Fact-checked by Grok 2 weeks ago

Elephant seal

Elephant seals are two extant species of very large pinnipeds in the genus Mirounga, belonging to the family Phocidae (true seals), distinguished by their enormous size, extreme sexual dimorphism, and the males' inflatable proboscis that resembles an elephant's trunk.^[1]^[2] The northern elephant seal (Mirounga angustirostris) and the southern elephant seal (Mirounga leonina) are the only members of this genus, with the southern species being the largest of all pinnipeds and the northern the second largest overall.^[3]^[4] These seals spend approximately 80–90% of their lives at sea, foraging in open ocean waters, and haul out on remote beaches primarily for breeding and molting.^[1]^[5] Adult northern elephant seal males can reach lengths of up to 5 meters and weights of up to 2,300 kilograms, while adult southern elephant seal males can reach lengths of up to 6 meters and weights of up to 4,000 kilograms; females of both species are significantly smaller at 2.5–3.5 meters and 400–900 kilograms, enabling males to dominate harems during the breeding season through aggressive displays and combat.^[1]^[2]^[4]^[6]^[7] The proboscis, which develops fully in mature males around 7–9 years of age, amplifies vocalizations used in territorial disputes and serves as a secondary sexual characteristic.^[5] Both species exhibit remarkable diving capabilities, routinely descending to depths of 500–1,000 meters for 20–30 minutes to hunt squid, fish, and occasionally small sharks or skates, with maximum recorded dives exceeding 2,000 meters.^[3]^[2]^[4] The northern elephant seal breeds on islands and coastal sites from Baja California to the Gulf of Alaska in the North Pacific, aggregating in rookeries during winter for polygynous mating where dominant "beachmaster" males control access to dozens of females.^[1]^[3] Females give birth to a single pup after a gestation of about 11 months (including delayed implantation), nurse it for 3–4 weeks—during which the pup gains up to 10 kilograms per day—before returning to sea, leaving the pup to learn swimming independently.^[5]^[1] In contrast, the southern elephant seal inhabits subantarctic islands and the Antarctic Peninsula across the Southern Ocean, with breeding occurring from October to November in similarly structured harems, though some populations have shown declines since the mid-20th century due to factors like climate variability and disease.^[2]^[4] Both species underwent severe population bottlenecks from 19th-century commercial hunting for oil and meat, reducing northern elephant seals to fewer than 100 individuals by 1890 and southern populations to historic lows, but conservation efforts have led to recoveries, with estimates around 180,000–200,000 for the northern (as of 2020) and approximately 650,000 for the southern prior to 2023.^[1]^[3]^[4]^[8]^[9] However, highly pathogenic avian influenza (H5N1) outbreaks since 2023 have caused significant mortality in southern populations, including an estimated 53,000 missing females (halving the South Georgia colony, the world's largest) and over 95% pup mortality at Peninsula Valdés in 2023–2024, with global numbers now substantially lower and long-term recovery potentially spanning a century.^[10]^[11]^[12]^[13] The International Union for Conservation of Nature (IUCN) classifies both as Least Concern, though the recent outbreaks have prompted concerns for southern populations, potentially warranting reassessment.^[10]

Taxonomy and Evolution

Taxonomy

Elephant seals belong to the genus Mirounga within the family Phocidae, the true seals, and the order Carnivora.^[3]^[14] The genus was established by British zoologist John Edward Gray in 1827, with the name Mirounga derived from "miouroung," an Australian Aboriginal term for these seals.^[15]^[16] There are two extant species: the northern elephant seal (Mirounga angustirostris), named for its narrow snout from the Latin angusti- (narrow) and rostris (beaked), and the southern elephant seal (Mirounga leonina), so called from the Latin leonina (lion-like) due to the males' resonant roars.^[17]^[18] Neither species recognizes formal subspecies, though population-level genetic variation exists within each.^[19] Phylogenetically, Mirounga forms the monotypic tribe Miroungini within the subfamily Phocinae, with molecular studies confirming the monophyly of the genus based on complete mitochondrial DNA coding regions.^[20] Genetic analyses place Mirounga as sister to the Lobodontini (Antarctic seals), with this clade closely related to the monk seals (Monachus) in the subfamily Monachinae, supporting a shared southern Hemisphere affinity among these lineages.^[21]^[22] Fossil and molecular evidence indicates that Mirounga diverged from its closest relatives, the Lobodontini, approximately 10–15 million years ago during the late Miocene, likely deriving from ancestors with otariid-like (eared seal) ambulatory traits before specializing in aquatic locomotion.^[23]^[24] This divergence aligns with the radiation of Phocidae in the North Atlantic before southward dispersal.^[25]

Evolutionary history

The evolutionary history of elephant seals (genus Mirounga) traces back to the broader radiation of pinnipeds, which began transitioning from terrestrial carnivorans to marine life during the late Oligocene to early Miocene, approximately 27–20 million years ago (Ma), primarily in the North Atlantic and Mediterranean regions.^[26] Phocids, the true seals including the monachine subfamily to which elephant seals belong, originated in this northern cradle before monachines dispersed southward, with molecular and fossil evidence indicating their diversification in the Southern Hemisphere around 10.8 Ma during the middle to late Miocene.^[25] Early pinniped ancestors, such as the desmatophocids Allodesmus and Desmatophoca from the Miocene North Pacific, represent transitional forms with adaptations for aquatic foraging, though these were more closely aligned with otariids (eared seals) than phocids; phocid precursors like stem monachines emerged concurrently in the Miocene, marked by fossils such as a late Miocene–early Pliocene mandible from southeastern Australia (~5.98–4.62 Ma) that shows affinities to early monachines like Neomonachus.^[27]^[26] Key fossils reveal the emergence of Mirounga-like forms in the late Pliocene, with the oldest unambiguous records consisting of fragmentary remains (including a maxilla, squamosal, and teeth) from the Petane Formation in New Zealand, dated to 2.4–2.1 Ma, supporting a Southern Hemisphere origin for the tribe Miroungini rather than a North Pacific one.^[24] These specimens exhibit diagnostic features like simplified triple-cusped teeth and a reduced M1, indicative of stem-Miroungini, while molecular divergence estimates place the split from related lobodontins at approximately 6.88 Ma.^[24] Subsequent fossils, such as Pleistocene Mirounga remains from Argentina and the North Pacific, document an antitropical distribution pattern, with northern colonization likely occurring in the early to middle Pleistocene following Pliocene diversification in southern waters.^[25] Evolutionary adaptations, including the male proboscis, are inferred to have arisen in the Pliocene as a vocalization aid for breeding displays in polygynous systems, though direct fossil evidence is limited due to soft-tissue preservation challenges.^[28] The adaptive radiation of elephant seals featured extreme sexual size dimorphism, with males evolving to be 3–10 times larger than females, linked to intense male-male competition in polygynous mating systems that emerged around 9.2–5 Ma during late Miocene to Pliocene monachine diversification in the Southern Ocean.^[25] This dimorphism, among the most pronounced in mammals, facilitated dominance hierarchies and harem defense, driving selection for larger body sizes and associated traits like the proboscis for amplified vocal signals.^[24] Genetic evidence from ancient DNA underscores a severe bottleneck in the northern elephant seal (M. angustirostris) during the 19th century, when hunting reduced the population to ~20 individuals, resulting in profoundly low modern genetic diversity (heterozygosity of 0.000176 ± 0.000013) compared to pre-bottleneck levels (0.00142 ± 0.00092), with increased runs of homozygosity and loss-of-function alleles persisting despite recovery to over 220,000 individuals.^[29] This event highlights how anthropogenic pressures can imprint long-term evolutionary legacies on population genetics.^[29]

