Harbor Seal Pups Research Articles

The paradox of learned song in a semi‐solitary mammal

AbstractLearning can occur via trial and error; however, learning from conspecifics is faster and more efficient. Social animals can easily learn from conspecifics, but how do less social species learn? In particular, birds provide astonishing examples of social learning of vocalizations, while vocal learning from conspecifics is much less understood in mammals. We present a hypothesis aimed at solving an apparent paradox: how can harbor seals (Phoca vitulina) learn their song when their whole lives are marked by loose conspecific social contact? Harbor seal pups are raised individually by their mostly silent mothers. Pups' first few weeks of life show developed vocal plasticity; these weeks are followed by relatively silent years until sexually mature individuals start singing. How can this rather solitary life lead to a learned song? Why do pups display vocal plasticity at a few weeks of age, when this is apparently not needed? Our hypothesis addresses these questions and tries to explain how vocal learning fits into the natural history of harbor seals, and potentially other less social mammals. We suggest that harbor seals learn during a sensitive period within puppyhood, where they are exposed to adult males singing. In particular, we hypothesize that, to make this learning possible, the following happens concurrently: (1) mothers give birth right before male singing starts, (2) pups enter a sensitive learning phase around weaning time, which (3) coincides with their foraging expeditions at sea which, (4) in turn, coincide with the peak singing activity of adult males. In other words, harbor seals show vocal learning as pups so they can acquire elements of their future song from adults, and solitary adults can sing because they have acquired these elements as pups. We review the available evidence and suggest that pups learn adult vocalizations because they are born exactly at the right time to eavesdrop on singing adults. We conclude by advancing empirical predictions and testable hypotheses for future work.

Phenology of harbor seal pupping and the influence of weather on pup counts, investigated by UAV

AbstractSurveys of harbor seals to assess pup production in Denmark are conducted at the assumed breeding season peak between 9 and 15 hr at winds <10 m/s, with no precipitation at least 6 hr before observations and at low tide in areas with a significant tidal range. Harbor seal pups can swim immediately after birth, so the fraction available for counting likely varies according to conditions. In the Limfjord, a separate harbor seal population is living in a large inlet in northern Denmark where >95% of pups are born at two haul‐out sites situated 4 km apart. Drone surveys of these two haul‐outs were conducted throughout the breeding seasons during 2017–2019. The effects of weather conditions and timing of surveys on counts were analyzed by generalized additive mixed models. The best‐performing model included date and wind speed. Pup counts grew from the onset of the observation period and were predicted to peak on June 22. Wind speed had a linear relationship with pup counts and > 50% more pups were counted at 5 m/s than at 1 m/s. To achieve representative pup counts careful consideration of survey conditions and possibly correction for these effects are necessary.

Variability in Body Condition and Growth Rates for Rehabilitated Harbor Seal (Phoca vitulina) Pups

In the United States, Canada, and Europe harbor seal (Phoca vitulina) pups are commonly rehabilitated after stranding and then released. Size at release is likely important to post-release survival; however, data have not been compiled to track the body condition of rehabilitated harbor seals at release across the U.S. To better understand spatiotemporal variations in harbor seal morphometrics during rehabilitation and at release, this study retrospectively analyzed body conditions, weights, lengths, and growth rates of rehabilitated harbor seal pups in the U.S. Body condition index (BCI) was calculated, and weight and BCI were modeled regionally and temporally. There was significant variation in weight, length, BCI, and growth rate for rehabilitated and released seals between the East and West Coasts of the U.S. and among different years. Growth rates during rehabilitation were slower than reported for wild pups from birth to weaning. Length at release was not a strong predictor of weight. Because animals of similar weights can have different lengths, weight alone might not be the best criterion for pre-release body condition. A body condition score incorporating weight, length, and possibly other variables such as age or axillary girth could be more informative; however, data on post-release survival are needed to evaluate these options.

Response of metabolic hormones and blood metabolites to realimentation in rehabilitated harbor seal (Phoca vitulina) pups.

