Hubbry Logo
Crabeater sealCrabeater sealMain
Open search
Crabeater seal
Community hub
Crabeater seal
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Crabeater seal
Crabeater seal
Crabeater seal
View on Wikipedia
from Wikipedia

Crabeater seal
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Parvorder: Pinnipedia
Family: Phocidae
Tribe: Lobodontini
Genus: Lobodon
Gray, 1844
Species:
L. carcinophaga
Binomial name
Lobodon carcinophaga
Distribution of crabeater seal
Synonyms

Phoca carcinophaga
Lobodon carcinophagus

The crabeater seal (Lobodon carcinophaga), also known as the krill-eater seal, is a true seal with a circumpolar distribution around the coast of Antarctica. They are the only member of the genus Lobodon. They are medium- to large-sized (over 2 m (6.6 ft) in length), relatively slender and pale-colored, found primarily on the free-floating pack ice that extends seasonally out from the Antarctic coast, which they use as a platform for resting, mating, social aggregation and accessing their prey. They are by far the most abundant seal species in the world.[2] While population estimates are uncertain, there are at least 7 million and possibly as many as 75 million individuals.[3] This success of this species is due to its specialized predation on the abundant Antarctic krill of the Southern Ocean, for which it has uniquely adapted, sieve-like tooth structure. Indeed, its scientific name, translated as "lobe-toothed (lobodon) crab eater (carcinophaga)", refers specifically to the finely lobed teeth adapted to filtering their small crustacean prey.[4]

Despite its name, the crabeater seal does not eat crabs.

As well as being an important krill predator, the crabeater seal's pups are an important component of the diet of leopard seals (H. leptonyx).

Taxonomy and evolution

[edit]

The genus name of the crabeater seal, Lobodon, derives from Ancient Greek meaning "lobe-toothed", and the species name carcinophaga means "crab eater".[4] The crabeater seal shares a common recent ancestor with the other Antarctic seals, which are together known as the lobodontine seals. These include the leopard seal (Hydrurga leptonyx), the Ross seal (Ommatophoca rossii), and the Weddell seal (Leptonychotes weddelli).[5] These species, collectively belonging to the Lobodontini tribe of seals, share teeth adaptations including lobes and cusps useful for straining smaller prey items out of the water column. The ancestral Lobodontini likely diverged from their sister clade, the Mirounga (elephant seals) in the late Miocene to early Pliocene, when they migrated southward and diversified rapidly in the relative isolation around Antarctica.[5]

Description

[edit]
Illustration of the skull

Adult seals (over five years old) grow to an average length of 2.3 m (7.5 ft) and an average weight of around 200 kg (440 lb). Females are on average 6 cm (2.4 in) longer and around 8 kilograms (18 lb) heavier than males, though their weights fluctuate substantially according to season; females can lose up to 50% of their body weight during lactation, and males lose a significant proportion of weight as they attend to their mating partners and fight off rivals.[6] During summer, males typically weigh 200 kilograms (440 lb), and females 215 kilograms (474 lb). A molecular genetic based technique has been established to confirm the sex of individuals in the laboratory.[7] Large crabeater seals can weigh up to 300 kg (660 lb).[8] Pups are about 1.2 metres (3.9 ft) in length and 20 to 30 kilograms (44 to 66 lb) at birth. While nursing, pups grow at a rate of about 4.2 kilograms (9.3 lb) a day, and grow to be around 100 kilograms (220 lb) when they are weaned at two or three weeks.[4][9]

These seals are covered mostly by brown or silver fur, with darker coloration around flippers. The color fades throughout the year, and recently molted seals appear darker than the silvery-white crabeater seals that are about to molt. Their body is comparatively more slender than other seals, and the snout is pointed. Crabeater seals can raise their heads and arch their backs while on ice, and they are able to move quickly if not subject to overheating. Crabeater seals exhibit scarring either from leopard seal attacks around the flippers or, for males, during the breeding season while fighting for mates around the throat and jaw.[4] Pups are born with a light brown, downy pelage (lanugo), until the first molt at weaning. Younger animals are marked by net-like, chocolate brown markings and flecks on the shoulders, sides and flanks, shading into the predominantly dark hind and fore flippers and head, often due to scarring from leopard seals. After molting, their fur is a darker brown fading to blonde on their bellies. The fur lightens throughout the year, becoming completely blonde in summer.[citation needed]

Crabeaters have relatively slender bodies and long skulls and snouts compared to other phocids. Perhaps their most distinctive adaptation is the unique dentition that enables this species to sieve Antarctic krill. The postcanine teeth are finely divided with multiple cusps. Together with the tight fit of the upper and lower jaw, a bony protuberance near the back of the mouth completes a near-perfect sieve within which krill are trapped.[4]

