Hydrurga Research Articles

Occurrence, residency, and habitat characterization of leopard seals in Chile

Leopard seals have traditionally been considered Antarctic predators with a Southern Ocean distribution. Historically, sightings north of the Antarctic Polar Front were considered extralimital. However, recent studies suggest a significant presence of leopard seals in subantarctic regions. Here, we assess the spatial occurrence, residency status, and temporal trends of leopard seals in Chile using historical records, stranding reports, standardized monitoring data, photo-identification (photo ID) catalogs, and sightings from four research expeditions. We also characterize glaciers where sightings are concentrated, identifying glaciological and geomorphic attributes that prolong iceberg residency time, which is linked to high leopard seal concentrations. Based on these attributes, we evaluated other potential suitable glacial habitats in Patagonia. We obtained 438 sighting records of leopard seals from 1927 to 2023. Over the last 15 years, we documented a 4-18% annual increase in stranding events reported to national authorities. Most sightings (75%) were concentrated in two hotspots: National Park San Rafael Lagoon, located in Northern Patagonia, and Parry Fjord in Tierra del Fuego. Using photo ID catalogs, we identified 19 resident leopard seals, including 16 multi-year residents observed between 2010-2023 (10 in San Rafael, 6 in Tierra del Fuego) and 3 potential residents (observed multiple months in the same year in Tierra del Fuego). San Rafael monitoring data showed no inter-annual trend, but seasonal trends were observed. We also provide evidence of breeding in Chile, with records of at least 14 pups born and at least two females giving birth in multiple years. Our habitat characterization suggests that calving flux, fjord sinuosity, and fjord width variation are crucial for prolonging iceberg residency in hotspot areas. Based on these attributes, we identified 13 additional fjords in Patagonia as “very likely” suitable for leopard seals. Our study confirms that Patagonia is part of the species’ breeding distribution, shifting the paradigm that leopard seals are merely visitors north of the Antarctic Polar Front. Given the limited number of suitable glaciers in Chile and the potential impacts of climate change, our assessment highlights glacial retreat as a major threat for the ecosystem of this pagophilic marine apex predator in South America.

First paired observations of sexual behavior and calls in wild leopard seals

Little is known about the reproductive biology of the leopard seal (Hydrurga leptonyx), a Southern Ocean predator. Here we observed sexual behavior in wild leopard seals in Laguna San Rafael, Chile during a 2 h courtship interaction between a female and male. The female was hauled out on ice, mostly lying still (69% of the time) or moving (19%). The male was mostly under water (87%) or at the water’s surface (11%). The female made seven in-air calls (i.e., thump pulse, noseblast, blast, growl). The male produced 65 underwater calls (i.e., low- and high-double trills, unidentified trills). The underwater calls appeared to be directed toward the female. After the primary male vocalized for an hour, one or two unidentified leopard seals briefly swam near the female. After leaving the area, we heard underwater calls for another 8 h. The next day, the primary male was hauled out on ice with a swollen genital opening. The male was bleeding from a laceration caudal to the preputial opening, suggesting the male attempted to mate and that the female, or another seal, was responsible for the injury. Together, we find that leopard seal courtship involves a suite of behavioral and acoustic behaviors by both sexes, both in air and under water. This is the first description of leopard seal sexual behavior in the wild. Our study also provides the first evidence that leopard seals mate in South America.

Underwater soundscape in Seaview Bay, Antarctica, and triple ascending trill of the leopard seal (Hydrurga leptonyx) underwater vocalizations.

