Despite these puzzling local variations, it is established that the long-tailed weasels of southern California are smaller than those from farther north. Also, the southern animal averages smaller in weight and size of skull, and the skull is differently proportioned. Specimens in series from Los Angeles County definitely are intermediate in size and shape of skull between latirostra from San Diego County and nigriauris from, say, Santa Clara County, but definitely more closely resemble latirostra from San Diego County than they do nigriauris. A skull of a young animal, not here identified to subspecies, from Potholes, in the Colorado River Valley, 10 miles northeast of Bard, Imperial County, California, may have closest relationship to M. f. latirostra. Additional comment on this specimen is offered in the account of M. f. neomexicana.
From the asphalt pits of Rancho La Brea, in Los Angeles County, a total of 57 skulls have been examined, more than half of which are reasonably complete. I have been unable to learn whether these came from pits regarded by students of the deposit as wholly Recent, from pits regarded as of Pleistocene age, or from both. Suffice to say that only two specimens were found which could be distinguished from skulls of the subspecies of weasel living in that area today.
These two specimens, lent to me by Professor Chester Stock, were with other skulls received from the Los Angeles Museum of History, Art and Science and bore identifying numbers as follows: 16/20-27, the anterior part of the skull of an adult, and 16, the skull posterior to the cribiform plate of a subadult or possibly young individual. The latter has a mastoid breadth of 28.0 millimeters, a tympanic bulla 16.1 long and other measurements in proportion. It is larger than any specimen of weasel, of any subspecies, seen from California and in the subgenus Mustela seems to be exceeded in size only by certain individuals of M. f. texensis. M. f. neomexicana attains relatively large size and comparisons were made with individuals of that subspecies. However, the young specimen from Rancho La Brea differs from neomexicana in that the tympanic bullae rise less steeply on the medial sides and the inferior lip of the external auditory meatus is less developed laterally. Age considered, the sagittal crest is less developed and the mastoid processes project more abruptly from the skull. The anterior part of the skull of the adult, no. 16/20-27 is larger than any specimen seen of M. f. latirostra or adjoining subspecies, and among California-taken specimens is equaled in size only by the largest males of M. f. munda from the northwest coastal district in Mendocino County. This adult from Rancho La Brea differs from neomexicana, sex and age taken into account, in greater postorbital breadth, lesser rostral width in comparison with the interorbital breadth, and in having the temporal ridges at the anterior end of the sagittal crest spread out into a Y-shaped, rather than a T-shaped, pattern. All these differences from neomexicana are features of agreement with the California bridled weasels of the subspecies latirostra, nigriauris, and munda. The same is true of the characters which set apart the young specimen from neomexicana. In summary: of 57 weasel skulls examined from the asphalt pits at Rancho La Brea, Los Angeles County, all but two are indistinguishable from the skulls of the Recent weasel living in that region today. These two skulls agree in qualitative characters with animals of the California coastal subspecies now living from Los Angeles northward to Humboldt County, but are larger. For the time being these two may be thought of as giants of the same type of animal inhabiting the Los Angeles region today.
Only one of 41 adult and subadult skulls examined for malformation of the frontal sinuses shows infestation by parasites.
Specimens examined.—Total number, 142, listed by counties from north to south. Unless otherwise indicated specimens are in the Museum of Vertebrate Zoölogy.
California. Santa Barbara County: Rincon Point, 1. Ventura County: Cuyama Valley, 2200 ft., 1[91]; Nordhoff, 3[59]; Santa Paula, 1[59]; Ventura, 7. Los Angeles County: near Owensmouth, 1[24]; Cahuenga, 1[91]; Llano, 10 mi. E Littlerock, 1; Flint Ridge, Pasadena, 1[59]; Pasadena, 3; Lankershim, 1[24]; 1 mi. S Lankershim, 1[24]; Duarte, 1[59]; Covina, 1[59]; Claremont, 1[91]; El Monte, 4 (2[75], 1[24]); Montebello, 1; Alhambra, 6 (5[2], 1[91]); El Nogal, 2[8]; Gardena, 1[26]; Palos Verdes Estate, 3; Rancho La Brea asphalt deposits, 57[70] and [92]. San Bernardino County: San Bernardino Valley, 1[75]; San Bernardino, 4 (2[20], 1[91]); Redlands, 2 (1[38]); Bluff Lake, 2 (1[59], 1[33]). Riverside County: West Riverside, 1; Arlington, 800 ft., 1[17]; 3-1/2 mi. E and 1/2 mi. N Beaumont, 2600 ft., 1; Banning, 1[91]; Cabazon, 1[91]; San Jacinto Plain, 1[20]; Tahquitz Valley, 8000 ft., 1; Elsinore, 1[1]. San Diego County: Twin Oaks, 1[91]; San Marcos, 2 (1[87], 1[41]); Escondido, 1; Witch Creek, 1[91]; Ballena, 1[20]; Santa Ysabel, 3 (2[20], 1[87]); Julián, 1; La Jolla, 1; Lakeside, 1[91]; El Cajon, 1[91]; El Vido (not found on map), 1[91]; San Diego, 9 (1[91], 1[20], 1[87], 1[32]); Jamacha, 2[87]; Chula Vista, 1[20].
Mustela frenata pulchra Hall
Long-tailed Weasel