Table Of ContentGreatBasinNaturalist54(3), © 1994,pp.287-289
NEW MAMMAL RECORD FOR FREMONT ISLAND
WITH AN UPDATED CHECKLIST OF MAMMALS
ON ISLANDS IN THE GREAT SALT LAKE
Kenneth L. Cramer^
Key words: Great Salt Lake, Reithrodontomys megalotis, Peromysciis maniculatus, mammals, islandbiogeography,
Freim^ntIsland.
Islands of the Great Salt Lake were first reported that the island had been connected
visited by Europeans when a party led by with the mainland b\' a sandbar20 miles to the
Fremont (1850) landed on Fremont Island in eastern shore ofthe lake for3 years since 1850
the northeast arm ofthe lake. Fremont named (the beginning of lake-level records) when
the island "Disappointment Island" due to its lake levels were near 4194 feet. Since 1938,
lack of fresh water and timber, although the lake levels were continuously below 4195 feet
island is somewhat of a disappointment to a from 1959 to 1971, possibly providingperiodic
mammalogist as well, with only three species connections over mudflats with the mainland
ofmammals recorded. Deer mice {Peromysciis at that time (Arnowand Stephens 1990).
maniciihitus), jackrabbit {Lepiis californicus), Since the 1938 census, publications con-
and ground squirrel (probably Spcnnophihis cerning the Great Salt Lake islands' faunahave
townsendii) have been found on the third been limited to literature reviews (Rawley et
largest island (approximately 1300 ha) in the al. 1974, Gwynn 1980), with no new sampling
lake (Goldman 1939, Marshall 1940). Goldman efforts reported until recently. However, even
(1939) ascribed subspecific status (P. m. brief studies on islands other than Fremont
inclanis) to deer mice from Fremont Island have revealed substantial changes in their
based on pelage differences from the mainland species lists since those compiled by Bowers
P. m. sonoriensis. One specimen ofjackrabbit (1982), who relied primarily on the 1938 cen-
was taken by Marshall (1940), who reported sus. Marti (1986), in a study ofBarn Owl diets
that, in addition to being recent immigrants, on Antelope Island, recorded six newmammal
they were also scarce. According to sheep- species for that island, including a shrew, two
herders on the island, rabbits may have crossed voles, and two rather common Great Basin
in the winter over ice and debris from Bear species, the Great Basin pocket mouse
River during winter of 1933-34. The ground {Perognathus parvus) and the western harvest
squirrel was a single specimen observed by mouse {Reithrodontomys megalotis). Paul (1983)
Stansbuiy (Marshall 1940), who considered it reported thatbadgerand fox occuron Antelope
an anomaly. island. Cramer et al. (1990) also reported dra-
Surveys of the islands in 1937 and 1938 matic changes in species composition ofmam-
(Goldman 1939, Marshall 1940) were per- mals on Dolphin Island. Given the recent
formed during a historic low in lake levels, additions ofcommon species to some islands'
when many islands were actually peninsulas species lists (Table 1), the relatively low trap-
connected to the mainland by sandbars. ping effort of the 1938 census (e.g., only 37
However, Fremont is one ofthe few Great Salt trap nights on Dolphin Island), and the unusu-
Lake islands that has been nearly continuously ally impoverished fauna recorded for Fremont
isolated from the mainland during the historic Island, I spent 3 days and 2 nights (20-23
record and probably into the evolutionaiy past lune 1992) trapping on Fremont Island to
(Arnow and Stephens 1990). Marshall (1940) determine whether known mammal records
'DepartmentofBioIog\,MonmouthCollege,700EastBroadway,Monmouth,Illinois61462.
