Perinatal activities in the Grey seal (Halichoerus grypus)

Births and postnatal behaviour were observed at a breeding assembly of Grey seals on North Rona. Birth is extremely rapid and the cow immediately turns to smell the pup. Smelling continues at intervals, particularly during the first 10 min after birth and allows the cow to establish the identity of her pup. She also smells the placenta and defends it against attack by gulls. Disturbance by gulls, neighbouring seals and human intrusion may lead to the cow failing to establish a bond with the pup and consequently abandoning it.     

Territorial behaviour in the Western Atlantic Grey seal (Halichoerus grypus)

Virtually all published accounts of territorial behaviour in the Grey seal apply to breeding males only. Long-range field studies reveal, however, that lactating cows also maintain territories for a period of several weeks. During the summer months, adults and sub-adults have specific resting places to which they return each day at low water and which they defend against other individuals of their own species.     

Seasonal movements and diurnal activity rhythms of the Grey seal (Halichoerus grypus)

The seasonal movements and diurnal activity rhythms of the Grey seals occurring along the Atlantic Coast of Nova Scotia and in the southern part of the Gulf of St Lawrence have been studied over a period of three and a half years. The seasonal movements of the adults can be divided into five periods or phases: (1) prepupping, (2) pupping and mating, (3) postmating, (4) spring concentration and (5) summer dispersal. The diurnal activity rhythm is attuned to the tides; the effects of the hours of daylight appear to be minimal. During the breeding season the cows go to sea as the tide is falling and return when it is rising. Adults of both sexes have a similar rhythm at other times of the year, except in mid-summer when the pattern is reversed.     

Reproductive behaviour of the Grey seal (Halichoerus grypus) on Sable Island, Nova Scotia

We describe an unusual mating system, observed in a land-breeding colony of Grey seal, Halichoerus grypus , in the western Atlantic. Males and females begin to visit the breeding beach about a week before the season begins, but none stay ashore for long until the first pup is born. The cows are gregarious, probably return to the same part of the beach to give birth from one year to the next, and tend to remain in the general vicinity of the birth site during their two and a half week sojourn ashore. Within these limits, however, they are quite mobile, and the size, location and composition of the temporary aggregations which they form vary from one day to the next. The cows become thinner and more sedentary as oestrus approaches, but otherwise they give no overt signs of receptivity. The males do not defend territories, nor do they form dominance hierarchies. Instead, they compete for tenure, the right to remain within the shifting population of females. Tenured bulls directly test the receptivity of nearby cows from time to time, and they continually manoeuvre in ways which maximize their chances of being next to cows which are either in oestrus or likely to become so in the near future. Bulls which fail to establish themselves amongst females try to intercept cows as they are leaving for the sea at the end of their season, but their reproductive success, estimated in several ways, is significantly lower than that of bulls with tenure.
The system would be adaptive for seals which breed on the pack ice, but it is unique amongst land-breeding pinnipeds. If, as some circumstantial evidence suggests, Grey seals were originally pack-ice breeders, the persistence of such a system in a land-breeding colony raises some interesting questions about the plasticity of mating behaviour.     

Characterization of ethoxyresorufin O-de-ethylase in grey seal Halichoerus grypus

Ethoxyresorufin O-de-ethylase (EROD), a typical mixed function oxidase enzyme, was studied in liver and kidney of adult and pup grey seals, Halichoerus grypus. EROD activity was present in most liver samples but was only barely detectable in a few of the kidney samples. Liver EROD activity was greatest at pH 7.5-8.0; activity increased with temperature from 20 degrees C to a plateau starting at about 33 degrees C and extending to 37 degrees C, and fell off sharply above 37 degrees C. Km values ranged from 3 X 10(-7) to 3 X 10(-6)M; Vmax ranged from 5 X 10(-12) to 1 X 10(-10) moles product formed X min-1 X mg protein-1. Liver EROD activity was not detectable in pups less than 1 day old, and activity increased with age in pups up to 5-12 days old. Adults had greater EROD activity than did pups.     

Suckling behaviour in the Grey seal (Halichoerus grypus) and the Northern elephant seal (Mirounga angustirostris)

The suckling behaviour of Grey seals and Northern elephant seals was investigated. Evidence suggested that in both species it is usual for females and young to select consistently the same suckling partner though certain conditions bring about changes in this behaviour. Instances of inconsistency in both species are described and the conditions that bring this about are discussed.     

