The Use of
Aerial Photography and GIS: A Part of a Reintroduction Viability Study of
Ocelots in Texas
By
Robert E. Thomas
For
Geography 26-
Data Acquisition, Spring 1999 American River College,
Sacramento, CA
And
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Science Division
Defenders of Wildlife, Washington, DC
ABSTRACT
The use of GIS and aerial photo to determine habitat
suitability and site selection has been common practice in wildlife
conservation and land ecology in recent times. At present, there is an
International multi-agency project that is comprised of individuals from
private, public, and non-profit institutions who seek recovery for endangered
felids; ocelots, jaguars, and jaguarundis throughout their historic range in
the American southwest (Arizona, New Mexico & Texas), and adjacent Mexican
states of Sonora, Chihuahua, and Tamaulipas.
The primary focus of this paper will be on the use of aerial photography
to examine areas that have been indicated using GIS to be suitable for these
cats. The Lower Rio Grande Valley region of south Texas will be the area of
attention for this study. As a pilot area, the area of concentration will be in
six counties: Maverick, Zapata, Cameron, Hildalgo, Starr, Kleberg, and
Wallacy (29.0625 to 26.4375 N; -97.6250
to -103.4375W). ArcInfo’s grid analysis module was used to assist in
determining percent coverage of vegetation after examining and evaluating the
photos for vegetation. The use of this
technique was reasonably successful in determining whither vegetation was
present in each view. In addition, the
use of ArcInfo’s grid analysis was only moderately successful, due to the
subjectivity of vegetation isolation in the analysis and quality of the image
being analyzed. Overall, this process could be beneficial as a preliminary tool
in habitat selection for these species.
INTRODUCTION
The use of Geographical Information Systems (GIS) to analyze
and help make decision about species habitat problems is extensive (Chou, 1997; DeMers, 1997; ESRI,
1997). In particular, the use of GIS in the study of small bordercats (i.e.
Ocelots, Jaguars & Jaguarundis, (Felis
pardalis, Panthera onca and Felis
yagouaroundi respectively)) in recent times has also occurred (Anderson, et. al., 1997; Haveson, Tewes
& Anderson, 1997).
At present, there is an International multi-agency project
that is comprised of individuals from private, public, and non-profit
institutions who seek recovery for ocelots, jaguars, and jaguarundis throughout
their historic range in the American southwest (Arizona, New Mexico &
Texas), and adjacent Mexican states of Sonora, Chihuahua, and Tamaulipas. One
of the working goals of this project is to focus on the decline of suitable
habitat and begin preserving suitable areas. To address this goal, studies will
build off the work of Anderson, et. al., did using GIS
to study ocelot habitat and the classification structure of the Asian Tiger
study done by the World Wildlife Fund and Wildlife Conservation Society (1997). The primary focus of this paper will be on the use of
aerial photography to examine areas that have been indicated using GIS to be
suitable for these cats. The Lower Rio Grande Valley region of south Texas will
be the area of attention for this study. As a pilot area, the area of
concentration will be in six counties: Maverick, Zapata, Cameron, Hildalgo,
Starr, Kleberg, and Wallacy (29.0625 to
26.4375 N; -97.6250 to -103.4375W). It is hoped that if this technique is successful,
the results of this study will be able to be generalized to the lager domain of
southern Texas (panhandle downward) as a whole when at a later time, it can be
used to determine the extent of decline in suitable habitat since the early
1900's to the present.
Background:
The Lower Rio Grande Valley (LRGV) region of south Texas is
composed of the counties of Starr, Hidalgo, Cameron and Willacy. In addition,
the counties of Maverick, Webb and Zapata have been included in this study area
because of their inclusion within the boundaries of the Tamaulipan Biotic
Province, a region known for containing Tamaulipan brushland ecosystem. The
importance of this area is that it is the only area of it's kind anywhere in
the United States that has the combination of climate, vegetation and
associated wildlife. The dense brush in this unique ecosystem provides food,
nest sites and cover for many wildlife species (Jahrsdoerfer
& Leslie, 1988). Many neotropical genera of mammals, reptiles and birds
reach the northern limits of their distribution in the LGRV (Blair, 1950). In
particular, the felid of this study, ocelots, use tracts of dense brush for
cover and travel lanes in this area (Tewes & Everett,
1982).