Mammals with increased requirements for adipose tissue stores, such as marine mammals, have altered nutrient allocation priorities compared to many terrestrial mammals and thus the physiological response to undernutrition (low nutritional status) and realimentation (refeeding) may differ. Key regulators of nutrient allocation and tissue specific growth include metabolic hormones of the somatotropic axis, growth hormone (GH) and insulin-like growth factor (IGF)-I, as well as satiety and adipose promoting ghrelin and the stress hormone cortisol. Longitudinal measurements of metabolic hormones, blood metabolites, and morphometrics were collected over a 10-week period in twelve (male n = 3, female n = 9) harbor seal pups (< 6weeks of age). Blood metabolites were used to indicate metabolic response during realimentation while morphometrics estimated tissue specific growth priorities. Harbor seal pups undergoing refeeding after nutritional deprivation show a preference for protein sparing despite severe malnutrition. Both BUN and total protein were negatively associated with GH and positively associated with IGF-I and ghrelin highlighting the importance of these metabolic hormones in the regulation of protein metabolism. While the response of the somatotropic axis to realimentation was typical of the mammalian pattern, the surprising increase of ghrelin across the study period suggests the priority of adipose accretion in addition to a possible mechanism regulating compensatory growth of vital adipose stores in a species, which prioritizes adipose accretion for survival.

In this issue

i DOI: https://doi.org/10.3318/BIOE.2020.22 Biology and Environment: Proceedings of the Royal Irish Academy,Vol. 120, No. 3, i–ii (2020). © Royal Irish Academy Cite as follows: Osborne, B. In this issue 2020 Biology and Environment: Proceedings of the Royal Irish Academy 2020. DOI: 10.3318/ BIOE.2020.22 IN THIS ISSUE Bruce Osborne Harbour seal pups and weaning The shift from parental dependence to individual responsibility is clearly an important stage in the life of a vast range of organisms, not just humans. Weaning, the gradual transition from a dependence on milk supplied by the mother, to individuals foraging for alternative food sources on their own, involves several complex behavioural and dietary changes and may even involve the mother rejecting its young. Whilst we know a lot about weaning in humans, less information is available for other animals, one of which is the harbour seal. Wilson and Jones, in this issue, address this deficiency in our understanding of the weaning process in harbour seals and add another dimension to this: namely, the influence of local habitat conditions. The authors examined the behaviour of pups in the absence of their mothers at two pupping sites in Dundrum bay in north east Ireland. Far from rejecting their young, mothers and pups often reunited for short periods even after the pups became more dependent on foraged food, indicating that some parental care continued even up to seven years of age. Although the reason(s) for the continued parental contact is not known, this flexibility in the weaning process may relate to food availability and/or the presence of predators.Clearly,the weaning process in harbour seals is not always abrupt, as often thought, nor is it common for mothers to reject their young, so a variety of factors will determine the duration of the weaning process. Pollen as a food source for stoneflies Stoneflies are an ancient order of insects with a fossil history extending back over 250 million years. Globally there are currently approximately 3,500 species, around 15% of which are found in Europe, with 20 species recorded in Ireland. Stoneflies (nymphs and adults) are invariably associated with water bodies, forming a large proportion of the invertebrate fauna particularly in headwater streams, and are an important food source for fish and terrestrial vertebrates. Although the winged adults live and survive out of water it was once believed that all adult stoneflies were, unlike their nymphs, incapable of feeding due to their limited mouth parts, and therefore only able to drink water. However, it was subsequently shown that many do feed when out of water. Unlike nymphs, which may be predators or feed on dead plant material and algal biofilms, the winged adults probably depend largely on pollen grains. This raises some interesting questions about whether there are any preferences for the pollen of particular plant species and if so, why? McGonigley et al., in this issue, investigated this by rearing captured stoneflies in the laboratory prior to exposing them to pollen from different tree species. Their results showed that there was a significant preference for the pollen from birch trees over that of spruce, supporting the authors’ contention that riverside vegetation and its conservation could have important implications for stonefly biology and ecology, with knock-on effects on riverine food webs.Whilst the reason(s) for this food preference was not identified pollen is a particular rich source of protein and vitamins and this could have had a significant influence on food choice. Pollen can also vary considerably in its digestibility and this too could have contributed to the selection of birch pollen over that of spruce. Zebra fish-again! Zebra fish have featured several times in Biology and Environment and have become the go-to organism for bioassays of a wide range of potential toxic chemicals, as well as providing a means of testing for the presence of environmental contaminants, including herbicides and pesticides present in water. Although the role of many synthetic herbicides may be diminishing with steady progress being made on the development of more environmentally compatible alternatives,they are still widely used and associated with several—albeit hotly contested— disadvantages, including...

