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The Marine Mammal Programme (MMP) conducts research on pinnipeds and killer whales Orcinus orca at Marion Island, Prince Edward Islands, under the auspices of the Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria. The history of the MMP, which has benefited from collaboration with leading national and international researchers, is described from its start through to current research. The setting up of long-term studies such as the mark-resighting of southern elephant seals Mirounga leonina commenced in 1983. The elephant seal population declined by 87% between an initial census in 1951 and 2004. This was followed by a stabilisation period and a current increase. The recovery, and subsequent increase of sympatric populations of Subantarctic fur seals Arctocephalus tropicalis and Antarctic fur seals A. gazella (following cessation of commercial sealing), are documented. Insights into many aspects of elephant seal and fur seal biology, including life history, demography, diet, growth, foraging and ranging behaviour are described. Ancillary work on morphology, genetics, anthropogenic influences and rare events are mentioned, as well as the extent of current research that addresses population dynamics in an ecosystem context. Opportunistic photographic identification of killer whales and recent dedicated observations at Marion Island are used to determine population size, seasonal abundance and sociality of this population, and to further understanding of its potential impact on resident pinniped populations. [ABSTRACT FROM PUBLISHER]

Antarctic krill Euphausia superba is a predominant species in the Southern Ocean, it is very sensitive to climate change, and it supports large stocks of fishes, seabirds, seals and whales in Antarctic marine ecosystems. Modern krill stocks have been estimated directly by net hauls and acoustic surveys; the historical krill density especially the long-term one in the Southern Ocean, however, is unknown. Here we inferred the relative krill population changes along the West Antarctic Peninsula (WAP) over the 20th century from the trophic level change of Antarctic fur seal Arctocephalus gazella using stable carbon (δ13C) and nitrogen (δ15N) isotopes of archival seal hairs. Since Antarctic fur seals feed preferentially on krill, the variation of δ15N in seal hair indicates a change in the proportion of krill in the seal's diets and thus the krill availability in local seawater. For the past century, enriching fur seal δ15N values indicated decreasing krill availability. This is agreement with direct observation for the past ∼30 years and suggests that the recently documented decline in krill populations began in the early parts of the 20th century. This novel method makes it possible to infer past krill population changes from ancient tissues of krill predators. [ABSTRACT FROM AUTHOR]

Emerging Bayesian analytical approaches offer increasingly sophisticated means of reconstructing historical population dynamics from genetic data, but have been little applied to scenarios involving demographic bottlenecks. Consequently, we analysed a large mitochondrial and microsatellite dataset from the Antarctic fur seal Arctocephalus gazella, a species subjected to one of the most extreme examples of uncontrolled exploitation in history when it was reduced to the brink of extinction by the sealing industry during the late eighteenth and nineteenth centuries. Classical bottleneck tests, which exploit the fact that rare alleles are rapidly lost during demographic reduction, yielded ambiguous results. In contrast, a strong signal of recent demographic decline was detected using both Bayesian skyline plots and Approximate Bayesian Computation, the latter also allowing derivation of posterior parameter estimates that were remarkably consistent with historical observations. This was achieved using only contemporary samples, further emphasizing the potential of Bayesian approaches to address important problems in conservation and evolutionary biology. [ABSTRACT FROM AUTHOR]

The article presents the study which compared the ecology of lactating Antarctic fur seals Arctocephalus gazella at a high density colony at Bird Island and a lower density colony at Cooper Bay, both in South Georgia. In the study, the seals were fitted with platform transmitter terminals (PTT) and time depth recorders (TDR) with external temperature sensors. The at-sea behaviour, diet and pup growth of the seal species were examined. The aims of the study include the evaluation of the plasticity of the behaviour of the animals within environmental and physiological obstacles.

Next-generation sequencing provides a powerful new approach for developing functional genomic tools for nonmodel species, helping to narrow the gap between studies of model organisms and those of natural populations. Consequently, massively parallel 454 sequencing was used to characterize a normalized cDNA library derived from skin biopsy samples of twelve Antarctic fur seal ( Arctocephalus gazella) individuals. Over 412 Mb of sequence data were generated, comprising 1.4 million reads of average length 286 bp. De novo assembly using Newbler 2.3 yielded 156 contigs plus 22 869 isotigs, which in turn clustered into 18 576 isogroups. Almost half of the assembled transcript sequences showed significant similarity to the nr database, revealing a functionally diverse array of genes. Moreover, 97.9% of these mapped to the dog ( Canis lupis familiaris) genome, with a strong positive relationship between the number of sequences locating to a given chromosome and the length of that chromosome in the dog indicating a broad genomic distribution. Average depth of coverage was also almost 20-fold, sufficient to detect several thousand putative microsatellite loci and single nucleotide polymorphisms. This study constitutes an important step towards developing genomic resources with which to address consequential questions in pinniped ecology and evolution. It also supports an earlier but smaller study showing that skin tissue can be a rich source of expressed genes, with important implications for studying the genomics not only of marine mammals, but also more generally of species that cannot be destructively sampled. [ABSTRACT FROM AUTHOR]

