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Three New Beavers from Utah

By

STEPHEN D. DURRANT and HAROLD S. CRANE

University of Kansas Publications

Museum of Natural History

Volume 1, No. 20, pp. 407-417, 7 figs. in text
December 24, 1948

University of Kansas
LAWRENCE
1948


UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Edward H. Taylor
~Volume 1, No. 20, pp. 407-417, 7 figs. in text~
~December 24, 1948~

UNIVERSITY OF KANSAS
Lawrence, Kansas

PRINTED BY
FERD VOILAND, JR., STATE PRINTER
TOPEKA, KANSAS
1948

22-3716

[Transcriber's Note: Words surrounded by tildes, like ~this~ signifies
words in bold. Words surrounded by underscores, like _this_, signifies
words in italics.]




Three New Beavers from Utah

By

STEPHEN D. DURRANT AND HAROLD S. CRANE


The subspecific identity of beavers from Utah seems never to have been
carefully investigated. With the exception of the name _Castor
canadensis repentinus_ applied to animals from Zion and Parunuweap
canyons by Presnall (1938:14), all other writers from 1897 until the
present time, have used for animals from Utah, the name combination
_Castor canadensis frondator_ Mearns, the type of which is from Sonora,
Mexico. Study of specimens of beavers from Utah, accumulated in the
collections of the Museum of Zoölogy, University of Utah, proves these
animals to be far more variable than formerly supposed, and discloses
the existence of three hitherto unnamed kinds, which are named and
described below.

We recognize the need for caution in proposing new names for American
beavers, because the transplanting of these animals from one watershed
to another may have permitted the animals of a given area to change
genetically, say, through hybridization, and may also have altered the
geographic distribution of the several kinds. The officials of the Utah
State Fish and Game Commission have assured us that such transplants
have not occurred in the areas where these three new kinds are found,
and further that nowhere in the state have transplants been made from
one major drainage system to another; such transplants as have been made
were only within the same major drainage system.

The capitalized color terms used in this paper are after Ridgway, Color
Standards and Color Nomenclature, Washington, D. C., 1912. All
measurements are in millimeters. We are indebted to the officials of the
United States National Museum for the loan of comparative materials.


~Castor canadensis pallidus~ new subspecies

_Type._--Female, adult, skin and skull, number 719, Museum of Zoölogy,
University of Utah; Lynn Canyon, 7,500 ft., Boxelder County, Utah;
September 7, 1932; collected by W. W. Newby.

_Range._--Known only from the Raft River Mountains.

_Diagnosis._--Size small; tail and hind foot short (see measurements).
Color (type): Pale, upper parts uniformly Ochraceous-Buff; underfur
Snuff Brown; underparts uniformly Light Buff, grading to Light
Ochraceous-Buff at base of tail; underfur Light Drab; front and hind
feet Light Ochraceous-Buff. Skull: Rostrum short; nasals broad (breadth
averaging 54 per cent of length), constricted posteriorly and barely
projecting posteriorly beyond premaxillae; zygomatic arches robust, but
not widely spreading (zygomatic breadth 77 per cent of basilar length);
mastoid breadth 73 per cent of zygomatic breadth; anterolateral margin
of orbit narrow (6.2); occipital condyles visible from dorsal view;
condylobasal length greater than occipitonasal length; upper incisors
narrow (Orange Chrome in color); coronoid processes high and wide; cheek
teeth narrow.

_Measurements._--Measurements of the type are as follows: Total length,
1040; length of tail, 380; length of hind foot, 157; length of ear, 35;
occipitonasal length, 129.1; basilar length, 116.6; mastoid breadth,
65.6; interorbital breadth, 23.6; length of nasals, 43.3; zygomatic
breadth, 89.7; breadth of nasals, 23.4; alveolar length of upper
molariform teeth, 30.4.

_Comparisons._--From topotypes and near topotypes of _Castor canadensis
taylori_, _C. c. pallidus_ differs as follows: Size smaller; tail and
hind foot shorter. Color: Markedly lighter throughout. Skull: Nasals
shorter and wider (breadth of nasals averages 54 per cent of length of
nasals, as opposed to 46 per cent); nasals barely projecting posteriorly
beyond premaxillae; rostrum shorter; zygomatic breadth relative to
basilar length less; mastoid breadth actually as well as relatively
greater; interorbital breadth greater; occipitonasal length shorter
rather than longer than condylobasal length; tympanic bullae smaller;
coronoid process higher and wider; cheek teeth narrower.