The underwater soundscape was recorded in Seaview Bay off Inexpressible Island, Ross Sea region Marine protected area, for 3 days in December 2021. Leopard seal Hydrurga leptonyx vocalizations were a prominent sound source that led to variations in ambient sound pressure levels in a frequency range of approximately 150-4500 Hz. Among the 14 call types previously identified, except ultrasound vocalizations, six types of broadcast calls were classified, and their acoustic characteristics were analyzed. We focused on the acoustic characteristics of four low-frequency calls, clustered in a relatively narrow bandwidth, which have been relatively less studied. We identified a new call type of a triple ascending trill consisting of three trill parts, expanding upon the findings of previous studies. The audio data extracted from leopard seal vocalization videos, recorded by a monitoring camera on sea ice, enhanced the reliability of identifications of the underwater triple ascending trill. We present the unique results of underwater passive acoustic monitoring conducted at Seaview Bay, designated as Antarctic Specially Protected Area No 178. Our results could contribute to the development of detection and localization algorithms for leopard seal vocalizations and can be used as fundamental data for studies related to the vocalization and behavior of this species.

Multispecies Discrimination of Seals (Pinnipeds) using Hidden Markov Models (HMMs)

Hidden Markov Models (HMMs) were developed and implemented for the discrimination of 5 available Seals (Pinnipeds), namely the Bearded Seal (Erignathus barbatus), Harp Seal (Pagophilus groenlandicus), Leopard Seal (Hydrurga leptonyx), Ross Seal (Ommatophoca rossii), and Weddell Seal (Leptonychotes weddellii). The main objectives of the experiments were to study the impact of the frame size and step size and number of states for feature extraction and acoustic models on classification accuracy. Based on the experiments using Mel-Frequency Cepstral Coefficients (MFCCs) extracted from the vocalizations (15 ms frame size and 4 ms step size), HMMs containing 20 states with single underlying Gaussian Mixture Model (GMM) produced discrimination of 95.77%. From the results, the framework could be applied to analysis for other marine mammals for both classification and detection of vocalizations and species.

Proactive Resource Allocation for Cloud Manufacturing: A Dynamic Approach with DNN-Based Hybrid Many Objective Leopard Seal Algorithm

In the domain of cloud manufacturing, diverse services and the escalating demand for efficient and cost-effective service composition selection in cloud manufacturing have spurred day by day. Traditional methods face several challenges such as the risk of convergence issues and suboptimal solutions, high dimensionality of decision space, increased computational complexity, and scalability issues. To overcome these complexities, this paper proposed a novel method named the Deep Neural Network (DNN) based Hybrid Many Objective Leopard Seal (HMOLS) algorithm. In this study, DNN is employed to predict future Quality of Service (QoS) for each service based on historical data and integrated features. These predictions are fed back into the optimization model, influencing the dynamic weight calculation for each objective function. In this work, the Leopard Seal Optimization is implemented for hyperparameter optimization to enhance the performance of the HMOLS algorithm. Various evaluation metrics namely accuracy, throughput, reliability, resource utilization, and scalability are utilized to evaluate the performance of the HMOLS method and compare its performance with existing methods. The experimental outcomes depict the effectiveness of the HMOLS approach for the effective selection of services and fusion for cloud manufacturing. DNN-based predictions utilize deep neural networks to predict resource demand or utilization patterns and enable more accurate allocation decisions. These predictions optimize resource allocation by reallocating resources accordingly and address the challenges of resource utilization. Meanwhile, this method is required to overcome the computational overhead for applicability in cloud manufacturing.

Evaluating the performance of semiautomated photographic identification programs for leopard seals

AbstractThe photographic identification (photo‐ID) of individual animals can be time‐consuming and erroneous. Recent efforts to collect photographs of leopard seals (Hydrurga leptonyx) from across their range have necessitated the technological streamlining of photo‐ID. We constructed a dataset containing 595 photographs of the head and body of individuals recorded in New Zealand between 2008 and 2022 to test the performance of semiautomated 3 photo‐ID programs: HotSpotter, Interactive Individual Identification System's Pattern+ (I3S), and Wild‐ID. We classified attributes of photographs (e.g., quality) and individuals (i.e., pelage patterns) to assess their effect on performance. We compared performance using Top20 and Top1 Accuracy, defined as the proportion of test photographs where the highest ranked correct identity was in the top 20 and top 1, respectively, matched reference photographs. HotSpotter outperformed I3S and Wild‐ID in both Top20 and Top1 Accuracy of most assessed attributes. Maximizing HotSpotter's performance may be achieved through several methods, including increasing the number and variety of photographs of individuals in the dataset. HotSpotter will likely perform better with photographs without obstructions (e.g., debris from beaches), such as on the pack ice of their primary Antarctic range. We highlight the viability of HotSpotter in assisting the photo‐ID of leopard seals, and more broadly, other species with similar markings.

