Weddell Seals Research Articles

A new method to quantify within dive foraging behaviour in marine predators.

Studies on diving behaviour classically divide a dive into three phases: the descent, bottom and ascent phases, with foraging assumed to occur during the bottom phase. The greater complexity of dive revealed through modern, high resolution data highlights the need to re-assess this approach and to consider a larger number of phases within individual dives. Two southern elephant seals (SES) were fitted with a head mounted Time Depth Recorder (TDR) and an accelerometer from which prey capture attempts were estimated. A Weddell seal was also fitted with a TDR. TDRs for both species recorded depth once per second. We quantified the within dive behaviour using an automated broken stick algorithm identifying the optimal number of segments within each dive. The vertical sinuosity of the segments was used to infer two types of behaviours, with highly sinuous segments indicating "hunting" and less sinuous segments indicating "transiting". Using the broken stick method the seals alternated between "hunting" and "transit" modes with an average of 6±2 and 7±0.02 behavioural phases within each dive for the Weddell seal and SES, respectively. In SES, 77% of prey capture attempts (identified from the acceleration data) occurred in highly sinuous phases (“hunting”) as defined by our new approach. SES spent more time in transit mode within a dive, and hunting mostly occurred during the bottom phase. Conversely the Weddell seal spent more time in hunting mode which also occurred during bottom phase but occurred mostly at shallower depths. Such differences probably reflect different foraging tactics and habitat use. For both species, hunting time differs significantly from bottom time previously used as a proxy for the time spent foraging in a dive. The hunting time defined by our method therefore provides a more accurate fine-scale description of the seals' foraging behaviour.

Comparison of analytical and predictive methods for water, protein, fat, sugar, and gross energy in marine mammal milk

Mammalian milks may differ greatly in composition from cow milk, and these differences may affect the performance of analytical methods. High-fat, high-protein milks with a preponderance of oligosaccharides, such as those produced by many marine mammals, present a particular challenge. We compared the performance of several methods against reference procedures using Weddell seal (Leptonychotes weddellii) milk of highly varied composition (by reference methods: 27–63% water, 24–62% fat, 8–12% crude protein, 0.5–1.8% sugar). A microdrying step preparatory to carbon-hydrogen-nitrogen (CHN) gas analysis slightly underestimated water content and had a higher repeatability relative standard deviation (RSDr) than did reference oven drying at 100°C. Compared with a reference macro-Kjeldahl protein procedure, the CHN (or Dumas) combustion method had a somewhat higher RSDr (1.56 vs. 0.60%) but correlation between methods was high (0.992), means were not different (CHN: 17.2±0.46% dry matter basis; Kjeldahl 17.3±0.49% dry matter basis), there were no significant proportional or constant errors, and predictive performance was high. A carbon stoichiometric procedure based on CHN analysis failed to adequately predict fat (reference: Röse-Gottlieb method) or total sugar (reference: phenol-sulfuric acid method). Gross energy content, calculated from energetic factors and results from reference methods for fat, protein, and total sugar, accurately predicted gross energy as measured by bomb calorimetry. We conclude that the CHN (Dumas) combustion method and calculation of gross energy are acceptable analytical approaches for marine mammal milk, but fat and sugar require separate analysis by appropriate analytic methods and cannot be adequately estimated by carbon stoichiometry. Some other alternative methods—low-temperature drying for water determination; Bradford, Lowry, and biuret methods for protein; the Folch and the Bligh and Dyer methods for fat; and enzymatic and reducing sugar methods for total sugar—appear likely to produce substantial error in marine mammal milks. It is important that alternative analytical methods be properly validated against a reference method before being used, especially for mammalian milks that differ greatly from cow milk in analyte characteristics and concentrations.

