BEARS

Under construction May 2011

BEARS

ORDER CARNIVORA (the carnivores)

Family Ursidae (the ursids)

Black Bear (Ursus americanus)

Brown Bear (Ursus arctos)

Polar Bear (Ursus maritimus)

LENGTH: Guard hairs tend to be long, maximum length of the hair more than 60mm, often up to 100 mm.  One black bear sample was 290mm, and a polar bear sample was 170mm.  Individual hairs are much longer than otters. (Mayer 1952). 

WIDTH: Ranges from 60-260 microns for black and brown bears, usually not over 200 microns for polar bears.

MEDULLA:  Telltale narrow medulla.  Narrower medulla than other carnivores at only about a quarter of the width. (Mayer 1952).  Simple amorphous medulla (Dove and Peurach 2002)

MEDULLARY INDEX:  As low as 0.1 for the brown bear, 0.2 – 0.3 common for brown and black bears, black bears up to 0.4.  Polar bears measured around 0.35

SCALE: Guard hairs have large individual scales with moderately spaced margins between them, only a few across.  Most samples seem to show smooth-edged scales near the base and torn-paper scales near the tip. In contrast to the black and brown bears which appear to have petal shaped bases, gradually becoming more closely spaced with torn-paper scales, polar bears have a more continuous scale pattern along the hair. The scales at the base are blocky and horizontal — like interlocking fingers — rapidly developping closer margins towards the tip. More comparative study of bear cuticular scales is needed to seek further conclusions.

UNDERFUR:  Scale pattern is usually diamond petal shapes, which may be a useful clue.  Underfur medulla can show a lot of variation in all the bears, from uniserial ladder to interrupted to absent, even in the same sample.  Medulla does tend to be very narrow, though.  Some black bear underfur hairs have been measured over 30mm long, which seems rare for brown bears.

COLOR: Bears are not banded.  Need to double check the glacier bears, but grizzled look comes from individual hairs of different colors. Black bears show a huge range of coloration, from black and brown to gray and even white.  Brown bears can also show a wide range.  Polar bears are always white or yellowish.

SUMMARY: No banding, long hairs, narrow medulla, scale pattern on guard hairs seems to be smooth-edged at base and raggedy-edged near tip.  Underfur petal-shaped scales.  Black bear and brown bear can be hard to distinguish, although it seems that black bear guard hair scales may have wider and smoother margins in contrast to the brown bear.

Comparative images of guard hair scale casts below:

 

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