In this issue

i DOI: https://doi.org/10.3318/BIOE.2020.22 Biology and Environment: Proceedings of the Royal Irish Academy,Vol. 120, No. 3, i–ii (2020). © Royal Irish Academy Cite as follows: Osborne, B. In this issue 2020 Biology and Environment: Proceedings of the Royal Irish Academy 2020. DOI: 10.3318/ BIOE.2020.22 IN THIS ISSUE Bruce Osborne Harbour seal pups and weaning The shift from parental dependence to individual responsibility is clearly an important stage in the life of a vast range of organisms, not just humans. Weaning, the gradual transition from a dependence on milk supplied by the mother, to individuals foraging for alternative food sources on their own, involves several complex behavioural and dietary changes and may even involve the mother rejecting its young. Whilst we know a lot about weaning in humans, less information is available for other animals, one of which is the harbour seal. Wilson and Jones, in this issue, address this deficiency in our understanding of the weaning process in harbour seals and add another dimension to this: namely, the influence of local habitat conditions. The authors examined the behaviour of pups in the absence of their mothers at two pupping sites in Dundrum bay in north east Ireland. Far from rejecting their young, mothers and pups often reunited for short periods even after the pups became more dependent on foraged food, indicating that some parental care continued even up to seven years of age. Although the reason(s) for the continued parental contact is not known, this flexibility in the weaning process may relate to food availability and/or the presence of predators.Clearly,the weaning process in harbour seals is not always abrupt, as often thought, nor is it common for mothers to reject their young, so a variety of factors will determine the duration of the weaning process. Pollen as a food source for stoneflies Stoneflies are an ancient order of insects with a fossil history extending back over 250 million years. Globally there are currently approximately 3,500 species, around 15% of which are found in Europe, with 20 species recorded in Ireland. Stoneflies (nymphs and adults) are invariably associated with water bodies, forming a large proportion of the invertebrate fauna particularly in headwater streams, and are an important food source for fish and terrestrial vertebrates. Although the winged adults live and survive out of water it was once believed that all adult stoneflies were, unlike their nymphs, incapable of feeding due to their limited mouth parts, and therefore only able to drink water. However, it was subsequently shown that many do feed when out of water. Unlike nymphs, which may be predators or feed on dead plant material and algal biofilms, the winged adults probably depend largely on pollen grains. This raises some interesting questions about whether there are any preferences for the pollen of particular plant species and if so, why? McGonigley et al., in this issue, investigated this by rearing captured stoneflies in the laboratory prior to exposing them to pollen from different tree species. Their results showed that there was a significant preference for the pollen from birch trees over that of spruce, supporting the authors’ contention that riverside vegetation and its conservation could have important implications for stonefly biology and ecology, with knock-on effects on riverine food webs.Whilst the reason(s) for this food preference was not identified pollen is a particular rich source of protein and vitamins and this could have had a significant influence on food choice. Pollen can also vary considerably in its digestibility and this too could have contributed to the selection of birch pollen over that of spruce. Zebra fish-again! Zebra fish have featured several times in Biology and Environment and have become the go-to organism for bioassays of a wide range of potential toxic chemicals, as well as providing a means of testing for the presence of environmental contaminants, including herbicides and pesticides present in water. Although the role of many synthetic herbicides may be diminishing with steady progress being made on the development of more environmentally compatible alternatives,they are still widely used and associated with several—albeit hotly contested— disadvantages, including...

Annual Residency Patterns and Diet of Phoca vitulina concolor (Western Atlantic Harbor Seal) in a Southern New Jersey Estuary

From 1996 to 2011, researchers observed Phoca vitulina concolor (Western Atlantic Harbor Seal) on regional overwintering grounds in the Great Bay–Mullica River estuary in southern New Jersey. Over this 15-y time series, 299 observations were completed, with maximum local abundance increasing from 100 individuals in 1996 to 160 individuals in 2011. Our study did not document the presence of Atlantic Harbor Seal pups. In addition, we analyzed 142 scat samples, resulting in 1419 sagittal fish otoliths recovered and identified. Dominant recovered otoliths were as follows: 48% Phycidae (Urophycis regia [Spotted Hake]/Urophycis chuss [Red Hake]; 25% Clupeidae (Clupea harengus [Atlantic Herring], Alosa sapidissima [American Shad], Brevoortia tyrannus [Atlantic Menhaden], A. pseudoharengus [Alewife], and A. aestivalis [Blueback Herring]); 13% Ammodytidae (Ammodytes americanus/A. dubius [sandlance]); 6% Pseudopleuronectes americanus (Winter Flounder); and 4% Scophthalmus aquosus (Windowpane Flounder). Average back-calculated prey lengths across all prey groups (min–max = 5–41 cm, average = 19.75 cm) indicated that Western Atlantic Harbor Seals might utilize both estuarine and ocean environments for foraging. This temperate estuary currently represents the southern limit of routine Western Atlantic Harbor Seal occupancy in the Northeast. As such, our results are valuable in monitoring future changes in habitat use potentially resulting from climate change.