Thyroid hormones in grey seal pups (Halichoerus grypus).

The aim of the present study was to describe the changes in thyroid hormone status in grey seal (Halichoerus grypus) pups from birth to weaning and moulting. Plasma concentrations of total thyroxine (tT4) were highest the first two days after birth, thereafter dropping to a lower, but stable level. This pattern may reflect a high transfer rate of maternal thyroxine prepartum, prior to parturition, or postpartum via colostrum, or it may be caused by active secretory thyrocytes in late foetal stage. Total triiodothyronine (tT3) concentrations were lowest in neonatal pups, and increased as a function of age, indicating that deiodination of T4 to T3 increases as a function of age. Plasma concentrations of free thyroxine (fT4) did not vary as a function of age. All hormone concentrations were higher than previously reported in adults, probably reflecting the important role of these hormones in regulating their high rates of metabolism and tissue synthesis and the growth of their juvenile pelage. Since polychlorinated biphenyls (PCBs) have been reported to affect plasma concentrations of thyroid hormones in seals, the information on thyroid hormone concentrations and dynamics reported in grey seal pups from a pristine Norwegian coastal environment provide valuable reference material for future studies on pups from more polluted areas.     

Movements and diving of grey seal females (Halichoerus grypus) in the Gulf of St. Lawrence, Canada

Five female grey seals were tracked with satellite-linked time-depth recorders during September to April 1993-1994. Seals remained in the northern Gulf of St. Lawrence (Gulf) for 1-2.5 months after capture. Four females dove primarily to depths <10 m and 20-70 m, while all dives of the fifth female, a blind animal, were <10 m. During October/November, all animals moved into the southern Gulf or onto the Scotian Shelf. This migration lasted 6-10 days, during which time animals covered 350-800 km. During that migration, all females, including the blind animal, dove up to 100 m, but the majority of dives were to depths of 40-70 m. Two seals stayed in the southern Gulf through the winter while the others left the Gulf in January. When in the southern Gulf and on the Scotian Shelf, dive depths and bathymetry information indicated that dives were to the bottom.     

Retinal epithelial fine structure in the grey seal (Halichoerus grypus)

The morphology of the retinal epithelium and the closely associated choriocapillaris and Bruch's membrane (complexus basalis) has been investigated in the eye of the grey seal (Halichoerus grypus) by electron microscopy. The retinal epithelium is composed of a single layer of cuboidal cells joined laterally by apically-located junctional complexes. Basally (sclerally) these cells display numerous infoldings while apically (vitreally) abundant processes enclose rod outer segments. Internally the large vesicular nucleus is centrally located. Smooth endoplasmic reticulum, mitochondria and lysosome-like bodies are abundant. Rough endoplasmic reticulum and polysomes while present are not plentiful. Phagosomes of outer-segment discs are only occasionally noted in the light-adapted state. As the entire fundus is overlain with a choroidally located tapetum cellulosum, only at the extreme periphery is an occasional melanosome present in these epithelial cells. The choriocapillaris endothelium is highly fenestrated and the profiles of these capillaries are deeply indented into the epithelial layer. Bruch's membrane (complexus basalis) is reduced to a trilaminate structure rather than the typical pentalaminate membrane seen in most mammalian species and when associated with capillary profiles is further reduced to a single thick basal lamina.     

Finescale topographical correlates of behavioural investment in offspring by female grey seals, Halichoerus grypus

Grey seals breed colonially on substrates ranging from ice to rocky or sandy beaches. Clear differences in seal behaviour patterns exist among such broad classes of breeding habitat. However, finer scale topographical variation is likely to influence individual behaviour with consequences for pupping success. We examined topographical influences on the behaviour of breeding female grey seals by quantifying topography at a subseal size resolution. Using submetre resolution digital terrain models of two sites within a rocky breeding colony, we compared site topography in relation to observed differences in female behaviour at these sites. Females at both sites preferred breeding close to water (standing pools or sea) and frequently commuted between their pups and water. Topographical models indicated that one site was more costly for seals in terms of their locations and movements within the site. This was due to a lack of low-elevation land adjacent to the main access points from the sea and the reduced availability of pools. Females at this site showed reduced pup attendance and an increase in energetically costly behaviours, whilst females at the lower-cost site spent more time interacting with their pups and resting. These topographically induced behavioural differences are likely to affect the quantity and quality of pup provisioning by mothers and influence individual pupping site selection. Less costly sites are likely to be colonized preferentially and by larger, older and more dominant females, potentially generating finescale spatial heterogeneity in female quality within the breeding colony. Copyright 2000 The Association for the Study of Animal Behaviour.     