The Antarctic fur seal, Arctocephalus gazella, in the eastern South Pacific Ocean, first reported on Hoste Island, Cape Horn in 1973, and then on the Juan Fernandez Archipelago in 1982 and 1983, was recorded again in October and December 2009 on the southern coast of Chile. Three different individuals were seen simultaneously on a single day at Punta Dungenes, Magellan Strait, and a fourth individual was sighted at the northeastern coast of Almirantazgo Sound, Tierra del Fuego. These records represent the first sightings of live Arctocephalus gazella in southern Chile. Although it is difficult to establish both their origin and rationale for dispersion outside of their distribution range, the substantial breeding population recovery in South Georgia and food shortages during the breeding and post-breeding season are suggested as possible explanations. [ABSTRACT FROM AUTHOR]

Abstract: The use of intrinsic biomarkers to infer the foraging ecology of marine predators has become a common alternative to traditional methods of estimating diets and foraging behavior. In this study we examined the ability of the stable isotope analysis (δ15N and δ13C) of milk to infer seasonal variations in the diets and foraging habitats of female Antarctic fur seals (Arctocephalus gazella) breeding at Cape Shirreff, Livingston Island, Antarctica. We found that the stable nitrogen values of lipid-free milk were correlated with seasonal changes in female diet composition during the lactation period identified from scat collections. While we could not fully quantifying female diets using isotopic analysis, evidence from both scat collections and stable isotope analysis suggest that Antarctic krill (Euphausia superba) remained a major dietary item throughout lactation. In addition, these two methods independently highlighted the increasing importance of fish and squid in the diets of females as the season progresses. Furthermore, the isotopic values of milk collected during the perinatal fast suggest that females may be foraging in high productivity areas north of the South Shetland Islands and consume a larger proportion of fish and/or squid prior to parturition. While more confirmatory studies are needed to refine these methods, our results suggests that the δ15N and δ13C values of lipid-free milk can be used as a proxy to describe the foraging ecology of female Antarctic fur seals prior to and across the lactation period. [ABSTRACT FROM AUTHOR]

Foragers show adaptive responses to changes within their environment, and such behavioural plasticity can be a significant driving force in speciation. We investigated how lactating Antarctic fur seals, Arctocephalus gazella, adapt their foraging within two contrasting ecosystems. Location and diving data were collected concurrently, between December 2003 and February 2004, from 43 seals at Bird Island, where krill, Euphausia superba, are the main prey, and 39 at Heard Island, where mostly fish are consumed. Seals at Heard Island were shorter and lighter than those at Bird Island and they spent longer at sea, dived more frequently and spent more time in the bottom phase of dives. Generalized additive mixed effects models showed that diving behaviours differed between the islands. Both populations exploited diel vertically migrating prey species but, on average, Heard Island seals dived deeper and exceeded their estimated aerobic dive limits. We propose that the recovery of the Heard Island population may be limited by the relative inaccessibility and scarcity of food, whereas at Bird Island, the presence of abundant krill resources helps sustain extremely high numbers of seals, even with increased intra- and inter-specific competition. Both populations of fur seals appear to be constrained by their physiological limits, in terms of their optimal diving behaviour. However, there does appear to be some flexibility in strategy at the level of trip with animals adjusting their time at sea and foraging effort, in order to maximize the rate of delivery of energy to their pups. [ABSTRACT FROM AUTHOR]

