Under Construction May 2011


Mustela erminea


Length: max 10mm (Mayer 1952), 5-10mm (Adorjan and Kolenosky 1969), 11mm max (Moore et al 1974), 9-15mm  (Toth 2002) 9-13mm (ASM #3 back), 45-50mm (ASM #3 tail), 15-20mm (ASM #4), Taper at the base is longer than the taper at the tip (ASM #4)

Diameter Range: 92-176 microns (Brown 1942), 97 microns max (Moore et al 1974), 92-117 microns (Toth 2002), 35-115 microns (Furskin 2006), 70-75 microns (ASM #1), 90-100 microns (ASM#3), 85-92 (ASM #4)

Medullary Index: 0.80 ave (Brown 1942), 0.77 ave (Toth 2002), 0.73-0.85 ( ASM#1), 0.77 – 0.8 (ASM #3), At the long narrow section of the base, the MI is 0.4 (ASM #4)

Medulla: Cells in the medulla not separated by pigment masses, like we see in canids.  Look at the base, edges have deep wavy s-curves?  Describes medulla of shaft as unicellular ladder, then an irregular unicellular ladder in the transitional part, and then cloisonné in the shield with scalloped medullar margins. (Toth 2002).  Medulla continuous nearer to the tip (Mayer 1952).

Medulla near the base shows a loosely connected network of cells that appear as fused bubble-like “H”, “Y” letters or like brain coral. The medulla transitions where the fiber becomes the shield (widest part). In this location the brain-coral like medulla becomes compacted and dense. The perimeter of the medulla appears as “deep wavy S-curves” as Toth (2002) describes.  ASM #4 has closely-stacked disks only one across at the base, becoming letterforms and wishbone shapes.

Color: Turns white in the winter, with a characteristic black-tipped tail. No pigment present in ASM#3 samples.  Moore et al (1974) describe a dark gray brown base, then lighter brown in the middle and finally dark brown at the tip (tricolor).  Winter hair is all white (Moore et al 1974).

Scales: Pectinate and diamond petal near the base, turning into regular distant wave and mosaic in the transitional area and then close regular-wave on the shield (Toth 2002). Edges of the scales are toothy near the tip (Furskin 2006).  At the base the scales are flower petal-like with each individual scale having one point. As the fiber moves toward the distal end the pattern changes to overlapping scales that look like torn paper edge. Change happens in the region of the shield  (ASM #4).


Length: 4-7mm (ASM #3 back) 7-8mm (ASM #3 tail) 5-10mm (ASM #4)

Diameter Range: 15-30 microns (Brown 1942) 5-15microns (Furskin 2006)

Medullary Index: 0.66 (Brown 1942). 0.6 (ASM#3).

Medulla: 10 microns, and appearing as uniserial ladder with hockey puck shaped cells, some of which are fused together creating a coiled telephone cord appearance.

Color: present in cortex? (Brown 1942). Not present in ASM #3 samples.

Scales: they are stacked cups at the base but petal shaped scales near the tip (Furskin 2006)  overall character is long pointy petals, but stacked cups at both ends.

Macro Qualities: 8.5 – 13” long White in winter with long black bushy tip of tail.  Tip of tail is also long and bushy black in summer, but the coat is brown with a white underside.  White line down hind legs joins the white underside with the white bottoms of the back feet (Forsyth 1999).  Up to 15” long.  Summer pelage of medium to dark brown above and yellowish white underparts, fully white in the winter except for a black tip of the tail which is also black tipped in summer (ADF&G 2008). Skin is 15-30cm long tail is 10-15cm and in the summer they are yellow-brown or red brown with white spots on the belly, throat and the insides of the legs  (Furskin 2006).  Guard hair dark brown in summer, white in winter, hairs at the tail tip are always black.  Underfur is light brown in the summer and white in the winter (Adorjan and Kolenosky 1969).  Samet (1950) describes prime fur when the guard hair fully covers the dense growth of underfur.  Blow gently to see the difference between guard hair and underfur.  Black should normally extend halfway up the tail of an ermine.  Samet reports that an ermine skin (no head) would measure about 8” x 3”

Cultures:  For example: Yup’ik men captured these small furbearers in the fall Fienup-Riordan (2007) Yuungnaqpiallerput: The Way We Genuinely Live.  Masterworks of Yup’ik Science and Survival.  Anchorage Museum Association.  p.245 

Notes: ASM #1 is from the Cargille reference Set F-5 commercial furs, ASM #2 is from an old slide in the ASM conservation lab, ASM #3 is from 93-3-41 in the ASM collection, ASM #4 is from the Juneau-Douglas City Museum fur touchboard.

Troubleshooting: Toth says that Mustela ermine and Mustela nivalis show significant differences only in length of hair, with M. ermine being longer.  If the length of the guard hair is more than 10mm, it seems that M. ermine is more likely.  M. nivalis averages about 8mm and M. ermine averages around 14mm.  He also says that the two weasels can be distinguished from the other mustelids because their hair shaft is narrow and then widens rapidly into a shield, while the hair shaft of other mustelids thickens more gradually (Toth 2002). The ermine, the underfur is 2/3 the length of the guard hair?  Fair “serviceability” according to Bachrach (1953).  Short Tailed Weasel and Least Weasel may be difficult to distinguish, although the guard hair is a significant clue.  The longest least weasel guard hair rarely exceeds 10mm, while short tailed weasel guard hair is usually over 10mm, especially on the tail where it may be 50mm.  The prominent black tip on the tail is also indicative of short tailed weasel, since the least weasel usually only has a few black hairs at the tip of the tail. If the back feet are present, the toes of the least weasel’s outstretched feet are only as long as the tail, but tail is much longer than feet on the short-tailed weasel.

Range: All of Alaska (Forsyth 1999). Not found on offshore islands of Bering Sea or Aleutian Islands beyond Unimak Island (ADF&G 2008). 

Names: Family Mustelidae (the mustelids)   Called “stoat” in the summer when coat is brown, “ermine” in the winter when coat is white (ADF&G 2008).  Given the name “miniver” when seen in English heraldic design.  M. cicognanii is 12″ long with 4″ of it tail  (Bachrach 1953).


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