Complementary use of stable isotopes and fatty acids for quantitative diet estimation of sympatric predators, the Antarctic pack-ice seals

The quantitative use of stable isotopes (SIs) for trophic studies has seen a rapid growth whereas fatty acid (FA) studies remain mostly qualitative. We apply the Bayesian tool MixSIAR to both SI and FA data to estimate the diet of three sympatric predators: the crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii) and leopard seal (Hydrurga leptonyx). We used SI data of their vibrissae and FA data of their outer blubber to produce comparable diet estimates for the same individuals. Both SI and FA models predicted the same main diet components, although the predicted proportions differed. For the crabeater seal, both methods identified krill, Euphausia superba, as the main, and almost exclusive, food item, although the FA model estimated a slightly lower proportion, potentially due to the low lipid content of krill compared to the fish species used in the model. For the Weddell seal the FA model identified the fish Pleuragramma antarcticum as the most important prey, whereas the SI model was not able to distinguish among prey species, identifying a ‘fish-squid’ group as the main diet component. For the leopard seal, both models identified krill as the main contributor; however, the predicted proportions for the secondary sources differed. Although vibrissae and outer blubber may not represent the same timeframe, the use of MixSIAR with FA data provides diet estimates comparable to those obtained with SI data, thus, both approaches were complimentary. The use of both biotracers offers a feasible option to study diets of wild animals in a quantitative manner.

Insights into the genetic diversity of the leopard seal (Hydrurga leptonyx), inferred from mitochondrial DNA analysis, at Danco Coast, Antarctic Peninsula

The leopard seal (Hydrurga leptonyx) is a genetically low-studied species. In order to conduct the first genetic diversity assessment of this species in Danco Coast (Antarctic Peninsula), 423 bp of the mitochondrial DNA Control Region (mtDNA-CR) was sequenced from 13 blood samples collected in Primavera Base (62º15’S, 58º39’W) during the 2011-2012 austral summer. Our results showed high haplotype diversity (h = 0.99), with various divergent haplotypes. Our findings suggest that leopard seals in the Danco Coast could represent different phylogroups; however, including more genetic markers are needed to confirm this hypothesis.

Predation Attempt by a Leopard Seal on two Dwarf Minke Whales

Introduction The diet of leopard seal Hydrurga leptonyx consists mainly of krill Euphorbia sp, penguins, other seals, fish and cephalopods in decreasing order of abundance no cetacean was mentioned [1-6].

Summer circumpolar acoustic occurrence and call rates of Ross, Ommatophoca rossii, and leopard, Hydrurga leptonyx, seals in the Southern Ocean

Two of the Antarctic pack ice seals, Ross, Ommatophoca rossii, and leopard, Hydrurga leptonyx, seals, are extremely difficult to study via traditional visual survey techniques, yet are ideal for an acoustic survey as they are highly vociferous and produce an array of underwater sounds during the austral summer. To determine their acoustic occurrence in the Antarctic pack ice, we use their calls, detected within 680 acoustic recordings made between 1999 and 2009 as part of two multinational programmes. Siren calls of Ross seals were detected mainly in January, and 9.88 calls per minute from low siren calls was the highest call rate for this species. High numbers of Ross seal calls were detected close to the ice edge in areas between 0° and 20° E and 60° and 130° E, suggesting these are important summer habitats. Leopard seal calls were detected mainly in December and January, and December had the highest percentage of calls. Call rate of 11.93 calls per minute from low double trills was the highest call rate for leopard seals. Leopard seal calls were detected throughout the Southern Ocean with more calls detected throughout the pack ice. There was little spatio-temporal overlap in call occurrence of Ross and leopard seals, but both species were more vocally active during the day. Longitude and latitude were the most important predictors of Ross seal occurrence, and month of the year highly predicted leopard seal occurrence. This is the first study to examine the circumpolar acoustic occurrence of Ross and leopard seals in the Southern Ocean pack ice.

Monitoring of the leopard seal population (Hydrurga leptonyx) in waters of the Argentine Islands (Ant-arctica)