Harbor seal pup dispersal and individual morphology, hematology, and contaminant factors affecting survival

AbstractUnderstanding the factors affecting individual harbor seal (Phoca vitulina) survival is essential for determining population level health risks. We estimated postweaning dispersal, and modeled the effects of morphology, hematology, and blubber contaminants on the survival of recently weaned harbor seal pups using a mark recapture framework. We deployed satellite transmitters on apparently healthy pups captured in San Francisco Bay (SFB, n = 19) and Tomales Bay (TB, n = 7), and pups released after rehabilitation that stranded along the central California coast preweaning (n = 21). Dispersal distances were further than previously reported for harbor seal pups (maximum = 802 km) which has implications for understanding risks to this vulnerable age class. We found differences in body condition, serum immunoglobulin and thyroxine (T4) concentrations, white blood cell count, and blubber organohalogen contamination (OH) among the three groups. Overall, increased T4, decreased OH, and increased mass were associated with greater survival probabilities; whereas, among stranded seals, greater mass gain, shorter time in rehabilitation, and admission to rehabilitation earlier in the season were associated with greater survival probabilities. Attention to these latter factors may improve the success of rehabilitation efforts. For wild pups, reduction of legacy contaminants and direct causes of mortality, such as ship strike, may enhance pup survival.

First Extralimital Record of an Eastern Pacific Harbor Seal (Phoca vitulina richardii) Pup at Guadalupe Island, Mexico

First Extralimital Record of an Eastern Pacific Harbor Seal (Phoca vitulina richardii) Pup at Guadalupe Island, Mexico

In this Issue

i IN THIS ISSUE Bruce Osborne Solution hollows in the Burren The Burren has, perhaps not surprisingly, figured significantly in Biology and Environment,given its status as one of the more botanically important areas nationally as well as globally (See volume 103B, no.3, for our special issue on the Burren). Whilst previous research has focussed on its botanical diversity and how best to manage the competing interests of farmers and conservationists, less work has been directed at the microbial communities and their significance . It is well known, however, that solution hollows—small depressions in the open limestone pavement that can be filled with rain water—are the sites of a rich microbial community. Cyanobacteria , mainly of the genus Nostoc, often dominate these communities, forming a melange of assorted colonies of various shapes, sizes and colours. However ,there may be a consortium of microbes present including the red chlorophyte Haematococcus pluvialis ; Doddy and Roden, in this issue, show that the solution hollows are the sites of significant primary productivity, presumably aided by the ability of Nostoc to both assimilate atmospheric nitrogen and carbon dioxide. Remarkably too, the Nostoc is extremely resilient and able to survive extended periods of desiccation, as the solution hollows often dry out, with rapid restoration of metabolic activity on re-wetting.Although often surmised,the authors show through in situ experiments that the microbes in the solution hollows are responsible for significant erosion and facilitate the colonization of the limestone pavement by vascular plants. Parental-pup interactions in Harbour Seals The Harbour or Common Seal has a predominantly western distribution in Ireland with few populations on the east coast. Seals when emergent generally occupy rocky ledges and sandbanks or beaches in intertidal coastal habitats.They are often regarded as solitary animals with only a rudimentary social structure but, like so many aquatic animals that spend most of their time in water, this is still open to debate. Adult males do come together during mating and there is a close bonding between mothers and juveniles after birth and early maturation, although mother-pup behaviour has often been poorly documented. Wilson and Jones, in this issue, report on a study of mother-pup interactions in intertidal habitats at Dundrum Bay, in the north east of Ireland. Using visual counts and video footage Wilson and Jones assessed interactions between mothers and their offspring in the water, at the­ water’s edge and at a dry ledge or beach.The majority of mothers gave birth at the beginning of July and pups always remained close to their mothers, although the ratio of pups to mothers varied with habitat. The attachment of young to their parents appeared to be strongest in water, perhaps reflecting the importance of less known social interactions that occur in water that are not routinely observed. Importantly, Wilson and Jones argue that a better understanding of social interactions between pup and mother will be important for the rehabilitation of orphan seals in captivity, prior to their release. Harbour seal pups can become separated from their mothers after birth and the care of these stranded pups needs to account for the social behaviour that they would normally experience in nature through, for instance, the use of companion pups and access to shallow water pools.Together with information obtained from comparisons of the behaviour of orphans in captivity with that observed in the field this could significantly improve the success of rehabilitation and re-introduction programmes. Are they there or are they not? An ability to accurately document changes in species numbers or abundance has become a crucial factor in ascribing any alterations to climate change or other anthropogenic factors.This is,however,not as easy as it seems. Often our assessments of change are dependent on historical data of uncertain quality in regard to their temporal and spatial coverage, or because of the failure to identify species correctly , or because of inter-annual climate variations. A further complication in aquatic habitats is that the presence or absence of a species may also depend on recruitment patterns. Even well-studied areas cannot escape these issues it seems.The Lough Hyne Marine Reserve in Co. Cork is an intensively studied...

