Energy transfer and female condition in nursing harp seals Phoca groenlandica

Lactating female harp seals, most with their pups, were collected on the "whelping" ice in the Gulf of St. Lawrence in 1976 and from 1978 to 1980. During lactation females lost weight at an average rate of 3.17±0.52 (SE_b) kg d⁻¹, for a total energy loss of approximately 250000 kcal. Pups grew at a mean rate of 2.78±0.19 kg d⁻¹ for a gain in production energy of about 194000 kcal. Compared to 1976, adult females sampled in 1978 to 1980 had lower energy reserves at the onset of lactation. Coincidentally there has been a decrease in newborn lengths and girths. Although compensatory growth in weight appears to occur, between-year differences in newborn lengths persist to weaning. Various reproductive strategies of female harp seals faced with reduced energy stores are discussed.     

Structure of the testis in neonate and adult harp seals,Pagophilus groenlandicus

Summary The structure of the seminiferous tubules in neonate harp seals, Pagophilus groenlandicus, was essentially similar in one-, five and ten-day old animals. The tubules were small in diameter, devoid of lumina and contained predominantly supportive cells. The interstitial cells in the neonates were large, numerous and highly vacuolated. They became smaller and appeared less active in the ten-day old animals compared with the one-day old seals, although they were still considerably more numerous and vacuolated than in testes taken from adult harp seals.The work was supported by grants from the National Science and Engineering Research Council of Canada (J.F.L. and K.R.) and from the Donner (Canadian) Foundation (K.R.)     

Structure of the adenohypophysis in parturient female and neonate harp seals,Pagophilus groenlandicus

Summary The pars distalis of parturient harp seals (Pagophilus groenlandicus) is divisible into three distinct zones based on the major cellular components of the different regions. A clear zonation is lacking in neonate seals, the medial basophilic wedge and the anterior gonadotrophic were small and difficult to identify. Five cell types were identified based on cytological characteristics: somatotrophs, mammotrophs, thyrotrophs, gonadotrophs and stellate cells; corticotrophs could not be identified, with any certainty, in any of the preparations, nor could the gonadotrophs be classified into LH, FSH, and ICSH cells.The pars intermedia enlarged during the early post-partum period and was large in the parturient females.Abbreviations Used LH luteinizing hormone - FSH follicle stimulating hormone - ICSH interstitial cell stimulating hormone - PAS periodic acid-Schiff We wish to thank Mrs. Lucy Lin for her technical assistance. The work was supported by grants-inaid of research to J.F.L. and K.R. from the National Research Council of Canada and a grant from the Donner Canadian Foundation to K.R.     

Radiative surface temperatures of harp seals

• 1.1. Ambient air temperature rather than wind speed or heat flow exerted the greatest effect on radiative heat loss from harp seal pup fur.
• 2.2. Fur conductance was higher when calculated using radiative temperature rather than air temperature as representative of ambient temperatures.
• 3.]3. An equation was derived from data on thermal properties of fur samples and adjusted to fit the expected in vivo heat loss to predict the radiative temperatures of harp seal pups on the ice.

     

Assessment of body condition of harp seals

We investigated the relationships between blubber content and a suite of condition indices in harp seals (Phoca groenlandica). Although blubber content was significantly correlated with xiphosternal blubber depth and Condition index they were insensitive indicators of condition. Blubber depth was most variable at a site ca. 60–70% down the length of the body and a more recent index incorporating length, mass and blubber depth devised for phocids was an improved indicator of blubbler mass. Blubber volume was calculated in three ways based on a geometric approximation of a cylinder and also via truncated cones. The cone method accounted for more variance than the other methods although it overestimated blubber mass. Surface area was ascertained using the girth measurements of serial cones and was significantly correlated with total body mass and total body water. We suggest that estimates of total body water generated from surface area could be used to calculate total fat mass and lean body mass     

Effects of environmental variables on surface temperature of breeding adult female northern elephant seals,Mirounga angustirostris,and pups