Physical Characteristics

Description

Elephant seals, belonging to the genus Mirounga, are the largest pinnipeds and consist of two species: the northern elephant seal (M. angustirostris) and the southern elephant seal (M. leonina). They exhibit a streamlined, torpedo-shaped body plan optimized for marine life, featuring a robust torso supported by a thick blubber layer that provides insulation, buoyancy, and energy reserves. Unlike eared seals (otariids), elephant seals lack external ear flaps and have short foreflippers for primary propulsion in water, paired with broader hindflippers for steering and maneuvering. Their skin is covered in sparse epidermal hairs and typically presents a grayish hue.^[3]^[30] In terms of size, southern elephant seals are marginally larger overall than their northern counterparts. Adult southern males can attain lengths of up to 6 m and weights exceeding 4,000 kg, while females reach about 3 m in length and 900 kg. For northern elephant seals, males grow to 4–5 m long and 2,000–2,500 kg, with females measuring 3–3.7 m and weighing 400–800 kg. These dimensions position elephant seals as the heaviest of all seals, with southern individuals holding the record for maximum mass among pinnipeds.^[3]^[31]^[30] Newborn pups of both species are born with a dark black or brown lanugo coat, measuring around 1.2 m in length and weighing 40–50 kg. This coat is shed during the first molt, typically within the first month, revealing a sleek silver-gray pelage beneath. As they mature, the fur transitions to a lighter silvery-brown or grayish tone in adults, and males often acquire battle scars and calluses on their necks and chests from agonistic interactions.^[5]^[2] A prominent morphological feature in adult males of both species is the development of an inflatable proboscis, resembling an elephant's trunk, which grows to significant proportions with age. This structure, combined with the overall size disparity between sexes, highlights extreme sexual dimorphism characteristic of elephant seals.^[3]^[2]

Sexual dimorphism and adaptations

Elephant seals display one of the most extreme cases of sexual size dimorphism among mammals, with adult males typically weighing 4 to 6 times more than females, a disparity driven by intense sexual selection arising from male-male competition for access to breeding harems.^[3] For instance, adult male northern elephant seals (Mirounga angustirostris) can attain lengths of 4 to 5 meters and masses up to 2,700 kg, while females reach about 3.7 meters and 800 kg; similar ratios apply to the southern species (Mirounga leonina), where males may exceed 3,700 kg compared to females at around 900 kg.^[3]^[32] This pronounced size difference evolved to favor larger males in establishing dominance and defending groups of females against rivals.^[32] A hallmark of male morphology is the proboscis, an inflatable nasal appendage that overhangs the lower lip by approximately 20 cm and serves to amplify deep, resonant roars used in territorial displays and intimidation during the breeding season.^[3] This structure begins developing in males around age 7, coinciding with puberty, and becomes fully prominent by sexual maturity at 8 to 10 years, with northern males exhibiting slightly larger proboscides than their southern counterparts.^[3]^[32] Females entirely lack this feature, maintaining a more streamlined head profile that, combined with their smaller body size, supports greater maneuverability and energy conservation during extended foraging trips at sea.^[32] Beyond size and the proboscis, males exhibit additional adaptations suited to agonistic encounters, including thicker necks reinforced with layers of fibrous tissue and collagen, broader skulls for delivering powerful blows, and extensive blubber deposits that provide both insulation and cushioning against injuries.^[32] These males also develop a thickened chest shield of scarred skin from repeated combats.^[3] In contrast, females have comparatively slender necks and less blubber accumulation, prioritizing agility over bulk, though both sexes rely on substantial blubber layers for thermal regulation in cold marine environments.^[32]

Distribution and Habitat

Geographic range

The northern elephant seal (Mirounga angustirostris) is endemic to the North Pacific Ocean, with its core range extending from Baja California, Mexico, to Alaska in the United States.^[3] Breeding occurs primarily on offshore islands and select mainland sites along the coasts of California and Oregon in the United States, as well as Baja California in Mexico. Key breeding colonies include the Channel Islands such as San Miguel and San Nicolas off southern California, mainland sites like Año Nuevo State Reserve and Piedras Blancas near San Simeon in California, and Isla Guadalupe off Baja California.^[3]^[33] Vagrant individuals have been documented far outside this range, including sightings in Japan and the Hawaiian Islands.^[34] The southern elephant seal (Mirounga leonina) has a circumpolar distribution throughout the Southern Ocean, primarily in subantarctic and Antarctic waters.^[35] Major breeding rookeries are concentrated on remote islands and peninsulas, including South Georgia in the South Atlantic, the Kerguelen Islands in the southern Indian Ocean, Macquarie Island in the subantarctic Pacific, and the Antarctic Peninsula.^[35] Global population estimates placed the species at 650,000–750,000 individuals as of the early 2020s, with these primary sites accounting for the majority of breeding activity. However, avian influenza outbreaks in 2024–2025 have caused significant declines at key rookeries, such as an estimated 53,000 absent females at South Georgia during the 2024 breeding season.^[36]^[11] Historically, both species faced severe population declines due to commercial hunting for oil and hides; the northern elephant seal was nearly extirpated by the 1890s, with only an estimated 20–100 individuals surviving, primarily at Guadalupe Island, before recovering to around 200,000 by the 2020s through legal protections.^[37] The southern elephant seal was similarly hunted intensively during the 18th and 19th centuries but showed variable recovery trends following international bans on sealing.^[38] The two species exhibit no sympatry, as the northern is confined to the Northern Hemisphere and the southern to the Southern Hemisphere, preventing overlap in their distributions.^[3] Northern elephant seals forage northward along migration routes reaching the Aleutian Islands.^[3] Recent observations indicate a northward expansion of the northern elephant seal's range, with increasing sightings and foraging occurrences in British Columbia waters, potentially linked to post-recovery dispersal and warming ocean conditions.^[39]

Habitat and migration patterns

Elephant seals primarily utilize remote, isolated beaches on sub-Antarctic and North Pacific islands for terrestrial habitats, favoring sandy or gravel substrates that provide suitable conditions for breeding and molting. Northern elephant seals (Mirounga angustirostris) breed on protected offshore islands such as the Channel Islands off California and sites in Baja California, Mexico, where they aggregate on sandy or rocky coastlines to minimize disturbance and predation risks.^[3]^[40] Southern elephant seals (Mirounga leonina) haul out on similar remote beaches across sub-Antarctic islands, including sandy, cobble, or gently sloping shores, as well as rocky terraces and occasionally sea ice or snow fields near the Antarctic continent.^[9]^[41] These sites are often wave-exposed yet sheltered enough to support large rookeries, deterring terrestrial predators while allowing access to the sea.^[42] In marine environments, elephant seals are pelagic foragers, with northern species targeting coastal upwelling zones in the northeast Pacific Ocean for nutrient-rich waters, while southern species exploit the Antarctic Convergence Zone, where cold Antarctic waters meet warmer sub-Antarctic currents, creating productive foraging grounds.^[3] Both species spend the majority of their lives at sea, transitioning between these oceanic realms and terrestrial haul-out sites in annual cycles tracked via biotelemetry devices.^[43] Migration patterns involve extensive seasonal movements, with adult females of both species undertaking round-trip journeys of 10,000 to 20,000 km following breeding, dispersing to distant feeding grounds for 3 to 8 months.^[3]^[44] Northern females typically migrate northward to the Gulf of Alaska or central North Pacific after pupping in winter, covering up to 15,000 km over 8 months before returning for molting in spring and breeding in late fall.^[44] Southern females follow circumpolar routes, often moving northward from breeding colonies as sea ice advances in winter, with trips averaging 5,000 to 11,000 km to shelf edges or open Southern Ocean waters.^[45]^[46] Juveniles of both species disperse more widely post-weaning, exploring broader oceanic areas to develop foraging skills before their first migrations.^[3]^[47] Climate variability significantly influences these patterns, with El Niño events disrupting northern elephant seal haul-outs and migrations by altering upwelling and prey availability, leading to reduced foraging success and elevated pup mortality rates up to 80% in severe cases like 1997–1998.^[48] Recent ocean warming has prompted shifts, such as northern seals foraging farther north since the 2010s and potential reductions in southward migration extent for Baja California populations.^[49] For southern seals, broader climate changes, including sea ice dynamics, affect post-breeding dispersal and survival, with models indicating variable impacts on male foraging trips.^[50]