Distribution and population

[edit]

Crabeater seals have a continuous circumpolar distribution surrounding Antarctica, with only occasional sightings or strandings in the extreme southern coasts of Argentina, South Africa, Australia and New Zealand.[4] They spend the entire year on the pack ice zone as it advances and retreats seasonally, primarily staying within the continental shelf area in waters less than 600 m (2,000 ft) deep.[10] They colonized Antarctica during the late Miocene or early Pliocene (15–25 million years ago), at a time when the region was much warmer than today. The population is connected and fairly well mixed (panmictic), and genetic evidence does not suggest any subspecies separations.[11] A genetic survey did not detect evidence of a recent, sustained genetic bottleneck in this species,[12] which suggests that populations do not appear to have suffered a substantial and sustained decline in the recent past.

Currently, no reliable estimates of the total crabeater seal population are available. Past estimates relied on minimal opportunistic sighting and much speculation, ranging from 2 million[13] to 50–75 million individuals.[14] Genetic evidence suggests that crabeater population numbers may have increased during the Pleistocene.[15] The most recent point estimate is 7 million individuals,[16] some 85 percent of all Antarctic seals,[2] but this 7 million number, too, is considered a likely underestimate.[1] An international effort, the Antarctic Pack Ice Seal initiative, is currently underway to evaluate systematically collected survey data and obtain reliable estimates of all Antarctic seal abundances.[4]

Behavior

[edit]
Two crabeater seals

Crabeater seals have a typical, serpentine gait when on ice or land, combining retractions of the foreflippers with undulations of the lumbar region.[3] This method of locomotion leaves a distinctive sinuous body track and can be extremely effective. When not subject to overheating (i.e. on cold days), speeds on land of 19–26 km/h (12–16 mph) have been recorded for short distances.[3] Satellite tracking data have resulted in conservative estimates of swimming speeds of 66 km/day and 12.7 km/h. While swimming, crabeaters have been known to engage in porpoising (leaping entirely out of the water) and spyhopping (raising the body vertically out of the water for visual inspection) behaviors.[3]

The most gregarious of the Antarctic seals, crabeaters have been observed on the ice in aggregations of up to 1,000 hauled out animals and in swimming groups of several hundred individuals, breathing and diving almost synchronously. These aggregations consist primarily of younger animals. Adults are more typically encountered alone or in small groups of up to three on the ice or in the water.[4]

individual crab eater seal
Young crabeater seal

Crabeater seals give birth during the Antarctic spring from September to December.[17] Rather than aggregate in reproductive rookeries, females haul out on ice to give birth singly. Adult males attend female-pup pairs until the female begins estrus one to two weeks after the pup is weaned before mating. Copulation has not been observed directly and presumably occurs in water. Pups are weaned in about three weeks,[18] at which time they are also beginning to molt into a subadult coat similar to the adult pelage.[3]

Curiously, crabeater seals have been known to wander further inland than any other pinniped. Carcasses have been found over 100 km (62 mi) from the water and over 1,000 m (3,300 ft) above sea level, where they can be mummified in the dry, cold air and conserved for centuries.[19]

Ecology

[edit]

Diet

[edit]
Illustration of the teeth of crabeater seals, which are used to strain krill from the water

Despite the common name of the species, the crabeater seal does not feed on crabs (the few crab species in its range are mostly found in very deep water[20]). Rather, it is a specialist predator on Antarctic krill (Euphausia superba), which comprise over 90% of the diet.[3] Their high abundance is a testament to the extreme success of Antarctic krill, the single species with the greatest biomass on the planet.[21] There is little seasonality in their prey preference, but they may target adult and male krill.[3] Other prey items include cephalopods and diverse Antarctic fish species.[3] Although the crabeater seal is sympatric with the other Antarctic seal species (Weddell, Ross and leopard seals), the specialization on krill minimizes interspecific food competition. Among krill-feeding whales, only blue whales (Balaenoptera musculus) and minke whales (B. acutorostrata) extend their range as far south as the pack ice where the crabeater seals are most frequent.[3] While no reliable historical population estimates have been done, population models suggest crabeater seal populations may have increased at rates up to 9% a year in the 20th century, due to the removal of large baleen whales (especially the blue whale) during the period of industrial whaling and the subsequent explosion in krill biomass and removal of important competitive forces.[22]

Predation

[edit]
Crabeater seal with visible scars on the neck

Young crabeater seals experience significant predation by leopard seals. Indeed, first-year mortality is exceedingly high, possibly reaching 80%, and up to 78% of crabeaters that survive through their first year have injuries and scars from leopard seal attacks.[1] Long scars and sets of parallel scars, visible on the otherwise pale and relatively unmarked pelage of crabeaters, are present on nearly all young seals. The incidence of visible scars falls off significantly after the first year, suggesting leopard seals primarily target the young of the year.[23] The high predation pressure has clear impacts on the demography and life history of crabeater seals, and has likely had an important role in shaping social behaviors, including aggregation of subadults.[3]

