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

Chapter 4: Amphibian and Reptile Inventory
Aaron D. Flesch, Don E. Swann, and Brian F. Powell
Previous Research
Little information is available on the distribution,
abundance, and habitat of amphibians and reptiles
(hereafter herpetofauna) in the Rincon Mountain
District, though the community composition is
well known and several species lists exist (Black
1982, Doll et al. 1986, Lowe and Holm 1991,
Swann 2004). Because of poor documentation,
we do not consider the lists of Black (1982)
or Doll et al. (1986). Lowe and Holm (1991)
ranked abundance (e.g. rare, uncommon, and
common) of herpetofauna in the district, but these
categories were from incidental observations, not
formal surveys within the district. Lowe (1992)
summarized some information on distribution of
herpetofauna in the district but focused mainly
on providing a regional biogeographic context
for understanding distribution patterns. Goode
et al. (1998) inventoried the district’s Expansion
Area in Rincon Valley and Murray (1996) and
Swann (1999b) inventoried both the Expansion
Area and the nearby Rocking K Ranch and
provided detailed information for these areas.
Most recently, Bonine and Schwalbe (2003)
inventoried the Madrona Pools of Chimenea
Creek but their effort was limited to only five
days in May. There have also been a number of
single-species studies in the district, including
those for the lowland leopard frog (Swann 1997,
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Swann et al. 2003b, Goldberg et al. 2004, Eric
Wallace, unpubl. data), desert tortoise (Swann
et al. 2002, Stitt et al. 2003, Edwards et al. 2004,
Jones et al. 2005), and tiger rattlesnake (Matt
Goode, unpubl. data). Because most previous
studies have been limited either spatially or
temporally, the inventory effort summarized
in this report represents the first attempt to
quantify distribution and abundance and provide
information on habitat of all amphibian and
reptile species in the district.
Methods
We surveyed herpetofauna in 2001 and 2002
using four field methods: (1) plot-based intensive
surveys, (2) non-plot based extensive surveys
(Table 4.1), (3) road surveys, and (4) incidental
observations. We used multiple methods
to ensure coverage across a broad range of
environmental features and to facilitate complete
species lists and estimates of relative abundance.
We chose the location of intensive surveys (at
focal-point transects) using a stratified random
design and stratified by elevation (see Chapter
1) then constrained surveys by time and area
(Crump and Scott 1994). We chose the location
of extensive surveys both randomly and nonrandomly;
some extensive surveys were located
Table 4.1. Characteristics of three major active survey methods used during surveys for herpetofauna,
Saguaro National Park, Rincon Mountain District, 2001 and 2002.
Survey type
Characteristic Intensive, plot-based Extensive – Random Extensive – Non-random
Random location Yes Partially No
Area constrained Yes No No
Configuration Plot based visual encounter Non-plot based visual encounter Non-plot based visual encounter
Area (ha) three 1-ha plots per transect Variable Variable
Time constrained Yes, 1 hour No No
Time of day Morning Morning Morning, afternoon, and evening
Advantages Facilitates comparison with other areas,
scope of inference to entire park, more
complete richness and abundance data
Disadvantages Inefficient for developing complete
species list
Larger scope of inference and potential
to detect less common species
Inefficient for developing complete
species list
Maximum flexibility facilitating
detection of rare species with
restricted distributions
Scope of inference applies only to
those areas surveyed