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

calculated relative abundance by plot group, type
of plot (random or non-random), and visit.
Pitfall Trapping
It is possible that the Arizona shrew (Sorex
arizonae) and vagrant shrew (Sorex vagrans)
occur in the Rincon Mountains; they have been
found in adjacent mountain ranges in southern
Arizona (Hoffmeister 1986). Also, pocket
gophers (Thomomys spp.) are very difficult to
capture using Sherman traps. To survey for
shrews and pocket gophers we placed pitfall
traps (3-quart buckets [19 cm tall x 14 cm wide])
in moist, north-facing slopes of the Rincon
Mountains in 2001. We placed traps adjacent to
a natural feature such as a fallen log or rock. We
attempted to check traps every 10 days to two
weeks.
Effort
We placed traps in three areas: North Slope Trail,
Italian Spring, and Spud Rock Spring (Fig. 6.3).
We placed 10 traps (22 May to 24 September) at
the North Slope Trail site, and four traps each at
Italian Spring and Spud Rock Spring (6 June to
10 October).
Bats
We surveyed for bats using two field methods:
roost-site visits and netting. For netting, we
concentrated our survey effort in areas that were
most likely to have bats, mostly riparian areas
with surface water present. We did not survey
for bats near focal points because of the low
probability of success in these areas.
Roosts
We visited roosts that were known to have bats,
based on historic records, or were likely to have
bats based on habitat characteristics. At roosts,
we observed bats with the aid of infrared-filtered
light and night-vision equipment or red-filtered
light. When bats were present, we worked
quickly to identify them to species, but if there
were no bats we used bright light, then searched
for and collected skeletal material.
Mist Netting
Because most insectivorous bats congregate
at water sites, we selected sites known to have
abundant surface water (Fig. 6.3). At most
sites we set mist nets directly over water and
varied the number of net hours among sites and
visits depending on field conditions. We used
monofilament nylon nets of three net sizes (5-m,
9-m, or 12-m) depending on the site and set nets
singly or stacked, depending on conditions. For
each bat captured, we recorded time of capture,
species, and sex. When appropriate, we also
recorded reproductive condition, forearm length,
mass, body condition, tooth wear, presence
of parasites, and other measurements. We
determined whether individuals were adult,
subadult (by closure of epiphyses), or juvenile (by
appearance). We estimated age by tooth wear.
For females, we recorded reproductive condition
as pregnant (palpation for fetal bones), currently
lactating (mammary gland with milk), previous
evidence of lactation (misshapen or scarred
nipples), or nulliparity (non-use of nipples). We
determined reproductive condition for males by
the degree of swelling of testes or the presence of
black epididymides and used this information to
determine if the male was not reproductive, semireproductive,
or reproductive. We marked all
captured bats with a temporary, non-lethal marker
to prevent counting the same individual more
than once in the same evening. We used sonar
detectors (Anabat and/or QMC Mini) at all sites
to aid in determining bat presence/absence and
relative activity as compared to the visual or mistnet
results. We listened passively for the call of
pallid bats, the only species in the area that can be
definitively identified by its directive call.
Effort
We visited three roosts that were known, or were
likely, to have bats. We netted bats at six sites
for a total of 13 nights of netting in 2001 and four
nights of netting in 2002 (Appendix J). Most of
our netting effort was at lower Rincon Creek and
at Manning Camp Pond; we netted at each site
for five nights. Deer Creek was the only site at
which we netted on the east slope of the Rincon
Mountains.
Analyses
We report the number of species and individuals
caught by site, but because of the extreme
differences in trapping effort among sites we
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