MAMMALS of CALIFORNIA Their Natural History, Systematic Status, and Relations to Man
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FUR~BEARING MAMMALS OF CALIFORNIA Their Natural History, Systematic Status, and Relations to Man BY JOSEPH GRINNELL JOSEPH S. DIXON, AND JEAN M. LINSDALE <>- CONTRIBUTION FROM THE MUSEUM OF VERTEBRATE ZOOLOGY UNIVERSITY OF CALIFORNIA IN Two VOLUMES' VOLUME II UNIVERSITY OF CALIFORNIA PRESS BERKRLEY, CALIFORNIA· 1937- , [GRINNELL, DIXON, LlNSDALE: FUR-nEARING MAMMALS OF CALIFORNIA: PLATE VIII] GOLDEN BEAVER BEAVERS GOLDEN BEAVER . Castor canadensis subauratus Taylor OTHER NAMEs.-Castor fiber~ part; Castor canadensis, part; Castor americanus; Castor pacificus; Castor subaU1'atus; Castor subauratus subauratus; Castor fiber var. canaden sh; Castor fiber americanus; Castor canadensis pacificus, part; American Beaver, part; California Beaver; Pacific Beaver, part; Beaver, part. General characters.-Size, largest of all the rodents (in adults, length of body about 30 in., of tail alone, 16 in., weight upwards of 40 lb.); strong incisor teeth, orange brown in color, protruding from mouth; pelage dense, consisting of long, glossy over hair and thick underfur; eyes and ears small; tail flattened horizontally, broadly paddle shaped, scaly; hindfeet large, toes completely webbed. (See PI. VIII, frontispiece.) Descrt'ption.-Adults: General tone of color, golden brown. More exactly: Under fur, very nearly unifor~ all over, varying around bister, warm sepia, and cinnamon brown, paling slightly on hinder part of belly and around muzzle; overhair on back, dose to ochraceous-tawny, on lower surface where much shorter and scantier, pinkish buff; on base of tail brightening to orange-cinnamon and even vinaceous-rufous. Be cause of notable gloss of overhair, the color tone varies greatly with the angle at which it is viewed. As a pelt is turned this way and that in good light, an impression of metal lic gold is given. Length of longest overhair on middoqum, 2 in. (50 mm.), on belly, IYs in. (28 mm.); depth of underfur on back, %-in. (I9 nun.), on middle of belly, )':i-in. (I3 mm.).Whiskers relatively short (longest up to 2% in. [70 mm.]), pale yellowish brown in color. Soles of both hind and fore feet and nose pad, naked, with skin rough, blackish brown in color; tops of feet devoid of underfur, covered with short overhair, russet in tone on hind feet and dull cinnamon-buff on forefeet. Front foot relatively small, but all five toes well developed and each armed with a heavy claw, the longest (middle one), Va-in. (22 mm.) long and %6-in. (5 mm.) wide. Toes';f hind foot each have a claw which projects beyond margin of webbing; claws of outermost three toes, stout, wider than high, the longest, I in. (25 mm.) long and Ya-in. (IO mm.) wide; claws of inner'two toes much smaller, second with horny blade underneath its claw which leaves a narrow slit; this' second-toe structure constitutes the so-called louse comb. Claws dark brown at bases to horn color at tips. Tail hairy at base continuously with body, terminal flat part (about % total length) scaly, meagerly beset with short hairs; "scales" wide and short, tending to form transverse and diagoI!-al rows; but these are not perfectly regular in arrangement a~ on a carp's body. Young, taken from house, small (length, including tail, 15 in. [380 mm.], weight 2IYz oz. [610 gm.]): LIke adult, but pelage "woolly" in texture and general color darker. Underfur on back deep clove brown; on lower surface, fuscous; overhair luster less, snuff brown on ·back, pale buff below. Feet like adult's; tail similar to adult's but flat part relatively narrower, and scaly surface shows fine hairs, of same dark brown color as rest of tail. The general features of the beaver's skull are shown "in figure 258. Detailed descrip tions and illustrations have' already been published, by Taylor (1916); and need not be repeated here. Our measurements from skull~ of the Californian races, as available to us, are given on pages 630 and 722. Fur-bearing Mammals of California Color vart'ation.