Development of the blood and muscle oxygen stores in gray seals (Halichoerus grypus): implications for juvenile diving capacity and the necessity of a terrestrial postweaning fast

To successfully transition from nursing to foraging, phocid seal pups must develop adequate diving physiology within the limited time between birth and their first independent foraging trip to sea. We studied the postpartum development of oxygen stores in gray seals (Halichoerus grypus, n=40) to better understand the ontogeny of diving capacity in phocids. Hemoglobin (Hb), hematocrit (Hct), blood volume (BV), and myoglobin (Mb) levels in newborn (3 d postpartum [DPP]) and newly weaned (17+/-0.4 DPP) pups were among the lowest measured across age classes. During the pups' terrestrial postweaning fast (PWF), Hb, Hct, mass-specific BV, and Mb increased by 28%, 21%, 13%, and 29%, respectively, resulting in a 35% increase in total body mass-specific oxygen stores and a 23% increase in calculated aerobic dive limit (CADL). Although Hb and Hct levels at the end of the PWF were nearly identical to those of yearlings, total body mass-specific oxygen stores and CADL of weaned pups departing for sea were only 66%-67% and 32%-62%, respectively, of those for yearlings and adult females. The PWF represents an integral component of the physiological development of diving capacity in phocids; however, newly independent phocids still appear to have limited diving capabilities at the onset of foraging.     

Validation of the use of phenylhydrazine hydrochloride (PHZ) for experimental manipulation of haematocrit and plasma haemoglobin in birds

The levels of haematocrit (Hct) and plasma haemoglobin (Hb) vary markedly through the annual cycle of birds, as well as among individuals at all life‐stages (embryos, chicks, adults). It is thus surprising that the functional, fitness‐related consequences of this variation are poorly understood. Putative ‘adaptive’ variation in these haematological traits has been associated with varying demands for aerobic capacity and oxygen transport, for example during migration, winter acclimatization, with increasing altitude, or during parental care. It has also been proposed that changes in Hct might reflect ‘costs’ of parental investment, for example during ‘reproductive anaemia’. However, almost all studies to date have been correlative. Here we describe a series of experiments that validate the use of phenylhydrazine hydrochloride (PHZ) for the transient, reversible experimental manipulation of Hct and Hb in birds. A single bolus injection (12.5 μg PHZ/g body weight delivered via intra‐muscular injection) caused a rapid decrease in Hct and plasma Hb within 24 h, from pretreatment values of 50–54% to 40–44% in non‐breeding Zebra Finches Taenipoygia guttata and European Starlings Sturnus vulgaris, and to 35% in breeding female Zebra Finches, changes within the normal physiological range. Hct and Hb returned to pre‐injection levels within 5–10 days of treatment. Changes in plasma Hb paralleled those for Hct. We suggest that PHZ treatment provides a widely applicable technique for use in experimental work to establish relationships between haematological status, aerobic capacity, workload (e.g. migration, parental care, thermoregulation), individual quality (of both adults and chicks) and trade‐offs such as costs of reproduction.     

Respiratory chemosensitivity during wake and sleep in harbour seal pups (Phoca vitulina richardsii)

In this study, we examined the cardiorespiratory patterns of harbour seal pups under normoxic/normocarbic (air), hypoxic/normocarbic (15%, 12%, and 9% O2 in air), and normoxic/hypercarbic (2%, 4%, and 6% CO2 in air) conditions while awake and sleeping on land. Animals were chronically instrumented to record electroencephalogram (EEG), electromyogram (EMG), and electrocardiogram (EKG) signals, which, along with respiration (whole-body plethysmography) and oxygen consumption (VO2), were recorded from animals breathing each gas mixture for 2-4 h on separate days. Our results show that for animals breathing air, VO2 was not significantly lower during slow-wave sleep (SWS; 7.71 +/- 0.39 mL O2 min(-1) kg(-1); all measurements are mean +/- SEM) than during wakefulness (WAKE; 8.80 +/- 0.25 mL O2 min(-1) kg(-1)) and was unaffected by changes in respiratory drive. Although there was no significant fall in VO2 associated with a decrease in arousal state, breathing frequency (f(R)) did decrease (from 18.80 +/- 1.50 breaths min(-1) in WAKE to 10.40 +/- 0.49 breaths min(-1) in SWS), while the incidence of long apneas (>20 s) increased (12.76 +/- 4.06 apneas h(-1) in WAKE and 31.95 +/- 2.37 apneas h(-1) in SWS). Breathing was rarely seen during rapid eye movement (REM) sleep. Tachypnea was present at all levels of increased respiratory drive; however, hypoxia induced a dramatic bradycardia regardless of arousal state, while hypercarbia produced a tachycardia in SWS only. The hypoxic and hypercarbic chemosensitivities of harbour seal pups were similar to those of terrestrial mammals; however, unlike terrestrial mammals, where hypoxic and hypercarbic sensitivities are often reduced during SWS, the sensitivity of harbour seal pups to hypoxia and hypercarbia remained unchanged during the decrease in arousal state from WAKE to SWS.     