Sea lions raise heart rate before deep dives

When aquatic mammals and birds plumb the depths, they have only the oxygen reserves that they carry on board to sustain them; yet, some animals can remain immersed for tens of minutes on a single lungful of air. All divers have evolved a suite of physiological responses to eke out their oxygen reserves, including increasing oxygen stores in venous blood and lowering the heart rate (bradycardia) to conserve oxygen stored in the blood. Birgitte McDonald and Paul Ponganis from the Scripps Institution of Oceanography, USA, explain that although the cardiac response of diving phocid seals (such as grey seals and Weddell seals) have been studied extensively, less was known about the cardiac responses of the otariids, such as fur seals and sea lions. As California sea lions are good divers, McDonald and Ponganis headed to San Nicolas Island, off the coast of Southern California, to measure the heart rates of the diving animals to find out how they cope with submersion (p. 1525).The duo captured five females and attached ECG electrodes, a pressure sensor, accelerometers and a radio transmitter to each animal; they then released the sea lions to venture off foraging. After retrieving the data loggers several days later, the team could see that the animals had two distinct heart activity patterns, depending on the dive depth. In short shallow dives lasting less than 2 min, the heart rated dropped rapidly during the descent, remained constant while the animal was at depth and increased rapidly as the seal ascended. However, when the seals undertook lengthier dives that exceeded 3 min and went as deep as 300 m, they raised their heart rate while at the surface prior to the dive before rapidly reducing their heart rate during the initial descent and slowing the heart rate decrease as they neared the bottom. The seals' heart rates then increased slightly while they foraged at depth, before gently increasing during the initial ascent and increasingly rapidly just before the seals returned to the surface. And when the sea lions remained submerged for more than 6 min, their heart rate fell as low as 6 beats min−1.The team suspects that the deep-diving sea lions use the pre-dive period when their heart rates are high to maximise their venous oxygen reserves in preparation for the long submersion, and they suggest that the very low heart rates experienced at the bottom of the dive might force the animals to consume oxygen stored in the muscle and protect them from absorbing too much nitrogen. The duo also points out that deep-diving emperor penguins use the same strategy, suggesting that this might be a common tactic used by endotherms that dive carrying a lungful of air.

The effect of lipid concentration on myosin heavy chain isoform expression in cultured Weddell seal skeletal muscle cells (1102.26)

Prior studies have shown that myoglobin expression is increased when muscle cells are exposed to hypoxia and a second stimulus such as exercise. Aerobic muscle fibers expressing either Type I or IIA myosin heavy chains (MHC) have more myoglobin than other fiber types, and changes in the expression of myoglobin are usually attributed to a change in fiber type. Recently, De Miranda et al. (2012) showed that cultured Weddell seal skeletal muscle cells grown in normoxic conditions experienced an increase in myoglobin expression in response to increased lipid concentration in the culture media. The objective of this study was to determine if increasing lipid in the media would affect the expression of MHC that would underlie the increase in myoglobin expression. Weddell seal cells from primary culture were proliferated in normoxic conditions for seven days in growth media supplemented with either 2.5% or 5.0% lipid, and both treatments were differentiated for seven days in either hypoxic (0.5% oxygen) or normoxic (21% oxygen) environments. Cells were homogenized, and protein was separated via gel electrophoresis and stained with Coomassie. A difference in the presence of MHC isoforms was not detected between the 2.5% and 5.0% treatment groups, in either oxygen condition. We conclude that lipid may be acting independent of changes in MHC via another undescribed pathway to increase myoglobin expression.Grant Funding Source: Supported by Colorado State University

Use of posterior predictive checks as an inferential tool for investigating individual heterogeneity in animal population vital rates.