Throughout this past century, human impacts on Tamaulipan
brushland have been tremendous. Since the 1920's, more than 95% of the native
brushland in the LRGV has been converted to agricultural or urban use (USFWS, 1980; Parvin, 1988a,b). More
than 90% of the riparian habitat on the US side of the Rio Grande has been
cleared (Collins, 1984). Of the lush subtropical region of the delta area of
the LRGV, it has been estimated that 98% in the US (USFWS,
1980), and a large percentage of similar habitat in Mexico has been cleared (Collins, 1984).
The
ocelot is a spotted medium-size neotropical cat with a moderately long tail
that ranges from southern Texas and Arizona south to Peru and northern
Argentina (Figure 1) (Murray & Gardner, 1997; Hall, 1981). It has been reported, as late as the 1800's, to
be found in east and central Texas, western Louisiana and southern Arkansas (Laack, 1991; Navarro-Lopez, 1985; Woodward, 1980). Historically, in the United States, two
subspecies of ocelots have been determined. The Texas ocelot, Felis pardalis albescens, and the Sonora
ocelot, Felis pardalis sonoriensis (Hall, 1981; Harwell & Siminsk,
1990). It has been documented that there are eight other subspecies of F. pardalis or Leopardus pardalis
(Murray & Gardner, 1997).
The ocelot, now listed as of 1982, as an Endangered Species
in Arizona and Texas (Federal Register, 1982) also is afforded international
protection since 1992 under CITES Appendix 1 (Conservation on
International Trade in Endangered Species of Wild Fauna and Flora,
1983). In spite of these listings, the
ocelots is still being trapped for the fur industry in central and south
America and the habitat crucial for their survival being destroyed worldwide. Finding and protecting large areas of
suitable habitat, will be a key to this species long-term survival.
MATERIALS AND METHODS
Electronic Data Sources:
All of the
data sets, maps and images are listed below with sources.
Base Map
Texas Parks & Wildlife
Department (TPWD) GIS Lab Homepage (http://www.tpwd.state.tx.us/admin/gis/download.htm).
Texas Vegetation
Natural Regions of Texas
Major
Natural Regions
Subregions
Texas Counties
ESRI Data & Maps CD#3 (Western
States of the US)
Texas Roads Data Set
Texas Rivers Data Set
Aerial Photography:
Microsoft
TerraServer (http://terraserver.microsoft.com/advfind.asp)
14 images of 6 counties
Data Preparations:
The creation of the base map done by extracting coverage's
from the downloaded .e00 files from TPWD and converting them to shapefiles.
To determine possible habitat locations based on vegetation
data, literature reviews were conducted.
Based on associated plants listed in the various physiognomic regions,
13 vegetation classes chosen and mapped.
Roads and River data were brought in as separate themes and overlaid
onto the possible habitat map, to determine possible fragmentation due to these
to barriers. Next using a historical
sightings maps by county (Davis & Schmidly, 1994), points were on-screen
digitized. Doing a theme-by-theme
selection, all vegetation classes that fell within the sightings area were
clipped and mapped as possible habitat locations.
Using these county locations, aerial photos of various
locations within these areas were downloaded from the Microsoft/USGS
TerraServer. Each corner point of these
photos was brought into ArcView and overlaid on the base map of possible
habitat.
Using ArcInfo, photos were imagegrid processed. After
determining the lightest dark spot that indicated vegetation, the photos were
reclassified to 1's & 0's (W or B) (Namecover = con (photoname < ##, 1,
0)) based on the cellvalue. They were then brought ArcView as grid
coverages. Using Spatial Analyst,
coverages were evaluated. Looking at
the cell counts (the 0's & 1's), in the legend editor, the counts were
brought into Excel and percent cover computed (1's/total).
