Density-dependent effects on reproductive output in a capital breeding carnivore, the northern elephant seal (<i>Mirounga angustirostris</i>)

Holser, Rachel R.; Crocker, Daniel E.; Robinson, Patrick W.; Condit, Richard; Costa, Daniel P.

doi:10.1098/rspb.2021.1258

Cited by 14 publications

(10 citation statements)

References 72 publications

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“…Predators integrate lower trophic levels; disturbances that impact primary producers or low‐level consumers can be seen in dietary shifts, habitat use changes, reductions in reproductive success, or even reduced survival in predator populations (Fretwell, 1987; Lindeman, 1942; Scherber et al., 2010). Northern elephant seals exhibited reduced reproductive output following the first year of the Blob (Holser et al., 2021). Further investigation of their behavior paired with the oceanographic data presented here would benefit our understanding of MHW effects on mesopelagic biomass.…”

Section: Resultsmentioning

confidence: 99%

Extent and Magnitude of Subsurface Anomalies During the Northeast Pacific Blob as Measured by Animal‐Borne Sensors

et al. 2022

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Marine heatwaves (MHWs) are prolonged warm water events that are increasing in frequency and magnitude due to rising global temperatures. The Northeast Pacific Blob was an unusually widespread MHW that affected ecosystems across the Northeast Pacific, from producers to top predators. Temperature and salinity data collected by northern elephant seals (Mirounga angustirostris) from 2014 to 2017 show significant (>2 sd) warm anomalies throughout the top 1,000 m of the water column, with peak warming in late 2015. Using temperature and salinity as a tracer of layers of constant density, we looked at how lateral advection may have contributed to the development of the Blob. Temperature and salinity anomalies and the expansion of the water column at the base of the pycnocline both indicate that northward advection of warm, salty water played an important role in the observed accumulation of warm water, in addition to surface warming. These findings contribute to our understanding of the physical dynamics of the Blob, especially the thermal content and structure of the water column, and offer mechanisms for its formation and maintenance, which are crucial to assessing the ecological effects of MHWs now and in the future.

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Section: Resultsmentioning

confidence: 99%

Extent and Magnitude of Subsurface Anomalies During the Northeast Pacific Blob as Measured by Animal‐Borne Sensors

et al. 2022

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“…Elephant seal pups may therefore represent a significant step in the bio-transport pathway. The average mortality of northern elephant seal pups, calculated from 1984 to 2020 at the mainland Año Nuevo colony, was 7.2%; thus, pup mortality based on the average number of pups born annually from 2010 to 2020 would result in the annual delivery of mercury into nearshore and terrestrial ecosystems 97 from 113 carcasses as well as from the lanugo of 1575 pups 100 . In 2010, approximately 40,684 northern elephant seal pups were born at colonies in California.…”

Section: Discussionmentioning

confidence: 99%

Foraging behavior and age affect maternal transfer of mercury to northern elephant seal pups

Peterson,

Ackerman

et al. 2024

Sci Rep

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Deep ocean foraging northern elephant seals (Mirounga angustirostris) consume fish and squid in remote depths of the North Pacific Ocean. Contaminants bioaccumulated from prey are subsequently transferred by adult females to pups during gestation and lactation, linking pups to mercury contamination in mesopelagic food webs (200–1000 m depths). Maternal transfer of mercury to developing seal pups was related to maternal mercury contamination and was strongly correlated with maternal foraging behavior (biotelemetry and isotopes). Mercury concentrations in lanugo (hair grown in utero) were among the highest observed worldwide for young pinnipeds (geometric mean 23.01 μg/g dw, range 8.03–63.09 μg/g dw; n = 373); thus, some pups may be at an elevated risk of sub-lethal adverse health effects. Fetal mercury exposure was affected by maternal foraging geographic location and depth; mercury concentrations were highest in pups of the deepest diving, pelagic females. Moreover, pup lanugo mercury concentrations were strongly repeatable among successive pups of individual females, demonstrating relative consistency in pup mercury exposure based on maternal foraging strategies. Northern elephant seals are biosentinels of a remote deep-sea ecosystem. Our results suggest that mercury within North Pacific mesopelagic food webs may also pose an elevated risk to other mesopelagic-foraging predators and their offspring.