The investigation of individual heterogeneity in vital rates has recently received growing attention among population ecologists. Individual heterogeneity in wild animal populations has been accounted for and quantified by including individually varying effects in models for mark–recapture data, but the real need for underlying individual effects to account for observed levels of individual variation has recently been questioned by the work of Tuljapurkar et al. (Ecology Letters, 12, 93, 2009) on dynamic heterogeneity. Model-selection approaches based on information criteria or Bayes factors have been used to address this question. Here, we suggest that, in addition to model-selection, model-checking methods can provide additional important insights to tackle this issue, as they allow one to evaluate a model's misfit in terms of ecologically meaningful measures. Specifically, we propose the use of posterior predictive checks to explicitly assess discrepancies between a model and the data, and we explain how to incorporate model checking into the inferential process used to assess the practical implications of ignoring individual heterogeneity. Posterior predictive checking is a straightforward and flexible approach for performing model checks in a Bayesian framework that is based on comparisons of observed data to model-generated replications of the data, where parameter uncertainty is incorporated through use of the posterior distribution. If discrepancy measures are chosen carefully and are relevant to the scientific context, posterior predictive checks can provide important information allowing for more efficient model refinement. We illustrate this approach using analyses of vital rates with long-term mark–recapture data for Weddell seals and emphasize its utility for identifying shortfalls or successes of a model at representing a biological process or pattern of interest.We show how posterior predictive checks can be used to strengthen inferences in ecological studies. We demonstrate the application of this method on analyses dealing with the question of individual reproductive heterogeneity in a population of Antarctic pinnipeds.

An evolutionary perspective on reproductive individual heterogeneity in a marine vertebrate

Although the quantification of individual heterogeneity in wild populations' vital rates has recently attracted growing interest among ecologists, the investigation of its evolutionary consequences remains limited, mainly because of the difficulties in assessing fitness and heritability from field studies on free-ranging animals. In the presence of individual variability, evaluation of fitness consequences can notably be complicated by the existence of trade-offs among different vital rates. In this study, to further assess the evolutionary significance of previously quantified levels of individual heterogeneity in female Weddell seal (Leptonychotes weddellii Lesson) reproductive rates (Chambert etal. ), we investigated how several life-history characteristics of female offspring were related to their mother's reproductive rate, as well as to other maternal traits (age and experience) and environmental conditions at birth. The probability and age of first reproduction (recruitment) of female offspring was not related to their mother's reproductive rate, suggesting the absence of a maternal trade-off between the number and quality of offspring a female produces. Evidence of a positive, but relatively weak, relationship between the reproductive rates of a mother and her female offspring was found, suggesting some degree of heritability in this trait. Using a simulation approach based on these statistical findings, we showed that substantial differences in the number of grandchildren, produced through female progeny, can be expected among females with different reproductive rates. Despite the presence of substantial stochastic variability, due to environmental fluctuations and other unidentified mechanisms, and in the light of the fact that the metrics obtained do not provide a full measure of real fitness, our results do suggest that the individual reproductive variability found in female Weddell seals could potentially have important fitness consequences.

Improving the Precision of Our Ecosystem Calipers: A Modified Morphometric Technique for Estimating Marine Mammal Mass and Body Composition

Mass and body composition are indices of overall animal health and energetic balance and are often used as indicators of resource availability in the environment. This study used morphometric models and isotopic dilution techniques, two commonly used methods in the marine mammal field, to assess body composition of Weddell seals (Leptonychotes weddellii, N = 111). Findings indicated that traditional morphometric models that use a series of circular, truncated cones to calculate marine mammal blubber volume and mass overestimated the animal’s measured body mass by 26.9±1.5% SE. However, we developed a new morphometric model that uses elliptical truncated cones, and estimates mass with only −2.8±1.7% error (N = 10). Because this elliptical truncated cone model can estimate body mass without the need for additional correction factors, it has the potential to be a broadly applicable method in marine mammal species. While using elliptical truncated cones yielded significantly smaller blubber mass estimates than circular cones (10.2±0.8% difference; or 3.5±0.3% total body mass), both truncated cone models significantly underestimated total body lipid content as compared to isotopic dilution results, suggesting that animals have substantial internal lipid stores (N = 76). Multiple linear regressions were used to determine the minimum number of morphometric measurements needed to reliably estimate animal mass and body composition so that future animal handling times could be reduced. Reduced models estimated body mass and lipid mass with reasonable accuracy using fewer than five morphometric measurements (root-mean-square-error: 4.91% for body mass, 10.90% for lipid mass, and 10.43% for % lipid). This indicates that when test datasets are available to create calibration coefficients, regression models also offer a way to improve body mass and condition estimates in situations where animal handling times must be short and efficient.