Although heterozygosity–fitness correlations (HFCs) are widely reported in the literature, most studies use too few markers to allow the proximate mechanisms to be convincingly resolved. Two competing hypotheses have been proposed: the general effect hypothesis, in which marker heterozygosity correlates with genome-wide heterozygosity and hence the inbreeding coefficient f, and the local effect hypothesis, in which one or more of the markers by chance exhibit associative overdominance. To explore the relative contributions of general and local effects in a free-ranging marine mammal population, we revisited a strong HFC found using 9 microsatellite loci for canine tooth size in 84 male Antarctic fur seals Arctocephalus gazella (Hoffman JI, Hanson N, Forcada J, Trathan PN, Amos W. 2010. Getting long in the tooth: a strong positive correlation between canine size and heterozygosity in the Antarctic fur seal Arctocephalus gazella. J Hered.). Increasing the number of markers to 76, we find that heterozygosity is uncorrelated across loci, indicating that inbred individuals are rare or absent. Similarly, while the HFC based on overall heterozygosity is lost, stochastic simulations indicate that when an HFC is due to inbreeding depression, increasing marker number invariably strengthens the HFC. Together these observations argue strongly that the original HFC was not due to inbreeding depression. In contrast, a subset of markers show individually significant effects, and these are nonrandomly distributed across the marker panel, being preferentially associated with markers cloned from other species. Using basic alignment search tool searches, we were able to locate 94% of loci to unique locations in the dog genome, but the local genes are functionally diverse, and the majority cannot be linked directly to growth. Our results suggest that inbreeding depression contributes little if at all to the relationship between heterozygosity and tooth size but that instead the primary mechanism involves associative overdominance. These findings contribute to a growing body of evidence suggesting that general effects are likely to be uncommon in natural populations. [ABSTRACT FROM PUBLISHER]

Most studies of heterozygosity–fitness correlations (HFCs) in natural populations relate to fitness traits expressed early in life, whereas traits that are often more difficult to measure such as longevity and adult body size remain elusive. Teeth provide a window on an individual's life history, allowing the reliable estimation of both age and body size. Consequently, we collected paired upper canine teeth and tissue samples from 84 adult male Antarctic fur seals Arctocephalus gazella that died of natural causes at Bird Island, South Georgia. Tooth size is a good predictor of skull and body size both within and across taxa, and we similarly find a strong relationship with skull size in our species. In turn, tooth size is itself predicted strongly by genetic heterozygosity estimated using 9 microsatellites. With only 9 loci, the exact mechanisms involved remain unclear, although the observed pattern appears largely attributable to a small subset of loci, suggesting that associative overdominance rather than inbreeding depression provides the proximate mechanism. In addition, locating these markers in the dog genome reveals proximity to genes involved with fat metabolism and growth. Our study illustrates how canine teeth, and potentially other structures such as tympano-periotic bone, waxy inner earplugs, or otoliths, may be used to explore links between genetic variation and important life-history traits in free-ranging vertebrate populations. [ABSTRACT FROM PUBLISHER]

The article presents research on the spatial and temporal distribution of foraging behavior of lactating Antarctic fur seals Arctocephalus gazella at Heard Island. The authors reveal that they used satellite telemetry and time-depth recorders. They indicate that deep dives were common among fur seals in the deeper shelf waters of the Kerguelen Plateau, which usually occur after sunset and before sunrise. They also observe that shallow dives were more common in slope waters. They explain that the diving strategies of fur seals are influenced by the location and time of foraging.

The study of scats of adult male Antarctic fur seals Arctocephalus gazella (AFS) revealed occasional frequent capture of penguins. Although AFS adult males have been occasionally reported to kill king penguins Aptenodytes patagonicus at the shore, here we report the first observations of at-sea predation by AFS on adult king penguins in the Crozet archipelago, southern Indian Ocean. During our 20 days survey, we observed 17 penguins attacked and either severely injured or killed and consumed. Only AFS adult males were seen catching king penguins successfully. Some adult females and sub-adults also attempted to catch penguins, either at sea or in land, and so did subantarctic fur seals Arctocephalus tropicalis individuals. Our results confirm the ability of fur seals to catch and predate large seabirds, even at sea. [ABSTRACT FROM AUTHOR]

We report two observations of adult male Antarctic fur seals, Arctocephalus gazella, preying on large octopods at subAntarctic Marion Island during July and August 2008. If Antarctic fur seals take cephalopods opportunistically, as previously suggested, our observations may be a rare event representing such opportunistic predation. [ABSTRACT FROM AUTHOR]

