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Phoca larghaspotted seal

By Lara Johnson

Geographic Range

Spotted seals can be found throughout the North Pacific and on the east coast of Asia. They are common in the Bering, Chukchi, Beaufort, and Okhotsk Seas where they prefer to remain over the continental shelf. They can also be found in the Sea of Japan and the Yellow Sea. Three population groups (Distinct Population Segments, or DPSs) of spotted seals are recognized based on location: the Southern DPS, the Sea of Okhotsk DPS, and the Bering Sea DPS. ("Spotted Seal (Phoca largha)", 2010; "Status Review of the Spotted Seal (Phoca largha)", 2009)

Habitat

Spotted seals are a pagophilic (ice-loving) species. They reside on sea ice through late autumn and winter while breeding and whelping, moving to nearshore and onshore environments during spring through early autumn. They prefer to remain near the ice front where ice floes are smaller and the water is relatively shallow. They are rarely found far into the ice pack or out in the open ocean. (Lowry, et al., 2000; Simpkins, et al., 2003)

  • Terrestrial Biomes
  • icecap

Physical Description

Pups are born with a dense white coat called a lanugo. The lanugo is normally shed at 2 to 4 weeks of age, giving way to a smooth grey-white coat with dark spots. Juveniles sometimes have a dark dorsal stripe that gradually fades into more spotting as they age. Spotted seals are of a medium size and build. Female adults weigh from 65 to 115 kg and grow to lengths of 151 to 169 cm while male adults typically weigh from 85 to 110 kg with lengths of 161 to 176 cm. Spotted seals share several distinguishing characteristics with all seals, such as lack of an external ear, a streamlined body, and a thick layer of blubber. Their hind flippers are fixed behind them and cannot be turned forward as in members of the family Otariidae (sea lions and fur seals). Spotted seals are very similar in appearance to light-colored harbor seals (Phoca vitulina) and, for a time, they were considered a subspecies of harbor seal. However, harbor seal pups lose their lanugo coat while still in the womb and there are also several skeletal and cranial characteristics that differ considerably between harbor and spotted seals. These and several behavioral differences led to the spotted seal eventually being recognized as a separate species. ("Status Review of the Spotted Seal (Phoca largha)", 2009; Berta, 2009; Lowry, et al., 1998)

  • Sexual Dimorphism
  • male larger
  • Range mass
    65 to 115 kg
    143.17 to 253.30 lb
  • Range length
    151 to 176 cm
    59.45 to 69.29 in

Reproduction

Spotted seals are unusual among seals in that they are annually monogamous rather than polygynous. Mating pairs form when the female is about to give birth to a pup from the previous year’s mating. The pair remain together until that pup weans and the female goes into oestrus and will copulate once again. Mating occurs underwater and copulation is preceded by increased vocalizations and physical contact, such as nosing. Mating pairs tend to form a small group of two or three individuals depending on if there is a pup present or not. ("Status Review of the Spotted Seal (Phoca largha)", 2009; Atkinson, 1997; Beier and Wartzok, 1979)

Female spotted seals reach sexual maturity when they are 3 to 4 years old. Males usually take 4 to 5 years before maturing. Breeding is normally in the spring, around April or May, but can occur as early as January in Asian waters. A single pup is born the following spring. Gestation lasts 7 to 9 months, but a delay in implantation of the blastocyst after breeding can extend the length of the entire pregnancy to almost a year. Pups are weaned after 2 to 4 weeks, when their lanugo is shed and they can leave the ice to begin learning to forage for themselves in the water. ("Status Review of the Spotted Seal (Phoca largha)", 2009; Beier and Wartzok, 1979; Rugh, et al., 1997)

  • Breeding interval
    Spotted seals breed once yearly.
  • Breeding season
    Breeding occurs from January to May, depending on the location.
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    7 to 12 months
  • Range weaning age
    2 to 4 weeks
  • Range time to independence
    2 to 4 weeks
  • Range age at sexual or reproductive maturity (female)
    3 to 4 minutes
  • Range age at sexual or reproductive maturity (male)
    4 to 5 minutes

Pups nurse for 2 to 4 weeks after birth. Both the mother and her current mate remain with the pup during this time. The male probably doesn’t contribute much to the pup’s care since it is not his, but mostly focuses on being near the female. Once the pup has been weaned (at about a month old), it is abandoned by the mother and left to fend for itself. Female spotted seals have been observed adopting strange pups if they are separated from their own. ("Status Review of the Spotted Seal (Phoca largha)", 2009; Burns, et al., 1972)

  • Parental Investment
  • precocial
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

