Primiparous females do not exhibit reduced maternal care in gray seals (Halichoerus grypus)

We compared the behaviors of primiparous and multiparous gray seal (Halichoerus grypus) females over the course of lactation to examine whether poorly developed maternal behaviors may play a role in the reduced lactation performance observed in primiparous females. Overall, primiparous females spent as much time interacting with their pups as multiparous females. The proportion of time spent nursing their pup increased significantly between early and peak lactation in both primiparous and multiparous females. Although there was no significant difference in the duration of nursing bouts as a function of reproductive status, primiparous females nursed significantly more frequently (bouts/hour) and, therefore, spent a significantly greater proportion of time nursing than multiparous females throughout lactation. Primiparous gray seal females were also significantly more active than multiparous females, however, the difference in activity represented only a small proportion of the overall time budget. We conclude that poorly developed maternal behaviors resulting from a lack of prior reproductive experience are unlikely to account for lower levels of milk energy transfer to pups in primiparous gray seals.     

Microsatellite variation in grey seals (Halichoerus grypus) shows evidence of genetic differentiation between two British breeding colonies

Eight highly variable microsatellite loci were used to examine the genetic variability and differentiation of grey seals (Halichoerus grypus) at two widely spaced British breeding colonies. Samples were collected from adults and pups on the island of North Rona, off the north-west coast of Scotland, and on the Isle of May, situated at the mouth of the Firth of Forth on the east coast Highly significant differences in allele frequencies between these two sites were found for all eight loci, indicating considerable genetic differentiation. Thus, although grey seals are known to range over very large areas outside the breeding season, site fidelity of adults and philopatry of pups for these breeding colonies must be sufficiently common to have effects, through genetic drift, at the sub-population level. Migration rate was estimated using Wrighf's fixation index (F_ST), Slatkin's private alleles model and the new statistic, R_ST, which is analogous to (F_ST) but which takes into account the process of microsatellite mutation. An almost 8-fold discrepancy between the values we obtained provides cautionary evidence that microsatellite loci may contravene one or more of the assumptions on which these methods are based.     

Patterns of parental relatedness and pup survival in the grey seal (Halichoerus grypus)

Levels of parental relatedness can affect offspring survival and susceptibility to disease. We investigated parental relatedness of live and dead Halichoerus grypus pups between and within island populations and between possible causes of mortality. Nine microsatellites were used to calculate internal relatedness (IR) and standardized mean d2. We find that pups with higher than average levels of IR have significantly lower survival and that this varied between island populations and that certain loci contributed to the effect more than others. Although, there were no significant differences between causes of mortality, peritonitis, infection and stillborn had the highest levels of IR. These results provide evidence that parental relatedness is an important determinant of pre-weaning pup survival in the grey seal and that this may vary with cause of mortality given a larger sample size.     

Onset and duration of gray seal (Halichoerus grypus) molt in the Wadden Sea,and the role of environmental conditions

Surveys of gray seals (Halichoerus grypus) during the molt period, when they are abundant on land, can be used to monitor changes in population size, but accurate interpretation of results requires an understanding of the molt process and how it may vary between years. This study investigates variability in onset (start date) and duration of visible molt by gray seals in the Wadden Sea, and the influence of environmental conditions on the onset. Molt was monitored in nine captive seals and observed molt phases were applied to wild seals over seven annual molt periods between 2004 and 2010, monitored using aerial photography. The onset of visible molt varied significantly between years, for example it differed 28 d between 2008 and 2009. Model selection by AIC retained one environmental variable that correlated with molt onset; however, its effect was inconsistent within the molt season and did not explain some of the apparent observed annual variation. Hence, the main causes of interannual variability in the onset of molt remain unclear and warrant further study. Researchers should account for annual variability in the onset of molt when interpreting survey results based on molt counts.     

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.     

Geographic variation of the major histocompatibility complex in Eastern Atlantic grey seals (Halichoerus grypus)

Pathogen-driven balancing selection maintains high genetic diversity in many vertebrates, particularly in the major histocompatibility complex (MHC) immune system gene family, which is often associated with disease susceptibility. In large natural populations where subpopulations face different pathogen pressures, the MHC should show greater genetic differentiation within a species than neutral markers. We examined genetic diversity at the MHC-DQB locus and nine putatively neutral microsatellite markers in grey seals (Halichoerus grypus) from eight United Kingdom (UK) colonies, the Faeroe Islands and Sable Island, Canada. Five DQB alleles were identified in grey seals, which varied in prevalence across the grey seal range. Among the seal colonies, significant differences in DQB allele and haplotype frequencies and in average DQB heterozygosity were observed. Additionally, the DQB gene exhibited greater differentiation among colonies compared with neutral markers, yet a weaker pattern of isolation by distance (IBD). After correcting for the underlying IBD pattern, subpopulations breeding in similar habitats were more similar to one another in DQB allele frequencies than populations breeding in different habitats, but the same did not hold true for microsatellites, suggesting that habitat-specific pathogen pressure influences MHC evolution. Overall, the data are consistent with selection at MHC-DQB loci in grey seals with both varying selective pressures and geographic population structure appearing to influence the DQB genetic composition of breeding colonies.     

