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As important marine mesopredators and sensitive indicators of Antarctic ecosystem change, penguins have been a major focus of long-term biological research in the Antarctic. However, the vast majority of such studies have been constrained by logistics and relate mostly to the temporal dynamics of individual breeding populations from which regional trends have been inferred, often without regard for the complex spatial heterogeneity of population processes and the underlying environmental conditions. Integrating diverse census data from 70 breeding sites across 31 years in a robust, hierarchical analysis, we find that trends from intensely studied populations may poorly reflect regional dynamics and confuse interpretation of environmental drivers. Results from integrated analyses confirm that Pygoscelis adeliae (Adélie Penguins) are decreasing at almost all locations on the Antarctic Peninsula. Results also resolve previously contradictory studies and unambiguously establish that P. antarctica (Chinstrap Penguins), thought to benefit from decreasing sea ice, are instead declining regionally. In contrast, another open-water species, P. papua (Gentoo Penguin), is increasing in abundance and expanding southward. These disparate population trends accord with recent mechanistic hypotheses of biological change in the Southern Ocean and highlight limitations of the influential but oversimplified \"sea ice\" hypothesis. Aggregating population data at the regional scale also allows us to quantify rates of regional population change in a way not previously possible.

Fast climate changes in the western Antarctic Peninsula are reducing krill density, which along with increased fishing activities in recent decades, may have had synergistic effects on penguin populations. We tested that assumption by crossing data on fishing activities and Southern Annular Mode (an indicator of climate change in Antarctica) with penguin population data. Increases in fishing catch during the non-breeding period were likely to result in impacts on both chinstrap (Pygoscelis antarcticus) and gentoo (P. papua) populations. Catches and climate change together elevated the probability of negative population growth rates: very high fishing catch on years with warm winters and low sea ice (associated with negative Southern Annular Mode values) implied a decrease in population size in the following year. The current management of krill fishery in the Southern Ocean takes into account an arbitrary and fixed catch limit that does not reflect the variability of the krill population under effects of climate change, therefore affecting penguin populations when the environmental conditions were not favorable.

Aim To predict the at‐sea distribution of chinstrap penguins across the South Orkney Islands and to quantify the overlap with the Southern Ocean krill fishery. Location South Orkney Islands, Antarctica. Methods Penguins from four colonies across the South Orkney Islands were tracked using global positioning systems (GPSs) and time depth recorders (TDRs). Relationships between a variety of environmental and geometric variables and the at‐sea distribution of penguins were investigated using general additive models for the three main phases of the breeding season. Subsequently, the final models were extrapolated across the South Orkney archipelago to predict the at‐sea distribution of penguins from colonies where no tracking data are available. Finally, the overlap between areas used by chinstrap penguins and the krill fishery was quantified. Results The foraging distribution of chinstrap penguins can be predicted using two simple and static variables: the distance from the colony and the direction of travel towards the shelf‐edge, while avoiding high densities of Pygoscelis penguins from other colonies. Additionally, we find that the chinstrap penguins breeding on the South Orkney Islands use areas which overlap with frequently used krill fishing areas and that this overlap is most prominent during the brood and crèche phases of the breeding season. Main conclusions This is the first step in understanding the potential impacts of the krill fishery, for all colonies including those where no empirical tracking data are available. However, with the available data, it is not currently possible to infer an impact of the krill fisheries on penguins. With this in mind, we recommend the implementation of monitoring schemes to investigate the effects of prey depletion on predator populations and to ensure that management continues to follow a precautionary approach and is addressed at spatial and temporal scales relevant to ecosystem operation.