The number of Antarctic fur seals Arctocephalus gazella hauled out at Signy Island in the South Orkneys was monitored annually between 1977 and 2008. Over the study period seal abundance showed a tenfold increase, from a minimum of 1,643 seals in 1978 to a maximum of 21,303 in 1994. The majority of individuals observed were young adult males, likely to be migrants from South Georgia, with small numbers of female seals and only 65 pups recorded during the survey period. Variability in counts showed a similar pattern to Laurie Island, also in the South Orkneys archipelago, suggesting a similar annual immigration of seals to these two islands. The date of first seal arrival was correlated with the date of fast-ice breakout at Factory Cove, Signy Island, and years in which break out was exceptionally late (>21 December) corresponded with years of reduced seal abundance. While the presence of fast-ice during the early breeding season may currently inhibit the establishment of a major breeding population of fur seals at Signy Island, it is important that routine monitoring should continue, particularly in the light of current patterns of climate warming in the Antarctic. [ABSTRACT FROM AUTHOR]

Antarctic fur seals Arctocephalus gazella and macaroni penguins Eudyptes chrysolophus are the two main land-based krill Euphausia superba consumers in the northern Scotia Sea. Using a combination of concurrent at-sea (predator observations, net hauls and multi-frequency acoustics), and land-based (animal tracking and diet analysis) techniques, we examined variability in the foraging ecology of these sympatric top predators during the austral summer and autumn of 2004. Krill availability derived from acoustic surveys was low during summer, increasing in autumn. During the breeding season, krill occurred in 80% of fur seal diet samples, with fish remains in 37% of samples. Penguin diets contained the highest proportion of fish in over 20 years of routine monitoring (46% by mass; particularly the myctophid Electrona antarctica), with krill (33%) and amphipods ( Themisto gaudichaudii; 21%) also occurring. When constrained by the need to return and feed their offspring both predator species foraged to the northwest of South Georgia, consistent with an area of high macrozooplankton biomass, but fur seals were apparently more successful at exploiting krill. When unconstrained by chick-rearing (during March) penguins foraged close to the Shag Rocks shelf-break, probably exploiting the high daytime biomass of fish in this area. Penguins and seals are able to respond differently to periods of reduced krill abundance (in terms of variability in diet and foraging behaviour), without detriment to the breeding success of either species. This highlights the importance of myctophid fish as an alternative trophic pathway for land-based predators in the Scotia Sea ecosystem. [ABSTRACT FROM AUTHOR]

The onshore distributions and the abundances of Antarctic fur seals Arctocephalus gazella and Subantarctic fur seals A. tropicalis were determined at Prince Edward Island during 16-20 December 2008. This repeats a survey conducted in December 2001 and extends the area surveyed to include the entire south-west coast of Prince Edward Island. Of the two colonies of Antarctic fur seals, the colony among Subantarctic fur seals north of Boggel Beach remained small, with increased numbers of Subantarctic fur seals and putative hybrids. The other Antarctic fur seal breeding colony at Penguin Beach remained free of Subantarctic fur seals and had expanded at a mean intrinsic rate of natural increase of 11.4% per year from 2001. With an estimated 810 pups, the Antarctic fur seal is still in the rapid recolonisation phase of population growth. The distribution of the more widespread and abundant Subantarctic fur seals also had increased, with several new breeding colonies along the east coast and one at Kent Crater on the west coast. The annual pup production was conservatively estimated at 14 130 pups. The mean intrinsic rate of natural increase has declined to -0.3% per year over the last seven years, compared to the 9.3% per year between 1987/1988 and 2001/2002, and the population is in the mature phase of population growth. [ABSTRACT FROM AUTHOR]

Nine dinucelotide microsatellite loci were developed in the Antarctic fur seal Arctocephalus gazella. Each locus possessed between 4 and 9 alleles in a sample of twenty individuals sampled from Bird Island, South Georgia, and expected heterozygosity ranged from 0.52 to 0.84. All but one of the loci conformed to Hardy-Weinberg equilibrium and no evidence was found for genotypic disequilibrium. Additionally, all of the loci successfully cross-amplified in the South American fur seal Arctocephalus australis, the New Zealand fur seal Arctocephalus forsteri and the Steller's sea lion Eumetopias jubatus, and six also yielded products in the more distantly related harbour seal Phoca vitulina and walrus Odobenus rosmarus. These loci should prove useful for studies of the population genetics of Antarctic fur seals and other important otariid species. [ABSTRACT FROM AUTHOR]