Attempted Predation of a Harbor Seal Pup (Phoca vitulina) by an American Mink (Neovison vison) in the Salish Sea

Abstract A single incident of attempted predation of a Harbor Seal (Phoca vitulina) pup by an American Mink (Neovision vision) was observed on Blakely Island, Washington in 2015. San Juan County Marine Mammal Stranding Network members responded, investigated the event, and performed a necropsy on the seal. Predation is the most parsimonious explanation for the attack due to the American Mink's opportunistic predatory tendencies and the vulnerability of the moribund Harbor Seal. With both the American Mink and Harbor Seal populations documented as abundant or at carrying capacity, respectively, mink predation on vulnerable Harbor Seal pups could increase or influence Harbor Seal haul-out behavior.

Diving Related Changes in the Blood Oxygen Stores of Rehabilitating Harbor Seal Pups (Phoca vitulina).

Harbor seal (Phoca vitulina) pups begin diving within hours of birth, stimulating the development of the blood oxygen (O2) stores necessary to sustain underwater aerobic metabolism. Since harbor seals experience a brief nursing period, the early-life development of these blood O2 stores is necessary for successful post-weaning foraging. If mothers and pups become prematurely separated, the pup may be transported to a wildlife rehabilitation center for care. Previous studies suggest that the shallow pools and lack of diving in rehabilitation facilities may lead to under-developed blood O2 stores, but diving behavior during rehabilitation has not been investigated. This study aimed to simultaneously study the diving behaviors and blood O2 store development of rehabilitating harbor seal pups. Standard hematology measurements (Hct, Hb, RBC, MCV, MCH, MCHC) were taken to investigate O2 storage capacity and pups were equipped with time-depth recorders to investigate natural diving behavior while in rehabilitation. Linear mixed models of the data indicate that all measured blood parameters changed with age; however, when compared to literature values for wild harbor seal pups, rehabilitating pups have smaller red blood cells (RBCs) that can store less hemoglobin (Hb) and subsequently, less O2, potentially limiting their diving capabilities. Wild pups completed longer dives at younger ages (maximum reported <25 days of age: 9 min) in previous studies than the captive pups in this study (maximum <25 days of age: 2.86 min). However, captivity may only affect the rate of development, as long duration dives were observed (maximum during rehabilitation: 13.6 min at 89 days of age). Further, this study suggests that there may be a positive relationship between RBC size and the frequency of long duration dives. Thus, rehabilitating harbor seal pups should be encouraged to make frequent, long duration dives to prepare themselves for post-release foraging.

