FIRE EFFECTS AND USE
WILDLIFE SPECIES: Spermophilus townsendii | Townsend's Ground Squirrel 



DIRECT FIRE EFFECTS ON ANIMALS : 
Wildfire normally occurs in summer or fall in Townsend's ground squirrel
habitats, after grasses have cured.  Since Townsend's ground squirrels
are aestivating in their burrows at that time, wildfire probably has no
direct effect on them [11,28].


HABITAT RELATED FIRE EFFECTS : 
Due to the arid climate, postfire recovery of vegetation in Townsend's
ground squirrel habitats is slow.  In the short term, fire usually
reduces abundance of Townsend's ground squirrels because less forage is
available on burned sites, and because predation increases with reduced
escape cover [8].  Studies on the long-term effects of fire on
Townsend's ground squirrels have only been conducted in communities
invaded by exotic annuals.  In these communities, frequent fire has
harmed the Townsend's ground squirrel.  Occasional fire in other
Townsend's ground squirrel habitats probably benefits the species in the
long term by reducing shrub density and providing a nutrient pulse to
grasses and other Townsend's ground squirrel forage.

Examples:  A year following a July 1985 wildfire on the SRBPSA, more
than twice as many active Townsend's ground squirrel holes were found on
unburned control plots than on burned, partially burned, and
burned-rehabilitated plots.  Burned-rehabilited plots had been
drill-seeded to crested wheatgrass, yellow sweet clover (Melilotus
officinalis), and fourwing saltbush (Atriplex canescens) the fall and
spring after fire.  In the first postfire summer, the burned, paritally
burned, and burned-rehabilited sites were dominated by cheatgrass,
whereas the unburned control sites were dominated by fourwing saltbush.
Cheatgrass cover was 26 percent on burned, 9 percent on partially
burned, 14 percent on burned-rehabilitaed, and 5 percent on control
sites.  Winterfat, an important food source for Townsend's ground
squirrels on the SRBPSA, had 7 percent cover on control sites, less than
1 percent cover on burned sites, and was absent on partially burned and
burned-rehabiliated sites.  Bottlebrush squirreltail (Elymus elymoides)
and Sandberg bluegrass, which, along with winterfat, presumably
comprised the bulk of the Townsend's ground squirrel diet prior to
cheatgrass invasion, were present only on partially burned and control
sites.  At postfire year 1, numbers of active Townsend's ground squirrel
burrows were [8]:

                    B          P         R          C     
---------------------------------------------------------
burrows             9         19         7         29   
---------------------------------------------------------
B=burned
P=partially burned
R=burned-rehabilitated
C=control

Groves and Steenhof [8] speculated that Townsend's ground squirrel
numbers may have been reduced in the cheatgrass-dominated areas by
impeded movement through the thick stands of cheatgrass, which affected
breeding and population size, increased predation due to loss of shrub
cover, and changed available food resources.

Fire in wet years:  Townsend's ground squirrel populations may show a
short-term increase when fire is followed by above-average
precipitation.  Townsend's gound squirrel numbers increased after fire
in a big sagebrush-bluebunch wheatgrass (Psuedoroegneria spicata)
community in southeastern Washington.  A wildfire occured in August
1973, when Townsend's ground squirrels were belowground and dormant,
burning 10,000 acres (4,000 ha).  Townsend's ground squirrels had been
trapped prior to the fire, from March to May of 1973, for census.  They
were trapped on the same site from March to May of 1974.  Precipitation
from October to May was 4.8 inches (120 mm) in 1973 and 13.2 inches (330
mm) in 1974.  Townsend's ground squirrel numbers were [11]:

                                   Prefire                    Postfire
                                   -------                    --------     
                               Mar   Apr   May             Mar  Apr  May    
------------------------------------------------------------------------
Townsend's ground squirrels     13    20    18              10   33   28 
------------------------------------------------------------------------

Where fires are frequent in Townsend's ground squirrel habitats, the
species may decline.  As fire frequency has increased in shrub steppe of
the Great Basin and Columbia Plateau, shrubs have been lost and
cheatgrass and other annuals have become dominant.  With short fire
return intervals, annuals are able invade large blocks of land.  The
effects on Townsend's ground squirrel will probably be increased
vulnerability to predation and to annual climatic fluctuations, with
attendant unpredictability of forage [21].  With fewer bunchgrasses and
forbs, exotic annual communities have lower plant species diversity and
thus less nutritional variety for Townsend's ground squirrels.  Although
Townsend's ground squirrel numbers will increase during years when
exotic annual production is high, unreliable production will probably
result in high-amplitude population fluctuations of Townsend's ground
squirrels [28].


FIRE USE : 
NO-ENTRY


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Spermophilus townsendii | Townsend's Ground Squirrel