Physiology

Diving and respiratory adaptations

Elephant seals are renowned for their exceptional diving prowess, routinely descending to depths of 500–1,000 meters for durations of 20–40 minutes during foraging expeditions at sea.^[3] These capabilities enable them to access prey in the mesopelagic zone, with recorded maximum depths exceeding 2,200 meters, including a verified dive to 2,388 meters by a southern elephant seal.^[51] In northern elephant seals, adult females typically achieve greater average dive depths than males, often exceeding 600 meters compared to males' 300–500 meters, reflecting adaptations to their respective foraging demands.^[52] The respiratory system of elephant seals features specialized mechanisms to withstand prolonged apnea and high pressures. During deep dives, the alveoli collapse under increasing hydrostatic pressure, shifting air into the larger airways where gas exchange is minimized, thereby preventing the absorption of excess nitrogen that could lead to narcosis or decompression sickness.^[53] This collapse occurs progressively from the lung periphery, starting at depths around 30–50 meters, and allows the seals to avoid lung compression injuries while maintaining structural integrity. To support extended submergence, elephant seals store substantial oxygen reserves, with high concentrations of hemoglobin in the blood and myoglobin in skeletal muscles—up to eight times greater than in humans—enabling efficient oxygen delivery to vital organs during dives.^[54] Approximately two-thirds of their total oxygen store resides in the blood, supplemented by muscle myoglobin, which facilitates aerobic metabolism for much of the dive duration.^[55] Cardiovascular adaptations further enhance diving efficiency through the classic mammalian dive response. Upon submersion, heart rate plummets to bradycardia levels of 4–15 beats per minute, drastically reducing cardiac oxygen consumption and prioritizing blood flow to the brain, heart, and lungs.^[56] Concurrently, peripheral vasoconstriction diverts oxygenated blood away from non-essential tissues like the muscles and digestive organs, conserving oxygen for central organs and minimizing overall metabolic demand during the dive.^[57] These responses are triggered by apnea and facial immersion, intensifying with dive depth and duration to sustain aerobic conditions as long as possible.^[58] Elephant seals exhibit remarkable tolerance to gas exchange challenges, including elevated carbon dioxide levels from anaerobic metabolism toward the end of longer dives. This hypoxemic and hypercapnic tolerance allows them to endure respiratory acidosis without behavioral disruption, supported by efficient buffering systems that mitigate pH changes.^[59] Following a dive, seals surface for brief recovery periods of 2–5 minutes, during which they replenish oxygen stores through rapid breathing at rates up to 0.29 Hz, restoring arterial oxygenation before resuming submergence.^[60] These short intervals optimize time at sea, with surface recovery independent of preceding dive length in routine foraging.^[61] Sex and age variations in diving are pronounced, driven by physiological and ecological factors. Adult females generally perform deeper and more frequent dives to meet energetic needs for reproduction and pup rearing, averaging longer submergences than males, who may prioritize shorter, shallower dives due to their larger body mass and different foraging strategies.^[62] These patterns have been documented through satellite-linked time-depth recorders deployed since the 1990s, with studies spanning to the 2020s revealing consistent dimorphism: females target pelagic depths for squid and fish, while juveniles of both sexes develop diving proficiency rapidly, reaching adult-like capabilities within months.^[43] Such data from archival tags highlight how foraging imperatives shape these adaptations across life stages.^[63]

Sensory and thermoregulatory physiology

Elephant seals possess large eyes well-adapted for low-light conditions underwater, enabling effective vision in the dim pelagic environments where they forage. These eyes feature a high density of rod photoreceptors and a tapetum lucidum that reflects light to enhance sensitivity, making their visual system the most light-sensitive among mammals.^[64] The pupils can dilate extensively to maximize light intake during dives, while the nearly spherical lens corrects for underwater distortion.^[65] Color vision is limited, relying primarily on a single cone type sensitive to blue-green wavelengths, consistent with the monochromatic or dichromatic capabilities typical of pinnipeds.^[66] Underwater hearing in elephant seals is acute, particularly for low frequencies below 1 kHz, facilitating navigation and prey detection in acoustically complex oceanic environments. This sensitivity arises from specialized middle and inner ear structures that provide low hearing thresholds across a broad frequency band up to approximately 20 kHz, allowing passive acoustic orientation without active sound production.^[67] In males, the proboscis serves as a nasal resonator during vocalization, expanding to channel air and amplify low-frequency calls by lowering their fundamental frequency and increasing amplitude through resonant vibrations in the nasal cavity.^[68] The vibrissae, or whiskers, of elephant seals function as hydrodynamic sensors, detecting subtle water movements and vortex trails left by swimming prey even in complete darkness. These specialized mystacial vibrissae, with undulating profiles that minimize self-generated flow noise, enable precise tracking of prey at distances up to 10 meters by transducing mechanical stimuli into neural signals via follicle sinus complexes.^[69] Olfactory capabilities are reduced compared to terrestrial relatives, with a minimized cribriform plate and fewer olfactory receptor genes, reflecting adaptations to an aquatic lifestyle where scent detection is less critical on land and ineffective underwater.^[70] Thermoregulation in elephant seals balances extreme cold in subantarctic and Antarctic waters with overheating risks during terrestrial phases. A thick blubber layer, reaching up to 30 cm in adult males, provides primary insulation against water temperatures as low as -2°C by trapping heat and minimizing conductive loss.^[71] Peripheral countercurrent heat exchangers in the flippers and forelimbs conserve core temperature by routing warm arterial blood alongside cooler venous return, reducing heat dissipation in frigid conditions.^[72] On land, during breeding or molting, excess heat from fasting-induced metabolism is dissipated through mud wallowing, where seals aggregate in cool mud pools to lower skin temperature and enhance evaporative cooling via peripheral vasodilation.^[73] Physiological tolerance to cold extremes is supported by molecular adaptations, including differential gene expression in blubber and muscle tissues that upregulate lipid metabolism and antioxidant defenses during prolonged exposure to near-freezing waters. Recent genomic analyses reveal intact uncoupling protein 1 (UCP1) genes in most pinnipeds, including elephant seals, facilitating non-shivering thermogenesis in brown adipose tissue to maintain homeostasis in polar environments.^[74]

Behavior and Life Cycle

Elephant seals exhibit a highly polygynous mating system, where dominant adult males, known as beachmasters, establish and defend harems consisting of 10 to 100 females on breeding beaches.^[75]^[76] The breeding season lasts approximately 4 to 6 weeks for individual harems, occurring during winter months (December to March) for northern elephant seals (Mirounga angustirostris) and spring to early summer months (September to November) for southern elephant seals (Mirounga leonina).^[3]^[2] Beachmasters, typically aged 9 to 12 years and weighing up to 4,000 kg, arrive first to claim territories and maintain control through aggressive displays and combat, allowing them exclusive mating access to females within their harems.^[3] Male-male competition is intense and ritualized, beginning with vocal threats and trunk inflation to display size and dominance, often escalating to physical confrontations involving bites to the chest and neck.^[76] These fights, while rarely fatal for mature males, contribute to high overall mortality rates among young males, estimated at 80-90% before they reach breeding age, primarily due to accumulated injuries and energy expenditure during repeated challenges.^[77] Subordinate males, including subadults, employ opportunistic "sneaker" strategies to approach females peripherally but face eviction by beachmasters.^[78] Females arrive on breeding beaches already pregnant from the previous season, giving birth to a single pup within 3 to 6 days of hauling out.^[79] They nurse the pup for 4 to 5 weeks, producing milk with a fat content reaching 50-55%, enabling rapid pup growth from about 35 kg at birth to over 150 kg at weaning.^[79]^[80] During the final 1 to 4 days of nursing, females enter a brief estrus period lasting 1 to 2 days, mating primarily with the dominant beachmaster before abruptly weaning the pup and departing to sea.^[81]^[30] Social structure is organized around a strict dominance hierarchy determined by body size, age, and fighting ability, with alpha males at the apex controlling prime beach sections.^[3] Subadult males and non-breeding adults form loose bachelor groups offshore or on peripheral beaches, where they practice combat skills and await opportunities to challenge superiors.^[2] Females aggregate in matrilineal clusters within harems but show limited social bonding beyond mother-pup pairs during the breeding season.^[82] Recent acoustic monitoring studies have revealed that male vocalizations, used in threat displays and rival assessment, typically range from 50 to 100 Hz, with lower frequencies correlating to larger body sizes and higher dominance status.^[83] Post-2010 research on tourism impacts indicates that regulated viewing at breeding colonies does not significantly alter harem formation or mating success, as evidenced by stable pup production rates despite increased human presence.^[84]

