Harbor Seal Pups Research Articles

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.

Concentrations of Selected Essential and Non-essential Elements in Blood of Harbor Seal (Phoca vitulina) Pups of the German North Sea

This study on harbor seal (Phoca vitulina) pups of the North Sea evaluated concentrations of 14 essential and non-essential elements (Al, As, Be, Ca, Cd, Cr, Fe, Mn, Mo, Ni, Pb, Se, Sn, and Zn) in whole blood samples. The essential elements are analyzed to give references for health status determinations of pups. The measurement of classic toxic metals, like Pb or Cd, and other elements that may be in toxic concentrations in blood, is important due to their influence on health, particularly on the immune system. Blood samples of six seal pups found on the German Wadden Sea coast of Schleswig-Holstein in 2004 and transported to the Seal Centre Friedrichskoog, Germany were collected. The blood sampling was performed three times, immediately after collection of the newborns, after 1.5 months, and after 2 months before their release back into the wild. Inductively coupled plasma mass spectrometry and total reflection X-ray fluorescence spectrometry were used to determine the element concentrations. We found higher concentrations of Al, As, Fe, Mo, and Zn in blood samples of newborns compared to samples collected later, probably due to transplacental and lactational transfer from mother to fetus. Furthermore, there is a high need for, in particular, Fe and Zn in the developing organism, which may cause reduced values after some month. In contrast, the concentrations of Be, Cd, Ca, Cr, Pb, Mn, Ni, Se, and Sn, which were low in newborns and increased during the study, may be due to the fish fed to infant pups. Compared to free-ranging adults, in pups, the concentrations of Al, Ni, and Pb were higher in contrast to lower concentrations of As, Mn, and Mo. This case study is the first report on element levels in harbor seal pups of the North Sea.

Comparison of the Somatotropic Axis in Free-ranging and Rehabilitated Harbor Seal Pups (Phoca vitulina)

The somatotropic axis, including growth hormone (GH), insulin-like growth factor (IGF)-I, and IGF binding proteins (IGFBP), is a bridge between growth physiology, developmental age, and nutritional status in domestic animals. However, the importance of the somatotropic axis in nutrition, growth, and development of harbor seals has not been previously explored. Given the difficulty of conducting longitudinal studies in free-ranging harbor seals, this study focused on the potential use of harbor seals in rehabilitation facilities as a model for free-ranging seals. The purpose of this research was to compare concentrations of components of the somatotropic axis in free-ranging versus rehabilitated harbor seal pups. The hypothesis was that measurements of the somatotropic axis will be similar between individuals of comparable age and nutritional status (fasting versus feeding). To investigate this hypothesis, harbor seal pups (n=8) brought to The Marine Mammal Center (Sausalito, California, USA) or Mystic Aquarium (Mystic, Connecticut, U.S.A.) were initially assessed and determined to be healthy but abandoned. All pups were less than 2 wk of age upon arrival at rehabilitation facilities. Standard length was assessed at the time of arrival and again at release. Body mass was measured every week and blood samples were collected from each pup at 0, 4, and 8 wk of rehabilitation. Blood was collected and morphometrics assessed in free-ranging harbor seal pups (n=8) from the Gulf of Maine. Sera were analyzed for GH, IGF-I, and IGFBP concentrations. Concentrations of GH, IGF-I, and IGFBP-2 and -3 in rehabilitated pups were within a similar range compared with free-ranging pups when considered in the context of presumed nutrient intake. These data suggest that rehabilitated harbor seals may provide a useful model to investigate the effects of nutrient intake on growth and development of harbor seals, and will provide insight into phocid endocrinology and metabolism.

Contaminant-associated disruption of vitamin A and its receptor (retinoic acid receptor α) in free-ranging harbour seals ( Phoca vitulina)