Predation by killer whales (Orcinus orca) is poorly documented, though all ages are hunted.[24] While most predation occurs in the water, coordinated attacks by groups of killer whales creating a wave to wash the hauled-out seal off floating ice have been observed.[25] Crabeaters and other Antarctic seals are mainly targeted by the B1 variety of killer whales.[26]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Crabeater seal

View on Grokipedia
from Grokipedia
The Crabeater seal (Lobodon carcinophaga) is a species of true seal (Phocidae) endemic to the region, distinguished by its specialized lobed teeth that function as a for straining from seawater. It inhabits the pack ice zones surrounding and is the most abundant species globally, with an estimated population of 7 to 75 million individuals. Despite its common name, the species consumes almost no crabs, deriving it instead from early misconceptions about its diet; it is classified as Least Concern by the due to its vast numbers and stable status. Physically, adult Crabeater seals measure 2.0 to 2.6 meters in length and weigh around 200 to 300 kilograms, with females slightly larger than males; their fur is dark gray dorsally and lighter ventrally, often scarred from encounters with predators like leopard seals. The most notable adaptation is their unique : the upper and lower teeth feature triangular projections and cusps that interlock to filter euphausiid (Euphausia superba), which comprises over 95% of their diet, supplemented rarely by or . They are agile swimmers, capable of dives up to 430 meters deep, though most foraging occurs in shallow, nocturnal dives less than 40 meters. Crabeater seals are circumpolar in distribution, primarily occupying the seasonal pack ice of the from 60°S southward, with occasional vagrants reaching subantarctic islands, , , and during winter migrations. They form loose aggregations on ice floes but are generally solitary or in small family groups outside the breeding season, which occurs from to December on stable pack ice. Females give birth to a single pup, weighing 20 to 30 kilograms at birth, after an 11-month gestation period involving delayed implantation; pups are weaned after 2-3 weeks and reach at 3-6 years, with a lifespan averaging 20 years in the wild. Although protected under the and rarely harvested, Crabeater seals face potential threats from climate change-induced pack ice loss and competition for from expanding fisheries, though their large population buffers immediate risks. Their ecological role as a primary consumer underscores their importance in food webs, influencing populations of predators such as , seals, and whales.

Taxonomy and evolution

Taxonomy

The crabeater seal bears the binomial name Lobodon carcinophaga, the sole species within the monotypic Lobodon in the Phocidae, the true seals. The name Lobodon originates from the Greek terms lobos (lobe) and odous (), alluding to the distinctive lobed cusps on its postcanine teeth that function as a for straining from seawater. The specific epithet carcinophaga derives from Greek karkinos () and phagein (to eat), translating to "crab-eater," a given that , not crabs, forms over 95% of its diet. Its complete classification follows the hierarchy: Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Carnivora, Suborder Caniformia, Family Phocidae, Subfamily Monachinae, Tribe Lobodontini, Genus Lobodon, Species L. carcinophaga. The species was originally described in 1842 by French naturalists Jacques Bernard Hombron and Honoré Jacquinot as Phoca carcinophaga based on specimens collected during the French Antarctic Expedition aboard the corvettes L'Astrolabe and Zélée. In 1844, British zoologist erected the genus Lobodon to accommodate it, establishing the current ; an earlier junior synonym is Phoca carcinophaga. No are currently recognized, as mitochondrial and nuclear genetic analyses reveal a largely panmictic population with minimal structuring across the circumpolar range, indicating high despite vast distances. Phylogenetic studies place Lobodon carcinophaga within the monophyletic tribe of southern phocids, sister to the genera Hydrurga (), Leptonychotes (), and Ommatophoca ().

Evolutionary history

The Phocidae family, to which the crabeater seal (Lobodon carcinophaga) belongs, originated during the epoch, approximately 23-5 million years ago, with the divergence from otariids (eared seals) estimated at around 20-25 million years ago based on analyses. This split reflects the early radiation of pinnipeds into true seals adapted to diverse marine environments. The earliest phocid fossils date to the early in the North Atlantic, indicating an initial northern origin before southward expansion. Fossil evidence suggests that phocids colonized Antarctic waters during the , coinciding with global cooling events around 7-5 million years ago that enhanced ice formation and created new ecological niches. Lobodontine fossils, the tribe including the crabeater seal, appear in the record (approximately 6.7-5.2 million years ago), marking the group's arrival and adaptation to the cooling . The of involved key morphological innovations, such as the of specialized, multi-cusped teeth for filtration, which likely emerged post-Miocene as the group diverged from other monachines around 5-10 million years ago according to estimates. This divergence positioned the crabeater seal as the basal member of the clade, separating from relatives like the leopard seal (Hydrurga leptonyx) and (Leptonychotes weddellii) approximately 7.1 million years ago. Mitochondrial DNA analyses confirm the close phylogenetic relationship within , with Lobodon forming a to the Hydrurga-Leptonychotes , supporting the tribe's and Antarctic-centric evolution. These genetic studies underscore the rapid diversification driven by the exploitation of krill-rich waters following environmental shifts.

