Tropical Weasel
Mustela stolzmanni Taczanowski, Proc. Zoöl. Soc. London, 1881:835, November 15, 1881; Allen, Bull. Amer. Mus. Nat. Hist., 35:105, April 28, 1916.
Mustela stolzmanni stolzmanni, Hall, Carnegie Instit. Washington Publ. 473:111, November 20, 1936; Hall, Physis, 16:167, pl. 1, figs. 5, 6, 1939.
Type.—Female, adult, mounted skin, with skull separate; no. 563, Mus. Polonais d'Hist. Nat. (Warsaw, Poland); Yurimaguas, Perú; 1880; obtained by J. Stolzmann.
The skull (plate [40]), mounted with the skin but removed by me for study, consists of the premaxillae, maxillae, two halves of the lower jaw and dentition. Of these parts, right m2, left coronoid process, right P4 and M1 and adjacent part of maxilla are lost. The skin is well mounted, in a good state of preservation and shows no fading due to exposure to light. Inguinal mammae are distinctly shown on the skin and prove that the specimen is a female. Except for a few scattered hairs on the lower throat, a spot six by eight millimeters on the medial side of the region of the olecranon of the left foreleg and another of similar size in the left axilla, the underparts are, excepting the ventral longitudinal, abdominal stripe, unmarked by color of the upper parts.
Range.—Known from the Tropical Life-zone of eastern Ecuador and Perú from Jatun Yacu south to Valle del Perené. See figure [29] on page [221].
Characters for ready recognition.—Differs from Mustela frenata, the only other geographically adjacent species of the genus, in presence of median, longitudinal, abdominal stripe of same color as upper parts and naked foot soles, in absence of p2 and in reduced size of tympanic bullae (see pls. 28, 29, 30, 39 and 40) and from Mustela africana africana by darker color of upper parts which, although near Chestnut Brown, are 11' n instead of 10' l as in M. a. africana.
Description.—Size.—Male: unknown.
Female: Taczanowski (1881:836) gives, among others, the following measurements of the type specimen: Total length, 523, length of body, 260; length of tail without hair, 190 (with hair 224); length of hind foot, 54. Whether or not the measurements were taken from the animal when in the flesh I do not know. Allowing for shrinkage of hind feet and changes due to the posture of the now mounted specimen, I get from it essentially the same measurements. Collectors' measurements of a subadult from Moyobamba and a young female from Valle del Perené, are respectively, as follows: 469, 415; 184, 160; 57, 52. My own measurements of the dry hind feet on the skins are respectively, 48 and 49.
Externals.—As described in M. a. africana except that the length of the concave sides of the claws are approximately one and one-fourth times the depth; thus the claws are relatively longer than in M. a. africana.
Color.—As described in M. a. africana with the following noted exceptions: Upper parts near (11' n) Chestnut-Brown; area of lighter ventral coloration on the throat and sides of head less strongly tinged with yellow; pelage more dense, finer and softer than in M. a. africana.
Skull and teeth.—Male: Skull unknown.
Female: See measurements and plate [39] and [40]. As described in male of Mustela africana africana except that: Weight, 4.7 grams. As contrasted with M. a. africana, the dentition of the lower jaw is lighter; the transverse diameter of m2 is 1.2 mm. in the type and also in the specimen from Moyobamba as against 1.5 to 1.7 in three male topotypes of M. a. africana.
Remarks.—After the Polish naturalist, Stolzmann, in the course of his explorations in Perú, obtained the single specimen which was made the type, no other naturalist, so far as known, visited the type locality until thirty-two years later when Wilfred H. Osgood and M. P. Anderson spent more than a month collecting at Yurimaguas (see Osgood, 1914:147), but secured no topotypes of this little-known weasel. C. O. Schunke took the second specimen in the Valle del Perené in April, 1921; L. Rutter on January 25, 1924, took the third specimen, and W. Clark-MacIntyre took the fourth specimen on the Jatun Yacu. This obscure place name is shown on the map (fig. 4, p. 827) published by Brown (1941) and is the stream flowing from the west to the town of Napo. Napo is situated at approximately 1° 2' S and 77° 49' W.
In the female from Moyobamba there are only 3 pairs of mammae. One pair is inguinal and two pairs are on the posterior part of the abdomen.
Taczanowski (1881:836) relates that this species was taken in the forest to which it appears to be restricted since the inhabitants of the village did not know of the animal. He points out also that the previously known Peruvian species [M. f. macrura and M. f. agilis] live in the treeless territory of eight to eleven thousand feet altitude whereas M. stolzmanni was found in the humid forest of the great plain of the Maynas at an elevation of 500 feet or less above sea level. The frontal sinuses of the specimens seen reveal no malformation as a result of infestation by parasites.
Specimens examined.—Total number, 4, as follows:
Ecuador: R. Tatun [= Jatun] = Yacu, 1, Mus. Comp. Zoöl.
Perú: Yurimaguas, 1 in Mus. Polonais d'Hist. Naturelle, Warsaw; Moyobamba, 2700 ft. [6° S, 77° W], 1 in Brit. Mus. Nat. Hist.; Valle del Perené, 1200 meters, 1 in Amer. Mus. Nat. Hist.
EXPLANATION OF CRANIAL MEASUREMENTS APPEARS ON PAGE 417