We investigated the variation of Antarctic fur seal ( Arctocephalus gazella) pup growth rates in response to sex, breeding season and duration of both maternal foraging trip and attendance bouts. Data were collected during five consecutive rearing seasons at Cape Shirreff, the most important breeding colony in the South Shetland Islands, Antarctica. Our results showed significant interannual and sexual variations in pup growth rates. Male pups grew significantly faster than female pups during 2000, 2001, 2002 and 2004 seasons, whilst during 2003 no difference was found. The interannual variation in pup growth rates was correlated with the interannual fluctuation in maternal foraging trip and attendance bouts. There was a significant effect of pup sex and maternal foraging trip duration on pup growth rates, which varied between years having foraging trip duration a major effect during 2003, when females spent more time at sea and interestingly on that year there were no sexual differences in pup growth rates. The effect of attendance bout on pup growth rates was not significant. Diet analysis showed that Antarctic krill ( Euphausia superba) was the most frequent prey item during the study period. Analysis of krill size distribution showed a significant difference in krill length, during 2003, when A. gazella preyed upon the smallest sizes of krill. In this study, sex was the most important factor on pup growth rates, but when prey availability seemed more limited, there are longer foraging trips and shorter attendance bouts the sex factor became less significant. [ABSTRACT FROM AUTHOR]

Twinning in natural pinniped populations is often inferred from observations of suckling behavior, but this approach has been criticized because nonfilial nursing occurs at high frequencies in many seal species. Consequently, we used 9 highly polymorphic microsatellite markers to examine the parentage of 11 putative pairs of twins in Antarctic fur seals (Arctocephalus gazella) breeding at Bird Island, South Georgia. Only 3 pairs (27%) were found to be genuine twins, indicating that suckling observations are an unreliable means of identifying twins in this species. All of the twins were female; 1 pair was monozygotic and the other 2 were dizygotic. Using a strict exclusion approach, paternity was assigned to the monozygotic but not the dizygotic twins. However, likelihood tests revealed that, of the latter, 1 pair was significantly more likely to be full siblings against the null of half sibship suggesting shared paternity, whereas the other pair was more likely to be half siblings against the null of full sibship indicating probable multiple paternity. Our results provide novel insights into the reproductive ecology of fur seals and also support an earlier study showing that molecular genetic analysis can provide an effective means of validating field observations of pinniped twins. [ABSTRACT FROM AUTHOR]

We document five cases of unusual colouration in Antarctic fur seals, Arctocephalus gazella, at Cape Shirreff, Livingston Island, from 1991–1992 to 2005–2006 austral summer seasons. This is the first time that these colour patterns have been reported for this species. These included four rare light coloured animals and one piebald individual. The incidence of this atypical colouring was low and the lack of resightings in previous and subsequent seasons suggests that these morphs are not common in Antarctic fur seals. Although the causes of these atypical light colour patterns are uncertain the subject is interesting for study and more observations on these atypical colourations are required for a proper assessment of the ecological and physiological implications of this condition in otariids can be conducted in the future. [ABSTRACT FROM AUTHOR]

The diet of non-breeding male Antarctic fur seals, Arctocephalus gazella, was investigated at Stranger Point, King George Island, through the analysis of scats during three consecutive summer seasons (1996, 1997, 1998). Overall, fish and krill were the most frequent prey occurring, respectively, in an average of 82.9% and 78.8% of samples ( n = 131), followed by penguins (22.8%) and cephalopods (17.8%). Myctophids constituted almost 90% of the fish predated, with Electrona antarctica and Gymnoscopelus nicholsi being the most abundant and frequent species consumed. All fish taxa identified were krill feeding species suggesting that seals foraged mainly on a krill and a fish community associated with krill aggregations. However, a seasonal change was observed in the relative proportions of the different prey taxa, with a progressive decrease with time in the occurrence of krill and a concomitant increase of fish, penguins and squid. Possible influence of the strong 1997/98 ENSO event is discussed. [ABSTRACT FROM AUTHOR]

The prey of Antarctic fur seals, Arctocephalus gazella, was investigated through scat analysis at Marion Island from 1996 until 2000. A total of 25 different prey species were identified from scats, of which 21 were fish, 1 crustacean and 3 cephalopods. Fish were by far the main prey item, occurring in 96.1% of samples, followed by crustaceans (2.7%) and cephalopods (1.2%). Fishes from the family Myctophidae ( Gymnoscopelus piabilis, Electrona carlsbergi, G. fraseri and E. subaspera) were the most abundant prey (97.2%) every year, while those from the families Notothenididae, Paralepididae, Notosudidae, Microstomatidae and Gempylidae were present in small numbers. G. piabilis, E. carlsbergi, E. subaspera and G. nicholsi contributed the most in terms of biomass to the diet. Significant seasonal differences existed in the diet when comparing summer and winter. G. piabilis, K. anderssoni, P. bolini and P. choriodon dominated in summer as opposed to E. carlsbergi, E. subaspera, G. fraseri and G. nicholsi that dominated in winter. The fish varied in size and mass, from the small K. anderssoni to the large Paranotothenia magellanica. Cephalopods and the crustacean Nauticaris marionis, in very low numbers and in winter, appeared in the scats, but not in all years of study. Unidentified penguin remains rarely turned up in scats. [ABSTRACT FROM AUTHOR]