Acoustic analysis of airborne, underwater, and amphibious mother attraction calls by wild harbor seal pups (Phoca vitulina)

Pinnipeds have great potential for comparative studies of mother–pup recognition due to the contrasting maternal strategies adopted by otariids and phocids. Typically, otariid mothers perform foraging trips during lactation, leaving their pups in the colony, whereas phocid mothers remain close by their pups during the entire nursing period. Unlike most phocids, harbor seal (Phoca vitulina) females forage during the nursing period, which exacerbates the need for effective mother–pup vocal recognition in this species. Individual differences and ontogeny-related changes in airborne and underwater harbor seal mother attraction calls were investigated. Acoustic differences between aerial and underwater components of amphibious pup calls were also assessed. Sixteen acoustic parameters were measured on 1,072 calls from 88 pups recorded during the 2011–2013 breeding seasons in the St. Lawrence Estuary, Canada. Discriminant function analysis (DFA) correctly assigned 42.6% and 44.2% of airborne and underwater calls, respectively, to individual pups. A majority of highly individualized acoustic parameters were affected by pup age and body length. These results indicated that harbor seal pup calls encode an individual signature that might allow recognition of young by mothers, in which case females must continuously learn their pup’s changing voice throughout of the rearing period. The fundamental frequency, total duration, and frequency-modulation slopes were constant between aerial and underwater components of amphibious calls. This could facilitate females’ memorization of these highly individualized acoustic parameters to identify their offspring’s call in both media.

Blood and Hair Mercury Concentrations in the Pacific Harbor Seal (Phoca vitulina richardii) Pup: Associations with Neurodevelopmental Outcomes.

Monomethylmercury (MeHg(+)) is an environmental pollutant, which at sufficiently high exposures, has induced neurotoxicosis in several animal species, including humans. Adverse neurological effects due to gestational exposure are of particular concern as MeHg(+) readily crosses the blood-brain and placental barriers. The degree to which environmental concentrations in marine prey affect free-living piscivorous wildlife, however, remains largely undetermined. We examined associations of gestational exposures to mercury on neurodevelopment and survival using hair and blood concentrations of total mercury ([THg]) in a stranded population of Pacific harbor seal pups from central California. A positive association was determined for the presence of abnormal neurological symptoms and increasing [THg] in blood (P = 0.04), but not hair. Neither hair nor blood [THg] was significantly associated with survival, or the neurodevelopmental milestone 'free-feeding', which was measured from the onset of hand-assisted feeding to the time at which pups were able to consume fish independently. Both hair and blood [THg] exceeded threshold values considered potentially toxic to humans and other mammalian wildlife species. The higher [THg] in blood associated with abnormal neurological symptoms may indicate an adverse effect of this pollutant on neurodevelopment in harbor seal pups. These data have broader implications with respect to human health and public policy as harbor seals and humans consume similar fish species, and it is possible that safeguard levels established for marine mammals could also extend to human populations that regularly consume fish.

Immune-relevant and new xenobiotic molecular biomarkers to assess anthropogenic stress in seals

Harbour seals as top predators and indicators for ecosystem health are exposed to increasing pressure caused by anthropogenic activities in their marine environment. After their lactation period of about 24 days pups are weaned and left to hunt on their own. Little is known about the development of their immune system and a better understanding of anthropogenic impacts on the general health and immune system of harbour seal pups is needed. mRNA transcription of six immuno-relevant biomarkers was analysed in 13 abandoned harbour seal pups from the North Sea, fostered at the Seal Centre Friedrichskoog, Germany. RNAlater blood samples were taken at admission, day 22 and before release and analysed using RT-qPCR. Significant differences in HSP70, cytokine IL-2 and xenobiotic biomarkers AHR, ARNT and PPARα transcription were found between admission, during rehabilitation and before release. Highest levels at admission may result from dehydration, handling, transport and contaminant exposure via lactation. The significant decrease is linked to health improvement, feeding and adaptation. The increase before release is suspected to be due to infection pressure and contaminant exposure from feeding on fish. Molecular biomarkers are a sensitive tool to evaluate health and pollutant exposure and useful to serve as early warning indicators, monitoring and case-by-case tool for marine mammals in human care and the wild.

Causes and Patterns of Harbor Seal (Phoca vitulina) Pup Mortality at Smith Island, Washington, 2004–2010

Harbor Seals (Phoca vitulina) are the most common and widely distributed pinniped in Washington State coastal waters. Serving as sentinels of marine ecosystem health, stranded animals are useful in detecting environmental disease and contaminant levels. From 2004 to 2010, we examined mortality rates and causes of death of Harbor Seal pups at Smith Island, a principal haulout site in the eastern Strait of Juan de Fuca, Washington, conducting 21 site surveys during the pupping season (June through August). We documented and externally examined 245 dead pups and of these, 72 were deemed suitable for more detailed internal examination and were collected for necropsy to determine cause of death. Minimum estimated neonatal mortality varied widely by year and ranged from 3 to 25%. The highest number of dead pups, nearly half of the total for the study, were found in 2005; this was also the year with the highest estimate of pups born and highest proportion of pups born that were documented dying. Infection was the leading primary cause of death in most years including 2005, when 40% of the pups died from an infectious process. The 2nd leading cause of death was malnutrition; other causes included prematurity and dystocia. This study documents some of the major annual differences that can occur in both mortality rates and causes of death in Harbor Seals.