Characterizing foodweb structure to identify potential ecosystem effects of fishing in the Ross Sea, Antarctica

AbstractThe potential ecosystem effects of fishing for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea region were investigated. Mixed trophic impact analysis was applied to a model of the Ross Sea foodweb and used to calculate the relative trophic importances of species and trophic groups in the system. The trophic impact of toothfish on medium-sized demersal fish was identified as the strongest top-down interaction in the system based on multiple-step analysis. This suggests a potential for a strong predation-release effect on some piscine prey of toothfish (especially grenadiers and ice-fish on the Ross Sea slope). However, Antarctic toothfish had moderate trophic importance in the Ross Sea foodweb as a whole, and the analysis did not support the hypothesis that changes to toothfish will cascade through the ecosystem by simple trophic effects. Because of limitations of this kind of analysis, cascading effects on the Ross Sea ecosystem due to changes in the abundance of toothfish cannot be ruled out, but for such changes to occur a mechanism other than simple trophic interactions is likely to be involved. Trophic importances were highest in the middle of the foodweb where silverfish and krill are known to have a key role in ecosystem structure and function. The six groups with the highest indices of trophic importance were (in decreasing order): phytoplankton, mesozooplankton, Antarctic silverfish, small demersal fish, Antarctic krill and cephalopods. Crystal krill and small pelagic fish also had high trophic importance in some analyses. Strengths and limitations of this kind of analysis are presented. In particular, it is noted that the analysis only considers trophic interactions at the spatial, temporal and ecological scale of the whole Ross Sea shelf and slope area, averaged over a typical year and in 35 trophic groups. Interference and density-dependent effects were not included in this analysis. Effects at smaller spatial and temporal scales, and effects concerning only parts of populations, were not resolved by the analysis, and this is likely to underestimate the potential risks of fishing to Weddell seals and type-C killer whales.

The device that revolutionized marine organismal biology

![Figure][1] > Jeremy Goldbogen and Jessica Meir discuss Gerald Kooyman's classic paper, ‘Maximum diving capacities of the Weddell seal, Leptonychotes weddelli’, published in Science in 1966. As recently as 50 years ago we had very little information on where marine mammals and seabirds

Brucella antibody seroprevalence in Antarctic seals (Arctocephalus gazella, Leptonychotes weddellii and Mirounga leonina)

Brucellosis is a worldwide infectious zoonotic disease caused by Gram-negative bacteria of the genus Brucella, and Brucella infections in marine mammals were first reported in 1994. A serosurvey investigating the presence of anti-Brucella antibodies in 3 Antarctic pinniped species was undertaken with a protein A/G indirect enzyme-linked immunosorbent assay (iELISA) and the Rose Bengal test (RBT). Serum samples from 33 Weddell seals Leptonychotes weddelli were analysed, and antibodies were detected in 8 individuals (24.2%) with the iELISA and in 21 (65.6%) with the RBT. We tested 48 southern elephant seal Mirounga leonina sera and detected antibodies in 2 animals (4.7%) with both the iELISA and the RBT. None of the 21 Antarctic fur seals Arctocephalus gazella was found positive. This is the first report of anti-Brucella antibodies in southern elephant seals. The potential impact of Brucella infection in pinnipeds in Antarctica is not known, but Brucella spp. are known to cause abortion in terrestrial species and cetaceans. Our findings suggest that Brucella infection in pinnipeds is present in the Antarctic, but to date B. pinnipedialis has not been isolated from any Antarctic pinniped species, leaving the confirmation of infection pending.