The state of the leopard seal population (Hydrurga leptonyx Blainville, 1828) in waters of the Argentine Islands was studied during the periods April 2015 — March 2016 and April 2018 — March 2019 according to the objectives of the State Target Scientific and Technical Research Programme of Ukraine in Antarctica for the period 2011–2020. During the study period, 14 males and 16 females were recorded within the archipelago (1M : 1.1F ratio). About 7 % of the seals were young individuals and more than 90% were adults. Leopard seals were recorded during all periods of the year. In the summer-autumn period, within the archipelago, there were 2 to 4 individuals simultaneously. The maximum period of stay of the predators in waters of the archipelago was about two weeks. Two individuals for at least two weeks were recorded twice in waters of the archipelago. The maximum period of absence of the seals in waters of the archipelago was 118 days. It was found that the occurrence of leopard seals and hence the traces of their life activities in various years were of different nature. In the autumn (April–May) of 2015, they were seen less frequently, on average every 6.3 ± 2.5 days, and in the autumn of 2018, on the contrary, more frequently, on average every 2.5 ± 0.5 days. The activity of the leopard seal in the winter (June, August) of 2015 decreased by half. It was recorded that the animals appeared in waters of the archipelago on average every 12.7 ± 5.5 days, and in the winter of 2018 — 5.5 ± 1.9 days. In the autumn of 2018, the predators and traces of their vital activities were seen less often — every 6.6 ± 1.6 days. During the study period, out of 78 recorded cases of the leopard seal’s occurrence, about 56 % of cases were recorded when they were on ice floes, in other cases (44 %) — when they were in water. In addition, several crabeater seals were recorded three times on an ice floe at an insignificant distance from a leopard seal. One of the main prey items for leopard seals within the archipelago are birds, in particular the gentoo penguin (Pygoscelis papua), as well as crabeater seals (Lobodon carcinophagus). The presence of two penguin colonies on Galindez Island attracts leopard seals to the archipelago. During the study period, successful leopard seal predation on penguins was recorded more than 20 times. Penguins were the most frequent prey of leopard seals in spring and summer, while crabeater seals in winter.

Food caching by a marine apex predator, the leopard seal (Hydrurga leptonyx)

The foraging behaviors of apex predators can fundamentally alter ecosystems through cascading predator–prey interactions. Food caching is a widely studied, taxonomically diverse behavior that can modify competitive relationships and affect population viability. We address predictions that food caching would not be observed in the marine environment by summarizing recent caching reports from two marine mammal and one marine reptile species. We also provide multiple caching observations from disparate locations for a fourth marine predator, the leopard seal (Hydrurga leptonyx (de Blainville, 1820)). Drawing from consistent patterns in the terrestrial literature, we suggest the unusual diversity of caching strategies observed in leopard seals is due to high variability in their polar marine habitat. We hypothesize that caching is present across the spectrum of leopard seal social dominance; however, prevalence is likely to increase in smaller, less-dominant animals that hoard to gain competitive advantage. Given the importance of this behavior, we draw attention to the high probability of observing food caching behavior in other marine species.

The Preservation of Two Leopard Seals (Hydruga leptonyx), Ten Years Apart

Discussing the process from death to display for two significant Rāpoka, leopard seals, (Hydrurga leptonyx) undertaken as preservation projects by the Otago Museum. The first of these is a large female which died within the takiwa (district) of Kāti Huirapa Rūnaka ki Puketeraki in 2008. This seal was significant in the sense that it was the first marine mammal preservation project undertaken by the museum in collaboration with local iwi in the following the Ngāi Tahu Treaty of Waitangi settlement, where iwi regained the management rights of kā kararehe o takaroa (marine mammals) remains within the Marine Mammal Protection Act framework. This preservation project became a successful model for collaboration between iwi, government wildlife organisations, researchers and the museums when a marine mammal dies in the Otago Region. In 2017 the death of a neonate leopard seal pup, significant given its birth on St Kilda Beach, Dunedin within the takiwa of Te Rūnanga o Ōtākou sees the Otago Museum working to preserve this important leopard seal. This talk discusses the parallels and differences between the two projects, the importance of collaboration, recent applications of Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scanning preservation methods as well as using more traditional methods of taxidermy and skeltonisation. The guiding principles have been to preserve voucher information for the future, educate visitors about this Antarctic species, to expose our local community to the ongoing links between Māori and the natural world, and to demonstrate how wildlife management, science, museums and practitioners in indigenous knowledge can successfully collaborate in the practical and interpretive context of curation.

Revising the Dead Art of Skeleton Preparation for Today’s Museum Collections

Many museums have an eclectic mix of skeletons in their collections. These curiosities from across the globe were processed from the carcass using a variety of techniques with varying degrees of success. The details of how these animals have journeyed from death to collection item are scarce. The old techniques and skill involved in constructing skeletons, from large down to the most delicate and tiny, can still be marveled at today. However some skeletons were poorly articulated, others incomplete or put together borrowing bones from another animal or bird. In the case of animals not known as live specimines ignorance may have been a factor in achieving an incorrect stance while other specimines were intentionally exaggerated to impress rather than appear true to nature. A selection of methods for the preparation of skeletons have been used, such as carcinogenic chemicals, bleaches, detergents and solvents, fresh and seawater maceration, flesh-eating dermestid beetles, boiling bones to remove the oils and flesh, and composting. Skeletons were articulated for display by drilling and pinning the bones, sometimes using irreversible glues or ferrous wire that rusted over time. Over the past 18 years I have prepared and articulated native bird and marine mammal skeletons for the Otago Museum collection. To ensure the bones are not contaminated by chemicals or physically damaged, methods and requirements have evolved over a relatively short time, as conservation has become an integral part of museum practice. This presentation will provide an overview of the fresh water maceration process, some lessons learnt, the articulation method developed using an external stainless steel wire armature to hold each bone in position, and organizing bones with safety, articulation and transportation in mind. I will share the journey from corpse to collection item of Autahi the leopard seal and other skeletons I have worked with.