Elephant Island sits on the front lines of ecological change in the Scotia Arc region, but most of the island has remained unsurveyed for nearly 50 years. As a result, there has been no way to establish whether changes on the island reflect those to the south along the Western Antarctic Peninsula or whether, in contrast, populations have remained stable, as on the more northerly South Sandwich Islands. At the core of the Chinstrap Penguin (Pygoscelis antarcticus) breeding range, at the southern edge of the Macaroni Penguin (Eudyptes chrysolophus) and (very recently) King Penguin (Aptenodytes patagonicus) ranges, at the northern limit of the Adélie Penguin (Pygoscelis adeliae) range, and in an area where Gentoo Penguin (Pygoscelis papua) populations are expanding southward, Elephant Island is situated at a unique ecological crossroads, hosting both sub-Antarctic and Antarctic seabirds, the former of which may be responding favorably to the very same climate changes that imperil the latter. Fortunately, an exhaustive census of the island in 1970–71 provides a rigorous baseline against which to document ecological change. Here, we report on the first complete survey of the island since 1970–71, conducted from January 9–20, 2020. Results indicate a decrease in Chinstrap Penguin populations, a doubling of Gentoo Penguins, a stable number of Macaroni Penguins, continuing occupancy by a few Adélie Penguins, and evidence of King Penguin breeding expansion. Our findings demonstrate that Elephant Island’s seabird community has changed dramatically over the past five decades and that these changes appear to be ongoing.

Marine predators are integral to the functioning of marine ecosystems, and their consumption requirements should be integrated into ecosystem-based management policies. However, estimating prey consumption in diving marine predators requires innovative methods as predator–prey interactions are rarely observable. We developed a novel method, validated by animal-borne video, that uses tri-axial acceleration and depth data to quantify prey capture rates in chinstrap penguins ( Pygoscelis antarctica ). These penguins are important consumers of Antarctic krill ( Euphausia superba ), a commercially harvested crustacean central to the Southern Ocean food web. We collected a large data set ( n = 41 individuals) comprising overlapping video, accelerometer and depth data from foraging penguins. Prey captures were manually identified in videos, and those observations were used in supervised training of two deep learning neural networks (convolutional neural network (CNN) and V-Net). Although the CNN and V-Net architectures and input data pipelines differed, both trained models were able to predict prey captures from new acceleration and depth data (linear regression slope of predictions against video-observed prey captures = 1.13; R 2 ≈ 0.86). Our results illustrate that deep learning algorithms offer a means to process the large quantities of data generated by contemporary bio-logging sensors to robustly estimate prey capture events in diving marine predators.

Assessing the biological characteristics of high-latitude winter habitats of migratory marine predators is necessary for conservation and management in Antarctica. Tracking data from chinstrap penguins ( Pygoscelis antarcticus ) and southern elephant seals ( Mirounga leonina ), key Antarctic predators with different diets and foraging habits, indicate that some individuals undertake long-distance winter migrations to remote regions south of 55°S and west of 120°W. There, localized hotspots of increased use, with general reductions in mean swimming speed are evident. Presumably, these predators migrate to areas with higher productivity, however the marine productivity in this remote region during winter is unknown. Light limitation during winter precludes the use of optical satellite data to characterize marine productivity here, but biogeochemical-Argo floats can provide year-round chlorophyll data. These data inform the Biogeochemical Southern Ocean State Estimate (B-SOSE), which provides year-round estimates of marine productivity. The predator hotspots overlap with two areas with year-round elevated surface chlorophyll levels predicted by B-SOSE, consistent with previous studies indicating enhanced mixing in those areas. Our results suggest that persistent areas of elevated chlorophyll centered near 160°W and 120°W near the boundaries of the Ross Gyre and the southern boundary of the Antarctic Circumpolar Current support a productive food web capable of supporting the diverse foraging niches of pelagic species during winter.

Theory predicts that sympatric predators compete for food under conditions of limited resources. Competition would occur even within the same species, between neighboring populations, because of overlapping foraging habits. Thus, neighboring populations of the same species are hypothesized to face strong competition. To test the hypothesis that intra-specific competition is more intense than inter-specific competition owing to a lack of niche partitioning, we estimated the foraging area and diving depths of two colonial seabird species at two neighboring colonies. Using GPS and time-depth recorders, we tracked foraging space use of sympatric breeding Chinstrap and Gentoo penguins at Ardley Island (AI) and Narębski Point (NP) at King George Island, Antarctica. GPS tracks showed that there was a larger overlap in the foraging areas between the two species than within each species. In dive parameters, Gentoo penguins performed deeper and longer dives than Chinstrap penguins at the same colonies. At the colony level, Gentoo penguins from NP undertook deeper and longer dives than those at AI, whereas Chinstrap penguins did not show such intra-specific differences in dives. Stable isotope analysis of δ13C and δ15N isotopes in blood demonstrated both inter- and intra-specific differences. Both species of penguin at AI exhibited higher δ13C and δ15N values than those at NP, and in both locations, Gentoo penguins had higher δ13C and lower δ15N values than Chinstrap penguins. Isotopic niches showed that there were lower inter-specific overlaps than intra-specific overlaps. This suggests that, despite the low intra-specific spatial overlap, diets of conspecifics from different colonies remained more similar, resulting in the higher isotopic niche overlaps. Collectively, our results support the hypothesis that intra-specific competition is higher than inter-specific competition, leading to spatial segregation of the neighboring populations of the same species.