Molting process

Elephant seals undergo a distinctive catastrophic molt, in which they shed their entire outer layer of skin and fur simultaneously over a period of 3 to 6 weeks, contrasting with the gradual molting observed in most other pinniped species.^[85] This process occurs annually following the breeding season, with northern elephant seals (Mirounga angustirostris) molting in spring—females typically in March to May and males later in May to August—while southern elephant seals (Mirounga leonina) molt in austral summer (December to February).^[3]^[85]^[86] The molt is triggered by environmental cues such as photoperiod changes, with recent studies in the 2020s highlighting the role of hormonal shifts, including surges in prolactin, in initiating epidermal renewal.^[87] During the molt, elephant seals haul out onto beaches for 20 to 30 days, remaining largely immobile to minimize energy expenditure while fasting on accumulated blubber reserves from prior foraging trips.^[88] This fasting leads to substantial mass loss, averaging 25% of body weight in adult females (approximately 3 kg per day), primarily through fat catabolism, with water loss accounting for up to 30% of initial body mass due to transepidermal dehydration.^[88]^[89] The emerging skin appears gray, wrinkled, and taut, providing a fresh protective barrier against the marine environment upon completion.^[85] Juveniles also participate in this haul-out process for their initial post-weaning molt during the first year, though they exhibit greater individual variation in timing compared to adults.^[90] The physiological demands of the catastrophic molt are significant, including an elevated metabolic rate—up to twice the basal level—to support keratin production and skin regeneration, which increases vulnerability to dehydration, hyperthermia, and potential infections during the haul-out.^[88] Heat flux measurements in southern elephant seals reveal that terrestrial habitats exacerbate these costs through reduced convective cooling, potentially amplifying energy expenditure by 20-30% compared to aquatic environments.^[73] Recent observations indicate that while most individuals adhere to fasting, some southern females intermittently return to sea for shallow dives and limited ingestion, possibly to mitigate thermoregulatory stress under warmer conditions.^[89] Behavioral adaptations during molting emphasize energy conservation, with seals forming dense aggregations on beaches to reduce exposure and huddling to limit heat loss, particularly in juveniles and females who face shorter but intense haul-outs.^[91] Variations exist between sexes and populations; adult females typically endure shorter molting durations (around 6 days of visible shedding) than males, whose larger body size prolongs the process, while reproductive success in females can delay molt onset by up to 19 days relative to non-breeding individuals.^[90] These differences reflect trade-offs in life-history timing, ensuring synchronization with foraging and breeding cycles.^[87]

Foraging and diet

Elephant seals exhibit a diet dominated by squid and mesopelagic fish, such as lanternfish (myctophids), with additional consumption of skates and rays, particularly in northern populations where benthic foraging on these prey occurs along continental margins.^[92] Southern elephant seals incorporate Antarctic krill (Euphausia superba) into their diet, especially during seasonal foraging in shelf regions near the Antarctic continent, alongside fish like Antarctic jonasfish.^[94] These prey preferences reflect opportunistic feeding on abundant, energy-rich resources in deep oceanic layers, with cephalopods comprising over half of the identified prey in stomach content analyses for both species.^[95]^[96] Foraging strategies involve prolonged deep dives to target patchy prey distributions in the mesopelagic zone, with individuals spending over 80% of their time at sea engaged in diving activities to locate and capture food.^[92] Jaw tag telemetry and stomach temperature sensors have revealed that northern elephant seal females conduct 1,000 to 2,000 feeding events per day, primarily on small prey items averaging 5.6–11.2 g, enabling continuous foraging without extended rest periods.^[92]^[97] Female consumption rates range from 4–6 kg per day during migrations, supporting mass gains essential for reproduction and fasting periods ashore.^[97] Southern females similarly achieve high intake, estimated at around 26 kg per day during post-breeding trips, fueling an energy budget where foraging accounts for 63–68% of annual expenditure.^[98]^[99] Ontogenetic shifts in foraging behavior are evident, with juveniles initially targeting near-surface or frontal zone prey before transitioning to deeper, more specialized habitats as they mature.^[100] In southern elephant seals, young seals forage primarily in the Polar Frontal Zone, broadening their diet and increasing trophic levels with age, while adults, particularly males, specialize in Antarctic shelf areas with shallower dives compared to pelagic-focused females.^[100]^[101] These changes enhance foraging efficiency, with adults exhibiting greater dietary variability and specialization.^[102] Elephant seals play a key role in nutrient cycling, transferring oceanic nitrogen and phosphorus to terrestrial ecosystems through feces, urine, and carcasses deposited during haul-outs, which elevate soil nutrient levels and support local vegetation growth.^[103] Recent stable isotope analyses from the 2010s and 2020s indicate shifts in foraging ecology, with declining δ¹³C values in blood samples suggesting changes in at-sea distribution and prey base, potentially linked to ocean warming that alters squid availability and drives prey deeper.^[104]^[105] These adaptations highlight the species' resilience amid environmental pressures, though reduced access to preferred prey may impact energy budgets over time.^[106]

Ecology and Interactions

Predators and predation

Elephant seals face predation primarily from orcas (Orcinus orca) at sea, which target juveniles and weakened adults during foraging migrations, and great white sharks (Carcharodon carcharias) in the northern Pacific populations. Orcas, as apex predators, often attack weaned pups and subadults near rookeries or along coastal routes, with documented observations of 29 successful predations on elephant seals, 24 of which were on weaned pups. Great white sharks pose a notable risk to northern elephant seals (Mirounga angustirostris), particularly during nearshore activities, though their predation is modulated by orca presence, which can displace sharks from feeding grounds.^[107]^[108]^[109] Predation rates vary by location and year, but orcas can inflict high pup mortality in vulnerable colonies; adults are seldom taken except during molting, when immobility on beaches heightens risk from both marine and terrestrial threats. On land, predation is rare but occurs, with coyotes (Canis latrans) scavenging or attacking stranded pups in shared coastal habitats. Beach haul-outs, essential for breeding and molting, increase vulnerability to these terrestrial predators by limiting escape options.^[108]^[110]^[111] To counter these risks, elephant seals exhibit anti-predator behaviors tailored to sea and shore. At sea, individuals perform rapid, deep dives to evade orcas and sharks, adjusting migration paths based on perceived predation hotspots known as "lightscapes of fear." On beaches, group vigilance within harems enables collective threat detection, prompting stampedes to safer areas or loud vocal warnings to alert the colony; males often position themselves peripherally to monitor for intruders.^[112]^[113] An associated interaction, though not true predation, is opportunistic milk stealing, where non-breeding females, subadults, or weaned pups attempt to suckle from nursing mothers, potentially reducing milk availability for offspring and noted as a form of intraspecific competition during breeding seasons.^[114]

Parasites and diseases

Elephant seals are host to a variety of external parasites, primarily seal lice of the genus Lepidophthirus, such as L. macrorhini in southern elephant seals (Mirounga leonina), which infest the skin and fur during haul-out periods on breeding beaches.^[115] These lice are obligate ectoparasites that feed on host blood and can survive extreme conditions, including the deep dives of their hosts, though infestations peak during terrestrial phases when seals are aggregated, leading to higher transmission rates.^[116] Leeches, such as species in the family Piscicolidae, have also been observed attaching to the skin of southern elephant seals during coastal strandings, causing localized irritation but generally low-intensity infestations.^[117] Internal parasites are predominantly nematodes acquired through the seals' diet of fish and squid, including species like Contracaecum spp. and Anisakis spp., which inhabit the stomach and intestines, and lungworms such as Otostrongylus circumlitus that affect the respiratory tract in northern elephant seals (Mirounga angustirostris).^[118] Tapeworms (cestodes) of genera like Diphyllobothrium are commonly found in the intestines, with larval stages ingested via prey and adults causing potential nutrient malabsorption, though most infections remain subclinical in healthy adults.^[119] These gastrointestinal and pulmonary nematodes often aggregate in stranded or rehabilitated seals, contributing to secondary infections if untreated.^[120] Among diseases, leptospirosis, caused by Leptospira interrogans, has caused outbreaks in northern elephant seal populations, with notable cases in stranded individuals during the 1990s, including acute renal failure and mortality in rehabilitated seals, linked to exposure during haul-outs on contaminated rookeries.^[121] Serological evidence indicates prior exposure in wild populations since at least the late 20th century, with intraspecies transmission possible in dense colonies.^[122] Risks from canine distemper virus (CDV) and related phocine distemper virus (PDV) exist due to potential terrestrial contact at rookeries, though no major outbreaks have been documented in elephant seals; these morbilliviruses could pose threats via immune suppression and respiratory complications if introduced.^[123] Health monitoring efforts have detected Brucella spp. antibodies in southern elephant seals, with serological surveys from Antarctic populations showing low but persistent seroprevalence, as reported in studies from the early 2000s analyzed in the 2020s, indicating possible endemic exposure without clinical disease.^[124] Additionally, plastic ingestion, often mistaken for parasitic blockages in necropsies, leads to gastrointestinal inflammation and reduced foraging efficiency, exacerbating disease susceptibility in affected individuals.^[125] Since 2023, highly pathogenic avian influenza (HPAI) H5N1 has caused mass mortalities in southern elephant seal populations, particularly at breeding sites in South America and sub-Antarctic islands like South Georgia. Outbreaks led to the death of approximately 97% of pups at some locations in 2023–2024 and an estimated 47% decline in breeding females at South Georgia as of 2024, marking one of the largest recorded mortality events for the species. The virus likely spread from infected seabirds, with ongoing monitoring and concerns for further impacts. No major outbreaks have been reported in northern elephant seals, though vaccine trials using them as surrogates began in 2025 to prepare for potential threats.^[126]^[11] Parasite loads in elephant seals increase with population density during breeding and molting haul-outs, where close contact facilitates transmission of both external lice and internal nematodes, potentially regulating numbers in recovering populations by elevating pup mortality and reducing adult condition.^[127] This density-dependent effect is evident in northern elephant seal colonies, where higher aggregation correlates with greater helminth burdens, influencing overall population dynamics post-historic recoveries.^[128] Parasites are primarily acquired during foraging dives on infected prey, though haul-out behaviors amplify exposure in crowded rookeries.^[129]