Antarctic fur seals show extreme sexual size dimorphism and their breeding strategies place very different constraints on the behaviour of males and females. Whereas the foraging behaviour of lactating females is well studied, very little is known about males. We tracked 14 adult males during a period when they are observed around South Georgia to compare their behaviour with that of 41 lactating females tracked from the same island. There was significant spatial segregation between the sexes in both the horizontal and the vertical dimensions. Female fur seals foraged near the surface, mostly at night, concentrating their efforts at the shelf break and in deeper off-shelf waters. Males foraged closer to the breeding beaches and their time at sea was concentrated in waters over the continental shelf. Males dived significantly deeper and longer and spent longer in the bottom phase of a dive than females. Females dived mostly at night, whereas males dived much more during the day and overall had greater variability in their behaviour within a trip. Sex was a better predictor of dive durations than mass when depth was considered. Categorizing dives into three types showed that males often foraged on or near the bottom, a behaviour not observed in females. We suggest that body size dimorphism causes sexual differences in foraging behaviour (e.g. dive depth, duration, etc.) but how this is manifested (i.e. trip distance, foraging location) is dependent on the local environment and the related prey resources. [Copyright &y& Elsevier]

A leucistic immature male Antarctic fur seal, Arctocephalus gazella, was sighted at Marion Island in April 2006; the first such sighting in three decades of extensive field presence of biologists at this locality. The same animal returned to the island in July/August 2006, when it was moulting, and was marked with unique flipper tags, after which it was sighted in early October 2006 again. Considering that individuals of this species are capable of moving far from their natal population, we suggest that the animal could likely have come from South Georgia, where this colour morph is relatively common. [ABSTRACT FROM AUTHOR]

Modelling fur seal populations requires the accurate assessment of demographic parameters such as age-specific mortality. Owing to the highly variable mortality rates that pups are subject to, mortality of this age class is perhaps the most important factor determining the number of surviving individuals within each cohort. Early pup mortality,sex ratio and median pupping date were determined for sympatric populations of Subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) at Marion Island, Southern Ocean. Mortality for this species was density dependent, varying from 0.8% at low density sites to 10.9% at high density sites. More accurate methods employed at low-density sites showed a substantially higher pup mortality at three weeks of 1.3-3.4% for Subantarctic fur seals. The same method yielded a mortality estimate at four weeks of age of 1.1-5.1% for Antarctic fur seals. Despite the underestimate inherent in island-wide counts for Subantarctic fur seals, these estimates are still useful for observing temporal and spatial patterns. Sex ratios were at parity for newborns of both species. The sex ratio of eight-week- old Subantarctic fur seal pups was also at parity, which is unusual for fur seal populations. The median pupping dates determined for Subantarctic fur seals and Antarctic fur seals did not differ substantially from previous estimates. [ABSTRACT FROM AUTHOR]

Abstract: Entanglements of Antarctic fur seals Arctocephalus gazella were recorded during four summers from 1996 to 2002 at the subantarctic island, Bouvetøya. Rates of entanglement varied between 0.024% and 0.059%. These rates are low for a pinniped population and might be because of the geographic isolation of the haulout site. An apparent decrease in the levels of entanglement over the course of the study was likely due, at least in part, to the removal of entanglements by observers. At least two-thirds of entangling materials were generated by fishery sources. Since there is no known local source of anthropogenic marine pollution, seals become entangled either in waters distant from the island, or when materials drift into local waters. Significantly more subadults were found entangled than expected from the postulated population age class distribution. [Copyright &y& Elsevier]

Counts at Marion Island during the 2003/04 breeding season indicated a pup production of 16 045 for Subantarctic fur seals, Arctocephalus tropicalis, and 759 for the sympatric population of Antarctic fur seal, A. gazella. While the mean annual rate of increase of 5.2% for the Subantarctic fur seal population at Marion Island for the period 1994/95-2003/04 was approximately half of that recorded between 1951 and the late 1980s, that of the Antarctic fur seal population for the same period continues to be high (17.0%). We suggest that the dissimilarity in population growth between the two species is due to differences in the availability of preferred terrestrial habitat, since their diets are very similar. Together with the neighbouring Prince Edward Island, this archipelago supports a population of approximately 150 000 Subantarctic fur seals, which has grown at a mean annual rate of 5.3% over the past 15 years. The population of Antarctic fur seals numbers approximately 5800, and has grown at a mean annual rate of 14.8% over the past 21 years. While there appears to be limited opportunity for heterospecific mating, low levels of hybridization continue. [ABSTRACT FROM AUTHOR]