Polychlorinated biphenyls (PCBs) have been associated with a number of toxic effects in marine mammals such as endocrine disruption and immunotoxicity that, in turn, are widely thought to have contributed to population level impacts including reproductive failure and outbreaks of disease. In this study, the dietary hormone vitamin A and expression levels of one of its receptors, retinoic acid receptor α (RARα), were used as biomarkers of PCB-associated health effects in harbour seals. Harbour seal pups ( n = 24) were live-captured in coastal British Columbia, Canada, and Washington State, USA, and sampled for whole blood (to obtain peripheral blood mononuclear cells, PBMCs) and blood plasma, as well as biopsies of blubber and skin. Concentrations of circulatory vitamin A (retinol) in plasma and stored vitamin A in blubber were negatively associated with blubber PCB concentrations ( R = −0.518, p = 0.013 and R = −0.645, p = 0.009, respectively). However, vitamin A concentrations in skin, an important target tissue, remained constant, which likely reflects a compensatory transfer from blubber to maintain physiological functions. In addition, we characterized the harbour seal RARα, and investigated its expression levels as a potential biomarker in seals. RARα expression in blubber, but not on PBMCs, was elevated in more contaminated animals ( R = 0.580, p = 0.009). This may represent a direct contaminant-related effect, or, a compensation for the contaminant-related disruption of (circulatory and/or blubber) hormone levels. Since vitamin A is critical to developmental, reproductive and immunological health, our observations of a contaminant-related disruption of its physiology in free-ranging seals may portend population level consequences. Vitamin A concentrations and RARα expression levels can therefore represent relevant and sensitive biomarkers of PCB-associated toxic effects in toxicological studies of marine mammals.

DEVELOPMENT OF DIVING BY HARBOR SEAL PUPS IN TWO REGIONS OF ALASKA: USE OF THE WATER COLUMN

AbstractSatellite‐linked dive recorders were attached to 53 harbor seal pups in Prince William Sound (PWS) and at Tugidak Island, Alaska, during 1997–1999. We used generalized additive models and bootstrap techniques to describe pup diving behavior during their first year of life. Pups increased their ability to dive during the first 3–6 mo, as indicated by increases in proportion of time in the water (time wet) and maximum dive depth achieved by a pup each day (max‐depth) values. Time wet and/or max‐depth later decreased, suggesting a seasonal component to diving behavior. Monthly time wet varied from an overall minimum of 0.68 at tagging in July to a maximum of 0.89 in November. Pups spent half of their time wet swimming in water <25 m deep, the shallowest 30% of the available water column. They spent only 5% of their time swimming in the deepest 30% of the available water column, at depths >60–70 m. This strongly suggests they were not feeding on or near bottom during their first year. Average max‐depths and deepest actual dives were similar for PWS and Tugidak pups. PWS pups dove deeper sooner and spent less time wet than Tugidak pups during the first few months after tagging, probably as a result of regional bathymetric differences. Diving behavior and body condition suggest that food availability was not likely a major factor in the population decline in PWS during the period of this study.

Development of Body Oxygen Stores in Harbor Seals: Effects of Age, Mass, and Body Composition

Harbor seal pups are highly precocial and can swim and dive at birth. Such behavioral maturity suggests that they may be born with mature body oxygen stores or that stores develop quickly during the nursing period. To test this hypothesis, we compared the blood and muscle oxygen stores of harbor seal pups, yearlings, and adults. We found that pups had smaller oxygen stores than adults (neonates 57%, weaned pups 75%, and yearlings 90% those of adults), largely because neonatal myoglobin concentrations were low (1.6+/-0.2 g% vs. 3.8+/-0.3 g% for adults) and changed little during the nursing period. In contrast, blood oxygen stores were relatively mature, with nursing pups having hematocrit (55%+/-0.2%), hemoglobin (21.7+/-0.4 g%), and blood volume (12.3+/-0.5 mL/kg) only slightly lower than the corresponding values for adults (57%+/-0.2%, 23.8+/-0.3 g %, and 15.0+/-0.5 mL/kg). Because neonatal pups had relatively high metabolic rates (11.0 mL O2/kg min), their calculated aerobic dive limit was less than 50% that of adults. These results suggest that harbor seals' early aquatic activity is primarily supported by rapid development of blood, with immature muscle oxygen stores and elevated use rates limiting aerobic diving ability.

Rapid Communication: Organohalogen Levels in Harbor Seal (Phoca Vitulina) Pups Increase with Duration of Nursing

Maternal transfer of persistent marine contaminants to offspring via milk has been documented in marine mammals, but temporal dynamics of this phenomenon throughout the lactation period are poorly understood. Exposures to organohalogens were investigated in harbor seal pups admitted to a rehabilitation center in north central California during the lactation periods of 2001 and 2002. Ten congeners of PCBs, three congeners of PBDEs, and p,p′ -DDE were quantified in whole blood samples. Levels of contaminants increased with admit date, assumed to correlate positively with pup age. This trend was significant when latitude of stranding site, body condition, and body length were included as variables in the model. Contaminant–admit date relationships appeared nonlinear (i.e., threshold or exponential), with greatest increases in contaminant concentrations during late lactation.