Conservation and Human Impact

Population status

The northern elephant seal (Mirounga angustirostris) is classified as Least Concern by the IUCN Red List, with an increasing population trend. As of 2024, the total population is estimated at approximately 225,000 individuals, a substantial recovery from fewer than 100 seals remaining in the 1890s after commercial sealing in the 19th century decimated numbers by over 90%. Bans on hunting, starting with Mexico in 1922 and followed by the United States in the 1920s, enabled this resurgence, supported by stable annual growth rates of 3-4% observed since the late 20th century.^[33] Populations are monitored through aerial surveys of pups at breeding colonies, which provide minimum abundance estimates, and mark-recapture methods to assess total numbers and movements across rookeries.^[130] The severe historical bottleneck has resulted in low genetic diversity, limiting adaptability despite overall population stability.^[131] Regional variations include ongoing northward expansion, with increasing haul-outs documented in areas like Puget Sound since the 1980s.^[110] The southern elephant seal (Mirounga leonina) is likewise classified as Least Concern by the IUCN Red List (assessed 2014), but with an increasingly uncertain population trend due to recent events. Pre-outbreak estimates from the early 2020s ranged from 607,000 to 750,000 individuals, derived from breeding colony counts in the 2010s and 2020s.^[4] However, since 2023, a highly pathogenic avian influenza (H5N1) outbreak has caused major declines at key sites, including a 47% reduction in breeding females at South Georgia (approximately 53,000 absent as of 2024) and over 95% pup mortality at Península Valdés, Argentina.^[126]^[12]^[11] Like its northern counterpart, the species suffered major reductions from 19th-century commercial sealing, with protections from the 1920s onward allowing recovery; however, the overall trend is now uncertain, with intensified monitoring and potential need for IUCN reassessment.^[35]

Threats and conservation efforts

Northern elephant seals (Mirounga angustirostris) were hunted intensively for their blubber to produce oil from the early 1800s until the 1890s, reducing the population to fewer than 100 individuals surviving primarily on Guadalupe Island, Mexico.^[33] Southern elephant seals (Mirounga leonina) endured similar commercial exploitation in the 19th century across sub-Antarctic sites including South Georgia, where an estimated 800,000 were harvested in total for oil and meat.^[132] These activities nearly drove both species to extinction, but legal protections in the early 20th century allowed remnant populations to recover. Contemporary threats include minor but persistent entanglement in fishing gear, which can cause injury or death, particularly for northern elephant seals during foraging migrations; NOAA Fisheries actively works to mitigate these interactions through gear modifications and monitoring.^[3] A primary emerging threat to southern elephant seals is highly pathogenic avian influenza (H5N1), which since 2023 has caused mass mortalities, including the loss of approximately 53,000 breeding females at South Georgia and nearly all pups at other sites like Península Valdés; long-term recovery from this outbreak may take decades.^[126]^[133] Risks from climate change are also altering prey distributions, with post-2010s reductions in Antarctic krill abundance impacting southern elephant seals' foraging success, as evidenced by their role as ecosystem sentinels detecting ocean shifts.^[134] Ocean acidification exacerbates this by potentially decimating krill populations, indirectly affecting seal prey chains.^[135] Tourism at rookeries poses disturbance risks, stressing breeding and molting seals through proximity and noise.^[136] Additional human impacts encompass vessel strikes in coastal shipping lanes and underwater noise pollution from shipping and seismic surveys, which disrupt northern elephant seals' deep dives and migrations.^[110] Conservation measures have been pivotal: northern elephant seals are safeguarded under the U.S. Marine Mammal Protection Act of 1972, which prohibits unauthorized take and supports population recovery to over 200,000 individuals.^[3] Mexican reserves on Guadalupe Island provided critical refuge for the surviving northern population in the early 1900s.^[137] For southern elephant seals, the Convention for the Conservation of Antarctic Seals (1972), integrated into the Antarctic Treaty System, bans commercial harvesting and mandates ecosystem protection across their sub-Antarctic breeding grounds.^[138] Ongoing efforts include NOAA-led tagging programs since the 1990s, deploying satellite and archival tags on northern elephant seals to track foraging patterns, health, and responses to environmental changes.^[139] Ecotourism guidelines, enforced by agencies like the National Park Service, require observers to maintain at least 100 feet from rookeries to reduce stress during sensitive periods.^[140] International initiatives, such as the Scientific Committee on Antarctic Research (SCAR), facilitate long-term monitoring of southern elephant seal demographics and habitat use through collaborative expeditions, now including surveillance for diseases like H5N1. Looking ahead, post-2020 climate models forecast 10-20% range contractions or shifts for southern elephant seals due to warming oceans and prey relocation, potentially accelerating declines if combined with human pressures and disease outbreaks; this underscores the need for adaptive management to avoid reversing recovery gains.^[141]