Physical characteristics

Morphology and size

The crabeater seal (Lobodon carcinophaga) exhibits minimal , with adult females generally slightly larger than males. Adult males typically measure 2.0–2.6 m in length and weigh 200–300 kg, while females reach 2.2–2.8 m in length and 200–300 kg, though measurements during breeding show means of 2.19 m and 257 kg for males (n=10–18) and 2.18 m and 228 kg for females (n=8–12), with no significant differences detected. Pups at birth are approximately 1.1–1.4 m long and 20–40 kg. The body is streamlined and spindle-shaped, with a relatively short and a long, narrow adapted for aquatic efficiency. The torso tapers toward the rear, facilitating hydrodynamic movement through waters. Foreflippers are elongated (mean 43 cm) and used primarily for , featuring well-developed manual claws; hindflippers are broader (mean 44 cm) for , with reduced pedal claws forming horny points. No external ear flaps are present, consistent with phocid morphology. The is elongated and narrow, with a slightly concave dorsal profile and a mean condylobasal length of 27.8 cm. is specialized, with a of I 3/2, C 1/1, PC 5/5 (totaling 34 teeth). The postcanine teeth feature unique trifid cusps—one anterior and two to three posterior—forming a sieve-like structure for straining prey. Females appear more robust during breeding due to their marginally greater size.

Coloration and sensory adaptations

The adult Crabeater seal displays coloration, with its dorsal surface typically silvery-gray to tawny brown and fading to a lighter blonde or white ventrally, enhancing in waters. This pattern is accentuated by dark markings around the flippers and a reticulated arrangement of spots and rings on the shoulders, sides, and flippers, which become more prominent with age to blend with ice floes. Newborn pups are covered in a woolly, grayish-brown coat that is darker overall with lighter underparts, providing initial camouflage on pack ice. The fur lightens dramatically over the year due to fading and wear, resulting in a pale tan, gray, or whitish appearance by late summer. An annual molt occurs during the austral summer (January–February), when seals haul out on pack ice to replace their pelage; pups molt into a subadult shortly after at 2–3 weeks, transitioning to a darker brown dorsally that fades to blonde ventrally. This process restores the sheen to freshly molted , which is initially darker and gradually pales. The coloration aids in avoiding underwater predators by making the seal less visible from above or below during dives. Crabeater seals possess large eyes adapted for vision in low-light conditions beneath ice, similar to other phocid seals, with a high density of rod cells enabling detection in dim Antarctic waters. Their hearing is acute underwater, facilitated by bone conduction that transmits sound efficiently through the skull, allowing navigation and prey detection in noisy sub-ice environments. The vibrissae, or whiskers, are undulated and short (pale to clear), numbering around 32–35 mystacial vibrissae per side, and serve as hydrodynamic sensors to detect water currents and subtle prey vibrations without generating significant wake. In contrast, their sense of smell is reduced compared to terrestrial mammals, with small olfactory bulbs limiting aerial olfaction but permitting some underwater chemosensory cues. Thermoregulation in Crabeater seals relies on a thick layer, reaching up to approximately 5 cm in late summer, which provides insulation and in subzero waters. Complementing this, their dense consists of a soft underfur layer for trapping air and longer guard hairs for protection, fully covering the foreflippers and contributing to heat retention during haul-outs on .

Habitat and distribution

Geographic range

The crabeater seal (Lobodon carcinophaga) exhibits a circumpolar distribution exclusively within the region of the , inhabiting waters south of the Polar Front (approximately 55–60°S) to the southern pack ice edge. This range encompasses the dynamic pack ice zones surrounding the continent, where the species is most commonly observed on loose pack ice rather than fast ice or the continental coastline. Although generally absent from the mainland, higher concentrations occur near the coast due to favorable ice conditions extending close to shore in that sector. Habitat preferences center on year-round occupancy of loose pack ice, where individuals haul out on ice floes for resting, molting, and breeding, while avoiding land-based sites entirely. Seasonal movements track the advancing and retreating pack ice, often following swarms northward to about 60°S in austral winter and southward during summer, though sightings north of the remain rare and typically involve vagrants stranding on sub-Antarctic islands. Foraging occurs in the beneath the ice, with most dives shallow and typically less than 50 m deep, though the species is capable of dives up to 430 m or more. Recent 2020s surveys and models indicate potential distributional shifts due to melt, with projections of expanded foraging habitat toward offshore waters in response to changing distributions under climate warming.

