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In an era of rapid environmental change and increasing human presence, researchers need efficient tools for tracking contaminants to monitor the health of Antarctic flora and fauna. Here, we examined the utility of leopard seal whiskers as a biomonitoring tool that reconstructs time-series of significant ecological and physiological biomarkers. Leopard seals (Hydrurga leptonyx) are a sentinel species in the Western Antarctic Peninsula due to their apex predator status and top-down effects on several Antarctic species. However, there are few data on their contaminant loads. We analyzed leopard seal whiskers (n = 18 individuals, n = 981 segments) collected during 2018-2019 field seasons to acquire longitudinal profiles of non-essential (Hg, Pb, and Cd) and essential (Se, Cu, and Zn) trace elements, stable isotope (ẟ

To understand and predict current and future distributions of animals under a changing climate it is essential to establish historical ranges as baselines against which distribution shifts can be assessed. Management approaches also require comprehension of temporal variability in spatial distributions that can occur over shorter time scales, such as inter-annually or seasonally. Focussing on the Southern Ocean, one of the most rapidly changing environments on Earth, we used Species Distribution Models (SDMs) and satellite ocean data to reconstruct the likely historical foraging habitats of Antarctic fur seals (Arctocephalus gazella) from three populations during the non-breeding winter (Marion Island, Bird Island and Cape Shirreff), to assess whether habitat quality has changed in recent decades. We then quantified temporal variability in distributions to assess overlap with management areas (CCAMLR – Commission for the Conservation of Antarctic Marine Living Resources) and the potential for competition with fisheries. Despite notable physical ocean changes, the quality of foraging habitat during the non-breeding season has remained relatively consistent over 20 years at Marion and Bird Islands, but less so at Cape Shirreff, where reduced sea ice cover has improved habitat accessibility. Spatio-temporally explicit SDMs identified variability in habitats across the winter. Some areas overlapped significantly with fisheries activities, suggesting a potential for competition for prey resources at several key periods. A significant component of core habitat at all populations was not within the CCAMLR Convention Area. Although organisations such as CCAMLR adopt a precautionary, ecosystem-based approach to fisheries management, changes to the physical environment and developments in the fishing industry can affect how dependant species are impacted. The hindcasting of historical spatial distributions shown here are baselines against which future changes can be assessed. Given recent proposals for a system of marine protected areas (MPAs) in the Southern Ocean, our results can be used in the design and evaluation of MPAs, be they static or dynamic. Our study also demonstrates that the core habitat of species may fall outside of areas of active management, providing an important context for the interpretation of monitoring programs and management efforts.

Quantification of the physical and biological environmental factors that influence the spatial distribution of higher trophic species is central to inform management and develop ecosystem models, particularly in light of ocean changes. We used tracking data from 184 female Antarctic fur seals (Arctocephalus gazella) to develop habitat models for three breeding colonies for the poorly studied Southern Ocean winter period. Models were used to identify and predict the broadly important winter foraging habitat and to elucidate the environmental factors influencing these areas. Model predictions closely matched observations and several core areas of foraging habitat were identified for each colony, with notable areas of inter-colony overlap suggesting shared productive foraging grounds. Seals displayed clear choice of foraging habitat, travelling through areas of presumably poorer quality to access habitats that likely offer an energetic advantage in terms of prey intake. The relationships between environmental predictors and foraging habitat varied between colonies, with the principal predictors being wind speed, sea surface temperature, chlorophyll a concentration, bathymetry and distance to the colony. The availability of core foraging areas was not consistent throughout the winter period. The habitat models developed in this study not only reveal the core foraging habitats of Antarctic fur seals from multiple colonies, but can facilitate the hindcasting of historical foraging habitats as well as novel predictions of important habitat for other major colonies currently lacking information of the at-sea distribution of this major Southern Ocean consumer.

Antarctic fur seals ( Arctocephalus gazella ) are polygynous and both sexes are typically faithful to a breeding site. These characteristics could promote remating among individuals over time, leading to increased relatedness levels and negatively affecting genetic diversity. To examine this issue, the reproductive output of 55 females was monitored annually for 12 years and their pups were sampled (n = 280) and genotyped using 17 microsatellite markers. A full likelihood pedigree inference method was used to confirm maternities inferred in the field and estimate the number of full sibling pups born across years. Relatedness coefficients were estimated for pairs of individuals in the pedigree and compared to simulated values for each relationship category. There were nine cases where a female mated with the same male twice and one case where a female mated with the same male three times over the study period. The observed relatedness coefficients estimated among the sampled pups matched the simulated distribution for half-siblings. In addition, no first order relatives were found among the fur seal mothers studied, nor did observed relatedness coefficient distributions differ significantly from simulated values. Together, these results suggest a low remating rate and a negligible effect of remating on pair-wise relatedness. Territorial male replacement over time as well as female small-scale movements, driven by suitable pupping habitat, likely contribute to the low remating frequency observed in Antarctic fur seals.