Hydrographic influences on the summer dive behaviour of Weddell seals (Leptonychotes weddellii) in Atka Bay, Antarctica

In order to gain insights into species-level behavioural responses to the physical environment, it is necessary to obtain information from various populations and at all times of year. We analysed the influences of physical environmental parameters on the mid-summer dive behaviour of Weddell seals (Leptonychotes weddellii) from a little-known population at Atka Bay, Antarctica. Dive depth distributions followed a typical bimodal pattern also exhibited by seals from other populations and seals targeted both shallow water layers of <50 m and depths near the seafloor. Increased stratification of temperature layers within the water column resulted in increased forage efforts by the seals through relatively high numbers of dives to the seafloor, as well as forage effort associated with shallow dives. We interpret these behavioural responses to be due to increased water temperature stratification resulting in the concentration of prey species in particular depth layers.

Isolation of human pathogen Escherichia albertii from faeces of seals (Leptonychotes weddelli) in James Ross Island, Antarctica

A set of nine gram-negative fermenting rods biochemically identified as Escherichia coli was isolated from faeces of seals. These bacteria were characterized by phenotypic classification, 16S rDNA sequence analyses, automated ribotyping, study of whole-cell protein profiles by SDS-PAGE and finally by bacteriocin production. The results of our polyphasic taxonomic study supported the recognition of P4652, P4653 and P4740 isolates as true members of Escherichia albertii species – probably a major enteric human pathogen. To our best knowledge, this is the first evidence showing that E. albertii produces bacteriocin, colicin D. Obtained data unambiguously showed incon-venience of commercial identification systems to distinguish both Escherichia species due to missing data of E. albertii in the commercial databases. The results of Escherichia isolates taxonomy suggest seals as a novel source of human and animal pathogen,E. albertii in the Antarctic region.

Individual heterogeneity in reproductive rates and cost of reproduction in a long‐lived vertebrate

Individual variation in reproductive success is a key feature of evolution, but also has important implications for predicting population responses to variable environments. Although such individual variation in reproductive outcomes has been reported in numerous studies, most analyses to date have not considered whether these realized differences were due to latent individual heterogeneity in reproduction or merely random chance causing different outcomes among like individuals. Furthermore, latent heterogeneity in fitness components might be expressed differently in contrasted environmental conditions, an issue that has only rarely been investigated. Here, we assessed (i) the potential existence of latent individual heterogeneity and (ii) the nature of its expression (fixed vs. variable) in a population of female Weddell seals (Leptonychotes weddellii), using a hierarchical modeling approach on a 30-year mark–recapture data set consisting of 954 individual encounter histories. We found strong support for the existence of latent individual heterogeneity in the population, with “robust” individuals expected to produce twice as many pups as “frail” individuals. Moreover, the expression of individual heterogeneity appeared consistent, with only mild evidence that it might be amplified when environmental conditions are severe. Finally, the explicit modeling of individual heterogeneity allowed us to detect a substantial cost of reproduction that was not evidenced when the heterogeneity was ignored.

Birth‐year and current‐year influences on survival and recruitment rates of female Weddell seals

AbstractIn long‐lived species, juvenile survival typically is lower and more variable than adult survival, and modeling such variation is important for understanding population dynamics. Variability in juvenile survival can be related to birth‐ or current‐year influences, and the birth‐year influences can be transient, persistent, or intermediate in duration. We used multi‐state models and data collected from 5,459 known‐aged prebreeder female Weddell seals (Leptonychotes weddellii Lesson) tagged in Erebus Bay, Antarctica from 1980–2007 to evaluate the duration of potential birth‐year influences on survival rates and the importance of birth‐ and current‐year influences on survival and recruitment rates. Survival rates differed for each birth cohort and were positively related to current‐year winter sea‐ice conditions. The estimated duration of birth‐cohort effects on survival was intermediate (6 years) rather than transient (2 years) or permanent. Estimated survivorship from birth to 6 years of age varied among cohorts from 0.13 (SE = 0.04) to 0.42 (SE = 0.06), and averaged 0.25 (SE = 0.02). Recruitment rates (probability of transitioning from prebreeder to breeder state) varied annually but apparently were not related to birth‐year conditions. Our results provide evidence that birth‐ and current‐year conditions act in combination to influence survival. Although for many long‐lived species the influences of either birth‐ or current‐year conditions on survival are well‐studied, we suggest that modeling survival rates as a function of birth‐ and current‐year influences simultaneously could lead to better understanding of survival and improved stochastic models to project population dynamics.