Population estimates

The crabeater seal (Lobodon carcinophaga) is the most abundant species worldwide, with global population estimates ranging from 7 to 75 million individuals as of 2012 surveys, comprising the vast majority of seals. These figures position it as a dominant component of the ecosystem, far outnumbering other seal species combined. Densities in prime pack habitats can reach local highs of over 100 individuals per km², particularly in regions of extensive cover. Estimates are primarily obtained through aerial photographic surveys and shipboard line-transect counts conducted during the austral spring and summer, when seals haul out on ice floes. The multinational Pack-Ice Seals (APIS) program, spanning multiple expeditions from 2000 onward, has contributed key data by surveying thousands of kilometers of pack ice and observing tens of thousands of individuals, helping refine circumpolar abundance models. While satellite-based methods like have advanced mapping since 2018, their direct application to seal population estimation remains limited, with traditional surveys providing the core data. Regionally, abundances are highest in the , with estimates of several million individuals, and the Bellingshausen Sea, with notable concentrations in the inner pack ice zones. Pup production is inferred to be on the order of several million annually based on breeding survey data, sustaining the overall population. These concentrations align with areas of optimal pack ice extent for hauling out and . Overall trends indicate a stable population, with models suggesting possible historical increases linked to reduced competition from whales, though no large-scale declines have been documented. Local variations, including some reductions in eastern sectors potentially tied to krill availability fluctuations, have been noted in regional surveys, but the faces no significant human harvest pressure due to Antarctic Treaty protections. Ongoing monitoring tracks potential impacts on abundance.

Behavior and life history

Social and foraging behavior

Crabeater seals exhibit a largely solitary , typically occurring alone or in small groups of 2 to 10 individuals during most activities, though they form loose aggregations of up to 1,000 animals on fast ice or during and haul-outs in pack ice regions. These gatherings lack territorial defense, with seals showing no evidence of maintaining exclusive areas outside of breeding contexts. Diving behavior in crabeater seals is characterized by short, shallow dives, with most (over 80%) occurring between 0 and in depth and lasting 5 to 20 minutes, though they are capable of dives up to 776 meters. They employ energy-efficient techniques such as porpoising at the surface and during descent and ascent to minimize oxygen consumption, particularly in deeper winter dives averaging 93 meters and 5.3 minutes. Circadian rhythms influence these patterns, with deeper and longer dives during daylight hours targeting prey near the seafloor, while shallower, shorter dives predominate at night, aligning with light cycles and prey vertical migration. Foraging strategies involve swimming through dense krill patches, where their specialized lobed teeth function as sieves to filter prey efficiently, often in loose groups that may enhance encounter rates without structured coordination. vocalizations, including trills and moans ranging from 360 to 4,525 Hz, are produced during dives, potentially aiding or communication in low-visibility pack environments. Recent studies have also detected ultrasonic vocalizations reaching up to 50 kHz, comprising about 17% of calls and potentially serving additional communication functions. Seals intersperse foraging with rest periods, hauling out on floes for an average of 8 hours daily to recover. Overall activity patterns show crabeater seals spending 70-80% of their time at , with approximately 45% in diving, 30% at the surface, and the remainder hauled out, reflecting high demands. They undertake seasonal migrations, dispersing northward along shifting edges in winter to follow retreating pack and krill distributions, with most individuals remaining within 300 kilometers of core areas but capable of travels up to 1,147 kilometers.

Reproduction and development

The crabeater seal exhibits a serially monogamous , in which males associate with one female at a time over the breeding but may seek additional mates sequentially, typically forming temporary pairs with individual females and defending them against rivals within a territory of approximately 50 meters on pack ice. Breeding occurs during the austral spring, with oestrus, , and conception taking place around early November, shortly after , and social groupings during this period consisting primarily of mated pairs or small family units of a female, her pup, and an accompanying male. Gestation lasts approximately 11.3 months (344 days) in total, including a period of of about 2.7 months (81 days) during which implantation is delayed, followed by an active of 8.8 months (264 days). Pups are born as singles (twins are rare) from late to early , peaking in mid-October, directly on stable pack ice floes, with newborns typically measuring 1.3–1.4 meters in length and weighing around 30.7 kilograms, covered in a woolly, light-brown coat and possessing about 1 centimeter of thickness. Lactation lasts 2–3 weeks (typically 14–21 days), during which females produce with approximately 40% content, enabling pups to gain about 4.2 kilograms per day and reach 80–110 kilograms by in early . Post-weaning, pups remain on the ice for around 10 days before beginning independent , molting their at about 2 weeks and rapidly accumulating to 4 centimeters thickness; they achieve near-adult size of around 2 meters within 2 years. Sexual maturity is attained by females at 3–4 years (ranging 2–6 years) and by males at 4–6 years (ranging 3–7 years), typically when individuals reach about 2.05 meters in length, with females capable of successful pregnancies from ages 5 to 25 years. Lifespan averages 20–25 years, with females up to 23 years and males up to 28 years, though maximum recorded age is 39 years. Breeding success is high, with annual rates of 76–87% and pup rates of 80–90%, though these are heavily influenced by pack stability, as unstable increases mortality risks during the early postnatal period.

