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

calculated percent netting success (PNS) for
comparisons among sites. We calculated PNS
as the number of animals caught divided by
effort (total length of net coverage multiplied
by amount of time nets were open multiplied
by 100). We do not attempt to present percent
netting success as a measure of relative
abundance because netting bats is somewhat a
function of chance; many more individuals and
species can be present in an area than are caught.
Large and Medium Mammals
Saguaro National Park initiated a medium and
large mammal inventory in 1999, prior to the
initiation of the UA inventory effort. In addition
to support from the NPS, this inventory effort has
been funded by several small grants to the park,
and reports have been generated for each of these
projects (Aslan 2000, Wolf and Swann 2002,
Swann et al. 2003a, Swann 2003). This report
combines data presented in these previous reports
with new data not previously reported.
Spatial Sampling Design
We used infrared-triggered cameras to detect
medium and large mammals at a combination of
random and non-random sites from January 1999
to June 2005 (Figs. 6.5, 6.6). We located nonrandom
sites (Fig. 6.5) primarily at known water
sources and animal trails. We chose the location
of these sites to be in areas that we believed
would have the highest species richness. The
location of random sites was primarily based on
the random coordinates chosen as focal points
for the plant and animal inventories (see Chapter
1), though many of these focal points were not
surveyed for the other taxonomic groups. To
avoid interference with other inventory activities
at sites where there was other inventory work
and to maintain consistency among all focal
points, we offset all camera locations from the
focal point by using the same coordinates but
with the NAD 27 map datum instead of NAD 83;
this moved the focal points approximately 200
m from the original location. We also generated
additional random camera locations to increase
sampling in some areas that were not represented
by focal points, particularly at high elevations and
on the east slope of the Rincon Mountains. When
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possible, we placed three camera units at each
location focal point using the following criteria
(Fig. 6.7):
(1) within 50 m of the random point
(2) at a random drainage point nearby
(selected either randomly within a 1-km
area; Aslan 2000) or at a random point
located at the nearest measured point in a
mapped drainage (Wolf and Swann 2002,
Swann et al. 2003a), and
(3) at a non-random point chosen by the field
technician, usually located between 80
and 500 m from the random point.
Temporal design
We generally returned to each camera one week
after initial setup to check that it was functioning
properly and to make repairs and change film,
if necessary. We then left the camera in place
for approximately two weeks, though the length
of time varied, especially in remote areas that
required long days of hiking to reach the camera.
Field methods
We primarily used the Trailmaster camera
system at focal points. The system (model 1500,
Goodson and Associates, Inc., Lenaxa, KS;
Kucera and Barrett 1993) consists of a transmitter
that emits an infrared beam, a receiver that
detects the beam, and a camera that is connected
to the receiver with a cable (Fig. 6.8). The
receiver triggers the camera to take a picture
when an animal breaks the beam. At all nonrandom
sites, and occasionally at focal points,
we also used the DeerCam (model DC-100, Nontypical,
Inc., Park Falls, WI) and the Trailmaster
500 and 1550 models. Because they have
identical functions, we do not further differentiate
equipment we used.
We baited each focal-point camera using
a fish-based canned catfood and a commercial
trapping lure that attracted predators. Generally,
we baited with catfood the first week, then the
trapping lure the second week, but for high-
elevation surveys in 1999 we randomly selected
only one bait and used it for two weeks. We
occasionally baited non-random sites. For visitor
safety reasons, we did not locate baited stations
within 200 m of a trail.