (Leptonychotes weddellii), the maximum breathhold capacity of adult ringed seals was suggested to be 26.1 min.


1998 ◽  
Vol 1 ◽  
pp. 9 ◽  
Author(s):  
Randall R Reeves

The ringed seal (Phoca hispida) has a circumpolar Arctic distribution. Because of its great importance to northern communities and its role as the primary food of polar bears (Ursus maritimus) the ringed seal has been studied extensively in Canada, Alaska, Russia, Svalbard and Greenland as well as in the Baltic Sea and Karelian lakes. No clear-cut boundaries are known to separate ringed seal stocks in marine waters. Adult seals are thought to be relatively sedentary, but sub-adults sometimes disperse over long distances. Stable ice with good snow cover is considered the most productive habitat although production in pack ice has been little studied. Populations appear to be structured so that immature animals and young adults are consigned to sub-optimal habitat during the spring pupping and breeding season. Annual production in ringed seal populations, defined as thepup percentage in the total population after the late winter pupping season, is probably in the order of 18-24%. Most estimates of maximum sustainable yield are in the order of 7%.The world population of ringed seals is at least a few million. Methods of abundance estimation have included aerial surveys, dog searches and remote sensing of lairs and breathing holes, acoustic monitoring, correlation analysis by reference to sizes of polar bear populations, and inference from estimated energy requirements of bear populations. Aerial strip survey has been the method of choice for estimating seal densities over large areas. Adjustment factors to account for seals not hauled out at the time of the survey, for seals that dove ahead of the aircraft, and for seals on the ice within the surveyed strip but not detected by the observers, are required for estimates of absolute abundance.Male and female ringed seals are sexually mature by 5-7 years of age (earlier at Svalbard). Pupping usually occurs in March or early April and is followed by 5-7 weeks of lactation. Breeding takes place in mid to late May, and implantation is delayed for about 3 months. In at least some parts of their range, ringed seals feed mainly on schooling gadids from late autumn through early spring andon benthic crustaceans and polar cod (Boreogadus saida) from late spring through summer. Little feeding is done during the moult, which takes place in late spring and early summer. Pelagic crustaceans offshore and mysids inshore become important prey in late summer and early autumn in some areas. Ringed seals have several natural predators, the most important of which is the polar bear in most arctic regions. Arctic foxes (Alopex lagopus) kill a large percentage of pups in someareas.From a conservation perspective, the ringed seal appears to be secure. Levels of exploitation of arctic populations have usually been considered sustainable, except in the Okhotsk Sea. Large fluctuations in production of ringed seals in the Beaufort Sea and Amundsen Gulf are thought to be driven by natural variability in environmental conditions. While concern has been expressed about thepotential impacts of industrial activity and pollution on ringed seals, such impacts have been documented only in limited areas. Because of their ubiquitous occurrence and availability for sampling, ringed seals are good subjects for monitoring contaminant trends in Arctic marine food chains. 


1989 ◽  
Vol 67 (9) ◽  
pp. 2212-2219 ◽  
Author(s):  
M. O. Hammill ◽  
T. G. Smith

The relationship between the distribution of ringed seals, Phoca hispida, and habitat was examined in Barrow Strait, Northwest Territories. Density of seal breathing holes was used as an index of seal abundance. Birth lairs were associated with the largest snowdrifts. Lair formation can occur within 24 h after a snowdrift forms over the top of a breathing hole. Seal structures were associated with ridges consisting of ice pieces 15–25 cm thick projecting upwards to a height of 80–150 cm. In 1975 and 1986, the combination of date of ice consolidation and snow depth were the most important habitat features affecting the distribution of ringed seals structures. This was also true with respect to distribution of birth lairs and undefined haul-out lairs, but no relationship was identified between density of structures used by males and habitat. Snow cover and date of ice consolidation were not identified as important habitat variables in 1984 and 1985 when overall distribution of ice in Barrow Strait was very different. Birth lairs were not seen before 4 April, but were found in increasing frequency as the season progressed. Male structures were evident in late March, but were not found after mid-May.


1998 ◽  
Vol 1 ◽  
pp. 130 ◽  
Author(s):  
Jonas Teilmann ◽  
Finn O Kapel

The ringed seal (Phoca hispida) is the most important game for the Inuit hunters of Greenland, providing many of the basic needs in the original culture. It is distributed all around Greenland with the main distribution north of 69°N on the west coast and north of 66°N on the east coast. During 1974-76, studies were conducted in the most important ringed seal catching area, Upernavik, Northwest Greenland, and a total of 7,089 ringed seals were sampled. The methods used for catching ringed seals were categorised into five different groups. The most common hunting method used in the municipality of Upernavik during 1974-76 was netting under the ice, accounting for almost half of the total annual catch. Seals shot on the ice and seals shot at the ice edge accounted for one fifth and one tenth of the annual catch, respectively. In this region seals shot in open water made up about one fifth of the annual catch of ringed seals, while netting in open water contributed only a few percent.Of the seals sampled in Upernavik in 1974-76, 60% were males and 40% were females. In the ringed seal samples collected all around Greenland in the 1980s and 1990s the males comprised 56% and the females 44% (n=923). Similar ratios were found for all age classes and for all hunting methods suggesting either a skewed sex ratio in the ringed seal stock(s) around Greenland or a differencein availability to the hunters of male and female ringed seals. In tagging experiments a higher mobility was found for females than for males, which suggests differences in the behaviour of the two sexes.Catch and trade statistics on ringed seals are reviewed and evaluated for the period of 1954 until 1994, and the seasonal and regional variation is examined. The peak season for ringed seal hunting in Greenland as a whole is from January through May. This is particularly evident for the northern regions, where relatively few ringed seals are taken during the open water season from June to September. In the southern regions, however, the great majority of ringed seals are caught in openwater.In all regions, the catch of ringed seals showed great annual and long-term variation. The variations were not identical in all regions, but similar trends were found for Northwest and Central West, and for Southwest and South. From 1954 to 1994 there was a general, significant increase in the reported catches of ringed seals in west Greenland. For Greenland overall, the catch of ringed seals wasaround 43,000 per year in the 1950s, peaked in the late 1970s at almost 100,000 per year, but since decreased to about 70,000 in the early 1990s.


1998 ◽  
Vol 1 ◽  
pp. 100 ◽  
Author(s):  
Randall R Reeves ◽  
George W Wenzel ◽  
Michael CS Kingsley

The ringed seal (Phoca hispida) has always been a staple in the diet and household economy of Inuit in Canada. The present paper was prepared at the request of the NAMMCO Scientific Committee to support their assessment of ringed seal stocks in the North Atlantic Basin and adjacent arctic and subarctic waters. Specifically, our objective was to evaluate recent and current levels of use of ringed seals by Canadian Inuit. Annual removals probably were highest (possibly greater than 100,000) in the 1960s and 1970s, a period when sealskin prices were particularly strong. Catches declined substantially in the 1980s following a collapse in sealskin prices, presumably related to the European trade ban on skins from newborn harp and hooded seals (Phoca groenlandica and Cystophora cristata, respectively). Recent catch levels throughout Canada (1980s and early 1990s) are believed to be in the order of 50,000 to 65,000 ringed seals, with a total average annual kill (including hunting loss) in the high tens of thousands. No reliable system is in place to monitor catches of ringed seals, so any estimate must be derived from a heterogeneous array of sources.


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