Microsatellite genotyping errors will be present in all but the smallest data sets and have the potential to undermine the conclusions of most downstream analyses. Despite this, little rigorous effort has been made to quantify the size of the problem and to identify the commonest sources of error. Here, we use a large data set comprising almost 2000 Antarctic fur sealsArctocephalus gazellagenotyped at nine hypervariable microsatellite loci to explore error detection methods, common sources of error and the consequences of errors on paternal exclusion. We found good concordance among a range of contrasting approaches to error-rate estimation, our range being 0.0013 to 0.0074 per single locus PCR (polymerase chain reaction). The best approach probably involves blind repeat-genotyping, but this is also the most labour-intensive. We show that several other approaches are also effective at detecting errors, although the most convenient alternative, namely mother–offspring comparisons, yielded the lowest estimate of the error rate. In total, we found 75 errors, emphasizing their ubiquitous presence. The most common errors involved the misinterpretation of allele banding patterns (n = 60, 80%) and of these, over a third (n = 22, 36.7%) were due to confusion between homozygote and adjacent allele heterozygote genotypes. A specific test for whether a data set contains the expected number of adjacent allele heterozygotes could provide a useful tool with which workers can assess the likely size of the problem. Error rates are also positively correlated with both locus polymorphism and product size, again indicating aspects where extra effort at error reduction should be directed. Finally, we conducted simulations to explore the potential impact of genotyping errors on paternity exclusion. Error rates as low as 0.01 per allele resulted in a rate of false paternity exclusion exceeding 20%. Errors also led to reduced estimates of male reproductive skew and increases in the numbers of pups that matched more than one candidate male. Because even modest error rates can be strongly influential, we recommend that error rates should be routinely published and that researchers make an attempt to calculate how robust their analyses are to errors. [ABSTRACT FROM AUTHOR]

This study examined the recovery process of an Antarctic fur-seal population, starting from minimal numbers after commercial exploitation to the now largest breeding population in the South Shetland Archipelago, Cape Shirreff and San Telmo Islets. It used direct census data from 20 breeding seasons (including 11 consecutive years) that spanned over 45 years. Since early population estimates, pup production increased at an intrinsic rate of ca. 20% which, during the last decade, dramatically slowed to 4.6%. The population-change trajectory is currently converging into a tightly bounded oscillation around an apparent equilibrium (carrying capacity), which is an order of magnitude lower than those levels before exploitation began. This pattern suggests the onset of an alternative stable state and highlights the far-reaching implications of strong and large-scale perturbations on marine systems. [ABSTRACT FROM AUTHOR]

This study investigated the degree to which the behavior of a predator in the marine environment can be used to indicate the availability of prey. It examined this in Antarctic fur seals (Arctocephalus gazella) feeding on krill, with a view to understanding how behavioral choices could lead to a nonlinear functional response. The study showed how fur seals adjusted their time budgets to maximize the mean rate of energy intake in response to varying prey abundance. The behavioral indicator of prey abundance was the amount of time spent by fur seals at the bottom of dives after adjustment for dive depth. This indicator was well correlated with independent measures of prey abundance. The indicator was calibrated in terms of net rate of energy intake from information about energy expenditures in Antarctic fur seals and was used within the framework of optimal foraging theory to examine how female fur seals organized their foraging activity within and between bouts. Foraging in Antarctic fur seals conformed to many of the predictions from energy rate-maximizing behavior. For example, the apparent net rate of energy intake by fur seals declined with time spent in a patch, and the rate of energy intake on leaving a patch declined as apparent food availability in the environment declined. In addition, the time spent in patches increased as apparent food availability declined. Antarctic fur seals were able to adjust their behavior to track highly variable prey distributions and densities. The simple decision about when to leave a patch in relation to current environmental prey availability appears to be responsible for allowing fur seals to maintain saturation of the foraging rate as food density declines. [ABSTRACT FROM AUTHOR]