Diverse papillomaviruses identified from Antarctic fur seals, leopard seals and Weddell seals from the Antarctic

Papillomaviruses (family Papillomaviridae) are non-enveloped, circular, double-stranded DNA viruses known to infect squamous and mucosal epithelial cells. In the family Papillomaviridae there are 53 genera and 133 viral species whose members infect a variety of mammalian, avian, reptilian, and fish species. Within the Antarctic context, papillomaviruses (PVs) have been identified in Adélie penguins (Pygoscelis adeliae, 2 PVs), Weddell seals (Leptonychotes weddellii, 7 PVs), and emerald notothen (Trematomus bernacchii, 1 PV) in McMurdo Sound and Ross Island in eastern Antarctica. Here we identified 13 diverse PVs from buccal swabs of Antarctic fur seals (Arctocephalus gazella, 2 PVs) and leopard seal (Hydrurga leptonyx, 3 PVs) in western Antarctica (Antarctic Peninsula), and vaginal and nasal swabs of Weddell seals (8 PVs) in McMurdo Sound. These PV genomes group into four genera representing 11 new papillomavirus types, of which five are from two Antarctic fur seals and a leopard seal and six from Weddell seals.

Anthropogenic debris in three sympatric seal species of the Western Antarctic Peninsula

Litter pollution is a growing concern, including for Antarctica and the species that inhabit this ecosystem. In this study, we investigated the microplastic contamination in three seal species that inhabit the Western Antarctic Peninsula: crabeater (Lobodon carcinophaga), leopard (Hydrurga leptonyx) and Weddell (Leptonychotes weddellii) seals. Given the worldwide ubiquity of this type of contaminant, including the Southern Ocean, we hypothesized that the three seal species would present anthropogenic debris in their feces. We examined 29 scat samples of crabeater (n = 5), leopard (n = 13) and Weddell (n = 11) seals. The chemical composition of the items found were identified using micro-Raman and micro-FTIR spectroscopies. All the samples of the three species presented anthropic particles (frequency of occurrence - %FO – 100 %). Fibers were the predominant debris, but fragments and filaments were also present. Particles smaller than 5 mm (micro debris) were predominant in all the samples. Leopard seals ingested significantly larger micro-debris in comparison with the other seal species. The dominant color was black followed by blue and white. Micro-Raman and micro-FTIR Spectroscopies revealed the presence of different anthropogenic pigments such as reactive blue 238, Indigo 3600 and copper phthalocyanine (blue and green). Carbon black was also detected in the samples, as well as plastic polymers such as polystyrene, polyester and polyethylene terephthalate (PET), polyamide, polypropylene and polyurethane These results confirm the presence of anthropogenic contamination in Antarctic seals and highlight the need for actions to mitigate the effects and reduce the contribution of debris in the Antarctic ecosystem.

An Optimum Load Forecasting Strategy (OLFS) for Smart Grids Based on Artificial Intelligence

Recently, the application of Artificial Intelligence (AI) in many areas of life has allowed raising the efficiency of systems and converting them into smart ones, especially in the field of energy. Integrating AI with power systems allows electrical grids to be smart enough to predict the future load, which is known as Intelligent Load Forecasting (ILF). Hence, suitable decisions for power system planning and operation procedures can be taken accordingly. Moreover, ILF can play a vital role in electrical demand response, which guarantees a reliable transitioning of power systems. This paper introduces an Optimum Load Forecasting Strategy (OLFS) for predicting future load in smart electrical grids based on AI techniques. The proposed OLFS consists of two sequential phases, which are: Data Preprocessing Phase (DPP) and Load Forecasting Phase (LFP). In the former phase, an input electrical load dataset is prepared before the actual forecasting takes place through two essential tasks, namely feature selection and outlier rejection. Feature selection is carried out using Advanced Leopard Seal Optimization (ALSO) as a new nature-inspired optimization technique, while outlier rejection is accomplished through the Interquartile Range (IQR) as a measure of statistical dispersion. On the other hand, actual load forecasting takes place in LFP using a new predictor called the Weighted K-Nearest Neighbor (WKNN) algorithm. The proposed OLFS has been tested through extensive experiments. Results have shown that OLFS outperforms recent load forecasting techniques as it introduces the maximum prediction accuracy with the minimum root mean square error.