Bearded seal (Erignathus barbatus) birth mass and pup growth in periods with contrasting ice conditions in Svalbard,Norway

Global climate warming has caused major reductions in sea ice in the Arctic, posing a serious threat to ice-associated marine mammals. Herein, novel data on birth mass and pup growth rates over a 15-year period (1993–2007; 10 years with growth data) are reported for bearded seals, as well as initial behavioral responses by this species to major, local declines in sea-ice in Svalbard, Norway. In total, 205 pups were captured; 64 of which were recaptured, some repeatedly, producing 85 growth intervals for nursing pups. Average birth mass of pups was 37.1 ± 3.8 (SD) kg (range 33–47 kg, n = 25); birth mass before vs. after the sea ice collapse (2006 onward) were not found to differ. Pups grew at a rate of 3.0 ± 0.7 kg/day (1.8–4.8 kg/day, n = 64) during the nursing period. LME models suggest that ice concentration did not affect the growth rate of pups. Most females shifted from traditional first-year ice floes to glacier-ice pieces for birthing and nursing their young, following the regional sea ice collapse. However, retraction of tidal glaciers will likely eliminate this replacement birthing and nursing habitat for bearded seals in Svalbard in the coming decades.     

Health status of young Alaska Steller sea lion pups (Eumetopias jubatus) as indicated by blood chemistry and hematology

Blood chemistry and hematology were examined in 238 Steller sea lion pups (Eumetopias jubatus) to assess the health status of pups <1 month of age. Failure of juvenile recruitment (possibly due to nutritionally or physiologically compromised pups) into breeding populations has been proposed as a cause of recent declines of this endangered species in Alaska. To identify potential correlations with areas of high population decline, blood chemistry data were considered for three areas: eastern Aleutian Islands (low rates of population decline to stable populations), Gulf of Alaska (high rates of decline), and Southeast Alaska (stable to increasing population). Southeast Alaska pups showed elevated ketone body concentrations (beta-hydroxybutyrate,(beta-HBA)) and depressed glucose levels than pups in the Gulf of Alaska. Over 40% of the pups from Southeast Alaska had elevated beta-HBA concentrations suggesting they underwent longer periods of fasting than seen in pups from other areas. Hematocrit (Hct), hemoglobin concentration (Hb) and water content of the blood exhibited typical mammalian relationships. In summary, blood chemistry and hematology data showed no indication that Steller sea lion pups <1 month old from areas of population decline were nutritionally compromised.     

Microbiome maturation during a unique developmental window

Shortly after birth, mammals are colonized by a multitude of microbes derived from the mother and the environment. Studies in model organisms have demonstrated that the structure and composition of the gut microbiome of offspring steadily mature with increasing diversity during nursing and weaning (Sommer & Bäckhed, 2013). This period of microbiome assembly is critical for young mammals because the gut microbes they acquire will help train their immune system (Lathrop et al., 2011) with potential long‐lasting effects on their health (Cox et al., 2014). In an article in this issue of Molecular Ecology, Stoffel et al. (2020) investigated the gut microbiota of northern elephant seals (Mirounga angustirostris) during a key developmental window. A month after giving birth, elephant seal mothers stop nursing their pups and return to the sea. As a consequence, their pups go from a diet of milk rich in fat to abruptly enter a post weaning fasting period which lasts for about two months while they remain with the colony. This particular life‐history trait therefore offered the authors a unique and exciting opportunity to evaluate intrinsic factors contributing to gut microbiota development in a wild marine mammal.     