-As· far as can be seen from external examination, the sexes are alike with regard to size, color, and texture of pelage. Only one molt takes place each year, occurring very slowly through summer and fall. The fur does not become prime before the first of December. Winter-taken pelts show but slight variation in color. The tone of the underfur is wonderfully uniform. Such variation as is shown in the overhair generally seems to be caused by the amount of "tipping"; whereas most· of this is individual, it may also be modified by abrasion and, perhaps, fading. The "golden brown" cast of color in Castor c. subauratus is so constant as to be diagnostic when com- parison is made with C. c. frondatol'. MEASUREMENTS (IN MILLIMETERS) OF SKULLS OF ADULT OR SUBADULT Castor canadensis subauratus FROM CENTRAL CALIFORNIA 'S "8 :1i ;'l 'S to ~ ;'l eli, 'E.~ ~ ;'l 'il§ j M No. "Ii, •• • 1 ""~~ :Be 0 0 ~~ Sex Locality ~ jj M.V.Z. .!! .p =-6 a ~~ ~~ ~" 'S ,,0 • ",' P ,,8 8 .~ ~ ·:di " 1 • ~- lie ~] 8" l ~ ~ :>: r:5~ ~ ~o ~~ -->'" ---- 16383 Grayson •••...•••.•••...••..• 120.6 96.0 25.6 65.2 49.3 26.1 11.1 19.0 31.7 31081 ,,' Mendota ....•. , ...•.• , ... , .. 127.0 105.6 28.3 68.8 56.8 27.9 10.1 19.1 33.9 31082 '" Mendota .•..•.. , .... , •...••. 121.0 100.3 26,9 6S .8 S3.7 24.7 11.9 19.7 31.8 31083 '" Mendota .........•...• , ...•. 121.5 102.8 26.7 66.5 53.4 24.8 12.7 .... 32.0 31084 '" Mendota ...••...••..•.•....• 125.0 99.3 27.1 65.9 53.1 25.8 10.4- 18.4 32.5 31108 ,,' Fair Oaks ..•.•....•.•...•..• 126.8 99.3 29.6 67.8 52.1 26,S 11.9 19.6 33.9 31255 " Hopeton .. , ............... ,. 123.6 95.9 25.6 68.0 52.9 26.6 12.:3 19.2 34.6 31276 . " Snelling .... , ...•............ 126.8 98.3 26.7 70.1 57.7 28.2 13.3 19.2 33.2 31285 " Hopeton •.••..... , ..... , •... 124.5 94.7 26.5 66.8 52.8 25.2 11-.9 20.3 33.7- 31302 " Snelling •. , ... , .............. 122.9 93.7 25.5 63,6 5:3 .8 26,4 12.8 19.:3 33.0 8987 ~' Grayson ..•..••. , •.•.. " ... -.' 113,1 88.8 23.3 63.5 50.2 24.0 10.8 18.4 29.8 12654 ~' Grayson., .. , .....• , ....• , ... 126.4 103.1 28.1 70.2 54.2 28.0 10.0 18.3 33.2 12669 ~, Grayson ...... , ......... , .... 115.2 94.0 25.4 66.4 51.0 25.7 12.4 18.8 30.9 31079 ~' Mendota." .. , .....•..••.• ,. 115.0 92.1 24.0 60.0 48.0 23.5 12.8 18.6 30.8 31273 ~ Snelling ........ " •. ,." .... , 127.3 97.3 27.1 69.7 57.3 27.9 13.6 21.2 34.2 31278 ~ Snelling .... " .. , ............ 130.5 97.5 27.3 68.4 56.6 27.5 11.9 19.5 34.2 i 31290 ~ Snelling, ......... " ..•.. , ... 123.3 92.8 24.5 66.1 52.7 24.8 11.2 18.5 31.3 31293 ~ Snelling ...... ,., .. , .. , ........ 116.0 90.8 26.0 64.8 51.6 24.3 12.0 19.2 29.7 31294 Snelling .. , ...• , .... , .••... ,. 123.2 93.9 26.5 67.7 51.1 26.S 11.4 19.7 32.3 ..ill' ~ 31296 ~ Snelling ........•.•.... , .... , 126.1 99.1 28.6 69.3 54.2 26.5 13,4 19.5 33.6 I -------------- ! General average, both sexes ... 122.7 96,7 26.5 67.7 53.1 26.0 11.9 19.2 32.5 * Tne sex as here recorded is as determined and written on the labels by the trappers, But, because of the difficulty known to have been experienced in sexing beavers, the accuracy of the records in those specimens starred in the table is, in our minds, open to some doubt; for this reason, separate averages for the sexes are not given. Measurements.-The following are average and extreme external measurements, in millimeters: Of 9 adult males: Total length, 1091 (1025-II75); tau vertebrae, 371 (35(}--405); scaly part of tail, 12ox28r; ratio,' per cent, width of tail to length of tail, 42.8 (37.9-48.3); hind foot, 188 (180-195); ear from crown, 26 (23-28). Of 15 adult fe males: Totallength, II07 (103o-r200); tail vertebrae,383 (345-420); scaly part of tail, r20 X 295; ratio, width of tail to length of tail, 40.5 (31.5-46.8); hind foot, 188 (175- 205); ear from crown, 28 (27-29). Of 24 adult examples (9 males and 15 females): Total length, I rOI (1025-1200); tail vertebrae, 379 (345-420); scaly part of tail, 120X289; ratio, width of tail to length of tail, 41.4 (31.5-48.3); hind foo1; 188 ('75- 205); ear from crown, 27 (23-29)' , -'~ --,--_. Fig. 258. Skull of golden beaver, side view, male (no. 3I085, Mus. Vert. Zo01.). trapped on February I7, I920, near Men~ dota, Fresno County. X 1. Noteworthy features include, as correlated with the beaver's special mode of existence: the huge incisor teeth for gouging and grasping, their .housing in the massiv~ rostrum and mandible, the great development of ridges for attachment of powerful muscles, and the corresponding relatively small size of the brain case. Fur-bearing Mammals of California MEASUllliMENTS (IN MILLIMETER.S) AND WEIGHTS (IN POUNDS) OF 61 Castor canadensis subattratus FROM VICINITY OF SNELLING II ~"O;;::'" > ~i1 ~ .g• ] 'il.~ d No, Total 8~t! Date Ago Sox Weight § M.V.z. length "e ~• ~~~ ] a 1 .9~B ~ J! ~ ~ ~ 0 '" ~ --- " 1920 '" --'" 31269 Feb. 25 adult d' 39 1080 350 13SX290 46.5 185 23 31271 Feb.