Specimens examined.—Total number, 16, listed by localities from north to south. Specimens are in the American Museum of Natural History, unless otherwise indicated.
Honduras: Alto Cantoral, 2; Cerro Grande La Paz, 1. La Flor Archaga, 1[75]; Comayagüela, 1[75]; vicinity of Tegucigalpa, 2; no locality more definite than Honduras, 1[4].
Nicaragua: San Rafel del Norte, 1; Matagalpa, 6; Ma[o]mbacho, 1.
Mustela frenata costaricensis Goldman
Long-tailed Weasel
Plates [25], [26], [27], [28], [29] and [30]
Mustela costaricensis Goldman, Proc. Biol. Soc. Washington, [25]:9, January 23, 1912.
Mustela brasiliensis, Gray, Ann. and Mag. Nat. Hist., 14(ser. 4):374, 1874.
Putorius (Gale) brasiliensis frenatus, Coues, Fur-bearing animals, p. 142, 1877 (part).
Putorius affinis, Merriam, N. Amer. Fauna, 11:31, June 30, 1896 (part).
Mustela affinis costaricensis, Allen, Bull. Amer. Mus. Nat. Hist., 35:101, April 28, 1916; Lönnberg, Arkiv för Zool., 14(no. 4):16, 1921.
Mustela frenata costaricensis, Hall, Carnegie Instit. Washington Publ. 473:109, November 20, 1936.
Type.—Male, young, skull and skin; no. 13770/37149, U. S. Nat. Mus.; San José, Costa Rica; obtained by C. H. Van Patten.
The skull (plates [28]-[30]) is complete and unbroken. All teeth are present and unworn. The skin apparently has been remade. It lacks the distal two-thirds of the tail. The head is somewhat shrunken. The color is possibly faded but if so only to a slight degree. Otherwise, the skin is in good condition. The orange color of the underparts is so intense as to suggest that the full, adult pelage has not been acquired. No white markings are present on the face. There is no sex mark on the label attached to the skin but the size and proportions of the skull and the scrotal pouch on the skin prove that the specimen is a male. The presence of sutures on the dorsal face of the rostrum and the short, wide, and low sagittal crest show the specimen to be young.
Range.—Costa Rica. Altitudinal and zonal range unknown. See figure [29] on page [221].
Characters for ready recognition.—Differs from M. f. panamensis in lighter color of upper parts (tone 2 rather than tone 4 of Reddish Black of Oberthür and Dauthenay, pl. 344) and longitudinally flat interorbital region of skull; from M. f. nicaraguae in darker color of upper parts (of Oberthür and Dauthenay, tone 2 of pl. 344 rather than tone 4 of pl. 342) and greater width (more than 7) of tympanic bulla.
Description.—Size.—Male: No collector's measurements available of fully grown animals. Estimated measurements of adult males: Total length, 470; length of tail, 165; length of hind foot (taken from dried skins of 3 adults), 52 (50-52). Tail estimated to average 55 per cent as long as head and body. Length of hind foot more or less than (about equal to) basal length.
Female: A subadult or adult, from the Candelaria Mountains, and a subadult from Irazú, measure, respectively: Total length, 370, 385; length of tail, 130, 150; length of hind foot, 40, 31. Tail 59 per cent as long as head and body. Length of hind foot probably about equal to basal length.
The estimated differences in external measurements of the two sexes are: Total length, 92; length of tail, 25; length of hind foot, 16 (probably average difference is less).
Externals.—As described in M. f. panamensis (figure [21]) except that foot soles are slightly more hairy.
Color.—As described in Mustela frenata panamensis except that: back is near Reddish Black, tone 2 of Oberthür and Dauthenay, pl. 344; chin, lips, and throat white or whitish; remainder of underparts near (c) Ochraceous-Buff; color of underparts rarely extending distally onto toes of forefeet. Least width of color of underparts, in eleven specimens, averaging 23 (10-36) per cent of greatest width of color of upper parts; black tip of tail, in six specimens, averaging 36 (31-38) per cent of length of tail-vertebrae.
Skull and teeth.—Male (based on 2 adults, no. 3.2.1.6. from vicinity of San José and no. 11408, U. S. Nat. Mus., from "Costa Rica"): See measurements and plates [25]-[30]; weight, 5.9 grams; basilar length 49 +; zygomatic breadth more than distance between condylar foramen and M1 or than between anterior palatine foramen and anterior margin of tympanic bulla; mastoid breadth less than postpalatal length; postorbital breadth in undiseased skulls less than length of upper premolars (less than distance between posterior borders of P2 and P4) and less than width of basioccipital measured from medial margin of one foramen lacerum posterior to its opposite; interorbital breadth more or less than distance between foramen opticum and anterior margin of tympanic bulla; breadth of rostrum more or less (about equal to) length of tympanic bulla; least width of palate less than length of P4; anterior margin of tympanic bulla as far posterior to foramen ovale as width of 5 upper incisors; height of tympanic bulla less than distance from its anterior margin to foramen ovale; tympanic bulla longer or shorter than (about equal to) lower molar and premolar tooth-row and longer or shorter than (about equal to) rostrum; anterior margin of masseteric fossa directly below posterior border of m2.
Female: Skull of adult unknown.
Comparison of the skull of the male with that of M. f. panamensis has been made in the account of that subspecies. As compared with that of M. f. nicaraguae the skull of M. f. costaricensis is heavier and in every measurement taken is larger. The skull is generally more massive and it follows that most measurements of depth and width are greater in relation to the basilar length as well as actually greater. The individual teeth are larger and the tympanic bullae wider and at their anterior ends are more projected from the braincase. Indeed the skull is more like that of M. f. goldmani than like that of M. f. nicaraguae.
Remarks.—The half dozen ill-prepared skins, with partial skulls inside, of this form in the United States National Museum long were referred either to Mustela brasiliensis or Mustela affinis. It was not until 1912 when Goldman studied these specimens that the distinctive characters of the Costa Rican weasel were recognized and made the basis of the name costaricensis.