The period of maternal dependence is a time during which mammalian infants must optimize both their growth and the development of behavioural skills in order to successfully meet the demands of independent living. The rate and duration of maternal provisioning, post weaning food availability and climatic conditions are all factors likely to influence the growth strategies of infants. While numerous studies have documented differences in growth strategies at high taxonomic levels, few have investigated those of closely related species inhabiting similar environments. The present study examined the body composition, metabolism and indices of physiological development in pups of Antarctic fur seals (Arctocephalus gazella) and subantarctic fur seals (Arctocephalus tropicalis), congeneric species with different weaning ages (4 months and 10 months, respectively), during their overlap in lactation at a sympatric breeding site in the Iles Crozet. Body lipid reserves in pre-moult pups were significantly greater (t[SUB28]=2.73, P<0.01) in subantarctic (26%) than Antarctic fur seals (22%). Antarctic fur seal pups, however, had significantly higher (t[SUB26]=3.82, P<0.001) in-air resting metabolic rates (RMR; 17.1 ± 0.6 mi O[SUB2] kg[SUP-1] min[SUP-1] than subantarctic fur seal pups (14.1 ± 0.5 mi O[SUB2] kg[SUP-1] min[SUP-1]). While in-water standard metabolic rate (SMR; 22.9±2.5 ml O[SUB2] kg[SUP-1] min[SUP-1) was greater than in-air RMR for Antarctic fur seal pups (t[SUB9] = 2.59, P<0.03), there were no significant differences between in-air RMR and in-water SMR for subantarctic fur seal pups (t[SUB12] = 0.82, P > 0.4), although this is unlikely to reflect a greater ability for pre-moult pups of the latter species to thermoregulate in water. [ABSTRACT FROM AUTHOR]

Attendance patterns of female Antarctic fur seals (Arctocephalus gazella) at Marion Island were studied during the 1998 to 2000 lactation periods, and compared with those recorded in 1987. Over the same period, body mass of pups close to the age of weaning was estimated to obtain an index of pup growth. Foraging trips were longest and pup growth was poorest in 1999, a year with unusually high sea-surface temperatures around Marion Island. Pup growth was greatest during the year with the shortest foraging trips. Foraging trip durations were longer than in 1987, but more years of study are required to investigate the relationship of attendance patterns and pup growth with changing population size and oceanographic conditions. [ABSTRACT FROM AUTHOR]

An experiment involving the supplementary feeding of pups was conducted on Antarctic fur seals to investigate the factors influencing maternal foraging-attendance cycles and the differential use of nutritional resources for growth, maintenance and storage by pups. For 40% of the lactation period, male pups were given a supplement mimicking the chemical composition of Antarctic fur seal milk at a dose equivalent to 35% of the normal mass-specific milk energy intake for the species. Milk consumption, body composition and growth rates were monitored during and after the supplementary feeding period and maternal foraging-attendance cycles were monitored throughout lactation. During the supplementary feeding period, treatment pups ( n=8) grew 32% faster and deposited greater adipose tissue stores than controls ( n=8) but consumed the same amount of maternal-delivered milk. When supplementary feeding was stopped (timed to coincide with peak maternal milk yield in this species), treatment pups lost mass whereas control group pups continued to grow. Treatment pups weaned at a younger age (109 days) than control pups (116 days) but at the same mass (13 kg). Maternal attendance durations did not differ between the treatment and control groups throughout lactation. However, mothers of treatment pups had significantly shorter foraging trip durations (3.74 days) than mothers of control pups (4.74 days) during the period of supplementary feeding (there were no significant differences throughout the rest of lactation). These findings are in accordance with predictions of a marginal-value model of fur seal lactation behaviour. [ABSTRACT FROM AUTHOR]

The article presents a study which aims to develop a model of the consequences of Antarctic krill harvesting on Antarctic fur seals. A krill-predator modeling procedure which assess the impact of krill harvesting on krill predator populations and the stochastic calculations taking account of the interannual fluctuations in the abundance of the krill are offered. Results which indicate that the modeling approach would lead to a depletion of the Antarctic fur seal population is explained.

A leucistic Antarctic fur seal ( Arctocephalus gazella) pup was born on subantarctic Marion Island during the austral summer of 2010/2011. This is the first confirmed record of a leucistic fur seal pup born outside the Scotia Arc islands. Additionally, we report on a leucistic adult female Antarctic fur seal producing typical black pups for five non-consecutive summers on Marion Island. The birth of a leucistic pup, together with the multiple black pups produced by the leucistic female, suggests that the recessive genes responsible for leucism are now entrenched within the Marion Island population. [ABSTRACT FROM AUTHOR]