Harbor seal use of glacier ice and terrestrial haul‐outs in the Kenai Fjords,Alaska

Harbor seals, Phoca vitulina, use diverse haul‐out substrates including ice calved by tidewater glaciers. Numbers of seals at glacial and terrestrial haul‐outs on the southeastern Kenai Peninsula, Alaska, were assessed using aerial, vessel, and video surveys. Mean annual abundance at glacial and terrestrial haul‐outs differed temporally. From 2004 to 2011, numbers of seals counted during the molt increased 5.4%/yr at glacial haul‐outs and 9%/yr at terrestrial haul‐outs while numbers of pups increased 5.0%/yr at glacial sites and 1.5%/yr at terrestrial sites. Numbers of seals without pups counted during pupping increased 7.96%/yr at glacial sites and 5.1%/yr at terrestrial sites. Results indicate that pupping and molting locations are not equivalent and population monitoring during the molt does not necessarily reflect habitat association of pupping seals. Ratios of pups to total seals counted during pupping and the subsequent molt were used to contrast habitat use. Low proportions of pups at terrestrial haul‐outs, relative to most glacial haul‐outs, indicate an overall preference for pupping in glacial haul‐outs. High proportions of pups at most glacial sites (during pupping and molting) suggest reduced use of tidewater glacier habitats by nonbreeders and molting seals. Results suggest more seals associate with glacial haul‐outs than currently estimated.     

Health status of young Alaska Steller sea lion pups (Eumetopias jubatus) as indicated by blood chemistry and hematology

Blood chemistry and hematology were examined in 238 Steller sea lion pups (Eumetopias jubatus) to assess the health status of pups <1 month of age. Failure of juvenile recruitment (possibly due to nutritionally or physiologically compromised pups) into breeding populations has been proposed as a cause of recent declines of this endangered species in Alaska. To identify potential correlations with areas of high population decline, blood chemistry data were considered for three areas: eastern Aleutian Islands (low rates of population decline to stable populations), Gulf of Alaska (high rates of decline), and Southeast Alaska (stable to increasing population). Southeast Alaska pups showed elevated ketone body concentrations (β-hydroxybutyrate, (β-HBA)) and depressed glucose levels when compared with animals from the Aleutian Islands and lower blood urea nitrogen (BUN) and glucose levels than pups in the Gulf of Alaska. Over 40% of the pups from Southeast Alaska had elevated β-HBA concentrations suggesting they underwent longer periods of fasting than seen in pups from other areas. Hematocrit (Hct), hemoglobin concentration (Hb) and water content of the blood exhibited typical mammalian relationships. In summary, blood chemistry and hematology data showed no indication that Steller sea lion pups <1 month old from areas of population decline were nutritionally compromised.     

Growth and survival of New Zealand sea lions, <Emphasis Type="Italic">Phocarctos hookeri:</Emphasis> birth to 3 months

Offspring birth mass and growth rate represent important life history traits, which influence many vital population and individual characteristics, while offspring survival is a key factor in variation in female reproductive success. For a threatened population of pinnipeds, such as New Zealand sea lions, Phocarctos hookeri, (Grey, 1844, NZ sea lions), understanding individual life history parameters and population dynamics is vital for their management and conservation. This is the first study of the behaviour of females during parturition, pup birth mass and growth, and pre-weaning survival of NZ sea lions, Enderby Island, Auckland Islands during austral summer breeding seasons, 2001/2002 to 2003/2004. Pregnant females arrived ashore 2.1 ± 0.16 days prior to giving birth. After parturition, mothers suckled their pups for 8.6 ± 0.16 days before leaving on their first foraging trip. Male pups were born significantly heavier than female (males 10.6 ± 1.4 kg, females 9.7 ± 0.9 kg). Pups lost on average 48 ± 0.14 g per day mass during the early postpartum period (between birth and mothers first foraging trip). Pup mortality did not vary by pup sex, birth mass, date of birth or any maternal characteristics however it varied significantly between years due to a bacterial infection epidemic (Pup mortality at 60 days: 2001 32%; 2002 21%; 2003 12%). The absolute growth rate per day for pups was 151 g/day over all years. Pup growth rate measured as the slope of linear line fitted to pup mass by age was consistently higher for pups with heavier birth mass, male pups and during the 2002 season. High offspring mortality and slow growth rates coupled with maternal foraging behaviour at their physiological limits may reflect a threatened species which has limited ability for population growth in an environment which is at the extreme of their historical range and impacted upon by fisheries.     