Incidental pinnipeds at high latitudes of the Vestfold Hills, Prydz Bay, East Antarctica

AbstractSpecies distributions are predicted to change with future climate-associated ecosystem changes such that so-called ‘vagrant’ individuals may become established or re-establish in areas currently thought to be beyond their principle ranges. Survey data were collated for occurrences of pinniped (seal) species at very high latitudes of the Vestfold Hills, East Antarctica. Aside from Weddell seals (Leptonychotes weddellii) and southern elephant seals (Mirounga leonina), which aggregate annually at the Vestfold Hills to breed and/or moult, three other pinniped species were observed with the recession of the fast-ice edge. Leopard seal (Hydrurga leptonyx) occurrences increased with an increase in a seasonally abundant prey resource, and crabeater seals (Lobodon carcinophaga) were seen at a time that coincides with their moult period. Occurrences of sub-adult male Antarctic fur seals (Arctocephalus gazella) increase the known southward range for this species and may reflect population increases at source populations in the Kerguelen Plateau area. Although there were no direct sightings of Ross seals (Ommatophoca rossii), their presence close to the Vestfold Hills was detected by underwater passive acoustic monitoring. Sightings of obligate drift-ice species and sub-Antarctic fur seals may change at the Vestfold Hills with climate-mediated changes in sea-ice conditions.

Protective Measures for Dalian Spotted Seal Reserve

Dalian Spotted Seal Reserve is one of the eight harbor seal breeding areas in the world. Leopard seals in the Liaodong Bay breeding area lack genetic gene exchange with other breeding areas in the world, and there is a phenomenon of reproductive isolation. They belong to a branch of the world's independently evolved leopard seals and have their own unique genetics, so are of high conservation value in this regard. This paper highlights the benefits that aquaculture and captive breeding bring to protected areas. The focus of aquatic products is mainly on the bottom-sown varieties. There is a foundation for artificial breeding, and what people need to do is to continue to expand the number and scope when there is sufficient funding. At the same time, this paper will clarify the relationship between them, and explain the measures and development of seal protection from the biological and economic perspectives. Both focus studies could help further protect seals.

Initial insights into leopard seal moult in Aotearoa New Zealand

Initial insights into leopard seal moult in Aotearoa New Zealand

Building bridges: Doug Cato’s remarkable career spanning underwater acoustics and animal bioacoustics

Doug Cato’s research includes pioneering studies of the underwater acoustic environment surrounding Australia and numerous contributions to our understanding of marine mammal acoustic behavior. Moreover, his relaxed avuncular manner allowed him to assemble collaborations spanning disparate disciplines while mentoring the next generation of acoustics researchers in Australia. Throughout his career, Doug built bridges between underwater acoustics and animal bioacoustics, and between Australian and international researchers. This talk highlights two international collaborations applying signal processing techniques to humpback whale songs and leopard seal calling bouts. These projects estimated the information entropy and structure of the sequences of sounds in these marine mammal vocalizations. Comparing sliding window entropy estimates with Markov models supports Doug’s earlier observations that Australian humpback song follows the hierarchical structure proposed by Payne & McVay for North Atlantic humpbacks [Miksis-Olds et al., JASA, 2008]. The same comparison of entropy estimators for leopard seal calling bouts reveals that most of the sequential structure of in these animals’ calls is captured by Markov models.

