Mustela frenata occisor (Bangs)
Long-tailed Weasel
Plates [16], [17], [18], [31], [32] and [33]
Putorius occisor Bangs, Proc. New England Zool. Club, 1:54, June 9, 1899.
Mustela occisor, Miller, U. S. Nat. Mus. Bull., 79:98, December 31, 1912.
Mustela frenata occisor, Hall, Carnegie Instit. Washington Publ. 473:104, November 20, 1936.
Type.—Male, adult, skull and skin; no. 9102, coll. of E. A. and O. Bangs in Mus. Comp. Zoöl.; Bucksport, Hancock County, Maine; January 15, 1899; obtained by Alvah G. Door but measured and sexed by O. Bangs.
The skin is well made and in good condition. It is in full, white winter-dress with black-tipped tail. The skull has the posterior half of the left zygomatic arch broken away; otherwise the skull is unbroken and complete. Left I3 and right P3 are missing. The teeth otherwise all are present and entire.
Range.—Maine; possibly north locally to south side of St. Lawrence River in Quebec and possibly occurring in western New Brunswick. Zonal range Canadian and probably Transition. See figure [29] on page [221].
Characters for ready recognition.—Differs from M. f. noveboracensis by a number of average differences including larger size, relatively longer tail and relatively wider skull (see page [225], and measurements on pages [418], [419]).
Description.—Size.—Male: Five adults yield average and extreme measurements as follows: Total length, 443 (430-465); length of tail, 163 (154-175); length of hind foot, 50 (47-54). Tail averages 58 per cent as long as head and body. Length of hind foot averages more than basal length.
Female: Measurements of two subadult female topotypes are as follows: Total length, 346, 318; length of tail, 116, 110; length of hind foot, 39, 35.5.
Tail amounts to 50 per cent and 54 per cent of body-length respectively. Length of hind foot more or less than (about equal to) basal length.
The average differences in external measurements of the two sexes are: Total length, 111; length of tail, 50; length of hind foot, 12.5.
Externals.—As described in Mustela frenata noveboracensis.
Color.—As described in Mustela frenata noveboracensis except that black tail-tip in series of 10 males in full winter pelage 60 (45-80) mm. long; thus averaging 39 per cent of length of tail vertebrae.
Skull and teeth.—Male (based on 3 adults): See measurements and plates [16]-[18]. As described in Mustela frenata noveboracensis except that: Weight, 4.2 (4.1-4.3) grams; basilar length, 45.7 (44.9-46.9); zygomatic breadth more or less than (about equal to) distance between anterior palatine foramen and anterior margin of tympanic bulla; least width of palate rarely less than length of P4; anterior margin of masseteric fossa behind or directly below posterior half of m2.
Female (based on 2 subadults): See measurements and plates [31]-[33]. As described in Mustela frenata noveboracensis except that: Weight, 2.0 (1.9-2.1) grams; basilar length, 37.3, 38.2.
Comparison of the skull with that of M. f. noveboracensis is made in the account of that subspecies.
Remarks.—Excepting a specimen in the Academy of Natural Sciences of Philadelphia, obtained in 1893, and two in the Boston Society of Natural History, obtained in 1925, I have seen no material of this subspecies in addition to that examined by Bangs at the time he prepared the original description in 1899.
Anderson (1945:56, 57) records a specimen, Canadian National Museum Catalogue Number 18426, from Kamouraska County, Quebec, as of this subspecies and thinks that occisor occurs north of Maine "locally to south side of lower St. Lawrence River in Quebec; probably also in western New Brunswick."
So far as the available material of occisor permits one to judge, it is distinguished from noveboracensis by a combination of characters no one of which invariably can be relied upon as diagnostic. Employing adult males, average differences indicate that M. f. occisor is larger in each of the external and cranial measurements; tail relatively longer; black tip of tail relatively shorter; mastoid and zygomatic breadth relatively greater and zygomatic arches more nearly square posteriorly.
Considering the large number of specimens of noveboracensis which are available in comparison with the few of occisor it is not surprising that some noveboracensis should be found which exceed in size those of occisor. This is the case as regards the basilar length of a very old male, no. 96518, U. S. Nat. Mus., from Lunenburg, Massachusetts. Also, the skull is actually broader than any of those of occisor. However, this specimen is much older than any occisor examined. In a female, no. 4260, Mus. Comp. Zoöl., from Liberty Hill, Connecticut, the skull is longer (but narrower) than in either of the two available females of occisor.