Birth and simultaneous rearing of two litters in a pack of captive African wild dogs (Lycaon pictus)

Two female African wild dogs (Lycaon pictus) in a pack of 10 animals at the Bronx Zoo gave birth to litters of nine and seven pups within a 2‐day period. Two pups from the litter of seven died before they were 2 weeks old, but the other 14 survived past weaning. Litter size, sex ratio, and pup developmental stages were all consistent with data obtained from other captive‐ and wild‐born litters. Both dams were very attentive to their litters, and during the pups' first 2 weeks spent >90% of their time in the dens with the pups. By 2 days after birth and during their first 2 weeks of life, the pups spent 86% of their time in a nursing position. Before parturition and during the first week post‐partum, one of the dams (DAL) was clearly dominant to the other (WHI). However, the females' dominance rank reversed 2 weeks post‐partum. On two occasions during the pups' first 2 weeks DAL stole and reared one of WHI's pups, but between Weeks 3 and 4 all of DAL's pups were stolen and WHI raised both litters as one until they were weaned. The pups began spending time out of their den at approximately 1 month of age. The timing of the births, the design of the wild dogs' management facility, and the presence of several dens in different enclosures within the facility all likely contributed to the successful rearing of the litters. The pups in both litters were very similar in size because of the short interval between births, so one litter did not have a competitive advantage over the other with respect to gaining access to the dam for milk. The facility's design helped mitigate aggression within the pack, and the presence of multiple dens enabled to dams to move the pups to different den sites and allowed the two females to stay visually and spatially apart from each other while remaining with the pack. Zoo Biol 0:1–17, 2006. © 2006 Wiley‐Liss, Inc.     

Lung collapse in the diving sea lion: hold the nitrogen and save the oxygen

Lung collapse is considered the primary mechanism that limits nitrogen absorption and decreases the risk of decompression sickness in deep-diving marine mammals. Continuous arterial partial pressure of oxygen profiles in a free-diving female California sea lion (Zalophus californianus) revealed that (i) depth of lung collapse was near 225 m as evidenced by abrupt changes in during descent and ascent, (ii) depth of lung collapse was positively related to maximum dive depth, suggesting that the sea lion increased inhaled air volume in deeper dives and (iii) lung collapse at depth preserved a pulmonary oxygen reservoir that supplemented blood oxygen during ascent so that mean end-of-dive arterial was 74 ± 17 mmHg (greater than 85% haemoglobin saturation). Such information is critical to the understanding and the modelling of both nitrogen and oxygen transport in diving marine mammals.     

Wildlife Recovery During Tropical Forest Succession: Assessing Ecological Drivers of Community Change

Despite the high proportion of secondary forests in the tropics, their conservation value remains poorly understood, particularly with regard to animals. Most theoretical studies of succession have focused on plants, linking life history trade‐offs to well‐known patterns of community change. However, the same trade‐offs proposed for plants should apply to animals, and indeed, animal studies show a change in community dominance from habitat generalist to forest specialist species during succession. Focusing on the diverse terrestrial small mammals of the endangered Atlantic Forest, we assessed which ecological drivers (habitat structure and food availability) affect community changes during succession. If the change in community dominance is driven by trade‐offs between productivity and efficiency, it should be mainly associated with a decrease in food availability. As expected, from younger to older forest, habitat generalists decreased in richness and total abundance, concurrent with a decrease in arthropod biomass. By contrast, the increase in richness and total abundance of forest specialists was not clearly supported by the data; however, this group was not affected by food availability. These results are congruent with a trade‐off between competitive ability and ability to use abundant resources, and indicate that the major community change during succession involves habitat generalists. Secondary forests may thus be valuable for conservation, at least where habitat loss and fragmentation are not high, and old growth forest is available.     

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.     