Records of leopard seals Hydrurga leptonyx ashore in South Australia, 2017–2022

The leopard seal Hydrurga leptonyx is one of five phocid species with a circumpolar distribution in the Southern Ocean. They do not breed on the Australian coast. We document records of 14 leopard seals (two collected specimens, 12 live sightings) in South Australia (SA) between November 2017 and November 2022, from Fowlers Bay to the mouth of the River Murray. We used records from the SA Museum, reports from coastal officers of SA Department for Environment and Water, and information from the public. All 14 seals were juvenile and most were in fair/thin body condition. Two collected specimens and two sighted animals showed evidence of blunt trauma. Stomachs contained fish remains and feathers, and one contained 21 semi-digested smooth toadfish Tetractenos glaber, a species which contains the toxin tetrodotoxin. Necropsies on two specimens involved gross, histopathological, and diagnostic assessment of pathogens, organs, and skin lesions. All records were between June and December, similar to the seasonal distribution reported previously in southern Australia. The 14 records over 5 years to 2022 averaged 2.8 per year, higher than during a previous study in SA that ran over three decades to October 2009 at 1.2 per year.

Traditional and digital examination of the baculum of a leopard seal (Hydrurga leptonyx)

Traditional and digital examination of the baculum of a leopard seal (<i>Hydrurga leptonyx</i>)

Genetic diversity and demographic history of the leopard seal: A Southern Ocean top predator.

Leopard seals (Hydrurga leptonyx) are top predators that can exert substantial top-down control of their Antarctic prey species. However, population trends and genetic diversity of leopard seals remain understudied, limiting our understanding of their ecological role. We investigated the genetic diversity, effective population size and demographic history of leopard seals to provide fundamental data that contextualizes their predatory influence on Antarctic ecosystems. Ninety leopard seals were sampled from the northern Antarctic Peninsula during the austral summers of 2008-2019 and a 405bp segment of the mitochondrial control region was sequenced for each individual. We uncovered moderate levels of nucleotide (π = 0.013) and haplotype (Hd = 0.96) diversity, and the effective population size was estimated at around 24,000 individuals (NE = 24,376; 95% CI: 16,876-33,126). Consistent with findings from other ice-breeding pinnipeds, Bayesian skyline analysis also revealed evidence for population expansion during the last glacial maximum, suggesting that historical population growth may have been boosted by an increase in the abundance of sea ice. Although leopard seals can be found in warmer, sub-Antarctic locations, the species' core habitat is centered on the Antarctic, making it inherently vulnerable to the loss of sea ice habitat due to climate change. Therefore, detailed assessments of past and present leopard seal population trends are needed to inform policies for Antarctic ecosystems.

Large and in charge: cortisol levels vary with sex, diet, and body mass in an Antarctic predator, the leopard seal

Evaluating physiological responses in the context of a species’ life history, demographics, and ecology is essential to understanding the health of individuals and populations. Here, we measured the main mammalian glucocorticoid, cortisol, in an elusive Antarctic apex predator, the leopard seal (Hydrurga leptonyx). We also examined intraspecific variation in cortisol based on life history (sex), morphometrics (body mass, body condition), and ecological traits (δ15N, δ13C). To do this, blood samples, life history traits, and morphometric data were collected from 19 individual leopard seals off the Western Antarctic Peninsula. We found that adult leopard seals have remarkably high cortisol concentrations (100.35 ± 16.72 μg/dL), showing the highest circulating cortisol concentration ever reported for a pinniped: 147 μg/dL in an adult male. Leopard seal cortisol concentrations varied with sex, body mass, and diet. Large adult females had significantly lower cortisol (94.49 ± 10.12 μg/dL) than adult males (120.85 ± 6.20 μg/dL). Similarly, leopard seals with higher isotope values (i.e., adult females, δ15N: 11.35 ± 0.69‰) had lower cortisol concentrations than seals with lower isotope values (i.e., adult males, δ15N: 10.14 ± 1.65‰). Furthermore, we compared cortisol concentrations across 26 closely related Arctoid taxa (i.e., mustelids, bears, and pinnipeds) with comparable data. Leopard seals had the highest mean cortisol concentrations that were 1.25 to 50 times higher than other Arctoids. More broadly, Antarctic ice seals (Lobodontini: leopard seal, Ross seal, Weddell seal, crabeater seal) had higher cortisol concentrations compared to other pinnipeds and Arctoid species. Therefore, high cortisol is a characteristic of all lobodontines and may be a specialized adaptation within this Antarctic-dwelling clade. Together, our results highlight exceptionally high cortisol concentrations in leopard seals (and across lobodontines) and reveal high variability in cortisol concentrations among individuals from a single location. This information provides the context for understanding how leopard seal physiology changes with life history, ecology, and morphology and sets the foundation for assessing their physiology in the context of a rapidly changing Antarctic environment.