Mass‐dependent energetics and survival in Harbour Seal pups

Summary Winter survival rate in Harbour Seal pups is significantly correlated with the autumn body mass of pups. Multi‐type mark–recapture statistics were applied to individual re‐sighting histories of branded seals, and survival probability was estimated with weight as a covariate. The probability of surviving to an age of 1 year is only 0·63 for the smallest pups at 17 kg, whereas pups at 32 kg have a survival probability of 0·96. An energetic model for juvenile Harbour Seals reveals how metabolic rate is related to body mass, skin surface area, blubber thickness and water temperature. There is an increasing thermal stress with decreasing body size of pups. Low winter water temperatures induce a negative energy balance in small pups, which is a probable cause of the observed mass‐dependent survival. This study explicitly links a physical property of the environment, sea‐water temperature, to energetics and life history. The approach opens possibilities for studying aspects of life‐history evolution, such as optimal weaning weight and pupping time, in marine mammals.

Correlation of depth and heart rate in harbour seal pups

Harbour seal (Phoca vitulina L., 1758) pups are aquatically active from birth and have been shown to develop increased cardiac control throughout the nursing period. In an attempt to quantify and compare these developmental changes, data previously collected on pups in the St. Lawrence River estuary, Quebec, Canada, were analyzed. Time–depth recorders and heart-rate recorders were employed on eight pups to obtain depth and heart-rate measurements simultaneously. Analyses involved partitioning the data into intervals of surface–dive–surface. These intervals were then allocated into nine consecutive segments: presurface, predive surface, descent, prebottom, bottom, postbottom, ascent, postdive surface, and postsurface. Mean heart rate for each segment was then correlated with the mean depth per segment and overall dive duration. With increasing dive depth, a decrease in heart-rate variability with age was observed. There was no apparent relationship between mean heart rate during the dive and overall dive duration. The proportion of time spent in the lower heart-rate mode was observed to increase with age during most phases of a dive. Relative changes in mean heart rate between consecutive dive segments indicated an initial decrease in mean heart rate prior to submersion and an increasing trend before surfacing. These findings indicate that harbour seal pups develop increased cardiac control prior to weaning and that anticipatory cardiac responses to diving and surfacing (bradycardia and tachycardia, respectively) may be evident.

Sexual Aggression by a Male Northern Elephant Seal on Harbor Seal Pups in Washington

Sexual Aggression by a Male Northern Elephant Seal on Harbor Seal Pups in Washington

Blood Chemistry, Hematology, and Morphology of Wild Harbor Seal Pups in Alaska

Recent declines in harbor seal (Phoca vitulina) populations in Alaska have emphasized the need to obtain health index biomarkers for comparative purposes. This study was designed to compare blood chemistry and morphology reference range values between 2 harbor seal pup populations in Alaska, 1 population in continued decline within Prince William Sound, and another population in recent increase on Tugidak Island. Significant site-specific differences occurred in 5 of the 8 mean hematology values as well as in 11 plasma chemistry values. We also determined significant year-to-year variability in 8 (36%) mean plasma chemistries. These results form the largest available field-based blood reference database for harbor seal pups. They demonstrate that blood values can vary on the population scale and that health assessment or ecophysiological studies involving blood chemistry must utilize an appropriate set of reference values for valid comparisons.

Behavior, Movements, and Apparent Survival of Rehabilitated and Free-Ranging Harbor Seal Pups

