E. Raymond Hall

“ In the northeastern part of the geographic range of L. c. merriami, as Nelson pointed out, the small size of the tympanic bullae was one of several evidences of intergradation there with Lepus californicus melanotis, the subspecies next adjacent to the north. In the light of present information, it seems that the smallness of the tympanic bullae in the specimens (3) from Padre Island may be an independent development—an adaptation to environmental conditions that reaches its fullest development on the same chain of islands eighty-odd miles southward of Matamoros. ”

“ A gradient series is evident in which the pikas and jack rabbits are the extremes. The black-tailed jack rabbit, for example, in relation to size of the entire animal, has the longest ears and longest hind legs. This kind of lagomorph takes alarm when an enemy, for example, a coyote, is yet a long way off. The jack rabbit seeks safety in running; even when being overtaken by a pursuer that is close behind, the jack rabbit still relies on its running ability instead of entering thick brush or a hole in the ground where its larger-sized pursuer would be unable to follow. ”

“ Actual intergradation, in the sense of interbreeding between individuals of a continuously distributed population of animals, probably does not occur regularly between S. f. cognatus and S. f. robustus nor between several populations within either one of these subspecies; in south-central Arizona and western Texas the animals are said to occur only in the higher parts of the mountains. Consequently a given population is separated from another by low-lying territory inhospitable to the species Sylvilagus floridanus. This low-lying territory is inhabited by another species, Sylvilagus audubonii. ”

“ Remarks.—The 22 specimens in the Chicago Natural History Museum are remarkably uniform in color in spite of differences in age; 17 are so young as to have the first upper molar only slightly worn and 5 are adults. In preparing the original description of R. c. seclusus, known only from specimens in the summer pelage, comparison of color was made with only the winter pelage of R. c. chrysopsis and it was pointed out that the differences noted in color between the two subspecies might be seasonal rather than subspecific. ”

“ It will aid in understanding the high degree of secondary sexual difference in richardsonii to visualize two kinds of weasels distributed over the northern half of the continent, thinking now of the geographic area in America occupied by the whole species Mustela erminea of which the subspecies richardsonii is only a part. One of the two kinds of weasel is the male ermine and the other the female. The decrease in size of the male, as measured by the weight of the skull, is in the ratio of 7 in the north to 2 in the south. ”

“ The color is lighter than in the average of specimens from the mainland (for instance those from Victoria and Soto la Marina) but can be matched by selected specimens. In animals of equal age, the hind foot and basilar length are shorter in S. h. solus than in berlandieri. The broadening of the rostrum, which occurs with advanced age, is attained in solus when the skull is yet short; the maximum breadth of the rostrum in the adults is more, instead of less, than a fourth of the basilar length. ”

“ The most popular small game mammal in nearly every part of North America is one or another of the species of rabbits or hares. The rabbit is one of the few species of wild game that still is hunted commercially and sold for food on the open market. The close association and repeated contact of man with these animals has resulted in his contracting such of their diseases as are transmissible to him. Consequently the rabbits and hares have figured in many investigations concerned with public health and medicine. ”

“ Study of a large series of one age of one sex of one species from one locality shows that some parts, of the skull for example, vary more than other parts. In illustration, among 22 male topotypes of Mustela frenata washingtoni the least interorbital breadth varied 25 per cent (9.0 mm. to 12 mm.) whereas the length of the tooth-rows varied only 13.3 per cent (15.6 mm. to 18.0 mm.) . In color the individual variation definitely is more in areas of intergradation between subspecies than in other areas. ”

“ Specimens collected after Merriam proposed the name for the weasel of Kodiak Island show the animal there to be less different from arctica of the adjacent mainland than he thought; small size is the most pro nounced distinction of kadiacensis and Merriam's male type specimen is smaller than any of the five additional males saved from Kodiak Island since that time. Even so the differences fully warrant subspecific recognition, in my opinion, although kadiacensis is not a strongly differentiated race. More adult females are needed to ascertain the norm of form and size for that sex. ”

“ Considering the delicate response of structure to climate, a person naturally questions whether or not natural selection accounts for all of the differences between subspecies. To show that natural selection determines the color of Mustela frenata, it would be necessary to assume that climate, color, and utility of color are positively correlated. Although climate (rainfall) and color are correlated in such a manner that three subspecies of weasel in places as far apart as New England, Perú, and the state of Washington are colored alike, other features of the three environments are unlike. ”

“ All sutures in the skull, except those between the tympanic bulla and the braincase, and those on the dorsal face of the rostrum, are obliterated while the animal is a subadult. Most kinds of mammals retain sutures throughout life or until the animals are well into adulthood. Therefore, skulls of weasels offer fewer features for estimating age than do those of most mammals and the skulls of weasels that are subadults or older are more difficult to classify accurately as to age than are the skulls of most other mammals. ”

“ Specific variations, that is to say specific characters, are provided by the color-pattern, length of tail, number of premolar teeth, shape of the tympanic bullae, and length of the braincase in relation to the length of the tooth-bearing parts of the skull. Subspecific characters are provided by color-pattern, color itself, size as measured by weight of the animal, and its linear measurements, size of the skull, and size and shape of parts of the skull. The characters distinguishing subspecies from one another are not of a different nature from those distinguishing species from one another. ”