Leopard seal optimization (LSO): A natural inspired meta-heuristic algorithm

The main objective of this paper is to introduce a new NIO algorithm inspired from the hunting strategy of the leopard seals called Leopard Seal Optimization (LSO)to provide a simple swarm intelligence algorithm that have a high flexibility to solve real-time engineering problems in a fast and more accurate manner without falling into local optima problem. LSO is compared against recent NIO algorithms considering feature selection for disease diagnosing as the underlying optimization problem. In experimental results, LSO has been statistically tested against a recent six swarm intelligence algorithms using Wilcoxon test and t-test with significance level equals 0.05 based on the common five benchmark functions. These recent algorithms are called Tuna Swarm Optimization (TSO), Pelican Optimization Algorithm (POA), Cat and Mouse-Based Optimization (CMBO), Aphid–Ant Mutualism (AAM), White Shark Optimizer (WSO), and Red Piranha Optimization (RPO). The statistical analysis proved that LSO outperforms other recent techniques in most cases where the most tested results are less than 0.05. Then, LSO has been tested against the same algorithms in binary version as feature selection algorithms using two metrics called accuracy and execution time. It is noted that LSO is faster and more accurate than other algorithms to determine the optimal set of features at all numbers of search agents. Finally, it is concluded that LSO outperforms other techniques using accuracy, execution time, Wilcoxon test, and t-test metrics. Compared to the recent techniques using the maximum iteration number=400, LSO provided the maximum accuracy value that equals 97.62% at the search agents number=120 and the minimum execution time that equals 1314 at the search agents number= 40.

Multispecies discrimination of seals (pinnipeds) using hidden Markov models (HMMs)

Hidden Markov models (HMMs) were developed and implemented for the discrimination of five available Seals (Pinnipeds), namely, the Bearded Seal (Erignathus Barbatus), Harp Seal (Pagophilus Groenlandicus), Leopard Seal (Hydrurga Leptonyx), Ross Seal (Ommatophoca Rossii), and Weddell Seal (Leptonychotes Weddellii). The main objectives of the experiments were to study the impact of the frame size and step size and number of states for feature extraction and acoustic models on classification accuracy. Based on the experimentation using Mel-Frequency Cepstral Coefficients (MFCCs) extracted from the vocalizations (15 ms frame size and 4 ms step size), HMMs containing 20 states with single underlying Gaussian mixture model (GMM) produced discrimination of 95.77%. From the results, the framework could be applied to analysis for other marine mammals for both classification and detection of vocalizations and species.

Legal analysis on the protection and development of the spotted seal population from a multi-dimensional perspective

Affected by human activities, the living environment of aquatic wildlife in Bohai Bay and Huanghai Bay of our country is deteriorating day by day. In accordance with the animal protection law and other relevant laws and regulations, our country has formulated an action plan and an action plan for the protection of leopard seals. The Action Plan is based on the multi-dimensional vision of the natural environment, the balance of nature, sustainable development and human care, in 2021, the Leopard Seal is listed as a first-class protected animal in the country. This paper expounds on the survival status of the spotted seal population by searching the judgments of criminal cases, administrative cases and on-the-spot investigation on the judgment network, this paper analyzes the main reasons for the endangered population of spotted seal and puts forward the corresponding protection countermeasures.