Vascular Plant and Vertebrate Inventory of Saguaro ... - USGS

focal point
marks” appeared to last for the duration of the
sampling period. For each animal we recorded
species, sex, age class (adult, subadult, or
juvenile), reproductive condition, weight, and
measurements for right-hind foot, tail, ear, head,
and body. For males we recorded reproductive
condition as either scrotal or non-reproductive;
for females we recorded reproductive condition
as one or more of the following: non-reproducing,
open pubis, closed pubis, enlarged nipples, small
or non-present nipples, lactating, post-lactating,
or non-lactating.
Spatial Sampling Design
The majority of our trapping effort in 2001
was at focal-point transects set throughout the
district (Fig. 6.3; see Chapter 1). We trapped
at a subset of nine random transects that were
surveyed for other taxonomic groups (two, four,
and three transects in the low-, medium-, and
high-elevation strata, respectively). We visited
1000 m
Figure 6.1. Layout of small-mammal trapping grids along focal-point transects, Saguaro National Park,
2001. See Fig. 6.2 for more details.
Figure 6.2. Detailed layout of small-mammal trapping grids at Saguaro National Park, 2001 and
2002. We used 3x7 trap grids in 50x100 m plots (A) from mid‑April through mid‑June and 5x5 trap grids in
50x50 m plots (B) from mid‑June through October.
70
seven of these transects twice in 2001; repeat
visits were two to four months apart (Appendix
I). In 2002 we trapped only at non-random sites
in areas that we believed would have high species
richness: two sites along Rincon Creek and one
site each at Juniper Basin and Douglas Springs
(Fig. 6.4). We did not revisit non-random sites.
Along each focal-point transect we
established three grids (Fig. 6.1) with either a
3x7 or a 5x5 trap configuration (Fig. 6.2). Traps
set in a 3x7 arrangement had 16.7 m spacing
among traps and traps in a 5x5 arrangement had
12.5 m spacing among traps. Occasionally we
also placed traps “preferentially,” meaning that
we set traps in locations that the field crews felt
contained areas with high species richness rather
than in grids. Typically these “preferential” sites
were near the random grids; the crew set out
5 to 70 additional traps after setting up the
random grids (Figs. 6.3, 6.4). At non-random
sites the layout of traps was variable, but typically
50 m
50 m