MARINE MAMMALS

Under construction May 2011

MARINE MAMMALS

Suborder/superfamily Pinnipedia (the pinnipeds)

Family Otarvidae (the otarvids)

Northern Fur Seal (Callorhinus ursinus)

Steller Sea Lion (Eumetopias jubatus)

Family Phocidae (the phocids=earless seals)

Bearded Seal (Erignathus barbatus)

Harbor Seal (Phoca vitulina)

Ribbon Seal (Phoca fasciata)

Ringed Seal (Phoca hispida)

Spotted Seal (Phoca largha)

LENGTH: Sea lion and fur seal guard hairs have lengths up to 20mm, while the true seals are rarely over 10mm long.

WIDTH:  Sea lion and fur seal have variation in width along the shaft but no shield.  Both have a range of around 160-190 microns wide.  The true seals have a wide range of widths, and a larger sample is needed to detect overall patterns.  Guard hair width can range from 110 to 230 microns.

MEDULLA: There is a significant difference between Family Otarvidae (“eared” seals like sea lion, Northern fur seal) who have a medulla, and the family Phocidae (“earless”) which have no

Medulla in the guard hair.  Sea lion medulla is very narrow.  The medulla is clumpy with very irregular margins, more sparse near the base and becoming more solid and tire-tread looking towards the tip.  Northern Fur Seal guard hair varies along the length of the shaft, and one hair can show two distinct regions of medulla.  Closer to the base, the medulla takes up at least half the width of the hair and has a lumpy intestine-like quality.  There is a transition area where the shaft begins to broaden where this kind of medulla peters out and there is almost no medulla at all, and then there is another distinct area of clumped medulla cells extending to the tip.

MEDULLARY INDEX: Sea lion MI is around 0.2-0.3, while fur seal is around 0.5

SCALE: For the Northern fur seal, the scale pattern on the narrow stalk near the base is distinctly snake-skin like with diamond petal shapes, but on the wider areas the scale pattern becomes closely spaced with rough edges.  The rest of the seals are very similar with a scale pattern that is closely spaced with rough edges but may show smoother edges towards the ends.  It is difficult to get a good scale cast from the marine mammals, but putting them under a coverslip with no mounting medium works well, and often limiting the amount of light transmitted can show the scale pattern well, particularly as there is no medulla for the true seals.

UNDERFUR: Northern fur seal has very dense underfur, while sea lion has very sparse short underfur.  Fur seal underfur has scales that look like long pointed petals, while sea lion and other seals all have stacked crown shaped underfur scales.  Fur seal underfur can be dyed, and in those cases the color will extend into the scales.  Bearded seal might have more underfur than other hair seals who tend to have “flat fur”, but more examination is needed.

COLOR: Sea lion cortex has a very yellow-orange look.  Northern fur seal is pale near the base, and brown in the wider areas.  The rest of the seals are very similar, although a larger sample size may reveal clues in distribution of pigment granules.  Underfurs all can have pigment in them.  Dyed fur can be recognized by coloration in the scales, which is unnatural.

SUMMARY: The intestine-looking narrow medulla is diagnostic for sea lion and fur seal, which can then be distinguished from each other by the density of the underfur. Sea lions have very sparse underfur, while the Northern fur seal are prized for the density and lushness of theirs.

The true (Phocid) seals are distinguished from other mammals by the lack of medulla in the guard hair, short overall length, and flattened cross section which appears under magnification as somewhat ribbon-like and able to bend, kink, and turn unlike most other hairs examined.  Tips of the hairs are often frayed.  Differentiating between the Phocid seals under the microscope is difficult, with length and width measurements on guard hairs and underfur being in similar ranges for all the true seals in Alaska.  Scale patterns and similar, and none have medullas.  Ribbon and ringed seals often have distinct pelt markings.  The bearded seal fur may be special in that individual guard hairs tend to be widely spaced and the underfur curlier and denser than other seals, giving a less “smooth” flat fur look, but more investigation is needed to confirm this observation

The following animals are rarely seen in Alaskan waters, perhaps only a few sightings (MacDonald and Cook 2009), and have therefore not been included:  Guadelupe Fur Seal (Arctocephalus townsendi), California Sea Lion (Zalophus californianus), Hooded Seal aka “crested seal” or “bladdernose seal” (Cystophora cristata), Northern Elephant seal (Mirounga angustirostris) Harp seal aka “Greenland seal” or “saddle-backed seal” (pagophilus groenlandicus).  The controversial cute young white seals or “whitecoats” used in the fur industry were usually harp seals.

Many baby “ice seals” are born with a wooly white coat known as “lanugo” which is essentially a fetal fur and is shed soon after birth.  Harbor seals are not ice seals and don’t have that fur.  We have some samples of baby seal fur at the Alaska State Museum, but I have been unable to pinpoint which seal species they are.  Harbor seals only have white lanugo in utero.  By the time they are born they are darker.  Sometimes lanugo can be seen in clumps on the beach as part of the afterbirth picked over by seabirds.  Lanugo may be mistaken for polar bear underfur on artifacts, but is distinct because seal fur has no medulla.

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