From specimens of _Castor canadensis baileyi_, from 20 miles north
northeast of Elko, Elko County, Nevada, _C. c. pallidus_ differs as
follows: Body smaller; tail longer; hind foot shorter; ears shorter:
Color: Markedly lighter throughout. Skull: Larger; nasals shorter and
wider (breadth of nasals averages 54 per cent of length of nasals as
opposed to 41 per cent); nasals barely projecting posteriorly beyond
premaxillae; rostrum broader; zygomatic breadth relative to basilar
length less; mastoid breadth actually as well as relatively greater;
occipitonasal length less rather than greater than condylobasal length;
tympanic bullae smaller; coronoid process higher and wider; cheek teeth
narrower.

From one topotype and two specimens of _Castor canadensis repentinus_,
from the Colorado River at Yuma, Yuma County, Arizona, _C. c. pallidus_
differs as follows: Tail and hind foot shorter. Color: Lighter
throughout. Skull: Narrower; nasals shorter and wider (breadth of nasals
averages 54 per cent of length of nasals as opposed to 47 per cent);
nasals barely projecting posteriorly beyond premaxillae; rostrum
shorter; zygomatic breadth relative to basilar length less; mastoid
breadth actually as well relatively greater; tympanic bullae narrower
and smaller; coronoid process higher and wider; cheek teeth narrower.

From one specimen of _Castor canadensis concisor_, from Trappers Lake,
Garfield County, Colorado, and from the original description of that
subspecies (Warren and Hall, 1939: 358), _C. c. pallidus_ differs as
follows: Size smaller. Color: Markedly lighter throughout. Skull:
Smaller, narrower; nasals shorter and wider (breadth of nasals averages
54 per cent of length of nasals as opposed to 48 per cent); rostrum
shorter; zygomatic breadth relative to basilar length less; mastoid
breadth relative to zygomatic breadth greater; tympanic bullae narrower
and smaller; jugals narrower; distal end of meatal tube smaller;
coronoid process shorter and wider; angular process shorter and rounded
rather than nearly pointed; cheek teeth narrower.

From the type and near topotypes of _Castor canadensis rostralis_, _C.
c. pallidus_ differs as follows: Size smaller; tail and hind foot
shorter. Color: Markedly lighter throughout. Skull: Smaller and
narrower; rostrum shallower and narrower; posterior end of nasals more
constricted and barely projecting posteriorly beyond premaxillae;
zygomatic breadth relative to basilar length less; mastoid breadth
actually as well as relatively greater; dorsal surface of lacrimal bone
larger; tympanic bullae narrower; coronoid process higher and wider;
angular process not projecting so far caudad; cheek teeth narrower.

From the type and near topotypes of _Castor canadensis duchesnei_, _C.
c. pallidus_ differs as follows: Size smaller; tail and hind foot
shorter. Color: Lighter throughout. Skull: Shorter, narrower and less
massive; nasals shorter and wider (breadth of nasals averages 54 per
cent of length of nasals as opposed to 46 per cent); nasals barely
projecting posteriorly beyond premaxillae; rostrum shorter and narrower;
zygomatic breadth relative to basilar length less; mastoid breadth
actually as well as relatively greater; tympanic bullae narrower and
smaller; coronoid process higher and wider; angular process not
projecting so far caudad; cheek teeth narrower.

_Remarks._--The Raft River Mountains of extreme northwestern Utah, where
_C. c. pallidus_ occurs, are the only mountains of the state within the
drainage of the Snake River. The Snake River proper lies 50 miles to the
northward in Idaho and contains another kind of beaver, _C. c. taylori_
(Davis, 1939: 273). Although occurring within the same drainage as _C.
c. taylori_, _C. c. pallidus_ is as distinct from it as from any other
named kind. The relationships of _C. c. pallidus_, as indicated by the
short rostrum and short, wide nasals, are rather more with _C. c.
rostralis_ of the Wasatch Mountains, than with _C. c. taylori_.

The pale color of the animals belonging to _C. c. pallidus_ was noted at
the time of capture, and is the same in the young specimen (625 mm.
total length) as in the type, an adult.

     _Specimens examined._--Total, 2, distributed as follows:
     _Boxelder County_: Raft River, 5 mi. S Yost, Raft River
     Mountains, 6,000 ft., 1; Lynn Canyon, Raft River Mountains,
     7,500 ft., 1.


~Castor canadensis rostralis~ new subspecies

_Type._--Male, young adult, skin and skull, number 5199, Museum of
Zoölogy, University of Utah; Red Butte Canyon, Fort Douglas, 5,000 ft.,
Salt Lake County, Utah; October 13, 1947; collected by Harold S. Crane
and Clifton M. Greenhalgh, original number 446 of Crane.