The large-scale spatial patterns and primary drivers of food web dynamics across seascapes can be investigated using isotope ratios in marine consumers. However, interpreting complex signatures from mobile animals can require good knowledge of spatial isotopic variations in the environment. This is particularly true in the Southern Ocean where regional differences in the physical environment affect habitat predictability and predator foraging. We applied a retrospective-isotope approach integrated with tracking locations for a model species, the Antarctic fur seal (Arctocephalus gazella), to generate large-scale spatially-explicit predictions of isotopic gradients (“isoscapes”) across the Southern Ocean. Vibrissae and blood samples were collected during post- and pre-breeding periods from both Antarctic and sub-Antarctic breeding environments. Stable isotope values from vibrissae growth and serially sampled blood enabled the reconstruction of an isotopic time-series that could be directly related to feeding locations at sea. Tracked seals were widely distributed in the southern Atlantic and Indian Oceans, with important foraging activity centred on productive upwelling areas, oceanic frontal zones and shelf environments. Corresponding seal δ13C and δ15N values were positively correlated to the Southern Ocean latitudes at which the tracked individuals foraged. Breeding site, bi-monthly foraging period and foraging location all explained significant variation in isotopic values during migration. Isotopic variation was largely driven by the latitudinal and inshore/offshore gradient in δ13C and δ15N at the base of the food web in neritic and oceanic waters. These delineate the spatio-temporal isotopic variability of important foraging habitats, providing a valuable perspective on the spatial and seasonal distribution of predators and forage availability. Differences in inferred predator distribution within and between breeding locations have implications for relative exposure to anthropogenic threats from fisheries interactions and climate change. This study demonstrates that isotope tracers in archival tissues are useful indicators of resource partitioning by marine consumers to directly inform spatial conservation planning and ecosystem management strategies at the cross-basin scale.

Genetic analyses can reliably determine the relationships among putative cases of twins in pinniped species. These studies demonstrate that field observations of nursing twins may often be cases of adoption or foster nursing of unrelated pups. A recent study of Antarctic fur seals ( Arctocephalus gazella ) on South Georgia Island found that only 3 of 11 putative twin cases were truly twins. Here we report results of genetic testing of eight putative cases of twinning (twin siblings and mother) observed at Cape Shirreff (62°27′30″S, 60°47′17″W), Livingston Island, Antarctica. Parentage and relatedness analyses using 18 microsatellite markers confirmed six out of the eight cases as twins and two cases of adoption/foster nursing of unrelated pups. All twins analyzed were dizygotic and in five out of six cases, the twins were likely full siblings (relatedness coefficient, or r xy μ = 0.46, σ 2 = 0.004). In one case, the twins were likely half-siblings ( r xy = 0.17), supporting a previous finding of heteropaternity in Antarctic fur seals. This result suggests that mate infidelity during estrus maybe common in Antarctic fur seals, which has implications for our understanding of this species's mating system. The twinning rate estimated at Cape Shirreff (0.12% or 6 twins per 4,965 births) is consistent with the scarcity of twin births observed in pinnipeds, which is associated with the high cost of nursing multiple pups in these animals.

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 (δ 15 N and δ 13 C) 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 δ 15 N and δ 13 C 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.

Diving animals offer a unique opportunity to study the importance of physiological constraint in their everyday behaviors. An important component of the physiological capability of any diving animal is its aerobic dive limit (ADL). The ADL has only been measured in a few species. The goal of this study was to estimate the aerobic dive limit from measurements of body oxygen stores and at sea metabolism. This calculated ADL (cADL) was then compared to measurements of diving behavior of individual animals of three species of otariids, the Antarctic fur seal, Arctocephalus gazella , the Australian sea lion, Neophoca cinerea , and the New Zealand sea lion, Phocarctos hookeri. Antarctic fur seals dove well within the cADL. In contrast, many individuals of both sea lion species exceeded the cADL, some by significant amounts. Australian sea lions typically dove 1.4 times longer than the cADL, while New Zealand sea lions on average dove 1.5 times longer than the cADL. The tendency to exceed the cADL was correlated with the dive pattern of individual animals. In both Antarctic Fur Seals and Australian sea lions, deeper diving females made longer dives that approached or exceeded the cADL ( P r 2 =0.54). Australian and New Zealand sea lions with longer bottom times also exceeded the cADL to a greater degree. The two sea lions forage on the benthos while the fur seals feed shallow in the water column. It appears that benthic foraging requires these animals to reach or exceed their aerobic dive limit.