Mustela frenata leucoparia (Merriam)
Long-tailed Weasel
Plates [1], [24], [25], [26], [29], [30], [36], [37] and [38]
Putorius frenatus leucoparia Merriam, N. Amer. Fauna, 11:28, June 30, 1896.
Putorius brasiliensis frenatus, Allen, Bull. Amer. Mus. Nat. Hist., 2:165, October 21, 1889.
Putorius frenatus frenatus, Allen, Bull. Amer. Mus. Nat. Hist., 22:259, July 25, 1906.
Mustela frenata leucoparia, Miller, U. S. Nat. Mus. Bull., 79:100, December 31, 1912; Hall, Carnegie Instit. Washington Publ. 473:108, November 20, 1936.
Type.—Male, adult, skull and skin; no. 34914/47179, U. S. Nat. Mus., Biol. Surv. Coll.; Pátzcuaro, Michoacán, México; July 27, 1892; obtained by E. W. Nelson; original no. 2960.
The skull (plates [29] and [30]) lacks most of the braincase; a fragment, consisting of the supraoccipital and the coalesced frontals and parietals remains. The rostrum, left zygomatic arch, palate, left pterygoid, left glenoid fossa and right postorbital process are intact. The teeth all are present and entire. The lower jaw lacks the right coronoid process and the lateral part of the articular condyle. The skin is well made and in good condition. It differs from an adult male topotype (36855, U. S. Nat. Mus.) and other referred specimens in having: the black of the head extended farther posteriorly on the neck, the maximum amount of white on the head, and a white stripe 50 mm. long extending down the middle of the nape from a point between the ears more than half way to the shoulders.
Range.—Sonoran and Transition life-zones of mountains west of México (city) in Michoacán and Nayarit. See figure [29] on page [221].
Characters for ready recognition.—Differs from M. f. goldmani in least width of color of underparts more than 47 per cent of greatest width of color of upper parts, hind feet colored like underparts rather than like upper parts; postorbital constriction less than, rather than more than, combined length of upper premolars; from M. f. macrophonius by same details of coloration as from goldmani and by ventrally concave rather than ventrally convex pretympanic part of squamosal; from M. f. perotae by least width of color of underparts more than 40 per cent of greatest width of color up upper parts; height of tympanic bulla more than three-fifths distance from its anterior margin to foramen ovale; from M. f. frenata by white facial markings that cover half of surface of head in front of ears, by extension of black of head onto neck halfway to shoulders and by narrower (less than 7.8) tympanic bullae; from M. f. neomexicana by Argus Brown rather than Buckthorn Brown color of upper parts and distance from anterior margin of tympanic bulla to foramen ovale more, rather than less, than four-fifths of height of tympanic bulla.
Description.—Size.—Male: Two adults and one young from Los Reyes and Pátzcuaro, Michoacán, yield average and extreme measurements as follows: Total length, 514 (510-523); length of tail, 206 (196-215); length of hind foot, 55 (52-58). Tail averages 67 per cent as long as head and body. Length of hind foot more than basal length.
Female: One adult from Artenkiki, Jalisco, and one subadult from Pátzcuaro, Michoacán, measure, respectively, as follows: Total length, 412, 400; length of tail, 159, 159; length of hind foot, 41, 42. Tail averages 64 per cent as long as head and body. Length of hind foot equal to or greater than basal length.
The average differences in external measurements of the two sexes are: Total length, 108; length of tail, 47; length of hind foot, 13.
Mustela frenata leucoparia has a greater total length and length of tail than either M. f. frenata or goldmani. The hind foot is longer than that of frenata and approximately the same as in goldmani. Relative to the body length, the tail averages longer than that of goldmani and shorter than that of frenata.
Externals.—As described in Mustela frenata frenata.
Color.—Broad white bands on sides of head, extending anterodorsally anterior to each ear, confluent with white spot between eyes and with color of underparts; posterior third of each upper lip white; remainder of sides and top of head, and neck posteriorly to point halfway to shoulders from ears, black; no dark spots at angles of mouth; tip of tail black; remainder of upper parts Argus Brown; chin white and sometimes also chest, neck and medial sides of hind legs; remainder of underparts near (16´) Ochraceous-Buff (near (a) Ochraceous-Buff in juvenal female), which color extends distally over all of each foreleg (except its lateral face proximally from about middle of forearm) and on medial side of hind leg and over most of upper side of each foot. Least width of color of underparts averaging, in eight specimens, 54 (extremes 44-61) per cent of greatest width of color of upper parts; black tip of tail averaging, in four males, 52 (extremes 38-78) mm. long, thus averaging 25 per cent of length of tail-vertebrae.
