Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If you need an accessible version of this item please contact JSTOR User Support

Distribution and Variation in the Native Sheep of North America

Ian McTaggart Cowan
The American Midland Naturalist
Vol. 24, No. 3 (Nov., 1940), pp. 505-580
DOI: 10.2307/2420858
Stable URL: http://www.jstor.org/stable/2420858
Page Count: 76
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
If you need an accessible version of this item please contact JSTOR User Support
Distribution and Variation in the Native Sheep of North America
Preview not available

Abstract

In the course of this study seven hundred and sixty-one specimens of North American mountain sheep have been examined. This material has formed the basis for a study of individual, seasonal, sex, age and geographic variation in the genus. It is suggested that Ovis nivicola of northeastern Asia, and Ovis dalli and Ovis canadensis of North America had a common ancestor in early Pleistocene or late Pliocene time. That during the Pleistocene sheep stocks survived in northeastern Siberia and Alaska and in western North America south of the ice cap; and that these three stocks thus isolated have evolved into the three species mentioned above. With the disappearance of the ice cap in North America O. canadensis has spread northward and O. dalli southward. The ranges of the two species have not as yet made contact but in the region of the Peace River, British Columbia are separated by less than one hundred miles. Secondary sexual variation is pronounced. It is most noticeable in the horns of adults, but occurs in size and shape of skull, degree of ankylosis of skull elements, general body form and in coat color in at least two races. Females are not found to be less variable than males. There is some evidence that in Ovis canadensis as in Odocoileus the size difference between males and females is greatest in the northern and least in the southern parts of the range. Age variation is exhibited in size and form of horns, degree of ankylosis of skull and in certain less important features. Size and form of skull varies little after the age of six years. No age variation in coat color was observed after the lamb coat was shed. Individual variation is extreme in size and shape of horns and in color of pelage. Adult skulls are remarkably constant as to size and form but dwarfed individuals occur relatively frequently and are represented by five individuals in the collections examined. Two of these have apparently served as types for supposed geographic races. Ten geographic races are found to be recognizable on the basis of existing specimens. Published and unpublished material has been used in an appraisal of the present distribution and abundance of the various races of mountain sheep inhabiting North America. Ovis c. auduboni is apparently extinct. O. c. californiana is represented by a small number of atypical specimens in California, a smaller number in northern Washington, and a fair but largely unappraised population in south-western British Columbia. Information regarding the status of weemsi and cremnobates in Lower California and mexicana in the Mexican part of its range, has been unobtainable. All other races, though they have suffered diminution in numbers and even local extermination, still exist in quantities that give hope of restoration up to the carrying capacity of the range now available. In large parts of eastern British Columbia, western Alberta, Yukon and Alaska sheep still exist under conditions relatively unaltered by man.

Page Thumbnails

  • Thumbnail: Page 
505
    505
  • Thumbnail: Page 
506
    506
  • Thumbnail: Page 
507
    507
  • Thumbnail: Page 
508
    508
  • Thumbnail: Page 
509
    509
  • Thumbnail: Page 
510
    510
  • Thumbnail: Page 
511
    511
  • Thumbnail: Page 
512
    512
  • Thumbnail: Page 
513
    513
  • Thumbnail: Page 
514
    514
  • Thumbnail: Page 
515
    515
  • Thumbnail: Page 
516
    516
  • Thumbnail: Page 
517
    517
  • Thumbnail: Page 
518
    518
  • Thumbnail: Page 
519
    519
  • Thumbnail: Page 
520
    520
  • Thumbnail: Page 
521
    521
  • Thumbnail: Page 
522
    522
  • Thumbnail: Page 
523
    523
  • Thumbnail: Page 
524
    524
  • Thumbnail: Page 
525
    525
  • Thumbnail: Page 
526
    526
  • Thumbnail: Page 
527
    527
  • Thumbnail: Page 
528
    528
  • Thumbnail: Page 
529
    529
  • Thumbnail: Page 
530
    530
  • Thumbnail: Page 
531
    531
  • Thumbnail: Page 
532
    532
  • Thumbnail: Page 
533
    533
  • Thumbnail: Page 
534
    534
  • Thumbnail: Page 
535
    535
  • Thumbnail: Page 
536
    536
  • Thumbnail: Page 
537
    537
  • Thumbnail: Page 
538
    538
  • Thumbnail: Page 
539
    539
  • Thumbnail: Page 
540
    540
  • Thumbnail: Page 
541
    541
  • Thumbnail: Page 
542
    542
  • Thumbnail: Page 
543
    543
  • Thumbnail: Page 
[544]
    [544]
  • Thumbnail: Page 
545
    545
  • Thumbnail: Page 
546
    546
  • Thumbnail: Page 
547
    547
  • Thumbnail: Page 
548
    548
  • Thumbnail: Page 
549
    549
  • Thumbnail: Page 
550
    550
  • Thumbnail: Page 
551
    551
  • Thumbnail: Page 
552
    552
  • Thumbnail: Page 
553
    553
  • Thumbnail: Page 
554
    554
  • Thumbnail: Page 
555
    555
  • Thumbnail: Page 
556
    556
  • Thumbnail: Page 
557
    557
  • Thumbnail: Page 
558
    558
  • Thumbnail: Page 
559
    559
  • Thumbnail: Page 
560
    560
  • Thumbnail: Page 
561
    561
  • Thumbnail: Page 
562
    562
  • Thumbnail: Page 
563
    563
  • Thumbnail: Page 
564
    564
  • Thumbnail: Page 
565
    565
  • Thumbnail: Page 
566
    566
  • Thumbnail: Page 
567
    567
  • Thumbnail: Page 
568
    568
  • Thumbnail: Page 
569
    569
  • Thumbnail: Page 
570
    570
  • Thumbnail: Page 
571
    571
  • Thumbnail: Page 
572
    572
  • Thumbnail: Page 
573
    573
  • Thumbnail: Page 
[574]
    [574]
  • Thumbnail: Page 
575
    575
  • Thumbnail: Page 
576
    576
  • Thumbnail: Page 
577
    577
  • Thumbnail: Page 
578
    578
  • Thumbnail: Page 
579
    579
  • Thumbnail: Page 
580
    580