References

[1]
Mirounga angustirostris (northern elephant seal) | INFORMATION
They typically aggregate in large groups while on land. These animals spend only 10% of their time on land, during reproduction and moulting.
[2]
Mirounga leonina (southern elephant seal) - Animal Diversity Web
Southern elephant seals live on land only when molting, breeding, and giving birth. When on land, they stay on beaches close to the ocean.
[3]
Northern Elephant Seal | NOAA Fisheries
Most of this time is underwater, diving to depths of about 1,000 to 2,500 feet for 20 to 30 minute intervals with only short breaks at the surface. They are ...
[4]
Mirounga leonina (Southern elephant seal) - Marine Mammal Science
The southern elephant seal (Mirounga leonina) is one of two species of elephant seals. It is the largest member of the clade Pinnipedia and the order Carnivora.Range And Population · Behaviour · Feeding And Diving
[5]
Northern Elephant Seal | The Marine Mammal Center
As part of the phocid, or true seal, family, elephant seals have ear holes and short front flippers that allow them to move on land by flopping on their bellies ...Missing: biology | Show results with:biology
[6]
https://elephantseal.org/about-the-seals/
[7]
https://www.asoc.org/learn/southern-elephant-seals/
[8]
Elephant Seal Fact Sheet | Blog | Nature - PBS
Jan 21, 2022 · Conservation Status: Both species are listed as of “Least Concern” by IUCN's Red List. Conservation Efforts: Northern elephant seals are ...
[9]
Elephant seals are pinnipeds - Earthguide
Jun 24, 2013 · The genus name Mirounga originates from an old Australian Aboriginal name for elephant seals, miouroung. In their classic book on elephant seals ...
[10]
Origins, Misnomers, and Bottleneck (Chapter 1) - Elephant Seals
Sep 23, 2021 · So, Mirounga, from Miouroung – an old Australian Aboriginal name for elephant seals – was proposed and has been the genus name since 1827 (Gray ...
[11]
https://www.bbc.com/future/article/20251105-the-impossible-decline-of-the-southern-elephant-seal
[12]
https://www.theguardian.com/environment/2025/nov/13/bird-flu-h5n1-kills-half-elephant-seals-south-atlantic-south-georgia-antarctic-aoe
[13]
Elephant Seals (Genus Mirounga) - iNaturalist
Elephant seals are large, oceangoing earless seals in the genus Mirounga. The two species, the northern elephant seal (M. angustirostris) and the southern ...
[14]
A phylogeny of the extant Phocidae inferred from complete ...
Although the monophyly of Mirounga spp. (elephant seals) has never been questioned, both extant species have not been included in a molecular phylogenetic ...
[15]
Journal of Biogeography | Wiley Online Library
Jun 13, 2005 · Lobodontini + Mirounga form a clade sister to Monachus. Molecular divergence dates indicate that the first split within the Monachinae ...
[16]
Historical biogeography and phylogeny of monachine seals ...
Aug 7, 2025 · Lobodontini + Mirounga form a clade sister to Monachus. ... Monachinae (southern seals), one of two subfamilies of Phocidae, includes extant monk ...<|separator|>
[17]
Phylogeny and divergence of the pinnipeds (Carnivora
Divergence dates. The fossil record suggests that the divergence of the two phocid subfamilies occurred sometime prior to the middle Miocene (> 14.6 mya) [77] ...
[18]
The origin of elephant seals: implications of a fragmentary late ...
Mirounga spp. are the largest bodied and deepest diving of all modern pinnipeds, and possess the greatest degree of sexual dimorphism of any mammal (Hindell & ...
[19]
First monk seal from the Southern Hemisphere rewrites ... - Journals
Nov 11, 2020 · Monachines are monophyletic and comprise five distinct lineages: a basal clade comprising Homiphoca, Acrophoca, Piscophoca and Hadrokirus; a ...
[20]
Oldest record of monk seals from the North Pacific and ...
True seals (crown Phocidae) originated during the late Oligocene–early Miocene (approx. 27–20 Ma) in the North Atlantic/Mediterranean region, ...
[21]
Black Rock pinniped fossils - Palaeontologia Electronica
Nov 12, 2022 · Here we report two new seal fossil remains from the late Miocene-early Pliocene of southeastern Australia, discovered from a new site, Black Rock.
[22]
Incredible Elephant Seals, Part 2 | Scientific American
Jun 26, 2017 · This suggests that the giant size of Mirounga is a recently evolved, post-Pliocene novelty. The Waipunga seal has a bony shelf region at the ...<|control11|><|separator|>
[23]
Genomics of post-bottleneck recovery in the northern elephant seal
Feb 21, 2024 · We sequenced 260 modern and 8 historical northern elephant seal nuclear genomes to assess the impact of the population bottleneck on individual northern ...
[24]
Southern elephant seal - Mirounga leonina - OBIS-SEAMAP
The southern elephant seal is the largest pinniped species. In both sexes, the body is robust and the neck is very thick. The head, muzzle, and lower jaw ...<|separator|>
[25]
Size and morphology of seals - Elephant Seal Research Group
Males may weight up to four tons while maximum recorded weight for females is around 900 kg, and the most of them are lighter.
[26]
https://pmc.ncbi.nlm.nih.gov/articles/PMC6548721/
[27]
[PDF] Elephant Seals of Sea Lion Island
Pre-breeding mortality of males is high, and just 5-10% of each male cohort reaches full sexual maturity. Elephant seal forage alone, but on land they are ...
[28]
History and present status of the northern elephant seal population
Sixty-four percent of 28,164 northern elephant seal pups born in 1991 were produced on two southern California Channel Islands, San Miguel and San Nicolas. The ...
[29]
Extreme dispersal or human-transport? The enigmatic case of an ...
Sep 2, 2020 · Elephant seals (Mirounga spp.) are the largest living pinnipeds, and the spatial scales of their ecology, with dives over 1 km in depth and ...
[30]
Estimation of total population size of southern elephant seals ...
Jun 11, 2023 · Available land censuses suggest that the three largest elephant seal breeding populations located in South Georgia, Kerguelen and Macquarie, ...Missing: rookeries | Show results with:rookeries
[31]
Genomic and fitness consequences of a near-extinction event in the ...
Sep 27, 2024 · Although the subsequent recovery was initially slow, there followed over half a century of explosive population growth and range expansion, and ...
[32]
Elephant Seals - UC Press E-Books Collection
The species was hunted for its oil in the eighteenth and nineteenth centuries and subsequently recovered under protection. The only large-scale industry this ...
[33]
Northern Elephant Seal - Channel Islands National Park (U.S. ...
Mar 17, 2020 · Males begin developing this enlarged nose, or proboscis, at sexual maturity (about three to five years of age) and it is fully developed by ...
[34]
Mirounga leonina (Southern elephant seal) - OBIS-SEAMAP
Southern elephant seals prefer sandy and cobble beaches, but will haul-out on sea ice, snow, and rocky terraces, and regularly rest above the beach in tussock ...
[35]
The southern elephant seal Mirounga leonina at Gough Island
Southern elephant seals Mirounga leonina selected mainly the gently sloping, smooth-surfaced beaches and vegetated areas of the sheltered north-east coast.
[36]
[PDF] Life history account for Northern Elephant Seal
Reproduction: All breeding activities take place on isolated or protected beaches on islands, or at a few mainland sites. Preferred breeding areas are ...
[37]
Two decades of three-dimensional movement data from adult ...
Dec 18, 2024 · We now know that adult female elephant seals can dive as deep as 1,764 m, nearly triple what the earliest records revealed. The extensive nature ...Background & Summary · Animal Handling · Diving DataMissing: facts | Show results with:facts<|control11|><|separator|>
[38]
Coherent movement patterns of female northern elephant seals ...
Oct 23, 2023 · Northern elephant seals engage in large-scale foraging migrations traveling up to 15000 Km over 8 months in the northeast Pacific.
[39]
Successful foraging zones of southern elephant seals from the ...
During this time, the seals covered an average distance of 5283±2779 km, with ... foraging top marine predators, Scientific Reports, 10.1038/srep18063, 5:1.<|separator|>
[40]
[PDF] Diving behaviour and foraging ecology of female southern elephant ...
The longest migration was a PM trip of 11 600 km. Females from Península Valdés, the only colony for the species with an increasing birth rate, do not feed ...
[41]
Tracking the foraging migrations of Marion Island southern elephant ...
Oct 9, 2023 · We describe the foraging trips (n = 29) of 16 underyearling southern elephant seals from sub-Antarctic Marion Island and compare these with trips (n = 152) of ...
[42]
Northern Elephant Seals - MarineBio Conservation Society
Northern elephant seals are threatened by El Niño events such as the 1997-98 event when northern elephant seal pup mortality rose to 80%. El Niño events ...<|control11|><|separator|>
[43]
Climate change and the northern elephant seal (Mirounga ...
The results obtained in this study suggest that numbers of northern elephant seals in Baja California colonies are decreasing, and the climate in the region is ...Missing: British Columbia
[44]
Modeling climate influences on male survival in the highly ...
Jun 10, 2024 · Southern elephant seal pups enter the population at a roughly equal sex ratio, with males being slightly larger and heavier than female pups ( ...
[45]
Deepest dive by a pinniped | Guinness World Records
Northern elephant seal. Where: United States (San Miguel Island,). When ... maximum depth of 1,529 m (5,017 ft). Records change on a daily basis and are ...
[46]
Elephant Seals - UC Press E-Books Collection