287
288 Great Basin Naturalist [Volume54
Table 1. CurrentrecordsofspeciesbyislandformammalsintheGreatSaltLake. Key: 1-Coldman (1939), Marshall
(1940),Durrant(1952);2-Crameretal. (1990); .3-\larti(1986); 4-Paul(1983); 5-presentstudy
1994] Notes 289
ofmammals previously recorded there, includ- Resources, assisted in the sui-vey and provid-
ing black-tailed jackrabbits and Townsend ed an outboard motor for access to the island.
ground squirrels. Jackrabbits reported on the Dr. Wayne Wurtsbaugh, Dr. Jim MacMahon,
island in 1938 clearly did not persist. The and William Ehmann provided a boat, traps,
complete absence of rabbit fecal pellets was and vehicle, respectively, for accessing the
particularly convincing evidence of the ab- study area. The Utah Division of Wildlife
sence ofrabbits on this island, although the re- Resources provided the necessary collecting
mains ofone were found near a Golden Eagle permit.
{Aqiiila chrysaetos) nest. The lone ground
squirrel recorded by Stansbury was obviously Literature Cited
not part ofaviable island population. I saw no
ground squirrels nor any evidence ofburrows Arnow,T,andD. Stephens. 1990. Hydrologiccharacter-
or runways. Other small mammals common to istics ofthe Great Salt Lake, Utah: 1847-1986. U.S.
GeologicalSurveyWater-SupplyPaper2332.
the area such as desert woodrats {Neotoma Bowers, M.A. 1982. Insularbiogeographyofmammalsin
lepida), pocket mice {Perognothus sp.), and the Great Salt Lake. Great Basin Naturalist 42:
kangaroo rats {Dipodomys sp.) are also con- 589-.596.
spicuously absent from Fremont Island. I saw Cr.'^mer, K. L., a. Lee Foote, andJ. A. Chapman. 1990.
no evidence of heteromyid burrows, particu- Small mammal records from Dolphin Island, the
larly in apparently suitable habitat on the Great Salt Lake, and other localities in the Bonne-
villeBasin,Utah.GreatBasinNaturalist50:283-285.
southeast comer ofthe island. Rocky crevices, Fremont, C. 1850. Report ofthe exploring expedition
normally common nest sites for desert wood- totheJ.Rock-yMountains. University Microfilms,Ann
rats, were completely unused; I found no nests Arbor, Michigan.327pp.
orfecal material. Goldman, E.A. 1939. Ninenewmammalsfromislandsin
Great Salt Lake, Utah. Journal of Mammalogy
Clearly, Fremont Island is truly depauperate 20:351-357.
in mammalian fauna. Apparently, deer mice Gwtnn,J. W. 1980. Great Salt Lake,ascientific, historical
and western harvest mice are the only native andeconomicover\iew. UtahGeologicalandMineral
mammals on the island, and many species Survey, Utah Department of Natural Resources
common to the adjacent mainland are absent. Bulletin 116.
The island is much larger than Carrington Marshall, W. H. 1940. A survey ofthe mammals ofthe
Island, which supports six species of mam- oisglyan2d1s:1in44G-r1e5a9t.SaltLake, Utah.JournalofMammal-
mals. Similarly, Gunnison, Bird, and Dolphin Marti, G. D. 1986. Barn Owl diet includes mammal
islands all support two species ofmammals on species new to the island fauna ofthe Great Salt
much smaller areas. It is tempting to suggest Lake. GreatBasinNaturalist46:307-9.
that the more isolated nature of Fremont Paul, D. S. 1983.Currentandhistoricalbreedingstatusof
the California Gull in the Great Salt Lake region.
Island and probable lack offrequent immigra-
Unpublished report, Utah Department ofNatural
tion have led to its simple mammalian fauna. Resources.71pp.
Habitat area and diversity may also be factors Rawley, E.v., B.C.Johnson,andD. M. Rees. 1974.The
affecting successful colonization since much of GreatSaltLakebioticsystem. UtahDivisionofWild-
the island's original bunchgrass and shrub lifeResourcesPublication74-13.431pp.
cover has been reduced by fire, grazing, and Received9September1993
cheatgrass invasion. Accepted13December1993
Acknowledgments
Joel Petersen, ofthe Natural Heritage pro-
gram of the Utah Division of Wildlife