The effect of diet and feeding level on survival and weight gain of hand‐raised harbor seal pups (Phoca vitulina)

Hundreds of stranded harbor seals pups (Phoca vitulina) are brought to wildlife rescue centers every year. Typical hand-rearing diets include artificial milk-replacers and diets based on macerated fish fed via gavage, but weight gains are often low and mortality rates can be high. This study compared survival and weight gain of orphaned seal pups fed either artificial milk-replacer or fish-formula. Pups admitted to the facility in summer 2007 (n=145) and 2008 (n=98) were randomly assigned to one of two diets and fed by gavage until weaning. In 2007, pups fed milk-replacer gained more (43 ± 12 g/d) than those fed fish-formula (loss of 13 ± 6 g/d; P<0.002). In 2008, when intake was increased from 8 to 11% of body weight daily, weight gain improved for both diets but remained higher in pups fed milk-replacer (123 ± 12 g/d, vs. loss of 6 ± 8 g/day; P<0.001). Pup survival to weaning was significantly higher in 2008 than 2007 (P<0.001) and was higher for pups on milk-replacer compared with those on fish-formula (P<0.05). Survival was also correlated with body weight at admittance (P<0.001). Although neither diet achieved the weight gains recorded in mother-raised pups (400-800 g/d), the artificial milk-replacer was clearly more successful, and pups fared better in the second year of the study when intake was higher.

Stomach Temperature Telemetry Reveals that Harbor Seal (&lt;I&gt;Phoca vitulina&lt;/I&gt;) Pups Primarily Nurse in the Water

Stomach Temperature Telemetry Reveals that Harbor Seal (&lt;I&gt;Phoca vitulina&lt;/I&gt;) Pups Primarily Nurse in the Water

Postnatal development of muscle biochemistry in nursing harbor seal (Phoca vitulina) pups: limitations to diving behavior?

Adult marine mammal muscles rely upon a suite of adaptations for sustained aerobic metabolism in the absence of freely available oxygen (O(2)). Although the importance of these adaptations for supporting aerobic diving patterns of adults is well understood, little is known about postnatal muscle development in young marine mammals. However, the typical pattern of vertebrate muscle development, and reduced tissue O(2) stores and diving ability of young marine mammals suggest that the physiological properties of harbor seal (Phoca vitulina) pup muscle will differ from those of adults. We examined myoglobin (Mb) concentration, and the activities of citrate synthase (CS), beta-hydroxyacyl coA dehydrogenase (HOAD), and lactate dehydrogenase (LDH) in muscle biopsies from harbor seal pups throughout the nursing period, and compared these biochemical parameters to those of adults. Pups had reduced O(2) carrying capacity ([Mb] 28-41% lower than adults) and reduced metabolically scaled catabolic enzyme activities (LDH/RMR 20-58% and CS/RMR 29-89% lower than adults), indicating that harbor seal pup muscles are biochemically immature at birth and weaning. This suggests that pup muscles do not have the ability to support either the aerobic or anaerobic performance of adult seals. This immaturity may contribute to the lower diving capacity and behavior in younger pups. In addition, the trends in myoglobin concentration and enzyme activity seen in this study appear to be developmental and/or exercise-driven responses that together work to produce the hypoxic endurance phenotype seen in adults, rather than allometric effects due to body size.

Albino Weddell seal at Cape Shirreff, Livingston Island, Antarctica

To our knowledge, this paper is the first record/report of a juvenile light-coloured Weddell seal (Leptonychotes weddellii) at Cape Shirreff, Livingston Island in January 1998, determining that it was an albino individual. Based on available literature, three cases of albino seals have been reported exclusively for Harbour seal pups, and no albino has been reported for Antarctic pagophilic true seals. Therefore, this is the first confirmed case of albinism in Antarctic pagophilic true seals species, indicating that this phenomenon is indeed of a rare occurrence.