Ecology

Diet and feeding

The crabeater seal's diet is highly specialized and consists almost exclusively of (Euphausia superba), which comprises over 90% of its intake, with isotopic analyses confirming krill contributions of 84–91% and only minor inputs from other prey such as or . Occasional consumption of amphipods or cephalopods occurs but remains negligible, underscoring the seal's reliance on krill as its primary nutritional resource. Adult crabeater seals consume 10–20 kg of daily, equivalent to 5–10% of their body weight, supporting their metabolic demands in the energy-poor environment. This daily intake translates to an annual consumption of approximately 5–7 tons of per individual, reflecting the seal's high foraging efficiency despite seasonal variations in prey availability. The seals employ a unique filter-feeding mechanism adapted for krill capture, using specialized, multi-cusped teeth that interlock like a sieve to strain from as they swim through swarms with mouths agape. Captured are then swallowed whole or in large gulps, with the diet's high-lipid content of providing essential energy for and in cold waters. Diving patterns, typically to depths of 20–50 m, facilitate access to krill aggregations beneath the ice. As a keystone predator, the crabeater seal collectively consumes 50–150 million tons of annually, exerting substantial control over dynamics in the . Isotopic studies further validate this dietary purity, showing minimal trophic diversification and highlighting the seal's critical role in maintaining balance within food webs.

Predators and natural threats

The primary predators of the crabeater seal (Lobodon carcinophaga) are leopard seals (Hydrurga leptonyx) and killer whales (Orcinus orca). Leopard seals predominantly target pups and juveniles, accounting for a substantial portion of the high first-year mortality rate, which can reach up to 80% in this species. Killer whales occasionally prey on crabeater seals across all age classes, though less frequently than leopard seals. No avian species are known to prey on crabeater seals. Pups are particularly vulnerable during the period and first year of life, when they are less mobile and more exposed on pack ice. crabeater seals mitigate predation risks through rapid swimming speeds of up to 25 km/h and evasion tactics such as seeking refuge on ice floes, snorting, hissing, baring teeth, and rolling repeatedly to deter attackers. Evidence of past encounters is common, with up to 78% of surviving adults bearing parallel scars matching the pattern of leopard seals. Beyond predation, crabeater seals face several natural environmental threats. Ice entrapment poses a risk, particularly to young seals that enter coastal inlets in late summer and become isolated as forms rapidly during freeze-up. can occur due to natural fluctuations in (Euphausia superba) abundance, their primary prey, driven by seasonal competition and environmental cycles in the pack ice zone. Parasitic infections, including nematodes such as those from the family Anisakidae in the and gut, are present but occur at low and intensity, rarely causing significant pathology or mortality. Predation by leopard seals plays a key role in regulating crabeater seal , primarily by limiting recruitment through high juvenile mortality, thereby maintaining balance in the .

Conservation

Status and protection

The crabeater seal (Lobodon carcinophaga) is classified as Least Concern on the , with the assessment conducted in 2015, indicating no immediate risk of due to its large and stable estimated at 15-40 million individuals. Legal protections for the species are provided primarily through the , established in 1959, which designates as a natural reserve devoted to peace and science, and the Convention for the Conservation of Antarctic Seals (CCAS) of 1972, which prohibits commercial harvesting of crabeater seals and sets precautionary catch limits that have never been approached. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), established in 1982, monitors incidental of seals in fisheries, where interactions remain negligible and no significant mortality has been reported. Historical human impacts on crabeater seals have been minimal; small numbers were killed in the early to mid-20th century to provide food for sled dogs during expeditions, and a Soviet commercial sealing operation harvested approximately 4,000 individuals in 1986–1987 before such activities ceased due to economic unviability and international prohibitions. Ongoing monitoring of crabeater seal populations is conducted through programs led by the Scientific Committee on Antarctic Research (SCAR) Group of Specialists on Seals, which prioritizes surveys of this species due to its ecological importance, and integrated ecosystem assessments under CCAMLR; no harvest quotas are required given the population's vast size and lack of observed declines.