Grey seal (Halichoerus grypus) pup production at North Rona: A study of birth and survival statistics collected in 1972

The Grey seal breeding assembly on North Rona was studied throughout autumn 1972. Weekly censuses provided data on birth rate and mortality. It is estimated that 1736 pups were born in 1972. This is about 500 less than the mean production estimate for this assembly during the period 1959–71, possibly a result of disturbance of the breeding site by the expedition. About 600 of the pups died before putting to sea. The mean date of birth and the duration of the pupping season agree closely with earlier work on North Rona, although the mean daily birth rate curve is somewhat irregular, perhaps because there was an unusually dry spell of weather at a critical time in the pupping season. An improved estimate of mortality at this assembly showed a relationship with pup density similar to that observed at the Fame Islands. Techniques for estimating pup production (and consequently total population), though not reliable for determining absolute values, are useful for indicating trends and they suggest a stable population of 8000–9000 animals at North Rona. Such estimates might be improved by the use of better methods of aerial photography.     

Vitamin E and fatty acids in the grey seal (Halichoerus grypus)

Summary Vitamin E levels in serum, liver and blubber (subcutaneous adipose tissue) were determined for 66 male and female grey seals of varying age in the pupping colony on Sable Island in the Northwest Atlantic by high-performance liquid chromatography (HPLC). Fatty acid concentrations were determined for all blubber specimens. Adult males and pups had significantly higher levels of vitamin E and cholesterol in serum than females and juveniles. A close relationship between vitamin E and cholesterol in serum could be observed. Suckling pups had significantly higher levels of vitamin E in liver (191 mg·kg^–1) than juveniles and adults (21–41 mg·kg^–1). Levels of vitamin E in blubber showed an age-dependent increase, with the highest levels being found in adult males; overall, these levels were much lower than in man. Vitamin E levels in blubber and liver of lactating females were only half that of adult males. This might be due to an intensive transfer of vitamin E from mother to pup during lactation, a process which may also explain the much higher levels of vitamin E in serum and liver of nursing pups. The low levels of vitamin E in blubber of seals might be a result of its high percentage of unsaturated fatty acids (79%). Highest percentage was represented by 18:1, 16:1, 22:6 and 16:0. Pups had lower values of monounsaturated, and a higher percentage of saturated fatty acids compared to mothers.     

Trichinella nativa in grey seal Halichoerus grypus: spill-over from a highly endemic terrestrial ecosystem

Trichinella spp. infections of marine mammals pose a human health risk in Arctic regions where game meat is an important part of the diet. In the last decade, the grey seal population of the sub-arctic Baltic Sea has reached a level at which hunting is possible and seal meat is now available for food. We conducted a survey on the occurrence of Trichinella spp. in grey seals Halichoerus grypus (n = 171) and ringed seals Phoca hispida botnica (n = 56) of the Baltic Sea in the coastal waters of Finland, a highly Trichinella sp. endemic area. Muscle samples were examined by a mechanically assisted digestion method during 2006-2010. One grey seal was positive for Trichinella nativa , while all samples from ringed seals were negative. Even though just 1 grey seal was infected, the finding here emphasizes the importance of proper meat inspection of seals intended for human consumption, especially in areas with high infection pressure.     

Movements and diurnal behaviour patterns in a Baltic grey seal (Halichoerus grypus)

A sub-adult grey seal was caught and tagged with a satellite relay data logger at Tihällan (61°2800N, 17°2540E), Sweden, on 21 August 1992. We tracked it for 115 days during which time we recorded 841 locations, data on 3556 dives and 80 haulout periods. It travelled 730 km in the first 12 days to the southern Archipelago Sea. It stayed most of the remaining time within 25 km of a haulout site, with a major exception of an 8-day trip of 520 km. Dive shape and swimming activity were used to distinguish dive types. Square-shaped foraging dives were more common over the midday period. Haulout periods were more common during the night.