Pinnipeds spend extended periods of time on shore during breeding, and some temperate species retreat to the water if exposed to high ambient temperatures. However, female northern elephant seals (Mirounga angustirostris) with pups generally avoid the water, presumably to minimize risks to pups or male harassment. Little is known about how ambient temperature affects thermoregulation of well insulated females while on shore. We used a thermographic camera to measure surface temperature (T_s) of 100 adult female elephant seals and their pups during the breeding season at Point Reyes National Seashore, yielding 782 thermograms. Environmental variables were measured by an onsite weather station. Environmental variables, especially solar radiation and ambient temperature, were the main determinants of mean and maximum T_s of both females and pups. An average of 16% of the visible surface of both females and pups was used as thermal windows to facilitate heat loss and, for pups, this area increased with solar radiation. Thermal window area of females increased with mean T_s until approximately 26 °C and then declined. The T_s of both age classes were warmer than ambient temperature and had a large thermal gradient with the environment (female mean 11.2±0.2 °C; pup mean 14.2±0.2 °C). This large gradient suggests that circulatory adjustments to bypass blubber layers were sufficient to allow seals to dissipate heat under most environmental conditions. We observed the previously undescribed behavior of females and pups in the water and determined that solar radiation affected this behavior. This may have been possible due to the calm waters at the study site, which reduced the risk of neonates drowning. These results may predict important breeding habitat features for elephant seals as solar radiation and ambient temperatures change in response to changing climate.     

Physiological effects of seawater intake in adult harp seals during phase I of fasting

Previous studies have shown that harp seals may drink considerable amounts of seawater. The current study was undertaken to study the physiological responses to bolus administration of seawater. Adult harp seals (Phoca groenlandica) were fasted without access to water for 48 h and then given 1000 or 1500 ml of seawater by a stomach tube. Changes in urine and plasma parameters were thereafter monitored for another 12-20 h. Urine production and urine excretion rate of Na+ and Cl- increased soon after administration and reached a maximum 3-4 h later. Urine osmolality was kept rather stable and high ( approximately 1500 mOsm x kg(-1)) following seawater administration, due to a drop in urine concentration of urea that was proportional to the simultaneous increase in urine concentration of NaCl. Plasma osmolality remained at approximately 340 mOsm x kg(-1), while plasma concentration of urea decreased some 20-25% due to increased excretion of urea when seawater was ingested. Despite bolus administrations of seawater of up to approximately 2% of body mass, homeostasis was maintained and no ill effects observed. It is concluded that the concentrating abilities of the kidneys of harp seals are sufficient to prevent net loss of body water following seawater ingestion. Seawater ingestion may, moreover, increase urinary osmotic space and thus serve as a mechanism to excrete additional urea produced during phase I of fasting.     

The effect of body fat on basal metabolic rate in adult harp seals (Phoca groenlandica)

Three adult harp seals (Phoca groenlandica) were fed different daily amounts of capelin (Mallotus villosus), and their body composition determined by use of the tritiated water method at different levels of fattening. Basal metabolic rate (BMR) was measured after 5 days of fasting by indirect calorimetry, and was on average 1.1 W.kg-1 when 45% of body mass (BM) was fat and 2.3 W.kg-1 when body fat was reduced to 13% of BM. This suggests that body fat contributes little to BMR in these animals. It follows, that predictions of BMR on the basis of BM is questionable in seals, in which body fat may change seasonally between 20 and 60% of BM.     

Insulation and thermal balance of fasting harp and grey seal pups.

1. Harp and grey seal pups were examined during the post-weaning period to quantify their thermoregulatory abilities and thermal limits. 2. Deep body temperatures of harp seals (37.8 +/- 0.8 degrees C) were not significantly different from those of grey seals (38.9 +/- 0.4 degrees C). 3. As blubber depth declined during the fast, temperature gradients extended increasingly deeper into the muscle layer potentially decreasing heat loss. 4. Blubber conductivity (approximately 0.18 W/m/degrees C) did not vary regionally within an animal, or between animals or species. 5. Calculated lethal cold limits in air were between -85.4 degrees C and -116.1 degrees C, suggesting that fasting, weaned pups can easily cope with temperatures they would normally experience.     

