This experiment was conducted at three sites, each with a
grassland-to-shrubland ecotone. Two of the sites, JER Pasture 9 and
JER Pasture 12A, occur on the USDA Agricultural Research Service
Jornada Experimental Range. One site, CDRRC Pasture 3, is located on
New Mexico State University’s Chihuahuan Desert Rangeland Research
Center. Climate is arid to semi-arid, with long-term (90-year) mean
annual temperature of 15C and mean annual precipitation of 250 mm,
over half of which occurs in summer (July–September).
Sites were chosen to contain 3 distinct habitat types (or
"ecotone positions"): grassland, ecotone, and shrubland.
Within each habitat type of each site, a 300m x 100m rectangular
trapping area was established. Trapping locations were arranged as a
16 x 6 grid within the trapping area with 20m spacing between traps,
yielding 96 traps per habitat and 288 traps per site for a total of
864 trapping locations for the entire study. The trapping area
encompasses the quadrats assessed for plant cover in data package
knb-lter-jrn.210262001, which was used to calculate annual net
primary productivity estimates available in data packages
knb-lter-jrn.210262004 and knb-lter-jrn.210262005.
Livetrapping was conducted annually over 4 consecutive nights using
Sherman model XLKR live traps baited with a seed mix. Traps were set
in late afternoon/early evening and checked the following morning.
Ear tags were affixed to rodents with ears large enough to support
them. Rodents too small to affix ear tags were given a unique ID
which was labeled on their ventral side with a permanent marker.
Blue permanent markers were used on rodents trapped on the first
night, black on the second night, and red on the third night. No
permanent markers were used on rodents caught on the fourth night,
but ear tags were still administered if possible. In addition to
tagging/marking, rodents were weighed, identified to species, and
assessed for sex, reproductive status, and maturity status. The
dataset includes only the first capture of each individual each
year, which can be used to estimate relative abundance.
From 2004 to 2007, livetrapping occurred mostly during July. From
2008 to 2018, when the project had become part of long-term sampling
by Jornada Basin LTER program, livetrapping occurred during October.
The three habitat types within each site were trapped during the
same week.
Observations in the dataset may have missing tags for several
reasons, including: 1) rodents caught on the fourth night whose ears
were too small for an ear tag, 2) rodents who escaped before an ear
tag could be read, 3) rodents who escaped before an ear tag could be
affixed, and 4) observer error. Reasons 2-4 may also apply to
observations with missing values for Sex, Rep, and Status.
Also available are measures of relative abundance and biomass of
rodents in data package knb-lter-jrn.210262010.