These datasets and accompanying syntheses provide a greater understanding of fundamental ecosystem processes in the Southern Ocean, support modelling of predator distributions under future climate scenarios and create inputs that can be incorporated into decision making processes by management authorities. In this data paper, we present the compiled tracking data from research groups that have worked in the Antarctic since the 1990s. The data are publicly available through biodiversity.aq and the Ocean Biogeographic Information System. The archive includes tracking data from over 70 contributors across 12 national Antarctic programs, and includes data from 17 predator species, 4060 individual animals, and over 2.9 million observed locations.Scientific Data | (2020) 7:94 | https://doi.org/10.1038/s41597-020-0406-x www.nature.com/scientificdata www.nature.com/scientificdata/ circum-Antarctic synthesis yet exists that crosses species boundaries. This deficiency prompted the Expert Group on Birds and Marine Mammals (EG-BAMM) and the Expert Group on Antarctic Biodiversity Informatics (EGABI) of the Scientific Committee on Antarctic Research (SCAR; www.scar.org) to initiate in 2010 the Retrospective Analysis of Antarctic Tracking Data (RAATD). RAATD aims to advance our understanding of fundamental and applied questions in a data-driven way, matching research priorities already identified by the SCAR Horizon Scan 9,21 and key questions in animal movement ecology 22 . For these reasons, we worked on the collation, validation and preparation of tracking data collected south of 45 °S. Data from over seventy contributors (Data Contacts and Citations 23 ) were collated. This database includes information from seventeen predator species, 4,060 individuals and over 2.9 million at-sea locations. To exploit this unique dataset, RAATD is undertaking a multi-species assessment of habitat use for higher predators in the Southern Ocean 24 .RAATD will provide a greater understanding of predator distributions under varying climate regimes, and provide outputs that can inform spatial management and planning decisions by management authorities such as the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR; www.ccamlr.org). Our synopsis and analysis of multi-predator tracking data will also highlight regional or seasonal data-gaps.Scientific Data | (2020) 7:94 | https://doi.

Seals that survived their first year were on average 2% and 4% heavier at birth and at weaning than the "non-survivors". First year survival rates calculated for weaners over 135 kg weaning masses showed these weaners had hgher survival rates than those less than 95 kg at weaning (71.55% and 54.15% respectively). Heavy weaners had greater fat reserves than light weaners and gained relatively more mass during lactation. Size, and therefore condition at weaning, influences first year survival.

Summary 1.To estimate concurrent age-specific survival for southern elephant seals at Macquarie and Marion islands, seals were marked from 1993 to 1997 in the first 3 weeks of life and resighted (recaptured) on return to their natal islands (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001). These recaptures formed the basis for the survival analysis in the mark-recapture program  . Weaning masses were collected at each location. 2. Recapture probabilities were ( = 376·480, P < 0·0001) higher at Marion Island than at Macquarie Island. There are two possible reasons: (1) the population at Marion Island is smaller and less dense than at Macquarie Island and (2) seals hauled out along a smaller section of the coast at Marion Island than at Macquarie Island, which: (1) facilitates the detection and individual identification of seals and (2) increases access to hauled out seals. 3. Age-specific survival estimates (corrected for preweaning mortality and tag loss) differed ( = 22·264, P < 0·05) at the two islands and were consistently higher at Macquarie Island. The survival estimates for male and female seals were different at Macquarie Island ( = 34·657, P < 0·0001) and Marion Island ( = 20·373, P = 0·002). Female survival estimates were higher than male survival estimates. The combined survival estimates for juvenile seals (1-3 years) differed between islands but survival of older seals (4-6 years) did not. The inclusion of gender in the survival models did not improve model performance and hence male and female estimates were considered jointly. 4. The mean wean masses of male and female seals combined from 1993 to 1998 were not different between islands (T 6837 = 1·169, P = 0·242). At Macquarie Island the mean annual wean mass was 118·8 kg (SD = 27·2, n = 6504) while at Marion Island it was 120·6 kg (SD = 24·7, n = 335). 5. The mean age at first breeding was different ( P < 0·001) at the two island populations. At Macquarie Island the mean age of first breeding was 4·68 years, and at Marion Island it was 3·95 years. More ( = 67·39, P < 0·0001) 3-year-old females breed at Marion Island (28·7%) than at Macquarie Island (1·2%) and the proportion of seals that had bred at least once by age 7 was greater at Marion Island than at Macquarie Island. 6. We conclude that the observed decreases in elephant seal numbers between the 1950s and 1990s in the Pacific and Indian Ocean sectors were driven principally by resource limitation in the Southern Ocean. A conglomerate of factors including local predation by killer whales and intraspecific resource competition is postulated as a cause for the inter-island (regional) differences in population trends. It appears that more resources are available per capita to the Marion Island population than are available to the Macquarie Island population.