About 45% of spotted seal pups die within their first year of life. If they survive to adulthood, they can live to a maximum of 30 to 35 years of age. ("Status Review of the Spotted Seal (Phoca largha)", 2009; Rugh, et al., 1997)

Behavior

Detailed studies on the behavior of spotted seals are difficult to conduct as the seals are wary and don’t tolerate human presence well. They quickly take to the water when they sense a possible threat. Spotted seals are solitary during parts of the year and gregarious at other times of year. They are often seen at haul-outs, which are sites on the shore or on ice where anywhere from a few individuals to large groups leave the water and gather. These sites are usually located near abundant food sources. The groups of seals gathered at these haul-out sites are sometimes termed “onshore associations” or OAs. There are four types of OAs seen throughout the year, divided up by the point in the life cycle at which they occur: preliminary, reproductive, molting, and recovery (a rehabilitative phase after the energy-intensive reproduction and molting phases). OAs can differ in the sex and age of participating individuals over the course of the year as the type of OA changes. (Bradford and Weller, 2005; Nesterenko and Katin, 2010)

Home Range

Home range sizes for spotted seals are not reported in the literature.

Communication and Perception

Olfaction is believed to be extremely important in maintaining relationships between individuals, especially between mates and between mothers and their offspring. One of the most important reasons for the gathering of many spotted seals at haul-out sites is so this olfactory (as well as tactile) contact can occur between individuals. If a mother and offspring are separated, they will call to each other and touch noses once reunited. Calling and nosing have also been observed between mating pairs. When navigating under ice, spotted seals rely mostly on vision, then on auditory and tactile cues. (Beier and Wartzok, 1979; Burns, et al., 1972; Elsner, et al., 1989; Nesterenko and Katin, 2010)

Food Habits

Fish are the primary component of the spotted seal's diet, most commonly herring (Clupea pallasii), pollock (Theragra chalcogramma), cod (Gadus macrocephalus), and capelin (Mallotus villosus). They also feed on mollusks and crustaceans. The pelagic zone of the ocean is where they spend most of their foraging time. The spotted seal's seasonal movements between sea ice and shore is believed to be partially driven by migration of these prey species. (Dehn, et al., 2007; Lowry, et al., 2000)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Predation

Predators known to occasionally prey on spotted seals include sharks, killer whales, walruses, sea lions, polar bears, brown bears, wolves, several species of birds, and, of course, humans. Spotted seals, however, do not constitute a significant portion of any of these predator's diets. They avoid predation by gathering at haul-out areas, being cryptically colored, and being agile in the water. ("Status Review of the Spotted Seal (Phoca largha)", 2009)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Spotted seals mainly feed in the pelagic zone of the ocean, where their primary prey is schooling fish. Depredation by seals has been shown to have an effect on populations of fish, but there has been no study done that definitively shows the role spotted seals play in the population changes of their prey species. Spotted seals are not thought to be important prey for any other species besides some humans that hunt them for subsistence. ("Status Review of the Spotted Seal (Phoca largha)", 2009; Chassot, et al., 2009; Dehn, et al., 2007)

Economic Importance for Humans: Positive

Alaska Natives and some Russian hunters rely on spotted seals as part of their subsistence lifestyle. In addition to using them as food, skins are used for clothing. The annual take of spotted seals isn’t well documented, but the yearly average in Alaska between 1966 and 1976 was estimated at 2,400. Seal oil has gained some popularity as a health supplement for lowering blood pressure. (Meyer, et al., 2009; Nelson, 2008; Rugh, et al., 1997)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Spotted seals sometimes take fish from nets. (Northridge, 1991)

Conservation Status

With climate change resulting in a reduction in the area of sea ice, there is concern for populations of spotted seals as well as other polar marine species as they face possible changes in habitat and prey distribution. Spotted seals are also victims of fishing bycatch and poaching. At this time the species is considered to be data deficient by the IUCN. Only the Southern DPS of spotted seals was listed as Threatened under the Endangered Species Act in 2010 by the National Marine Fisheries Service. This was due to reports of decreasing populations on Asian coasts. ("Spotted Seal (Phoca largha)", 2010; Bluhm and Gradinger, 2008; Won and Yoo, 2004)

Other Comments

Spotted seals were once considered a subspecies of harbor seal (Phoca vitulina largha). However, Shaughnessy and Fay in 1977 recognized spotted seals as a distinct species. Spotted seals and harbor seals are sympatric in some areas, and are believed to be sister groups within seals.