Post-release studies are essential to determine the efficacy of wildlife rehabilitation. Although an increasing number of Pacific harbor seal (Phoca vitulina richardsi) pups are admitted to rehabilitation centers, few studies have been conducted to monitor the behaviors and survival of rehabilitated pups released back into the wild. Our objectives were to compare diving behaviors, activity patterns, movements, and survival between rehabilitated pups (n = 29) and wild pups (n = 24). Pups were radiotracked for 5 months after release at Pebble Beach, California, during 1995, 1996, and 1998. Mean duration of dives (t 27 = 0.90, P = 0.37) and surface intervals (U = 52, P = 0.20) of rehabilitated pups did not differ from that of wild pups. Rehabilitated pups spent a greater proportion of their time in the water (t 18 = 2.12, P= 0.047) than did wild pups. Most pups traveled north from Pebble Beach, and movements were variable. Seal group (F 1 31 = 1.33, P= 0.26) or sex (F 1 31 = 0.22, P= 0.64) had no effect on maximum distance traveled. Survival curves between rehabilitated and wild pups were similar during 1995 (X 2 = 0.40, P> 0.05) and 1998 (X 2 = 1.34, P> 0.05), whereas rehabilitated pups had lower survival than wild pups during 1996 (X 2 = 3.94, P 0.05). In summary, the overall behavior, movement, and apparent survival of rehabilitated pups appeared similar to wild pups. Future studies should be conducted to assess the long-term survival of rehabilitated and free-ranging harbor seal pups.

Contaminant‐related disruption of vitamin a dynamics in free‐ranging harbor seal (Phoca vitulina) pups from british columbia, canada, and washington state, usa

AbstractMarine mammals can bioaccumulate high concentrations of lipophilic environmental contaminants, such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo‐para‐dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs), through the diet. Both laboratory and wildlife studies have shown that these persistent chemicals can disrupt the regulation of vitamin A (retinol), a dietary hormone required for immune function, reproduction, growth, and development. To determine whether environmental contaminants affect the circulatory vitamin A dynamics of free‐ranging harbor seals (Phoca vitulina), we live‐captured 61 pups from British Columbia, Canada, and Washington State, USA, and obtained blood and blubber biopsy samples. Harbor seal pups from Washington State were six times more contaminated with total PCBs than pups from British Columbia and had significantly lower circulatory retinol levels. However, when data were corrected for differences in nursing status and analyzed as ungrouped sets of data, circulatory retinol levels were positively correlated with contaminant levels in the blubber of nonnursing pups. This increase in retinol may have resulted from a mobilization of liver vitamin A stores into circulation following exposure to milk‐derived contaminants; this has been observed in laboratory animals exposed experimentally. The contaminant‐related disruption of vitamin A dynamics observed in our study occurs at a time when vitamin A is required for growth and development.

Polychlorinated Biphenyls and Organochlorine Pesticides in Harbor Seal Pups from the Inland Waters of Washington State

Blubber and liver samples from eight harbor seal (Phoca vitulina) pups, found dead at Puget Sound in 1990, have been analyzed for polychlorinated biphenyl (PCB) congeners including mono-ortho and non-ortho coplanar PCBs, hexachlorobenzene (HCB), p,p‘-DDE, and mirex. Four of the seals were from Smith Island in the Strait of Juan de Fuca, and four were from southern Puget Sound primary at Gertrude Island. The levels of total PCBs, p,p‘-DDE, and mirex are significantly higher in the seal samples from Gertrude Island than those from Smith Island. There was no significant difference in the level of HCB in seal samples between the two locations. PCB profiles were dominated by congeners 138, 153, and 180. The new PCB toxic equivalency factors (TEF) recommended by WHO (1), and the TEF for congener 81 from Harris et al. (2) was used for calculation of the contribution to dioxin-like toxicity from the PCB congeners. PCB congener 126 was the major contributor to PCB toxic equivalents (TEQs), followed by 156. The levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in marine mammals from Georgia Strait/Vancouver Island (3) were presented for reference purposes. Based on our studies of PCBs and PCDD/Fs data from the literature, the overall TEQs calculated for the monitored PCBs in Smith Island seals may contribute as much if not more dioxin-like toxicity as PCDD/Fs themselves.

Attachment between Harbour seal (Phoca vitulina) mothers and pups*

Behavioural interactions between Harbour seal mothers and pups at Miquelon revealed that the following behaviour of the pup generally ensures that the pair stay together, though the mother takes over this rôle when necessary. This relationship held true when the animals were hauled out on the sandflats, and when they were in the water. Our results imply, contrary to suggestions in the literature, that the pup is able to distinguish its mother from other females. The tendency of the pup to follow its mother is discussed in the context of imprinting as a bonding mechanism.

Notes on the Births and Deaths of Harbor Seal Pups at Double Point, California

Notes on the Births and Deaths of Harbor Seal Pups at Double Point, California

Birth of a Harbor Seal Pup

Birth of a Harbor Seal Pup