_Range._--Known from the western streams of the Wasatch Mountains;
probably occurs in all streams draining westward into the basin of
Pleistocene Lake Bonneville.

_Diagnosis._--Size large; tail and hind foot long (see measurements).
Color (type): Upper parts Snuff Brown, purest on head; underfur Brownish
Black (2); base of tail Cinnamon Buff; hind feet Carob Brown; ears
Blackish Brown (2); underparts Auburn, grading posteriorly to Cinnamon
Buff; underfur Light Drab. Skull: Large, massive; nasals short and broad
(breadth averaging 54 per cent of length) and moderately convex
transversely; rostrum deep and broad; ventral surface of rostrum
moderately concave dorsally; dorsal surface of lacrimal bone small;
frontal region generally flat; zygomatic arches robust and widely
spreading (zygomatic breadth averaging 82 per cent of basilar length).

_Measurements._--Measurements of the type and average and extreme
cranial measurements of 6 unsexed adults from Charleston, are,
respectively, as follows: Total length, 1,330; length of tail, 470;
length of hind foot, 170; length of ear, 34; occipitonasal length,
128.2, 134.3 (142.1-129.5); basilar length, 112.4, 117.2 (128.2-113.2);
mastoid breadth, 62.5, 64.3 (68.9-60.2); interorbital breadth, 27.9,
26.0 (26.9-26.0); zygomatic breadth, 91.3, 93.8 (105.8-90.8); length of
nasals, 44.9, 43.9 (51.3-41.5); breadth of nasals, 24.5, 23.7
(25.7-22.0); alveolar length of upper molariform teeth, 28.3, 30.9
(32.5-28.7).

_Comparisons._--From topotypes and near topotypes of _Castor canadensis
taylori_, _C. c. rostralis_ differs as follows: Color: Darker on upper
parts owing to darker underfur, guard hairs actually lighter. Skull:
Longer; nasals shorter and wider (breadth of nasals averages 54 per cent
of length of nasals as opposed to 47 per cent); extension of nasals
posterior to premaxillae less; rostrum shorter, broader and deeper;
dorsal surface of lacrimal bone smaller; zygomatic breadth relative to
basilar length greater; mastoid breadth relative to zygomatic breadth
less; coronoid process shorter; coronoid and condyloid processes farther
apart and space between them shallower.

From one topotype and two specimens from the Colorado River at Yuma,
Yuma County, Arizona, of _Castor canadensis repentinus_, _C. c.
rostralis_ differs as follows: Size larger; tail longer. Color: Darker
throughout. Skull: Longer; nasals shorter and wider (breadth of nasals
relative to length of nasals averages 54 per cent as opposed to 47 per
cent); extension of nasals posterior to premaxillae less; rostrum
shorter, deeper and wider; zygomatic breadth relative to basilar length
greater; mastoid breadth actually as well as relatively greater; dorsal
surface of lacrimal bone smaller; coronoid and condylar processes
farther apart and space between them shallower.

From specimens of _Castor canadensis baileyi_, from 20 miles north
northeast of Elko, Elko County, Nevada, _C. c. rostralis_ differs as
follows: Size larger; tail and hind foot longer. Color: Darker
throughout. Skull: Larger in all measurements taken; nasals markedly
wider (breadth of nasals relative to length of nasals averages 54 per
cent as opposed to 41 per cent); extension of nasals posterior to
premaxillae less; dorsal surface of lacrimal bone smaller; mastoid
breadth relative to zygomatic breadth less.

From one specimen of _Castor canadensis concisor_, from Trappers Lake,
Garfield County, Colorado, and from the original description of that
subspecies (Warren and Hall, 1939: 358), _C. c. rostralis_ differs as
follows: Color: Guard hairs lighter; underfur darker (blackish as
opposed to brownish). Skull: Longer and narrower; nasals broader and
shorter (breadth of nasals averages 54 per cent of length of nasals as
opposed to 48 per cent); dorsal surface of lacrimal bone smaller; distal
end of meatal tube smaller; distal end of angular process rounded
rather than pointed; coronoid process shorter; coronoid and condylar
processes farther apart and space between them shallower.

Among known kinds of _Castor canadensis_, _C. c. rostralis_ is most like
_Castor canadensis duchesnei_, from which the former subspecies differs
as follows: Tail and hind foot longer. Color: Darker throughout. Skull:
Nasals shorter and wider (breadth of nasals averages 54 per cent of
length of nasals as opposed to 46 per cent); nasals less arched
transversely; rostrum shorter, deeper and broader; ventral surface of
rostrum less concave dorsally; dorsal surface of lacrimal bone smaller.