Movements of adult female Weddell seals during the winter months

The focus of this study was the distribution of adult female Weddell seals during winter at the Vestfold Hills. Satellite tracking of Weddell seals had never been done before at this location. Hence, this was a pilot study to evaluate the following methods. We attached satellite transmitters to the lower back, where there was least potential to change the seals’ behaviour or to damage instruments on the ice. Location data were obtained only where the seals hauled out, not necessarily where they were feeding. All locations were within the area of fast-ice that was associated with the Vestfold Hills. There were gaps of up to 30 days in the location data sets. Each instrument (n=3) remained attached and functioning for ca. 6 months. During that time, two of the three seals hauled out within small areas adjacent to, or nearby, open water. The same seals hauled out sporadically. We inferred that these seals foraged offshore whilst returning to fast-ice to rest. If Weddell seals forage beneath dynamic ice but return to stable ice as their preferred resting substrate, then evidence of haulout sites will always be a biased measure of foraging range. Tracking seals in the water may be possible using alternative placement of transmitters. However, there is potential for instruments to interfere with movement (breathing and prey capture). For this reason, we recommend a combination of sensors, diet and tracking haulout sites to research winter foraging.     

Brucellosis in ringed seals and harp seals from Canada. lforbes@em.agr.ca

A novel Brucella sp. was isolated from lymph nodes of four ringed seals (Phoca hispida) collected near Pangnirtung (Baffin Island, Canada) in January and February 1995 and in one harp seal (Phoca groenlandica) collected near the Magdalen Islands (Gulf of St. Lawrence, Canada) in March 1996. Bacteriological characteristics were the same for all five isolates. The colonies were typical of Brucella spp., but took 2 to 5 days longer than the traditional species to appear on primary isolation media. Biotyping results did not match any of the known biovars of Brucella, but were similar to isolates of the genus Brucella previously reported from marine mammals inhabiting other areas of the northern hemisphere. This is the first confirmed report of brucellosis in marine mammals from Canada, and the first report of this organism in ringed and harp seals.     

The effects of climate change on harp seals (Pagophilus groenlandicus)

Harp seals (Pagophilus groenlandicus) have evolved life history strategies to exploit seasonal sea ice as a breeding platform. As such, individuals are prepared to deal with fluctuations in the quantity and quality of ice in their breeding areas. It remains unclear, however, how shifts in climate may affect seal populations. The present study assesses the effects of climate change on harp seals through three linked analyses. First, we tested the effects of short-term climate variability on young-of-the year harp seal mortality using a linear regression of sea ice cover in the Gulf of St. Lawrence against stranding rates of dead harp seals in the region during 1992 to 2010. A similar regression of stranding rates and North Atlantic Oscillation (NAO) index values was also conducted. These analyses revealed negative correlations between both ice cover and NAO conditions and seal mortality, indicating that lighter ice cover and lower NAO values result in higher mortality. A retrospective cross-correlation analysis of NAO conditions and sea ice cover from 1978 to 2011 revealed that NAO-related changes in sea ice may have contributed to the depletion of seals on the east coast of Canada during 1950 to 1972, and to their recovery during 1973 to 2000. This historical retrospective also reveals opposite links between neonatal mortality in harp seals in the Northeast Atlantic and NAO phase. Finally, an assessment of the long-term trends in sea ice cover in the breeding regions of harp seals across the entire North Atlantic during 1979 through 2011 using multiple linear regression models and mixed effects linear regression models revealed that sea ice cover in all harp seal breeding regions has been declining by as much as 6 percent per decade over the time series of available satellite data.     