In many seabirds, individuals abstain from eating during the moult period. Penguins have an intense moult that lasts for weeks, during which they are confined to land. Despite the importance for survival, it is still unclear how the faecal microbiota of Antarctic penguins changes in response to the moult fast. Here, we investigated the faecal microbiota of chinstrap (Pygoscelis antarcticus) and gentoo penguins (Pygoscelis papua) on King George Island, Antarctica. The bacterial community compositions during the feeding and moulting stages were compared for both species using bacterial 16S rRNA gene amplicon on an Illumina MiSeq platform. Our results showed that the moult fast altered the bacterial community structures in both penguin species. Interestingly, the bacterial community composition shifted in the same direction in response to the moult fast but formed two distinct clusters that were specific to each penguin species. A significant increase in bacterial diversity was observed in gentoo penguins, whereas no such change was observed for chinstrap penguins. By analysing the contribution of the ecological processes that determine bacterial community assembly, we observed that processes regulating community turnover were considerably different between the feeding and moulting stages for each penguin. At the phylum level, the relative abundances of Fusobacteria, Firmicutes and Proteobacteria were dominant in chinstrap penguins, and no significant changes were detected in these phyla between the feeding and moulting periods. Our results suggest that moult fast-induced changes in the faecal microbiota occur in both species.

Visitor Site Guidelines are the principal instruments guiding tourist activities and behaviour at intensively visited sites. These instruments attempt to minimize tourist impacts on Antarctic wildlife, including penguins. However, some recommendations still need to be reinforced by empirical research. Although penguins have enjoyed considerable research attention, a knowledge gap still exists regarding penguins' behavioural responses to realistic tourist activities, including talking sound, viewing distance and movement speed. To fill this gap, we conducted a series of experiments to simulate these activities on two penguin species breeding at an intensively visited site during the 2019–2020 season. We performed 106 replicates of passive and active human presence treatments. Responses varied between species, but active human presence consistently triggered significantly higher responses of strong vigilance behaviour. Our results reinforce Visitor Site Guidelines' recommendations of keeping quiet, moving slowly and increasing viewing distance if changes in behaviour are observed. We also recommend adopting a more conservative viewing distance in the early breeding season. Additional management-orientated empirical studies are needed, including on different species, sites and stages of the breeding season, as such results are valuable for strengthening tourism guidelines and assessing the efficacy of management measures under a post-COVID-19 scenario of increasing Antarctic tourism.

The South Sandwich Islands, in the South Atlantic Ocean, are a major biological hot spot for penguins and other seabirds, but their remoteness and challenging coastlines preclude regular biological censuses. Here we report on an extensive survey of the South Sandwich Islands, the first since the late 1990s, which was completed through a combination of direct counting, GPS mapping, and interpretation of high-resolution commercial satellite imagery. We find that the South Sandwich Islands host nearly half of the world’s Chinstrap Penguin ( Pygoscelis antarctica ) population (1.3 million breeding pairs), as well as c. 95,000 breeding pairs of Macaroni Penguins ( Eudyptes chrysolophus ), and several thousand breeding pairs of Gentoo Penguins ( Pygoscelis papua ). Despite being at the northern edge of their breeding range, we found an unexpectedly large (≥125,000 breeding pairs) population of Adélie Penguins ( Pygoscelis adeliae ). Additionally, we report that nearly 1900 pairs of Southern Giant Petrels ( Macronectes giganteus ) breed in the South Sandwich Islands, 4 % of the global population, almost all of which are found on Candlemas Island. We find that the South Sandwich Islands have not experienced the same changes in penguin abundance and distribution as the rest of the Scotia Arc and associated portions of the western Antarctic Peninsula. This discovery adds important context to the larger conversation regarding changes to penguin populations in the Southern Ocean.