Males and females have similar dive patterns, except that males dive approximately 180 m less deep than nonpregnant females, on average (table 13.2, fig. 13.2; ...
[47]
Seal Lungs Collapse During Free Diving: Evidence from Arterial ...
In a single dive, alveolar collapse and redistribution of blood nitrogen allow the seal to avoid nitrogen narcosis and decompression sickness.
[48]
Oxygen Capacity and Utilization - Friends of the Elephant Seal
In addition, the heart and skeletal muscles of elephant seals have a density of myoglobin, a molecule similar to hemoglobin, that is more than 8 times more ...
[49]
Extreme hypoxemic tolerance and blood oxygen depletion in diving ...
In phocid seals, such as the elephant seal, approximately two-thirds of the total body O2 store is in the blood (65). The contribution of the lung to total O2 ...
[50]
Cardiovascular adaptations to diving in the northern elephant seal ...
During water immersion the animals developed bradycardia, as low as 4 beats/min and intense peripheral vasoconstriction.
[51]
Oxygen - Earthguide: Elephant Seals
Jun 24, 2013 · The heart rate slows to reduce oxygen consumption (bradycardia) · Blood vessels and capillaries in extremities are constricted so that oxygen is ...
[52]
Heart Rates of Northern Elephant Seals Diving at Sea and Resting ...
Aug 1, 1997 · Heart rate at sea declined by 64 % from the surface rate of 107±3 beats min−1 (mean ± S.D.), while heart rate on land declined by 31 % from the ...ABSTRACT · Introduction · Materials and methods · Results
[53]
https://www.science.org/doi/10.1126/science.4023700
[54]
Characterization of postdive recovery using sound recordings and ...
Jun 16, 2015 · Using this method, we found that seals took successive identical breaths at high frequency (0.29 Hz) when recovering at the surface and that ...
[55]
Acoustic measurements of post-dive cardiac responses in southern ...
Elephant seals are assumed to drastically slow their heart rate (bradycardia) while they are deep underwater, and increase it (tachycardia) during the ascent ...
[56]
(PDF) Sex differences in diving and foraging behaviour of Northern ...
Males of both species foraged during daylight hours and tended to dive deeper than females. Females of both species had shorter dive bouts (i.e., duration of a ...
[57]
Two decades of three-dimensional movement data from adult ...
Dec 18, 2024 · An adult female northern elephant seal carrying a Wildlife Computers Mk-10 satellite tag on her head, and a Mk-9 time-depth recorder paired with ...
[58]
Large sensory volumes enable Southern elephant seals to ... - NIH
Oct 16, 2023 · Elephant seals have the most light-sensitive eyes of any mammal (10) and can likely still see prey at depths at which other visual predators ...
[59]
[PDF] DARK ADAPTATION AND VISUAL SENSITIVITY IN SHALLOW AND ...
In comparison to the human subject, both the California sea lion and the harbor seal dark-adapted relatively quickly and were more light sensitive. These ...
[60]
[PDF] Colour vision in aquatic mammals—facts and open questions
The spectral absorption curves of pinniped rod visual pigments are shifted to shorter wavelengths than those of terrestrial mammals, with a λmax at about 496 nm ...
[61]
[PDF] An animal-borne active acoustic tag for minimally invasive ...
Additionally, northern elephant seals have acute underwater hearing sensitivity with relatively low hearing thresholds occur- ring over a very broad ...
[62]
structure, ontogeny, and function of the elephant seal proboscis
Aug 6, 2025 · Vocalizations are a main component of elephant seal agnostic behavior (Sandegren, 1976;Sanvito and Galimberti, 2000), and vocalizations are ...
[63]
Whiskers as hydrodynamic prey sensors in foraging seals - PMC - NIH
Jun 13, 2022 · Underwater vision is limited for deep-diving predators. A gleam of bioluminescence is the primary light source in otherwise utter darkness (1).
[64]
Olfaction at depth: Cribriform plate size declines with dive depth and ...
For this reason, we predicted marine carnivorans would have reduced olfactory anatomy relative to closely related terrestrial carnivorans. Moreover, because ...
[65]
Distribution - ScienceDirect.com
A subantarctic and Antarctic seal is the southern elephant seal. In the ... cold waters. The relative inability to regulate body temperature adequately ...
[66]
[PDF] Environment and activity affect skin temperature in breeding adult ...
Most thermal studies in marine mammals have focused on counter-current heat-exchange systems, behavioral thermoregulation and thermoregulatory use of appendages ...
[67]
Metabolic heat loss in southern elephant seals (Mirounga leonina ...
Heat loss was lower in wallow and lower still in vegetation habitats. •. Body condition and skin temperature both decreased at the end of the moult.
[68]
Terrestrial Birth and Body Size Tune UCP1 Functionality in Seals
While fully aquatic mammals lost UCP1, most semiaquatic seals display intact UCP1 genes, apart from large elephant seals. Here, we show that UCP1 thermogenic ...
[69]
Sex on the beach: pressures of extreme polygamy may be driving ...
Mar 21, 2023 · Extreme polygamy may be driving male southern elephant seals to early deaths, new research suggests. A study of 14,000 southern elephant seals ...Missing: percentage | Show results with:percentage
[70]
December | Friends of the Elephant Seal
Through threat, intimidation and fights, alpha males establish control over portions of the beach. Their battles may be bloody but are almost never fatal.Missing: mortality rate
[71]
Male-male Competition and Reproductive Success in Elephant Seals
Aug 6, 2025 · Male-male competition is a major cause of pup mortality prior to weaning. The potential reproductive success of males is much greater than that of females.
[72]
Elephant Seal Monitoring Season Summary: Winter 2024-2025
Mar 27, 2025 · The harem in front of Ken Patrick Visitor Center has 27 cows and 21 pups as of 1/24/25. We saw a cow with a pink flipper tag 'N824' nursing a ...
[73]
Elephant Seal Monitoring Season Summary: Winter 2019-2020 ...
The total gestation period for northern elephant seals is approximately 11 months. After successful mating, female seals will delay implantation for about 3 ½ ...
[74]
Elephant Seals - California State Parks
Elephant seals are large, with males having long noses. They are large, 14-16 feet long, and weigh up to 2.5 tons. They spend most of their lives at sea.
[75]
Birthing and Breeding | Friends of the Elephant Seal
Birthing and breeding season takes place December through March. Adult male seals (bulls) and large sub-adult male seals begin to arrive in late November.
[76]
Social Giants | San Diego Zoo Wildlife Alliance
Aug 2, 2021 · Female elephant society is structured as a nested hierarchy of herds. ... bachelor herd, or affiliating within larger mixed family groups.
[77]
Rival assessment among northern elephant seals - Journals
Aug 1, 2015 · Further, the first frequency quartile (Q25) decreased with body size, with larger animals having lower frequency calls (table 2). None of the ...
[78]
[PDF] Best Practices from Elephant Seal (Mirounga sp.) Colonies
Tourist and Seal Numbers – Tourists did not negatively impact pup production or colony growth as evidenced by positive growth rates of both people and elephant ...Missing: post- | Show results with:post-
[79]
March: Catastrophic Molt: It's Not As Bad As It Sounds (U.S. National ...
Apr 25, 2024 · The elephant seal catastrophic molt (which simply means that their fur and top layer of skin comes off in large patches) is more dramatic than a few hairs in a ...Missing: review | Show results with:review
[80]
Reproductive success delays moult phenology in a polar mammal
Mar 26, 2019 · In seals (family Phocidae), some evidence suggests that moult is delayed in reproductively successful individuals; however, the effects of ...
[81]
Moult energetics of the northern elephant seal (Mirounga ...
Moulting takes place on land and lasts a mean of 32.0±6.6 days. During this time the mean mass loss of adult females was 24.7±6.1%.
[82]
Breaking the fast: first report of dives and ingestion events in molting ...
Jan 8, 2024 · To distinguish mud pools (wallows) from sea-water baths ... Water and energy flux in elephant seal pups fasting under natural conditions.
[83]
Individual variation in life-history timing: synchronous presence ...
Apr 17, 2024 · Elephant seals moult on a regular annual cycle, but we discovered that life-history timing is surprisingly variable and staggered across ...
[84]
Environmental and physiological determinants of huddling behavior ...
Feb 1, 2019 · Southern elephant seals aggregate in large groups, mostly in mud pools (wallows) ... thermoregulation and increase their rate of molt in ...Missing: wallowing | Show results with:wallowing
[85]
Round-the-clock deep foraging on small prey by elephant seals - PMC
May 12, 2021 · It is not easy to get fat: Seals' extreme foraging suggests evolutionary trade-off of large body size in marine mammals.
[86]
https://www.nature.com/articles/s41598-021-92635-9
[87]
Diet of Lanternfish & Krill in Southern Elephant Seals
Jan 30, 2025 · Models indicate that myctophid fish were the dominant prey item consumed (mean 45% of diet), followed by Antarctic krill and Antarctic jonasfish.
[88]
You are what you eat: describing the foraging ecology of southern ...
The southern elephant seal (Mirounga leonina) consumes large quantities of fish and squid prey in the Southern Ocean relative to other marine mammals; however, ...
[89]
Northern Elephant Seal (Mirounga angustirostris)
Cephalopods are an important component of the Northern elephant seal diet. Other prey includes Pacific whiting, skates, rays, sharks and pelagic red crabs.