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“…Early breeding and late breeding seals were targeted for sampling at approximately 5 and 23 days post-parturition, respectively, within a lactation period that lasts approximately 26 days . The molting period lasts approximately 43 days . Early molting females were handled within several days of arriving on land if they had been satellite-tracked during the preceding foraging trip.…”

Section: Methodsmentioning

confidence: 99%

“…Northern elephant seals provide a unique opportunity to study a wild mammalian system with naturally occurring variations in both cortisol and contaminant tissue concentrations because of extreme fluctuations in body mass driven by annual life history events that occur on land when animals are accessible for study. − In between biannual months-long foraging trips at sea, northern elephant seal females spend two periods of time ashore each year (one for breeding/parturition/lactation and another for molting), , during which time they fast and lose approximately 42 and 32% of their body mass, respectively. , Furthermore, the deep-sea marine foraging ecology of adult northern elephant seals results in high mercury concentrations within skeletal muscle and blood, with wide variations in mercury contamination among individuals . Additionally, tissue mercury concentrations change markedly within individuals as they undergo large fluctuations in body mass associated with bi-annual fasting and foraging periods .…”

Section: Introductionmentioning

confidence: 99%

Mercury Bioaccumulation and Cortisol Interact to Influence Endocrine and Immune Biomarkers in a Free-Ranging Marine Mammal

Peterson

Ackerman

Holser

et al. 2023

Environ. Sci. Technol.

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Mercury bioaccumulation from deep-ocean prey and the extreme life history strategies of adult female northern elephant seals (Mirounga angustirostris) provide a unique system to assess the interactive effects of mercury and stress on animal health by quantifying blood biomarkers in relation to mercury (skeletal muscle and blood mercury) and cortisol concentrations. The thyroid hormone thyroxine (tT4) and the antibody immunoglobulin E (IgE) were associated with mercury and cortisol concentrations interactively, where the magnitude and direction of the association of each biomarker with mercury or cortisol changed depending on the concentration of the other factor. For example, when cortisol concentrations were lowest, tT4 was positively related to muscle mercury, whereas tT4 had a negative relationship with muscle mercury in seals that had the highest cortisol concentrations. Additionally, we observed that two thyroid hormones, triiodothyronine (tT3) and reverse triiodothyronine (rT3), were negatively (tT3) and positively (rT3) associated with mercury concentrations and cortisol in an additive manner. As an example, tT3 concentrations in late breeding seals at the median cortisol concentration decreased by 14% across the range of observed muscle mercury concentrations. We also observed that immunoglobulin M (IgM), the pro-inflammatory cytokine IL-6 (IL-6), and a reproductive hormone, estradiol, were negatively related to muscle mercury concentrations but were not related to cortisol. Specifically, estradiol concentrations in late molting seals decreased by 50% across the range of muscle mercury concentrations. These results indicate important physiological effects of mercury on free-ranging apex marine predators and interactions between mercury bioaccumulation and extrinsic stressors. Deleterious effects on animals’ abilities to maintain homeostasis (thyroid hormones), fight off pathogens and disease (innate and adaptive immune system), and successfully reproduce (endocrine system) can have significant individual- and population-level consequences.

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Density-dependent effects on reproductive output in a capital breeding carnivore, the northern elephant seal (Mirounga angustirostris)

Cited by 14 publications

References 72 publications

Extent and Magnitude of Subsurface Anomalies During the Northeast Pacific Blob as Measured by Animal‐Borne Sensors

Extent and Magnitude of Subsurface Anomalies During the Northeast Pacific Blob as Measured by Animal‐Borne Sensors

Foraging behavior and age affect maternal transfer of mercury to northern elephant seal pups

Mercury Bioaccumulation and Cortisol Interact to Influence Endocrine and Immune Biomarkers in a Free-Ranging Marine Mammal

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