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

Chapter 6: Mammal Inventory
Don E. Swann and Brian F. Powell
Previous and Ongoing Research
Saguaro National Park has never had a
comprehensive survey of its mammals, and
surprisingly little research has been conducted
on mammals in the Rincon Mountain District
considering the park’s long history as a national
park. However, a few studies provide valuable
information on mammals, particularly Lowell
Sumner’s work in the mid-20 th Century (Sumner
1951) and Russell Davis and Ronnie Sidner’s
survey of mammals in the high country of the
Rincons in the early 1990s (Davis and Sidner
1992). H. Brown and L. Huey (unpubl. data)
made collecting trips to the Rincons in 1911 and
1932, respectively (Davis and Sidner 1992). In
addition, the park’s administrative records at the
Western Archaeological and Conservation Center
contain invaluable files (dating from the 1940s
and 1950s) on mammal sightings and species of
concern including the Mexican gray wolf and tree
squirrels.
More recently, M’Closkey (1980 and
citations therein) and Duncan (1990) trapped
small mammals in desert areas of the district.
Albrecht (2001) and Flesch (2001), using the
small-mammal trapping data from this inventory
effort, analyzed patterns of species richness
and relative abundance for both units of the
district. (Copies of these reports are available
in the archive locations cited in Chapter 1).
Small mammals were also included in surveys
of the Rincon Valley expansion area in the
1990s (Fitzgerald 1996, Bucci 2001) and in the
recent PULSE study of the Madrona Pools area
(Swann 2003). Both large and small mammals
were included in surveys of the Rocking K
Ranch adjacent to the district during the early
1990s, but most of the large mammals recorded
in these surveys (Lynn 1996) are based on
sightings by local residents that may not be
credible. The small mammal report by Fitzgerald
(1996) contains a species (hispid pocket mouse
[Perognatus hispidis]) not previously known to
occur in the Rincon Mountains and Fitzgerald did
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not collect a specimen voucher. Similarly, a large
mammal report for the expansion area (Fitzgerald
1996) is based largely on identification of scat
and burrows, which we do not consider reliable.
The inventory of bats is probably nearly complete
because of Ronnie Sidner’s extensive surveys
for the last 15 years (Sidner 1991, Sidner and
Davis 1994, Sidner 2003). Finally, park staff
have been collecting observations of wildlife
for several decades. Most of these sightings,
while not entirely reliable, have been entered
into a database and mapped in a GIS, and are
available in a supplement to this report. Other
sightings remain uncataloged in logbooks from
the Manning Camp Ranger Station and other
sources; many of these uncataloged sightings
were summarized by Davis and Sidner (1992).
Methods
We surveyed for mammals using five field
methods: (1) trapping for rodents and ground
squirrels (primarily nocturnal; hereafter referred
to collectively as small mammals), (2) infraredtriggered
photography for medium and large
mammals, (3) netting for bats, (4) pitfall traps
for shrews and pocket gophers, and (5) incidental
observations for all mammals.
Small Mammals
Field Methods
We trapped small mammals using Sherman
live traps (folding aluminum or steel, 3 x 3.5
x 9”; H. B. Sherman, Inc., Tallahassee, FL)
set in grids (White et al. 1983) along focalpoint
transects; Figs. 6.1, 6.2). We opened
and baited (one tablespoon: 16 parts dried
oatmeal to one part peanut butter) traps in the
evening, then checked and closed traps the
following morning. We placed a small amount
of polyester batting in each trap to prevent trap
deaths due to cold nighttime temperatures. We
marked each captured animal with a permanent
marker to facilitate recognition; these “batch