SGS-LTER Long-Term Monitoring Project: Spermophilus tridecemlineatus on Small Mammal Trapping Webs on the Central Plains Experimental Range, Nunn, Colorado, USA 1999 -2006, ARS Study Number 118

This data package was produced by researchers
working on the Shortgrass Steppe Long Term
Ecological Research (SGS-LTER) Project,
administered at Colorado State University.
Long-term datasets and background information
(proposals, reports, photographs, etc.) on the
SGS-LTER project are contained in a comprehensive
project collection within the Digital Collections
of Colorado
(http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429).
The data table and associated metadata document,
which is generated in Ecological Metadata
Language, may be available through other
repositories serving the ecological research
community and represent components of the larger
SGS-LTER project collection. Additional information and referenced materials can be found:
http://hdl.handle.net/10217/83456. Small mammals (rabbits, rodents) are integral
components of semiarid ecosystems because of their
roles as consumers of plants, seeds and
arthropods, as soil disturbance agents, and as
food for raptors, snakes and mammalian carnivores.
Because of their vagility and intermediate trophic
position, populations of small mammals may track
changes in vegetation and the abiotic environment
that may result from shifts in land-use and other
anthropogenic disturbances. However, these
populations are variable over space and time, and
their response to environmental changes may not be
immediately apparent given their behavioral
flexibility and relatively long life-spans and
generation times. Patterns in the distribution and
abundance of small mammals thus may simultaneously
reflect and affect the stability of the
shortgrass-steppe ecosystem. Long-term studies of
population and community dynamics therefore are
needed to fully understand the role of small
mammals in grassland ecosystems. Thirteen-lined
ground squirrels (Spermophilus tridecemlineatus,
SPTR) are the most widely distributed rodent
species in shortgrass steppe and the most
important in terms of abundance and biomass. Like
most rodents in shortgrass steppe, they are
omnivorous; unlike other species, however, they
are diurnal and active aboveground only 5-6 months
each year, and therefore required a separate
sampling scheme from other rodents. In 1999, we
initiated studies to track long-term changes in
relative abundance of ground squirrels in
representative habitats of shortgrass steppe. We
live-trapped squirrels twice each year, which
corresponded to periods of high aboveground
activity of adults (early June, SPR) and the
emergence of juveniles (mid-July, SUM). Three
3.14-ha webs were established in upland prairie
(GRASS) and saltbush-dominated (SHRUB) habitats.
Each web had 62 Sherman traps, which were spaced
20-m apart on 12 100-m spokes, with 30 degrees
between spokes. Two traps were set in the center
of the web. Traps were set for four consecutive
mornings in each trapping session. Traps were
baited with a mix of peanut butter and oats, set
at dawn and closed 4-6 hours later. Traps were
shaded with pieces of PVC pipe to reduce heat
mortality in traps. We recorded sex, age and
weight upon first capture of all individuals.
Because the ears of squirrels are too small to
consistently hold ear tags, all individuals were
batch-marked with a colored Sharpie felt marker to
distinguish recaptures ® from new (N) individuals,
providing the minimum information necessary to use
distance-sampling methods to estimate density.
NOTE: In this dataset, ages and weights may not
correspond well. Weight, combined with sampling
date, can be used to better determine age class;
contact Paul Stapp for more information.