Browsing by Author "Borras-Chavez, Renato"

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    Occurrence, residency, and habitat characterization of leopard seals in Chile
    (2024) Borras-Chavez, Renato; Soteres, Rodrigo L.; Gomez-Gonzalez, Gabriela; Martinez, Francisco; Fernandez-Ferrada, Nicolas; Castillo-Aguilar, Matias; Moreno Azua, Fredy; Dougnac, Catherine; Arredondo, Cristobal; Brown, Nicholi; Sperou, Emily S.; Bonin, Carolina A.; Goebel, Michael E.; Guerrero, Alicia I.; Donke, Marcelo; Kienle, Sarah S.
    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.
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    Plasticity in the morphometrics and movements of an Antarctic apex predator, the leopard seal
    (2022) Kienle, Sarah S.; Goebel, Michael E.; LaBrecque, Erin; Borras-Chavez, Renato; Trumble, Stephen J.; Kanatous, Shane B.; Crocker, Daniel E.; Costa, Daniel P.
    Animals that display plasticity in behavioral, ecological, and morphological traits are better poised to cope with environmental disturbances. Here, we examined individual plasticity and intraspecific variation in the morphometrics, movement patterns, and dive behavior of an enigmatic apex predator, the leopard seal (Hydrurga leptonyx). Satellite/GPS tags and time-depth recorders were deployed on 22 leopard seals off the Western Antarctic Peninsula. Adult female leopard seals were significantly larger (454 +/- 59 kg) and longer (302 +/- 11 cm) than adult males (302 +/- 22 kg, 276 +/- 11 cm). As females were 50% larger than their male counterparts, leopard seals are therefore one of the most extreme examples of female-biased sexual size dimorphism in marine mammals. Female leopard seals also spent more time hauled-out on land and ice than males. In the austral spring/summer, three adult female leopard seals hauled-out on ice for 10+ days, which likely represent the first satellite tracks of parturition and lactation for the species. While we found sex-based differences in morphometrics and haul-out durations, other variables, including maximum distance traveled and dive parameters, did not vary by sex. Regardless of sex, some leopard seals remained in near-shore habitats, traveling less than 50 kilometers, while other leopard seals traveled up to 1,700 kilometers away from the tagging location. Overall, leopard seals were short (3.0 +/- 0.7 min) and shallow (29 +/- 8 m) divers. However, within this general pattern, some individual leopard seals primarily used short, shallow dives, while others switched between short, shallow dives and long, deep dives. We also recorded the single deepest and longest dive made by any leopard seal-1, 256 meters for 25 minutes. Together, our results showcased high plasticity among leopard seals tagged in a single location. These flexible behaviors and traits may offer leopard seals, an ice-associated apex predator, resilience to the rapidly changing Southern Ocean.
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    Time and behavioral adjustments to lactation: Insights from a marine predator
    (2023) Borras-Chavez, Renato; Goebel, Michael E.; Villegas-Amtmann, Stella; Huckstadt, Luis A.; Rivera-Rebella, Carla; Costa, Daniel P.; Farina, Jose M.; Bozinovic, Francisco
    The energetic costs of lactation have been studied in many marine mammals, but little is known about the behavioral adjustments needed to cope with this event. By simultaneously measuring foraging behavior of lactating and nonlactating Antarctic fur seal females, we estimate the behavioral changes necessary to cope with the constraints of lactation and include the first comparative record of dive behavior between lactating and nonlactating female otariids. Nonlactating females exhibited highly variable foraging trip durations and spent long times onshore between trips. In contrast, lactating females exhibited consistently shorter trips and spent half the time hauled-out compared to nonlactating females likely to maximize offspring provisioning. Lactating females show a reduced mean time per dive but greater percentage of time per trip spent diving compared to nonlactating animals. The reduction in time onshore and trip duration, together with modifications in dive performance suggests additional effort of lactating females to compensate for the constraints of rearing a pup, which has not been observed previously due to the lack of simultaneous comparison of lactating and nonlactating individuals. When possible, future studies of maternal investment should also include nonlactating individuals, since lactation may have a strong synergistic effect with other aspects shaping foraging behavior.
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    Whiskers provide time-series of toxic and essential trace elements, Se:Hg molar ratios, and stable isotope values of an apex Antarctic predator, the leopard seal
    (2023) Charapata, Patrick; Clark, Casey T.; Miller, Nathan; Kienle, Sarah S.; Costa, Daniel P.; Goebel, Michael E.; Gunn, Heather; Sperou, Emily S.; Kanatous, Shane B.; Crocker, Daniel E.; Borras-Chavez, Renato; Trumble, Stephen J.
    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 (delta N-15 and delta O-13) values and to assess Hg risk with Se:Hg molar ratios. Whiskers provided between 46 and 286 cumulative days of growth with a mean similar to 125 days per whisker = 18). Adult whiskers showed variability in non -essential trace elements over time that could partly be explained by changes indict. Whisker Hg levels were insufficient (<20 ppm) to consider most seals being at "high" risk for Hg toxicity. Nevertheless, maximum Hg concentrations observed in this study were greater than that of leopard seal hair measured two decades ago. However, variation in the Se:Hg molar ratios over time suggest that Se may detoxify Hg burden in leopard seals. Overall, we provide evidence that the analysis of leopard seal whiskers allows for the reconstruction of time-series ecological and physiological data and can be valuable for opportunistically monitoring the health of the leopard seal population and their Antarctic ecosystem during climate change.