Brain size in neonatal and adult Weddell seals: Costs and consequences of having a large brain

AbstractLittle is known about the ontogeny of brain size in pinnipeds despite potential functional implications of brain substrate (glucose, oxygen) requirements for diving, fasting, growth, and lactation strategies. We measured brain mass (brM) and cranial capacity (CC) in newborn and adult Weddell seals. Neonatal Weddell seals had brM that represented ~70% of adult brM. Weddell seals have the largest neonatal brain, proportional to adult brain, reported for any mammal to date, which is remarkable considering the relatively small size of Weddell seal pups at birth (6%–7% of maternal body mass) compared to neonates of other highly precocial mammals. Provision of sufficient glucose to maintain the large, well‐developed brain of the neonatal Weddell seal has a nontrivial metabolic cost to both pup and mother. We therefore hypothesize that this phenomenon must have functional significance, such as allowing pups to acquire complex under‐ice navigation skills during the period of maternal attendance.

Profiling heat loss in an extreme polar mammal, the Weddell seal

A major weakness in predicting habitat change impacts in polar regions is that little is actually known about energetic costs of basic thermoregulation in high‐latitude seals and other apex predators. Characteristics of body size and condition (surface area: volume ratios, insulation) are likely to affect heat loss and manifest as altered thresholds for thermal homeostasis. We monitored the thermal interface between animal‐environment directly via skin surface heat flux sensors (HFS) and indirectly with infrared thermography (IRT) in Weddell seals (n=42) over 2–7d. Utilizing 4 life history categories—pups, juveniles, non‐reproductive adult females (skip breeders) and post‐weaning females—we tested for effect of body size and known insulation patterns (blubber depth via imaging ultrasound). IRT surface temperature maxima and range suggested 4 sites of interest for HFS placement and continued monitoring: axilla (variable hot), head (hot), flank (variable cold) and neck (cold). IRT‐generated surface temperature distribution histograms further permitted the partitioning of body surface area such that an integrated thermal profile could be modeled from HFS data collected at these 4 sites. With this tool we can for the first time examine thermal homeostasis in free‐ranging seals over a range of potentially changing environments. Funded by NSF Polar Programs.

Thermoregulation in polar seals: Profiling surface heat in Weddell seals

Our understanding of thermoregulation in marine mammals is ambiguous at best, due to the conflicting needs of homeostasis in air and water. Infrared imaging (IRT) has become increasingly applied to wildlife research given the non‐invasive nature of the technology, which is particularly desirable for work with species that are at risk and/or difficult to handle. Our prior work identified species‐specific patterns of heat loss by season and body condition under controlled conditions. As part of a larger study, we are assessing the use of IRT under extreme Antarctic field conditions to determine baseline and variation in thermal profiles in animals of known condition and physiological state. Weddell seals show consistent hot spots around the poorly insulated head and well‐insulated but active axilla. The trunk and neck are typically cool, whereas flippers are variable. Best fit LME showed ambient temperature, relative humidity and blubber depth to be the primary predictors of IRT signatures. Animal, body site and wind speed were not significant. Profiles were similar between wet and dry seals, however, dry animals can have surface temperatures that are only marginally above ambient, greatly minimizing heat loss. Funded by NSF.