Abstract. In the Southern Ocean, wide-ranging predators offer the opportunity to quantify how animals respond to differences in the environment because their behavior and population trends are an integrated signal of prevailing conditions within multiple marine habitats. Southern elephant seals in particular, can provide useful insights due to their circumpolar distribution, their long and distant migrations and their performance of extended bouts of deep diving. Furthermore, across their range, elephant seal populations have very different population trends. In this study, we present a data set from the International Polar Year project; Marine Mammals Exploring the Oceans Pole to Pole for southern elephant seals, in which a large number of instruments (N = 287) deployed on animals, encompassing a broad circum-Antarctic geographic extent, collected in situ ocean data and at-sea foraging metrics that explicitly link foraging behavior and habitat structure in time and space. Broadly speaking, the seals foraged in two habitats, the relatively shallow waters of the Antarctic continental shelf and the Kerguelen Plateau and deep open water regions. Animals of both sexes were more likely to exhibit area-restricted search (ARS) behavior rather than transit in shelf habitats. While Antarctic shelf waters can be regarded as prime habitat for both sexes, female seals tend to move northwards with the advance of sea ice in the late autumn or early winter. The water masses used by the seals also influenced their behavioral mode, with female ARS behavior being most likely in modified Circumpolar Deepwater or northerly Modified Shelf Water, both of which tend to be associated with the outer reaches of the Antarctic Continental Shelf. The combined effects of (1) the differing habitat quality, (2) differing responses to encroaching ice as the winter progresses among colonies, (3) differing distances between breeding and haul-out sites and high quality habitats, and (4) differing long-term regional trends in sea ice extent can explain the differing population trends observed among elephant seal colonies.

Commercial sealing in the 18th and 19th centuries had a major impact on the Antarctic and subantarctic fur seal populations (Arctocephalus gazella and A. tropicalis) in the Southern Ocean. The intensive and unrestricted nature of the industry ensured substantial reductions in population sizes and resulted in both species becoming locally extinct at some sites. However, both species are continuing to recover, through the recolonization of islands across their former range and increasing population size. This study investigated the extent and pattern of genetic variation in each species to examine the hypothesis that higher levels of historic sealing in A. gazella have resulted in a greater loss of genetic variability and population structure compared with A. tropicalis. A 316-bp section of the mitochondrial control region was sequenced and revealed nucleotide diversities of 3.2% and 4.8% for A. gazella and A. tropicalis, respectively. There was no geographical distribution of lineages observed within either species, although the respective PhiST values of 0.074 and 0.19 were significantly greater than zero. These data indicate low levels of population structure in A. gazella and relatively high levels in A. tropicalis. Additional samples screened with restriction endonucleases were incorporated, and the distribution of restriction fragment length polymorphism (RFLP) and sequence haplotypes were examined to identify the main source populations of newly recolonized islands. For A. tropicalis, the data suggest that Macquarie Island and Iles Crozet were probably recolonized by females from Marion Island, and to a lesser extent Ile Amsterdam. Although there was less population structure within A. gazella, there were two geographical regions identified: a western region containing the populations of South Georgia and Bouvetoya, which were the probable sources for populations at Marion, the South Shetland and Heard Islands; and an eastern region containing the panmictic populations of Iles Kerguelen and Macquarie Island. The latter region may be a result of a pronounced founder effect, or represent a remnant population that survived sealing at Iles Kerguelen.