Spotted seals are known by many different names to Alaskan Natives: qasigiaq (Inupiaq), gazigyaq (St. Lawrence Island Yupik), issuriq (Yup’ik), and issuri (Nunivak Island Cup’ig). ("Spotted Seal (Phoca largha)", 2010; "Status Review of the Spotted Seal (Phoca largha)", 2009; Burns, et al., 1972; Shaugnessy and Fay, 1977)

Contributors

Lara Johnson (author), University of Alaska Fairbanks, Link Olson (editor), University of Alaska Fairbanks, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Arctic Ocean

the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

delayed implantation

in mammals, a condition in which a fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nomadic

generally wanders from place to place, usually within a well-defined range.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

2010. "Spotted Seal (Phoca largha)" (On-line). Accessed December 11, 2012 at http://www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/spottedseal.htm.

National Oceanic and Atmospheric Administration. Status Review of the Spotted Seal (Phoca largha). NMFS-AFSC-200. Springfield, VA: Department of Commerce. 2009.

Atkinson, S. 1997. Reproductive biology of seals. Reviews of Reproduction, 2/3: 175-194.

Beier, J., D. Wartzok. 1979. Mating behavior of captive spotted seals (Phoca largha). Animal Behavior, 27/3: 772-781.

Berta, A. 2009. Encyclopedia of Marine Mammals. San Diego: Academic Press.

Bluhm, B., R. Gradinger. 2008. Regional variability in food availability for arctic marine mammals. Ecological Applications, 18/2: S77-S96.

Bradford, A., D. Weller. 2005. Spotted seal haul-out patterns in a coastal lagoon on Sakhalin Island, Russia. Mammal Study, 30/2: 145-149.

Burns, J., C. Ray, F. Fay, P. Shaughnessy. 1972. Adoption of a strange new pup by the ice-inhabiting harbor seal Phoca vitulina largha. Journal of Mammalogy, 53/3: 594-598.

Chassot, E., D. Duplisea, M. Hammill, A. Caskenette, N. Bousquet, Y. Lambert, G. Stenson. 2009. Role of predation by harp seals Pagophilus groenlandicus in the collapse and non-recovery of northern Gulf of St. Lawrence cod Gadus morhua. Marine Ecology Progress Series, 379: 279-297.

Dehn, L., G. Sheffield, E. Follmann, L. Duffy, D. Thomas, T. O'Hara. 2007. Feeding ecology of phocid seals and some walrus in the Alaskan and Canadian arctic as determined by stomach contents and stable isotope analysis. Polar Biology, 30/2: 167-181.

Elsner, R., D. Wartzok, N. Sonafrank, B. Kelly. 1989. Behavioral and physiological reactions of arctic seals during under-ice pilotage. Canadian Journal of Zoology, 67/10: 2506-2513.

Lowry, L., V. Burkanov, K. Frost, M. Simpkins, R. Davis, D. DeMaster, R. Suydam, A. Springer. 2000. Habitat use and habitat selection by spotted seals (Phoca largha) in the Bering Sea. Canadian Journal of Zoology, 78/11: 1959-1971.

Lowry, L., K. Frost, R. Davis, D. DeMaster, R. Suydam. 1998. Movements and behavior of satellite-tagged spotted seals (Phoca largha) in the Bering and Chukchi Seas. Polar Biology, 19/4: 221-230.

Meyer, B., A. Lane, N. Mann. 2009. Comparison of seal oil to tuna oil on plasma lipid levels and blood pressure in hypertriglyceridaemic subjects. Lipids, 44/9: 827-835.

Nelson, M. 2008. "Spotted Seal" (On-line). Alaska Department of Fish and Game. Accessed December 11, 2012 at http://www.adfg.alaska.gov/static/education/wns/spotted_seal.pdf.

Nesterenko, V., I. Katin. 2010. Cycle of transformation of the spotted seal (Phoca largha, Pallas 1811) onshore associations in Peter the Great Bay of the Sea of Japan. Russian Journal of Marine Biology, 36/1: 47-55.

Northridge, S. 1991. An updated world review of interactions between marine mammals and fisheries. Rome: Food and Agricultural Organization of the United Nations.

Rugh, D., K. Sheldon, D. Withrow. 1997. Spotted seals (Phoca largha) in Alaska. Marine Fisheries Review, 59: 1-18.

Shaugnessy, P., F. Fay. 1977. A review of the taxonomy and nomenclature of North Pacific Harbour seals. Journal of Zoology, 182/3: 385-419.

Simpkins, M., L. Hiruki-Raring, G. Sheffield, J. Grebmeier, J. Bengston. 2003. Habitat selection by ice-associated pinnipeds near St. Lawrence Island, Alaska in March 2001. Polar Biology, 26/9: 577-586.

Won, C., B. Yoo. 2004. Abundance, seasonal haul-out pattern and conservation of spotted seals (Phoca largha) along the coast of Bak-ryoung Island, South Korea. Oryx, 38/1: 109-112.

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