Wintertime Water Mass Modification near an Antarctic Ice Front

Abstract Under ice measurements by seals carrying a miniaturized conductivity–temperature–depth (CTD) instrument fill an important gap in existing observations. Here the authors present data from an instrumented Weddell seal that spent eight consecutive months (February–September) foraging in close proximity to the Filchner Ice Shelf, thus providing detailed information about the evolution of mixed layer hydrography during the austral autumn and winter. The resultant time series of hydrography shows strong seasonal water mass modification, dominated by an upper-ocean (0–300 m) salinity increase of 0.31, corresponding to 3.1 m sea ice growth, and the development of a 500-m thick winter mixed layer. Observations furthermore highlight a gradual salinity increase in a slow (3–5 cm s−1) southward flow on the continental shelf, toward the site, and suggest that the inferred ice production is better considered as a regional average rather than being purely local. No clear seasonality is observed in the properties of the underlying Ice Shelf Water.

Milk Composition in the Weddell SealLeptonychotes weddellii: Evidence for a Functional Role of Milk Carbohydrates in Pinnipeds

We propose that secretion of milk sugar has important consequences for the metabolic economies of lactating phocid seals and their pups. Milk was collected from 21 Weddell seals Leptonychotes weddellii in McMurdo Sound, Antarctica, and assayed by standard methods. Milk composition changed over the course of lactation, but at mid- to late lactation (16-40 d postpartum), Weddell seal milk composition was relatively constant at 33.8% +/- 0.82% water, 54.0% +/- 0.80% fat, 10.1% +/- 0.16% crude protein, 0.84% +/- 0.03% sugar, 0.75% +/- 0.02% ash, and 23.3 +/- 0.3 kJ g−1 whole milk (WM). At this stage, milk composition varied among individual seals in all assayed constituents except ash. The concentration of sugar in the aqueous phase of Weddell seal milk ( 24.9 +/- 0.6g sugar L−1 water) was ca. 44%-77% of levels found in terrestrial carnivores, indicating that the low sugar concentration of WM is primarily due to its high fat content, not alteration of the aqueous phase. In early lactation, fasting Weddell seals were estimated to devote 39 g d(-1) glucose to milk sugar synthesis, an amount similar to the estimated demand of the maternal brain. This additional glucose demand must be covered by gluconeogenesis in fasting animals and represents a considerable additional drain on maternal resources. However, provision of sugar to offspring at rates sufficient to meet neonatal substrate requirements appears to be essential for efficient fat and protein deposition and thus may be an important component of the phocid reproductive strategy of rapid growth and early weaning.

Особливості росту молоді тюленя Уедделла (Leptonychotes weddellii)

The peculiarities of growth of Weddell seal youngs (Leptonychotes weddellii) on the material collected during 11th, 14th, 16th Ukrainian Antarctic expeditions (2006-2007, 2009-2010, 2011-2012) within the territory of the Argentine Islands (West Antarctica) was investigated. According to the monitoring of L. weddelli pups the relatively large body size (131–140 cm) and weight (18–25 kg) were found compare to literature data. This can indicate the sufficient food supply for the pregnant females of the species in the waters of the archipelago. It was found that daily gain of pups is 3.6 kg on average. The highest absolute and average daily gains of the pups during nine day term was from 5 to 7 kg. This shows a strategy of the highest liveweight gain during the first week after birth that can be explained as the adaptation for another feeding schedule. It was found that the majority of pups up to 21 days of age are gaining more than 90 kg of weight. This enables them to move on to the water way of life, to dive and to maintain low water temperatures. It was noted that the initial terms of birth of Weddell seal youngs within the archipelago differ in time (ranging from late August to late September) and probably depend on the peculiarities of weather conditions during the spring season. The research of growth intensity dynamics of Weddell seal youngs enables us to evaluate and determine the quality of forage reserve in the region of Archipelago of Argentine Islands.