The terrestrial biota prior to the origin of land plants (embryophytes): a review of the evidence

It is often assumed that life originated and diversified in the oceans prior to colonizing the land. However, environmental constraints in chemical evolution models point towards critical steps leading to the origin of life as having occurred in subaerial settings. The earliest fossil record does not include finds from terrestrial deposits, so much of our understanding about the presence of a terrestrial microbial cover prior to the Proterozoic is based on inference and geochemical proxies that indicate biospheric carbon cycling during the Archaean. Our assessment is that by 2.7 Ga, microbial ecosystems in terrestrial settings were driven by oxygen‐generating, photosynthetic cyanobacteria. Studies of modern organisms indicate that both the origin and primary diversification of the eukaryotes could have occurred in terrestrial settings, shortly after 2.0 Ga, but there is no direct fossil evidence of terrestrial eukaryotes until about 1.1 Ga. At this time, it appears that the diversity of life in non‐marine habitats exceeded that found in marine settings where sulphidic seas may have impaired eukaryotic physiology and retarded evolution. Geochemical proxies indicate the establishment of an extensive soil‐forming microbial cover by 850 Ma, and it is possible that a rise in atmospheric oxygen at this time was due to the evolutionary expansion of green algae into terrestrial habitats. Direct fossil evidence of the earliest terrestrial biotas in the Phanerozoic consists of problematical palynomorphs from the Cambro‐Ordovician of Laurentia. These indicate that the evolution of the first land plants (embryophytes) during the Middle Ordovician took place within a landscape that included aeroterrestrial algae which were actively adapting to selection in subaerial settings.     

Moving in two worlds: aquatic and terrestrial locomotion in sea snakes (Laticauda colubrina,Laticaudidae)

Yellow‐lipped sea kraits (Laticauda colubrina) are amphibious in their habits. We measured their locomotor speeds in water and on land to investigate two topics: (1) to what degree have adaptations to increase swimming speed (paddle‐like tail etc.) reduced terrestrial locomotor ability in sea kraits?; and (2) do a sea krait’s sex and body size influence its locomotor ability in these two habitats, as might be expected from the fact that different age and sex classes of sea kraits use the marine and terrestrial environments in different ways? To estimate ancestral states for locomotor performance, we measured speeds of three species of Australian terrestrial elapids that spend part of their time foraging in water. The evolutionary modifications of Laticauda for marine life have enhanced their swimming speeds by about 60%, but decreased their terrestrial locomotor speed by about 80%. Larger snakes moved faster than smaller individuals in absolute terms but were slower in terms of body lengths travelled per second, especially on land. Male sea kraits were faster than females (independent of the body‐size effect), especially on land. Prey items in the gut reduced locomotor speeds both on land and in water. Proteroglyphous snakes may offer exceptional opportunities to study phylogenetic shifts in locomotor ability, because (1) they display multiple independent evolutionary shifts from terrestrial to aquatic habits, and (2) one proteroglyph lineage (the laticaudids) displays considerable intraspecific and interspecific diversity in terms of the degree to which they use terrestrial vs. aquatic habitats.     

Postharvesting population dynamics of the South American sea lion (Otaria byronia) in the southwestern Atlantic

Many pinniped populations precipitously declined during the 19th and 20th centuries due to overharvesting. In Uruguay, the South American sea lion (SASL) was harvested until 1986. Birth rates in two nearby breeding colonies have had opposite trends for at least 20 yr. We assessed different mechanisms that could explain opposite trends in birth rates in the two SASL colonies. We compared feeding habits (δ¹⁵N and δ¹³C) of breeding females, birth mass, individual growth rate and early survival of pups and the social structure between colonies. Breeding females from the two colonies did not differ in their feeding habits. However, male and female pups grew faster but had a lower survival in the second month in the smallest colony. We found differences in the social structures, with a higher proportion of males in the smallest colony. The latter is important because peripheral SASL males may abduct and kill pups, which may explain the lower survival of pups in smaller colonies. We believe that the cumulative effects of population extractions have lowered the local SASL population size and disrupted its social structure to the point where Allee‐like effects could become important and hamper the recovery of the Uruguayan SASL population.     