“ A rapid dash, and the bird or mouse is grabbed over the back of the skull, the fore legs encircle the animal as though hugging it, and the hind legs are brought up to scratch wildly at the captive. . . . If [the prey is] a large animal, as a rat, the weasel usually lies on its side, while the diminishing struggles of the rodent continue, but if a mouse or a small bird [is the object of attack] , the weasel is apt to crouch over its prey. ”

“ These areas may or may not be connected by a thin line of white color along the midline of the underparts. In size of animal, erminea probably exhibits the maximum variation among American species of weasels; an average-sized male of the race arctica weighs 4 times as much as one of the race muricus, and in the species frenata I doubt that the difference is quite as great between individuals of the smallest race, effera, on the one hand, and either of the largest races, texensis or macrophonius, on the other hand although actual weights are not available for these races of frenata. ”

“ When subspecific and specific variations are the objectives of study, seasonal variation must be understood, in order to be excluded from consideration, in the same way that variations ascribable to age, sex and individualism must be understood in order to be excluded from consideration. In weasels, change in color of the pelage is the seasonal variation most important for the systematist to understand. Other seasonal variations in the pelage are hairiness versus nakedness of the pads of the feet, length of the pelage on the body, and possibly the density of the pelage on the body. ”

“ White or light yellowish facial markings occur in subspecies of M. frenata from the southwestern United Stated to Central America. Subspecies having the most extensive light-colored facial markings have the remainder of the upper part of the head black. In weasels without light facial markings the upper parts of the head all are brown. In the two species, M. erminea and M. frenata, the extent to which the light color of the underparts extends down the insides of the legs and out on the underside of the tail, or the absence of light color on these parts, is a matter of geographic variation. ”

“ There have been reports of losses from time to time from neighbors, but on looking into details we find that there are very few farmers who have experienced more than three separate occasions of weasel depredation and the total loss per farmer in the last thirty years does not, we are sure, exceed ten birds. This is surely a remarkably small payment to weasels in general for the great good done by them in killing rodents.
"We wish to point out, too, that only the exceptional weasel becomes a poultry killer. In most cases apparently it is a fully-grown male that does the killing. ”

“ If as many specimens per unit area were available as there are of the species M. erminea from southern British Columbia, geographic variation warranting the division of muricus into more than one subspecies might be revealed. Evidence pointing in this direction is comprised in the pale color and small size of the pair of adults from Wheeler Peak on the eastern border of Nevada; the suggestion is that there is a distinct pale race of small individuals in the isolated spots of boreal life-zone in the mountains of the desert. ”

“ One skin is in white winter pelage and the other, a female, is in summer pelage which in coloration and color pattern agrees with that of spadix. External measurements of the male agree with those of longicauda. Measurements of the female agree with those of spadix except that the tail is shorter as in primulina. The skulls are as long as in longicauda but are more slender than in either longicauda or spadix although nearer the latter in this respect. In dorsal aspect, the skulls especially posteriorly to the orbital region, resemble primulina. ”

“ If natural selection alone determined the color, some difference in color would be expected between the weasel which needed to be obliteratively colored, that is camouflaged, the better to catch a Phyllotis in Perú and the weasel in Washington which needed nature's aid in catching Microtus. Mustela frenata goldmani of the highlands of southern México, which is known to attack the huge pocket gophers, Orthogeomys and Cratogeomys, has a weaker dental armature than Mustela frenata texensis which does not have to overcome prey so formidable as does goldmani. ”

“ A structure is not a system, as for example, the digestive system or osseous system. A character is some weight, linear dimension, volume, shape, color, or other perceptible attribute of a structure, of a system, or of an entire organism.
In recording the localities of capture of specimens examined, effort has been made to be exactly as precise as the locality data on the labels of the specimens permit. The word "County" is written out in full when the name of the county is written on the label of each specimen listed from that county. ”

“ In the northern half of North America, roughly speaking, seasonal change in color is so pronounced (white in winter and brown in summer) as to be easily recognized. South of this area, in the Austral and Sonoran life-zones, the color of the winter pelage differs only slightly from that of the summer pelage. In these more southern latitudes the winter pelage in almost all subspecies is of lighter color than the summer pelage and has a smoky suffusion. ”

“ The teeth of American species vary little except in size. The absence of P2 in Mustela africana is the only difference of a qualitative (presence or absence) nature that was detected. Also, the Central American subspecies of Mustela frenata exhibit a tendency to early loss of P2 and thus foreshadow the condition typical of M. africana.
As a whole the dentition of the weasel exhibits a high degree of specialization for a diet of flesh and this specialization is fully as evident in the deciduous dentition as in the permanent dentition. ”

“ Although in the long-tailed weasels (Mustela frenata) the underparts of all the races are pigmented with some form of red, orange or yellow, it seems probable to me that the additional color resulting from the soiling effect of this glandular secretion explains the greater variation, found at a single locality, in the color of underparts than of upper parts in the summer pelage.
[42]
I have neither seen nor heard of a black weasel in any part of the New World or of the Old World. I have found only one albino among American specimens. It is an adult female, no. ”

“ On the right side of the neck, all that area between the foreleg and ear is white from the mid-dorsal line (including 7 or 8 millimeters to the left of the mid-dorsal line) down to the throat, which is white as it is also in normal individuals. The toes of the right hind foot are more extensively white than in normal specimens of noveboracensis, and all of the right forefoot as well as the wrist is white. The tail is of striking appearance because of its tricolor pattern. The proximal part is of the normal brown color. ”