Climate change impacts

Climate change poses significant threats to the crabeater seal (Lobodon carcinophaga) primarily through the loss of Antarctic sea ice, which serves as essential breeding, resting, and haul-out habitat. Since the late 1970s, suitable sea ice habitat for crabeater seals in regions like the Western Antarctic Peninsula has declined by 21–28%, driven by warming temperatures and reduced ice extent. This reduction disrupts pup rearing on stable pack ice platforms and increases exposure to predators and harsh weather, potentially elevating energy demands for seals seeking alternative resting sites. Models project further habitat contraction, with up to 64% loss of suitable areas by 2100 under high-emission scenarios, as sea ice duration and coverage diminish. Recent record-low sea ice extents in 2023 and 2024, continuing into 2025, have intensified these pressures, leading to observed shifts in foraging patterns and potential increases in pup mortality. The crabeater seal's near-exclusive dependence on Antarctic krill (Euphausia superba), comprising over 90% of its diet, amplifies vulnerability to ocean warming and acidification, which are shifting distribution northward and reducing recruitment in traditional foraging grounds. Studies from 2021–2023 indicate that altered sea surface temperatures and levels could decrease suitability by regionally varying degrees, leading to foraging inefficiencies and elevated dietary stress for seals in affected areas. For instance, reduced abundance tied to ice melt forces seals to travel farther, increasing metabolic costs and potentially causing nutritional shortfalls during critical periods like . Recent modeling highlights compounding effects of these changes on prey availability, with biomass projected to decline substantially by mid-century. Population projections aligned with IPCC scenarios forecast a 15–25% decline in crabeater seal numbers by 2050, attributed to habitat loss and prey scarcity, alongside heightened pup mortality from unstable during breeding. Ice-dependent species like crabeater seals face replacement by more adaptable marine mammals in warming regions, with models indicating reduced breeding success and overall abundance. Increased open water exposes pups to risks and limits maternal , exacerbating demographic pressures in a estimated at 15-40 million individuals. Recent research, including 2022–2023 expeditions by the (UNCW), links record-low extents—such as the 2023 anomalies—to foraging inefficiencies, with seals exhibiting southward range shifts to access . These studies, involving satellite-tagged individuals, reveal elevated expenditure and physiological stress under warmer winter conditions, up to 10°C above norms. Similarly, 2024 Scientific Committee on Antarctic Research (SCAR) reports emphasize the need for updated population assessments amid ice melt, documenting adaptive behaviors like expanded offshore foraging but underscoring long-term viability risks.