Birth dates vary with fixed and dynamic maternal features,offspring sex,and extreme climatic events in a high‐latitude marine mammal

Reproductive synchrony tends to be widespread in diverse species of plants and animals, especially at higher latitudes. However, for long‐lived mammals, birth dates for different individuals can vary by weeks within a population. A mother's birth timing can reveal useful information about her reproductive abilities and have important implications for the characteristics and survival of her offspring. Despite this, our current knowledge of factors associated with variation in birth dates is modest. We used long‐term data for known‐age Weddell seals in Antarctica and a Bayesian hierarchical modeling approach to study how birth dates varied with fixed and temporally varying features of mothers, whether sex allocation varied with birth timing, and annual variation in birth dates. Based on birth dates for 4465 pups born to 1117 mothers aged 4–31, we found that diverse features of mothers were associated with variation in birth dates. Maternal identity was the most important among these. Unlike most studies, which have reported that birth dates occur earlier as mothers age, we found that birth dates progressively occurred earlier in the year in the early part of a mother's reproductive life, reached a minimum at age 16, and then occurred later at later ages. Birth dates were positively related to a mother's age at primiparity and recent reproductive effort. The earliest birth dates were for pups born to prime‐age mothers who did not reproduce in the previous year but began reproduction early in life, suggesting that females in the best condition gave birth earlier than others. If so, our finding that male pups tended to be born earlier than females provides support for the Trivers–Willard sex‐allocation model. Average birth dates were quite consistent across years, except for 2 years that had notable delays and occurred during the period when massive icebergs were present and disrupted the ecosystem.     

Fasting metabolism in Antarctic fur seal (Arctocephalus gazella) pups.

The metabolism of 52-73-day old Antarctic fur seal pups from Bird Island, South Georgia, was investigated during fasting periods of normal duration while their mothers were at sea foraging. Body mass decreased exponentially with pups losing 3.5-3.8% of body mass per day. Resting metabolic rate also decreased exponentially from 172-197 ml (O2) x min(-1) at the beginning of the fast and scaled to M(b)(0.74) at 2.3 times the level predicted for adult terrestrial mammals of similar size. While there was no significant sex difference in RMR, female pups had significantly higher (F(1,18)=6.614, P<0.019) mass-specific RMR than male pups throughout the fasting period. Fasting FMR was also significantly (t(15)=2.37, P<0.035) greater in females (823 kJ x kg(-1) x d(-1)) than males (686 kJ x kg(-1) x d(-1)). Average protein turnover during the study period was 19.3 g x d(-1) and contributed to 5.4% of total energy expenditure, indicating the adoption of a protein-sparing strategy with a reliance on primarily lipid catabolism for metabolic energy. This is supported by observed decreases in plasma BUN, U/C, glucose and triglyceride concentrations, and an increase in beta-HBA concentration, indicating that Antarctic fur seals pups adopt this strategy within 2-3 days of fasting. Mean RQ also decreased from 0.77 to 0.72 within 3 days of fasting, further supporting a rapid commencement of protein-sparing. However, RQ gradually increased thereafter to 0.77, suggesting a resumption of protein catabolism which was not substantiated by changes in plasma metabolites. Female pups had higher TBL (%) than males for any given mass, which is consistent with previous findings in this and other fur seal species, and suggests sex differences in metabolic fuel use. The observed changes in plasma metabolites and protein turnover, however, do not support this.     

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

Little 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.     

Telomere length and age in pinnipeds: The endangered Australian sea lion as a case study

Telomeres are the protective caps at the ends of all eukaryotic chromosomes. Because DNA replication of chromosome ends is incomplete, telomeres undergo sequence loss with each cell division resulting in the progressive shortening of their lengths. Telomere shortening with age is known from terrestrial mammals. We test whether this pattern is shared by marine mammals, by comparing telomere lengths between age classes in a pinniped species, the Australian sea lion (Neophoca cinerea). Telomere lengths were measured using a real‐time quantitative polymerase chain reaction (PCR) method in specimens from three age classes: pup (<1.5 yr), juvenile (1.5–5 yr), and adult (>5 yr). Mean telomere lengths of the adults were significantly shorter than the juvenile and pup classes. However, we were unable to differentiate between pups and juveniles. These findings confirm that the Australian sea lion shares the general pattern of shortening telomere lengths with age as documented in terrestrial mammals. The application of telomere lengths as an age determinant requires considerable development to refine the scale of the age estimates derived, which will require the use of known‐aged individuals. Nonetheless, measures of telomere lengths have the potential to become valuable tools in molecular ecology and forensics for assessing compliance in harvesting situations.