As compared with M. f. frenata and goldmani: white facial markings more extensive; color of underparts less restricted and more extended on legs; black tip of tail relatively of about same extent as in frenata and thus much less than in goldmani; black color of head extending farther posteriorly than in frenata but not so far as in goldmani.
Skull and teeth.—Male (adult): See measurements and plates [24]-[26], 29, 30. As described in Mustela frenata frenata except that: Weight (no. 128972) 6.3 grams; basilar length, 51.2; interorbital breadth less than distance between foramen opticum and anterior margin of tympanic bulla; anterior margin of tympanic bulla as far posterior to foramen ovale as width of 4 or 5 upper incisors; height of tympanic bulla more or less than (about equal to) distance from its anterior margin to foramen ovale; anterior margin of masseteric fossa anywhere from slightly anterior, to slightly posterior, to m2.
Female (based on no. 26153): See measurements and plates [37]-[39]. As described in Mustela frenata frenata except that: Weight, 3.6 grams; basilar length, 44.5; zygomatic breadth less than distance between condylar foramen and M1, or than between anterior palatine foramen and anterior margin of tympanic bulla; tympanic bulla as far posterior to foramen ovale as width of 4 or 5 upper incisors; height of tympanic bulla not more than distance from its anterior margin to foramen ovale; length of tympanic bulla more than length of lower molar and premolar tooth-row or than length of rostrum.
The skull of the female is 43 per cent lighter than that of the male.
Comparison of the skull with those of M. f. perotae, goldmani and neomexicana has been made in the accounts of those subspecies. As compared with that of frenata the main difference is the less inflated tympanic bulla, the height of which is approximately equal to, rather than decidedly more than, distance from its anterior margin to foramen ovale.
Remarks.—The first specimen known to have been preserved is the alcoholic in the British Museum of Natural History, taken in September, 1891, on the Río Santiago in Jalisco, by D. A. C. Buller. The other known specimens of this white-faced weasel are divided between the American Museum and the United States National Museum. The two referred specimens from Jalisco were the last of several helpful ones collected in México and Central America by J. H. Batty, and these two were taken less than three months before Batty's tragic death in Chiapas (see Allen, J. A., 1906:191). The five specimens from Michoacán were taken by Nelson or Nelson and Goldman together. Merriam had only three of these when he named the subspecies and remarked (1896:29) that "This form is the poorest subspecies described in the present paper." Although the form is not strongly marked, the two additional specimens from Michoacán and better comparative material than Merriam had confirm several of the differential characters ascribed to it by him and indicate the existence of still other characters.
M. f. leucoparia occurs in the Sonoran and Transition life-zones. No. 27258 from Los Masos, and no. 26153 from Artenkiki (see specimens examined for other spellings) approach true frenata in coloration. Each of these specimens has a few white hairs between the ears and the white patch between the eyes is confluent on one side only with the lateral white bands on the side of the head. No. 27258 from Los Masos has a dark spot at each angle of the mouth. The 7 other specimens are relatively uniform in coloration. Each has the white spot between the eyes confluent on both sides with the extensive white areas on each side of the face. None has a dark spot at either angle of the mouth. Of these 7 specimens, the type specimen and three others have white hairs forming a median line between the ears and a fifth specimen has a white spot behind each ear.
M. f. leucoparia is most like M. f. frenata. Unlike frenata, leucoparia has tympanic bullae that are less inflated, narrower and less projected, at their anterior margins, from the cranium. In these characters leucoparia is intermediate between M. f. frenata and M. f. goldmani. The latter subspecies has the least inflated, narrowest and least projecting tympanic bullae of the three. The black color of the head extends, on the average, farther posteriorly than in M. f. frenata but not so far as in M. f. goldmani. The general color, too, is intermediate between that of M. f. frenata and that of the much darker M. f. goldmani. The white facial markings are more extensive than in either M. f. frenata or M. f. goldmani. This applies to both the white area between the eyes and the one on each side of the head between the ear and eye. M. f. neomexicana, whose range possibly meets that of M. f. leucoparia, also has more extensive white facial markings than M. f. frenata but less extensive markings than M. f. leucoparia.