Microsatellite and mtDNA analysis of the population structure of grey seals (Halichoerus grypus) from three breeding areas in the Baltic Sea

The growing number of grey seals in the Baltic Sea has led to a dramatic increase in interactions between seals and fisheries. The conflict has become such a problem that hunting was introduced in Finland in 1998 and the Swedish Environment Protection Agency recommended a cull of grey seals starting in 2001. Culling has been implemented despite the lack of data on population structure. Low levels of migration between regions would mean that intensive culling in specific geographic areas would have disproportionate effects on local population structure and genetic diversity. We used eight microsatellite loci and a 489 bp section of the mtDNA control region to examine the genetic variability and differentiation between three breeding sites in the Baltic Sea and two in the UK. We found high levels of genetic variability in all sampled Baltic groups for both the microsatellites and the control region. There were highly significant differences in microsatellite allele frequencies between all three Baltic breeding sites and between the Baltic sites and the UK sites. However, there were no significant differences in mtDNA control region haplotypes between the Baltic sites. This genetic substructure of the Baltic grey seal populations should be taken into consideration when managing the seal population to prevent the hunting regime from having an adverse effect on genetic diversity by setting hunting quotas separately for the different subpopulations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Milk intake,growth and energy consumption in pups of ice-breeding grey seals (Halichoerus grypus) from the Gulf of St. Lawrence,Canada

In this study we document growth, milk intake and energy consumption in nursing pups of icebreeding grey seals (Halichoerus grypus). Change in body composition of the pups, change in milk composition as lactation progresses, and mass transfer efficiency between nursing mothers and pups are also measured. Mass transfer efficiency between mother-pup pairs (n=8) was 42.5±8.4%. Pups were gaining a daily average of 2.0±0.7 kg (n=12), of which 75% was fat, 3% protein and 22% water. The total water influx was measured to be 43.23±8.07 ml·kg^-1·day^-1. Average CO₂ production was 0.85±0.20 ml·g^-1·h^-1, which corresponds to a field metabolic rate of 0.55±0.13 MJ·kg^-1·day^-1, or 4.5±0.9 times the predicted basal metabolic rate based on body size (Kleiber 1975). Water and fat content in the milk changed dramatically as lacation progressed. At day 2 of nursing, fat and water content were 39.5±1.9% and 47.3±1.5%, respectively, while the corresponding figures for day 15 were 59.6±3.6% fat and 28.4±2.6% water. Protein content of the milk remained relatively stable during the lactation period with a value of 11.0±0.8% at day 2 and 10.4±0.3% at day 15. Pups drank an average of 3.5±0.9 kg of milk daily, corresponding to a milk intake of 1.75 kg per kg body mass gained. The average daily energy intake of pups was 82.58±19.80 MJ, while the energy built up daily in the tissue averaged 61.72±22.22 MJ. Thus, pups assimilated 74.7% of the energy they received via milk into body tissue. The lactation energetics of ice-breeding grey seals is very similar to that of their land-breeding counterparts.Abbreviations bm body mass - BMR basal metabolic rate - FMR field metabolic rate - IU international unit - RQ respiration quotient - HTO tritiated water - HT¹⁸O doubly labeled water - TBW total body water - VHF very high frequency     

Estimation of hooded seal (<Emphasis Type="Italic">Cystophora cristata</Emphasis>) pup production in the Greenland Sea pack ice during the 2005 whelping season

In March 2005 aerial surveys were carried out to estimate pup production of Greenland Sea hooded seals, Cystophora cristata in three whelping patches using photographic strip transects. The majority of whelping occurred 17–23 March and surveys were carried out on 24 March. The temporal distribution of births and estimated proportion of solitary bluebacks present within the survey area were used to correct the abundance estimates. The total estimated pup production (15,250 pups, s.e. = 3,470; CV = 22.8%) was lower than an estimate from a comparable study in 1997. The current estimate is considered to be negatively biased, as it is uncorrected for pups born outside the whelping concentrations. Population modeling suggests a substantial decline with subsequent stabilization at a lower level for Greenland Sea hooded seals in recent decades. It is suggested that future research on the population explore possible factors (e.g. reduced fertility, predation, food shortage, disease, reductions in ice cover) that may have contributed to the apparent prevailing low abundance.