SGS-LTER Long-Term Montioring Project: Arthropod Pitfall Trapping on Small Mammal Trapping Webs on the Central Plains Experimental Range, Nunn, Colorado, USA 1998-2006, 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/10217/83450. With the exception of heteromyids, eg kangaroo
rats and pocket mice, most small rodents in
shortgrass steppe are omnivorous. Depending on
season, arthropods (insects and arachnids) make up
40-85% of the diet of grasshopper mice and
thirteen-lined ground squirrels, the most
widespread rodents in northern shortgrass steppe.
Small mammals are among the most important
predators of ground-dwelling macroarthropods and
herbivorous insects provide a direct resource link
between weather and plant production.
Understanding temporal variability in the
abundance of arthropods is central to determining
the mechanisms that drive small rodent
populations. At present, there are no long-term
studies of arthropods in shortgrass steppe,
despite the important role that these taxa play in
grassland food webs. Beginning in 1998, we
implemented field protocols to track changes in
relative abundance of terrestrial macroarthropods
in grassland and shrub-dominated habitats of
shortgrass steppe. Sampling was conducted on the
six trapping webs (three upland prairie, three
lowland saltbush) where we studied rodent
populations, and was conducted approximately
monthly from May-September (4-5 sessions/year).
Ground-dwelling macroarthropods were sampled on
each web using pitfall traps, set in one
four-by-five grid, with 10 m between traps. Traps
consisted of plastic cups (90-mm diameter, 120 mm
deep), including a plastic funnel (90-mm
diameter), buried flush with the ground surface.
Traps were shaded with wooden covers held in place
with nails; traps could be closed when not
operational by nailing the cover flush to the
ground. Traps were usually open for 4 consecutive
days (ie 80 trap-days) during a trapping session.
On the 4th day, captured arthropods were removed
from the traps, identified and released. All
arthropods were identified to the ordinal level;
beetles (Coleoptera), crickets (Orthoptera), true
bugs (Hemiptera) and spiders were identified to
the familial level; and a few taxa, eg tenebrionid
beetles, were identified to species. We also
recorded any reptiles and amphibians captured. The
number of individuals of each taxa captured per
100 trap-days was used as an index of relative
abundance, with adjustments made for traps that
were flooded or disturbed by cattle or for changes
to the number of days that traps were open (range
4-7 days). We sampled grasshoppers by counting the
numbers flushed from 0.78-m2 circular plots
(hoops) placed on each web. Hoops were set out on
the day that pitfall traps were opened and were
surveyed on the day that traps were closed. A
technician used a wooden lath to flush and count
all grasshoppers from each hoop. Grasshoppers were
not identified to species. Surveys were conducted
in 1998, then were discontinued until 2002. In
1998 and from 2002-2005, nine hoops were sampled
on each web. Beginning in 2006, we sampled a total
of 20 hoops on each web.