Pre-partum diet of adult female bearded seals in years of contrasting ice conditions

Changing patterns of sea-ice distribution and extent have measurable effects on polar marine systems. Beyond the obvious impacts of key-habitat loss, it is unclear how such changes will influence ice-associated marine mammals in part because of the logistical difficulties of studying foraging behaviour or other aspects of the ecology of large, mobile animals at sea during the polar winter. This study investigated the diet of pregnant bearded seals (Erignathus barbatus) during three spring breeding periods (2005, 2006 and 2007) with markedly contrasting ice conditions in Svalbard using stable isotopes (δ(13)C and δ(15)N) measured in whiskers collected from their newborn pups. The δ(15)N values in the whiskers of individual seals ranged from 11.95 to 17.45 ‰, spanning almost 2 full trophic levels. Some seals were clearly dietary specialists, despite the species being characterised overall as a generalist predator. This may buffer bearded seal populations from the changes in prey distributions lower in the marine food web which seems to accompany continued changes in temperature and ice cover. Comparisons with isotopic signatures of known prey, suggested that benthic gastropods and decapods were the most common prey. Bayesian isotopic mixing models indicated that diet varied considerably among years. In the year with most fast-ice (2005), the seals had the greatest proportion of pelagic fish and lowest benthic invertebrate content, and during the year with the least ice (2006), the seals ate more benthic invertebrates and less pelagic fish. This suggests that the seals fed further offshore in years with greater ice cover, but moved in to the fjords when ice-cover was minimal, giving them access to different types of prey. Long-term trends of sea ice decline, earlier ice melt, and increased water temperatures in the Arctic are likely to have ecosystem-wide effects, including impacts on the forage bases of pagophilic seals.     

Vocal signature recognition of mothers by fur seal pups

Subantarctic fur seals, Arctocephalus tropicalis, come ashore to breed in dense colonies and lactating females have to alternate foraging trips at sea with periods ashore during which they suckle their pups. The effectiveness of vocal recognition between mothers and pups, has been shown experimentally. To see whether the recognition abilities of females differ from those of their offspring, we investigated how pups recognize their mother's calls. We used artificially modified signals in playback experiments to determine which acoustic parameters support the recognition process. Pups used both the energy spectrum and the ascending frequency modulation occurring at the beginning of each call. However, they seemed to rely mainly on spectral analyses. The vocal identification process at a perceptual level is therefore asymmetrical, as mothers mainly use temporal structures to recognize their pup's calls. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

Underwater calling rates of harp and Weddell seals as a function of hydrophone location

Stereo recordings of harp seal (Pagophilus groenlandicus) and Weddell seal (Leptonychotes weddellii) underwater vocalizations were made near breeding groups using separations between two hydrophones of 159–339 m. Within a large herd, harp seal call numbers varied slightly between channels. Counts of Weddell seal calls were higher near a small herd on the ice than 159–180 m away. Repeat counts of harp seal calls by a single observer differed significantly. Source levels of Weddell seal calls varied and higher amplitude calls would be detected up to 2 orders of magnitude farther away than quieter calls. Hydrophone location (especially near small groups), observer variability and call source level differences will bias the use of monitoring underwater seal vocalizations to index locations, population size or underwater behaviours. Using hydrophone arrays and multiple observers may mitigate these problems. Accepted: 15 September 2000     

Microsatellite diversity and fitness in stranded juvenile harp seals (Phoca groenlandica)

A positive relationship between genetic diversity at neutral markers and juvenile survival has been demonstrated for many vertebrate populations, although the correlation is typically weak and the explanation for it remains controversial. We assessed variation at 9-12 microsatellite loci in 65 juvenile harp seals (Phoca groenlandica) that stranded in poor condition around Long Island, NY, from 2001 to 2004. Compared with seals that died, surviving individuals had slightly higher measures of mean d(2), which reflects the size difference between alleles within an individual and provides an index of outbreeding. In contrast, there were no significant differences between survivors and nonsurvivors in heterozygosity or estimates of internal relatedness. This pattern is attributed to the fact that these microsatellite markers were exceptionally variable in this species (9-22 alleles per locus), and all individuals were heterozygous at most loci. Under these circumstances, mean d(2) may provide a powerful measure for assessing diversity-fitness correlations.