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.
- Biogeographic Regions
- nearctic
- palearctic
- arctic ocean
- pacific ocean
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.
- Habitat Regions
- polar
- saltwater or marine
- 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.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- male larger
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.
- Mating System
- monogamous
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- viviparous
- delayed implantation
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.
- Parental Investment
- precocial
- female parental care
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
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.
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.
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.
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.
- 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.
- 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.
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.
- Positive Impacts
- food
- body parts are source of valuable material
Economic Importance for Humans: Negative
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.
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).
Additional Links
Contributors
Lara Johnson (author), University of Alaska Fairbanks, Link Olson (editor), University of Alaska Fairbanks, Tanya Dewey (editor), University of Michigan-Ann Arbor.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Palearctic
-
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Arctic Ocean
-
the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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.
- pelagic
-
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- 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.
- 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.
- monogamous
-
Having one mate at a time.
- 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).
- 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
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- 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.
- young precocial
-
young are relatively well-developed when born
- female parental care
-
parental care is carried out by females
- natatorial
-
specialized for swimming
- motile
-
having the capacity to move from one place to another.
- nomadic
-
generally wanders from place to place, usually within a well-defined range.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- solitary
-
lives alone
- 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.
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- 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.
- food
-
A substance that provides both nutrients and energy to a living thing.
- carnivore
-
an animal that mainly eats meat
- piscivore
-
an animal that mainly eats fish
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