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A New Bog Lemming (Genus Synaptomys)
From Nebraska

BY

J. KNOX JONES, JR.

=University of Kansas=
=Lawrence=
1958




=University of Kansas Publications=
=Museum of Natural History=

Volume 9, No. 13,
pp. 385-388

May 12, 1958


Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Robert W. Wilson


PRINTED IN
THE STATE PRINTING PLANT
TOPEKA, KANSAS

1958

27-3033




A New Bog Lemming (Genus Synaptomys)

From Nebraska


BY

J. KNOX JONES, JR.


In the autumn of 1952, I obtained a southern bog lemming, _Synaptomys
cooperi_, at Rock Creek State Fish Hatchery, Dundy County, in extreme
southwestern Nebraska. This locality of record is the westernmost for
the species in North America. Subsequently, I reported this specimen in
the literature (Univ. Kansas Publ., Mus. Nat. Hist., 7:486, 1954),
provisionally assigning it to _Synaptomys cooperi gossii_, the
subspecies occurring in eastern Nebraska. In late November of 1956, J.
R. Alcorn collected three additional bog lemmings at the Rock Creek
Hatchery.

These specimens from Dundy County represent a relict population that
differs in several characteristics from _S. c. gossii_, and that differs
also from all other subspecies of the species. This relict population
is, therefore, here given subspecific recognition.


#Synaptomys cooperi relictus#, new subspecies

_Type._--Adult female, skin and skull, University of Kansas Museum of
Natural History no. 51617, from Rock Creek State Fish Hatchery, 5 mi. N,
2 mi. W Parks, Dundy County, Nebraska; obtained November 1, 1952, by J.
Knox Jones, Jr., original no. 995.

_Distribution._--Known only from the type locality.

_Diagnosis._--Size large for the species, both externally and cranially;
dorsal pelage dark; nasals broadly flared anteriorly (especially broad
in relation to nasal length); auditory bullae small; molariform
tooth-rows and incisive foramina long.

_Measurements (in millimeters)._--External measurements of the type
specimen, followed by those of another adult female (KU 72603), are:
Total length, 141, 145; length of tail-vertebrae, 24, 21; length of hind
foot, 20, 20; length of ear from notch, 11, 12. The type specimen
weighed 46.3 grams. Cranial measurements were taken in the manner
described by Wetzel (Jour. Mamm., 36:2-3, 1955) except that he did not
record the occipitonasal length. These cranial measurements of the type
and KU 72603 are: Occipitonasal length, 30.2, 29.8; condylobasilar
length, 27.2, 27.1; zygomatic breadth, 18.1, 17.9; lambdoidal breadth,
14.2, 13.8; length of nasals, 8.2, 8.3; breadth of nasals, 4.2, 4.0;
length of rostrum, 6.6, 6.6; breadth of rostrum, 6.1, 5.9; breadth of
upper incisors, 4.6, 4.2; length of maxillary tooth-row, 8.5, 8.4;
length of incisive foramen, 5.8, 5.5; interorbital breadth, 3.1, 3.5.

_Comparisons._--From _Synaptomys cooperi gossii_ (specimens from eastern
Nebraska and eastern Kansas, including one topotype), _S. c. relictus_
differs in: Dorsal coloration, in comparable pelages, darker, venter
lacking buffy tinge; skull averaging larger in all cranial dimensions
(except rostral length, which is approximately the same), especially
breadth of upper incisors and length of molariform tooth-rows; nasals
broader anteriorly; auditory bullae nearly equal in size, thus
relatively smaller. From _Synaptomys cooperi paludis_ (holotype and
paratypes) of Meade County, Kansas, _S. c. relictus_ differs in: Skull
averaging smaller in all cranial measurements except rostral length and
breadth of upper incisors, which are approximately the same, and breadth
of nasals, length of incisive foramina and length of molariform
tooth-rows, which measure more; nasals relatively (48 per cent of length
of nasals) as well as actually broader anteriorly; anterior border of
zygomatic plate more concave; auditory bullae smaller; infraorbital
foramina larger when viewed anterolaterally. _S. c. relictus_ closely
resembles _S. c. paludis_ in color and external proportions.

_Remarks._--The total population of _Synaptomys cooperi relictus_ may be
small because the only suitable habitat known to me for these mice is
the dense, grassy area, approximately 100 yards wide and one mile long,
around some of the rearing ponds and along the creek at Rock Creek
Hatchery. It has been taken there in association with _Cryptotis parva
parva_, _Blarina brevicauda carolinensis_, _Reithrodontomys megalotis
dychei_, _Peromyscus maniculatus nebrascensis_, _Microtus ochrogaster
haydenii_, and another relic, _Microtus pennsylvanicus finitis_. All
specimens of the newly named bog lemming are from the border zone
between the wet-substrate habitat of _M. p. finitis_ and the drier
habitat occupied by _M. o. haydenii_. Approximately 3000 trap nights
produced the four known specimens.

_S. c. relictus_, like _S. c. paludis_, represents a relict population
of the more southwesterly distribution of the subgenus _Synaptomys_
during Wisconsin and post-Wisconsin times. Additional relict populations
likely will be found in the eastern Great Plains.

The new subspecies is intermediate in some features between _paludis_
and _gossii_. The type locality is separated from that of _paludis_ (14
mi. SW Meade, Meade County, Kansas) by a distance of approximately 220
miles over habitats largely unsuitable for bog lemmings. The nearest
locality of record for S. c. _gossii_ to the east of the type locality
of _relictus_ is at Hunter, Mitchell County, Kansas (see Cockrum, Univ.
Kansas Publ., Mus. Nat. Hist., 7:196, 1952), approximately 200 miles
distant. The locality of record of _gossii_ in Nebraska nearest to the
type locality of _relictus_ is even farther eastward--1 mi. N Pleasant
Dale, Seward County (KU 50188).

_Specimens examined._--Four, from the type locality (KU 51617,
72601-03).

_Transmitted March 11, 1958._