For comparison with _Castor canadensis pallidus_, see account of that
subspecies.

_Remarks._--Animals from Kamas, in the drainage of the Weber River, are
intergrades between _C. c. rostralis_ and _C. c. duchesnei_, but their
short, wide nasals and wide rostra make them referable to _C. c.
rostralis_.

The available specimens of _C. c. rostralis_ are all from streams which
ultimately empty into Great Salt Lake, which is in the northern part of
the basin of Pleistocene Lake Bonneville. Some streams drain into the
Lake Bonneville Basin without emptying into Great Salt Lake proper.
Beavers from these streams, we suspect, when they become known, will be
found to be related to _C. c. rostralis_.

     _Specimens examined._--Total, 16 (2 skins and skulls, 14
     skulls only), distributed as follows: Summit County: Kamas,
     5,500 ft., 6. _Salt Lake County_: Red Butte Canyon, Fort
     Douglas, 5,000 ft., 1; Millcreek Canyon, 6 mi. above mouth,
     7,000 ft., 1. _Wasatch County_: Charleston, Heber Valley,
     5,500 ft., 8.


~Castor canadensis duchesnei~ new subspecies

_Type._--Male, young adult, skin and skull, number 4625, Museum of
Zoölogy, University of Utah; Duchesne River, 10 miles northwest of
Duchesne, 5,600 ft., Duchesne County, Utah; September 23, 1946;
collected by Dave Thomas, original number 160 of K. R. Kelson.

_Range._--Drainage of the Duchesne and White rivers in Utah and
Colorado.

_Diagnosis._--Size large; tail long (see measurements). Color (type):
Upper parts Sayal Brown, purest on head, grading to Cinnamon Buff at
base of tail; underfur Fuscous; hind feet Burnt Umber; ears Fuscous
Black; underparts Tawny Olive; underfur Smoke Gray. Skull: Large,
massive; nasals long, slender (breadth averaging 46 per cent of length)
and markedly convex transversely; rostrum long and attenuate; zygomatic
arches heavy and widely spreading (zygomatic breadth averaging 81.5 per
cent of basilar length); ventral surface of rostrum markedly concave
dorsally, especially immediately behind upper incisors; nasals extend
posterior to premaxillae.

_Measurements._--Measurements of the type and average and extreme
cranial measurements of 9 unsexed adults, from Currant Creek, are,
respectively, as follows: Total length, 1,176; length of tail, 458;
length of hind foot, 165; length of ear, 33; occipitonasal length,
123.6, 132.1 (138.5-122.3); basilar length, 98.6, 114.4 (125.8-99.2);
mastoid breadth, 60.4, 65.1 (67.2-64.1); interorbital breadth, 23.0,
25.1 (26.1-23.7); zygomatic breadth, 88.3, 94.2 (99.7-89.5); length of
nasals, 46.1, 48.4 (51.5-46.2); breadth of nasals, 20.5, 22.5
(24.5-18.8); alveolar length of upper molariform teeth, 28.9, 29.9
(32.2-26.5).

[Illustration: FIGS. 1-4 Dorsal views of skulls of _Castor canadensis_.
× 1/2]

     FIG. 1. _Castor canadensis rostralis_, male, young adult,
     no. 5199 (holotype), Mus. Zoöl., Univ. Utah.

     FIG. 2. _Castor canadensis pallidus_, female, adult, no. 719
     (holotype), Mus. Zoöl., Univ. Utah.

     FIG. 3. _Castor canadensis duchesnei_, male, young adult,
     no. 4625 (holotype), Mus. Zoöl., Univ. Utah.

     FIG. 4. _Castor canadensis concisor_, male, adult, no. 2090,
     Mus. Nat. Hist., Univ. Kansas, from Trappers Lake, Garfield
     County, Colorado, obtained by L. L. Dyche, October 22, 1891.

_Comparisons._--From topotypes and near topotypes of _Castor canadensis
taylori_, _C. c. duchesnei_ differs as follows: Color: Guard hairs
lighter, underfur darker. Skull: Nasals narrower; rostrum narrower;
mastoid breadth relative to zygomatic breadth less; zygomatic breadth
relative to basilar length greater; tympanic bullae narrower and
smaller; cheek teeth narrower.