References

  1. https://animaldiversity.org/accounts/Lobodon_carcinophaga/
  2. https://www.sealifebase.se/summary/Lobodon-carcinophaga.html
  3. https://www.pinnipeds.org/seal-information/species-information-pages/the-phocid-seals/crabeater-seal
  4. https://speciesstatus.sanbi.org/assessment/last-assessment/2106/
  5. https://www.science.smith.edu/departments/biology/VHAYSSEN/msi/pdf/772_Lobodon_carcinophaga.pdf
  6. https://seamap.env.duke.edu/species/622023/html
  7. https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=Scientific_Name&search_value=Lobodon%20carcinophaga
  8. https://marinemammalscience.org/facts/lobodon-carcinophaga/
  9. https://www.sciencedirect.com/science/article/abs/pii/S1055790304001940
  10. https://pmc.ncbi.nlm.nih.gov/articles/PMC2245807/
  11. https://pmc.ncbi.nlm.nih.gov/articles/PMC6548721/
  12. https://pmc.ncbi.nlm.nih.gov/articles/PMC8271676/
  13. https://palaeo-electronica.org/content/2020/3136-feeding-in-marine-mammals
  14. https://onlinelibrary.wiley.com/doi/10.1111/mms.12549
  15. http://globec.whoi.edu/globec-dir/Laws.pdf
  16. https://www.sciencedirect.com/science/article/pii/B9780124095427500056
  17. https://mmapl.ucsc.edu/phocid-normal-anatomy/phocid-special-senses
  18. https://onlinelibrary.wiley.com/doi/full/10.1111/mms.13166
  19. https://www.sciencedirect.com/science/article/pii/S0022098116303306
  20. https://npolar.no/en/themes/fauna-antarctica/
  21. https://www.cambridge.org/core/journals/antarctic-science/article/age-geographical-distribution-and-taphonomy-of-an-unusual-occurrence-of-mummified-crabeater-seals-on-james-ross-island-antarctic-peninsula/C24B89170137867C953252D931D79ED5
  22. https://documents.ats.aq/ATCM42/att/ATCM42_att079_e.pdf
  23. https://www.asoc.org/learn/crabeater-seal/
  24. https://www.nature.com/articles/s41598-020-67799-9
  25. https://www.antarctica.gov.au/about-antarctica/animals/seals/crabeater-seal/
  26. https://besjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2664.2007.01399.x
  27. https://www.ccamlr.org/en/system/files/science_journal_papers/Southwell-et-al.pdf
  28. https://s3.amazonaws.com/Antarctica/AJUS/AJUSvVIIn4/AJUSvVIIn4p70.pdf
  29. https://www.sciencedirect.com/science/article/abs/pii/S0967064510003243
  30. https://link.springer.com/chapter/10.1007/978-3-642-84074-6_29
  31. https://epic.awi.de/43080/1/Nachtsheim_2014.pdf
  32. https://conservationbytes.com/wp-content/uploads/2011/03/burns-et-al-2008-dsrii.pdf
  33. https://apps.dtic.mil/sti/tr/pdf/ADA423539.pdf
  34. http://hosting.uaa.alaska.edu/afjmb4/publications/rm3389.pdf
  35. https://www.cambridge.org/core/journals/antarctic-science/article/cooperative-foraging-behaviour-by-crabeater-seals-lobodon-carcinophaga-at-pleneau-island-antarctic-peninsula/438504335DEFE2E96B1C71FFA17956AE
  36. https://pubs.aip.org/asa/jasa/article/150/5/3353/899324/Acoustic-analysis-of-crabeater-seal-Lobodon
  37. https://whalescientists.com/seal-antarctica-vocalizations/
  38. https://pubmed.ncbi.nlm.nih.gov/12968944/
  39. https://www.researchgate.net/publication/237984391_Social_and_reproductive_behavior_of_crabeater_seals_Lobodon_carcinophagus_during_the_austral_spring
  40. https://pmc.ncbi.nlm.nih.gov/articles/PMC8585811/
  41. https://www.int-res.com/articles/meps2012/455/m455p287.pdf
  42. https://www.researchgate.net/publication/228328931_Diet_of_a_specialist_in_a_changing_environment_the_crabeater_seal_along_the_western_Antarctica_Peninsula
  43. https://digitalcommons.unl.edu/context/usdeptcommercepub/article/1337/viewcontent/Forcada_BC_2012_Responses_Antarctic.pdf
  44. https://www.researchgate.net/figure/Anatomical-features-associated-with-filter-feeding-in-crabeater-seal-Lobodon_fig2_343777584
  45. https://www.seashepherdglobal.org/latest-news/antarctic-krill/
  46. https://scholarworks.calstate.edu/downloads/7h149q62t
  47. https://www.ccamlr.org/en/system/files/03_Seals.pdf
  48. https://academic.oup.com/jmammal/article-pdf/52/1/175/2655604/52-1-175.pdf
  49. https://www.antarctica.gov.au/news/2017/starvation-drives-krill-population-cycles/
  50. https://www.researchgate.net/publication/225917509_Diseases_and_Parasites_of_Antarctic_and_Sub-Antarctic_Seals
  51. https://www.iucnredlist.org/species/12246/45226918
  52. https://www.ccamlr.org/en/organisation/history
  53. https://blog.tepapa.govt.nz/2012/03/01/our-far-south-all-at-sea/
  54. https://www.sciencedirect.com/science/article/abs/pii/S0006320712000948
  55. https://www.int-res.com/articles/meps_oa/m772p193.pdf
  56. https://nsidc.org/learn/parts-cryosphere/sea-ice/today-arctic-sea-ice
  57. https://theinvadingsea.com/2025/07/11/antarctic-sea-ice-climate-change-warming-temperatures-icebergs-seals-penguins-satellites-data/
  58. https://onlinelibrary.wiley.com/doi/10.1111/gcb.15828
  59. https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2025.1513013/full
  60. https://news-oceanacidification-icc.org/2025/06/17/antarctic-krill-habitat-suitability-changes-historical-trends-and-future-projections-under-climate-scenarios/
  61. https://www.ipcc.ch/report/ar6/wg2/chapter/ccp6/
  62. https://www.ipcc.ch/site/assets/uploads/2018/02/WGIIAR5-Chap28_FINAL.pdf
  63. https://ir.canterbury.ac.nz/bitstreams/24c346f2-b0a1-4106-972e-8d30a8a56573/download
  64. https://www.whqr.org/local/2023-08-17/uncw-researchers-return-from-antarctic-winters-spent-studying-climate-change-and-crabeater-seals
  65. https://scar.org/~documents/policy/antarctic-treaty/atcm-xlvii-and-cep-xxvii-2025-milan-italy/atcm47-ip154-scar-seals-ccas?layout=default
  66. https://www.researchgate.net/publication/340954124_Projected_shifts_in_the_foraging_habitat_of_crabeater_seals_along_the_Antarctic_Peninsula
Add your contribution
Related Hubs
User Avatar
No comments yet.