[90]
Time to eat: measurements of feeding behaviour in a large marine ...
Mar 31, 2009 · Time to eat: measurements of feeding behaviour in a large marine predator, the northern elephant seal Mirounga angustirostris. Carey E. Kuhn ...
[91]
Food consumption estimates of southern elephant seal females ...
Aug 6, 2025 · ... Kg day. 1. and. estimated that females consume around 6.2% of their. mass daily during the post-breeding aquatic phase. From our ﬁgures, ...
[92]
ESRG - Elephant seal biblio
The southern elephant seal (Mirounga leonina) consumes large quantities of fish and squid prey in the Southern Ocean relative to other marine mammals; however, ...
[93]
Shift in foraging grounds and diet broadening during ontogeny in ...
Dec 30, 2012 · Our study provides new information on the proportion of individuals using the two main foraging habitats. We found that males foraged mainly ...
[94]
[PDF] Ontogenetic niche partitioning in southern elephant seals ... - CEBC
These changes involve diving ability, foraging capacity, movement patterns, foraging habitat, and diet (e.g., Bailleul, Authier, et al., 2010; Chaigne et al., ...
[95]
Ontogenetic niche partitioning in southern elephant seals from ...
Dec 12, 2020 · Shift in foraging grounds and diet broadening during ontogeny in southern elephant seals from Kerguelen Islands. Marine Biology, 160(4), 977 ...
[96]
https://www.pinnipeds.org/seal-information/species-information-pages/the-phocid-seals/northern-elephant-seal
[97]
Decadal changes in blood δ13C values, at-sea distribution ... - NIH
Aug 19, 2020 · Changes in the foraging environment and at-sea distribution of southern elephant seals from Kerguelen Islands were investigated over a ...Missing: 2020s | Show results with:2020s
[98]
Warming Ocean Temperatures May Reduce the Survival Rate of ...
Feb 9, 2012 · Due to climate change, warmer waters are driving the seals' food source into deeper waters forcing the seals to dive deeper in search of a meal.
[99]
Elephant seals as sentinels of the ongoing changes affecting the ...
Females fast while nursing their pups using the energy reserves accumulated during the eight-month pre-breeding trip at sea (February – October, Jönsson, 1997), ...Missing: estrus | Show results with:estrus
[100]
Some Ocean Optimism Ep. 3: Elephant Seals
Sep 30, 2020 · Northern elephant seals are found in the North Pacific from Baja California, Mexico, to the Gulf of Alaska and Aleutian Islands. They are ...Missing: sympatry | Show results with:sympatry
[101]
[PDF] Killer Whale (Orcinus orca) Predation of Marine Mammals
The successful predation of 29 elephant seals was observed, 24 of which were weaned pups.
[102]
Killer whales redistribute white shark foraging pressure on seals
Apr 16, 2019 · This study suggests that intraguild interactions between killer whales and white sharks may result in cascading effects at lower trophic levels ...
[103]
Northern elephant seals in Puget Sound and vicinity
Nov 30, 2023 · Northern elephant seals were hunted heavily in the 19th century and believed to be extinct by 1892. However, a small remnant population ...Missing: expansion | Show results with:expansion
[104]
Coyote (Canis latrans) use of marine resources in coastal California
Seals and sea lions account for ~20% of Año Nuevo coyote diet throughout the year and this marine subsidy likely positively impacts coyote population size.
[105]
Lightscapes of fear: How mesopredators balance starvation and ...
Mar 17, 2021 · Predators are thought to play an important role in driving elephant seal behavior at sea. The core habitats of elephant seal predators including ...
[106]
https://www.sciencedirect.com/science/article/pii/S0048969725017656
[107]
https://www.marinemammalcenter.org/news/some-ocean-optimism-ep-3-elephant-seals
[108]
Under pressure: the extraordinary survival of seal lice in the deep sea
Jul 14, 2020 · We collected lice from elephant seals and submitted the different ... (B) This louse is a parasite of the elephant seal Mirounga leonina.
[109]
Host-parasite coevolution leads to underwater respiratory ... - Nature
Jun 4, 2025 · Lice are obligate ectoparasites ... We collected seal lice, Lepidophthirus macrorhini, from weaning pups of southern elephant seals Mirounga ...
[110]
Epibionts and parasites retrieved from a sub-adult Southern elephant...
We report four years (2012-2015) of consecutive observations of the same juvenile male Southern elephant seal along the coast Espírito Santo (ES), Brazil.
[111]
Fecal Parasite Surveillance of Northern Elephant Seals at Año ... - VIN
A number of parasites were found, including Parafilaroides sp., Anisakis sp., Contracaecum sp., as well as trematodes and cestodes. These results offer ...Missing: internal | Show results with:internal
[112]
Gastrointestinal Parasites and Bacteria in Free-Living South ...
Present study aimed to characterize gastrointestinal parasites and culturable bacteria from free-living South American sea lions (Otaria flavescens)
[113]
Characterization of Otostrongylus circumlitus from Pacific harbor and ...
The results suggest that O. circumlitus is the same species in Pacific harbor and northern elephant seals, and molecular methods make it possible to distinguish ...
[114]
Leptospirosis in northern elephant seals (Mirounga angustirostris ...
Leptospirosis was identified in six northern elephant seals (Mirounga angustirostris) that were stranded in 1995 along the coast of California (USA).
[115]
Acute Renal Failure and Mortality from Leptospirosis in ...
This study confirms the susceptibility of northern elephant seals to leptospirosis, indicates intraspecies transmission during rehabilitation, and reports the ...
[116]
Phocine Distemper Virus: Current Knowledge and Future Directions
Dec 22, 2014 · Phocine distemper virus (PDV) was first recognized in 1988 following a massive epidemic in harbor and grey seals in north-western Europe.
[117]
Serological screening for Brucella spp. and Leptospira spp ...
Dec 17, 2020 · Brucella spp. and Leptospira spp. antibodies were surveyed in 35 southern elephant seals (SESs) Mirounga leonina at Elephant Island (South Shetland Islands), ...
[118]
[PDF] IMPACTS OF PLASTIC POLLUTION ON A PELAGIC MARINE ...
Northern elephant seals (NES; Mirounga angustirostris) in particular allow us to study plastic pollution in a pelagic marine mammal. They spend 90% of their ...
[119]
Population density drives increased parasitism via greater exposure ...
Exposure to environmentally transmitted parasites should increase with population density due to accumulation of infective parasites in space.
[120]
Density-dependent effects on reproductive output in a capital ...
Oct 13, 2021 · We examine how variation in the environment and population density affect reproductive outcomes in a capital-breeding carnivore, the northern elephant seal.
[121]
Ecology of Marine Mammal Parasites - SpringerLink
May 16, 2025 · Evidence of possible density-dependent effects between parasite-induced mortality and population size exists for hookworms infecting ...
[122]
[PDF] U.S. Pacific marine mammal stock assessments: 2023
... GEOGRAPHIC. RANGE. California sea lions breed on islands located in ... The Pacific Temperate population includes rookeries within U.S. waters and ...
[123]
Genomic and fitness consequences of a near-extinction event in the ...
Sep 27, 2024 · Theory predicts that severe bottlenecks deplete genetic diversity, exacerbate inbreeding depression and decrease population viability.<|control11|><|separator|>
[124]
A History Of Fur & Elephant Seal Hunting In Antarctica
An estimated 800,000 elephant seals were plundered at the main Sub-Antarctic catching grounds of South Georgia, Kerguelen, Heard and Maquarie during the 19th ...
[125]
From Krill to Elephant Seals, Sentinel Species Detect Hidden Ocean ...
Mar 13, 2025 · A new research paper published in Science recognizes northern elephant seals as an “ecosystem sentinel” that can provide fishing fleets, fisheries managers, ...
[126]
A More Acidic Ocean May Wipe Out Antarctic Krill - Oceana USA
Jul 12, 2013 · A new study published Sunday in Nature Climate Change finds that ocean acidification could cause the Southern Ocean Antarctic krill population to crash by 2300.
[127]
Viewing Elephant Seals - Point Reyes - National Park Service
... entanglement in fishing gear, and intentional harm by people frustrated with the behavioral changes. Some of the items that are fed to marine mammals may be ...
[128]
Conservation success story - Earthguide: Elephant Seals
Jun 24, 2013 · "By 1922, the Mexican government gave protected status to elephant seals, and the U. S. government followed suit a few years later when the ...
[129]
[PDF] Conservation of Antarctic Seals - State.gov
This Convention may be applicable to any or all of the following species: Southern elephant seal Mirounga leonina,. Leopard seal Hydrurga leptonyx,. Weddell ...
[130]
Some Research Takes a Lifetime—Like the Northern Elephant Seal
Mar 14, 2024 · Over five decades, these researchers have tracked thousands of northern elephant seals at Año Nuevo, a state park in California south of San ...
[131]
Elephant Seal Monitoring FAQ (U.S. National Park Service)
May 7, 2018 · For your own safety, always observe elephant seals from a distance. · Stay at least 100 feet from any marine mammal. · Do not come between a cow ...Missing: programs NOAA ecotourism
[132]
Southern elephant seals are adaptable – but they struggle when ...
Mar 19, 2025 · Southern elephant seals are adaptable – but they struggle when faced with both rapid climate change and human impacts · A dynamic evolutionary ...