[Illustration: FIGS. 5-7 Lateral views of left side of skulls of _Castor
canadensis_. × 1/2]

     Fig. 5. _Castor canadensis rostralis_, male, young adult,
     no. 5199 (holotype), Mus. Zoöl., Univ. Utah.

     Fig. 6. _Castor canadensis pallidus_, female, adult, no. 719
     (holotype), Mus. Zoöl., Univ. Utah.

     Fig. 7. _Castor canadensis duchesnei_, male, young adult,
     no. 4625 (holotype), Mus. Zoöl., Univ. Utah.

From specimens of _Castor canadensis baileyi_, from 20 miles north
northeast of Elko, Elko County, Nevada, _C. c. duchesnei_ differs as
follows: Size larger; tail and hind foot longer. Color: Guard hairs
lighter, underfur darker. Skull: Larger in all measurements taken;
nasals broader and longer (breadth of nasals averages 46 per cent of
length of nasals as opposed to 41 per cent); rostrum broader and longer;
mastoid breadth relative to zygomatic breadth less; tympanic bullae
larger.

From one specimen of _Castor canadensis concisor_, from Trappers Lake,
Garfield County, Colorado, and from the original description of that
subspecies (Warren and Hall, 1939: 358), _C. c. duchesnei_ differs as
follows: Color: Lighter throughout. Skull: Nasals more convex
transversely; rostrum narrower; ventral border of rostrum more concave
dorsally, especially immediately behind upper incisors; distal end of
meatal tube smaller; angular process shorter and rounded rather than
pointed; cheek teeth smaller.

Among known subspecies of _Castor canadensis_, _C. c. duchesnei_ is most
like _Castor canadensis repentinus_, but differs from the latter as
follows: Size larger; hind foot shorter. Color: Darker throughout.
Skull: Basilar length less; mastoid breadth greater; nasals shorter and
narrower; extension of nasals posterior to premaxillae less; nasals more
convex transversely; cheek teeth smaller.

For comparisons with _Castor canadensis pallidus_ and _Castor canadensis
rostralis_, see accounts of those subspecies.

_Remarks._--The extent of the range of _C. c. duchesnei_ within the
drainage of the White River is not definitely known. Three animals from
9-1/2 miles southwest of Pagoda Peak, Rio Blanco County, Colorado, from
the drainage of the White River, are intergrades between _C. c.
concisor_ and _C. c. duchesnei_. They are like the latter subspecies in
shape and length of the nasals, less expanded distal end of the meatal
tube and the rounded angular process, and it appears best, pending the
acquisition of more material, to refer them to C. c. duchesnei. Another
specimen, number 2090, Museum of Natural History, University of Kansas,
from Trappers Lake, Garfield County, Colorado, at the headwaters of the
White River, and only 16 miles distant from the three aforementioned
animals, is, however, nearly typical of _C. c. concisor_. Relying upon
the original description (Warren and Hall, 1939: 358), this animal is
like _C. c. concisor_ in size and shape of the jugals, in size of the
distal end of the meatal tube and in the pointed end of the angular
process. Warren and Hall (_loc. cit._) noted that animals assignable to
_C. c. concisor_ occurred throughout the mountainous parts of Colorado,
and recorded them from the headwaters of nearly all the major rivers of
that state. Apparently _C. c. concisor_ also occurs in the headwaters of
the White River, while the main part of the river is inhabited by
animals referable to _C. c. duchesnei_.

     _Specimens examined._--Total, 15 (4 skins and skulls, 11
     skulls only), distributed as follows: Utah: _Wasatch
     County_: Currant Creek, Strawberry Valley, 6,000 ft., 11.
     _Duchesne County_: Duchesne River, 10 mi. NW Duchesne, 5,600
     ft., 1. Colorado: _Rio Blanco County_: 9-1/2 mi. SW Pagoda
     Peak, 7,700 ft., 3 (Museum of Natural History, University of
     Kansas).




LITERATURE CITED


DAVIS, WILLIAM B.

1939. The Recent mammals of Idaho. The Caxton Printers, Caldwell, Idaho,
400 pp., 2 full page half-tones, 33 figs. in text, April 5, 1939.

PRESNALL, C. C.

1938. Mammals of Zion-Bryce and Cedar Breaks. Zion-Bryce Mus. Bull.,
2:1-20, January, 1938.

WARREN, EDWARD R. and HALL, E. RAYMOND.

1939. A new subspecies of beaver from Colorado. Journ. Mamm.,
20:358-362, 1 map, August 14, 1939.


_Transmitted, May 15, 1948._

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End of Project Gutenberg's Three New Beavers from Utah, by Stephen D. Durrant