RESULTS
The evaluation of the vegetation classes (149 classes within
8 physiognomic regions) yield 13 classes:
Oak-Mesquite-Juniper Parks/Woods
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Mesquite_Lotebrush_Brush
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Mesquite_Juniper_Live_Oak_Brush
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Mesquite_Juniper_Brush
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Mesquite_Juniper_Shrub
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Mesquite_Granjeno_Woods
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Mesquite_Granjeno_Park
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Mesquite_Saltcedar_Brush/Woods
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Creosotebush_Lechuguilla_Shrub
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Mesquite_Hackbarry_Brush/Woods
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Juniper_Mixed_Brush
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Mesquite_Blackbrush_Brush
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Yucca_Ocotilo_Shrub.
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These classes encompassed 254/1533 polygons, which
calculated out to be ~39779142 acres or ~twelve % of the state. After conducting the overlay process of
sightings, four classes were left; Creosotebush_Lechuguilla_Shrub,
Mesquite_Blackbrush_Brush, Mesquite_ Granjeno_Woods and Mesquite_Granjeno_Park,
for a total of ~10925482 acres or ~6.3 % of the state.
Of the fourteen photos that were processed, only one could
be analyzed for percent-coverage due to problems with software (segmentation
error-ArcView) (Table 1).
Images
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No Vegetation Cells
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Vegetation Cells
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Total Cell Count
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% of Coverage
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Match Rating Lw/Med/Hi
(1-3)
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Cam1Cover
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Cam2Cover
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Hid1Cover
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Hid2Cover
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Hid3Cover
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Klb1Cover
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Klb3Cover
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MavCover
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71,477
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61,131
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132,608
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46.1%
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3
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Mav1Cover
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Mav2Cover
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Str1Cover
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Str2Cover
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Wal1Cover
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Wal2Cover
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Zap1Cover
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Summary (Averages)
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X
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X
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X
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The Maverick county photo-1 (Mav1Cover) produced a total
count of 132,608 cells of which 61131 cells that met the color value of the
photo (has vegetation) for a percent coverage of 46.1% and a matchablility
index of high (3).
The use of this technique was reasonably successful in
determining whither vegetation was present in each view. In addition, the use of ArcInfo’s grid
analysis was only moderately successful, due to the subjectivity of vegetation
isolation in the analysis and quality of the image being analyzed.
CONCLUSION
This technique’s success and failure are due to the
limitations of the process. For example
the variations in photo quality ( 2nd generation photos, darkness,
& tiling done by USGS/MS Terraserver) and the subjectivity of color
determination, and the imagegrid, all had limitations, could have synergistic
negative effect on the process. As an example, the USGS logo was picked up as
vegetation due to the black lettering fit the selection criteria. Though this
is a negligible amount of cells, it nevertheless shows the lack of precise
control necessary to increase to accuracy.
Overall, this process could be beneficial as a preliminary
tool in habitat selection of this species.
WORKS CITED
Anderson, G. L., M. Bray, D. Griffin, P. K. McDowell, W.
Swanson, and M. E. Tewes 1997. Using remote sensing and GIS to map vegetation
and determine Ocelot habitat. Proceedings
of the 16th Biannual Remote Sensing Workshop, Weslaco.
Blair, W. F. 1950. The biotic
provinces of Texas. Texas Journal of
Science, 2(1):93-117.
Chou, Y, 199x. Exploring spatial analysis
in geographical information systems. OnWord Press:Santa Fe:29.
Collins, K. 1984. Status and management
of native south Texas brushland. U.S Fish and Wildlife Service, Ecological
Service, Corpus Christi, TX.
Conservation on International Trade in
Endangered Species of Wild Fauna and Flora (CITES), 1983. CITES
appendices-Mammals. U.S. Department of the Interior. Washington, DC.
Davis, W. B. and D. J. Schmidly, 1994. Distribution of the Ocelot in Texas based on
known county records. The mammals of Texas- online edition
(http://www.nsrl.ttu.edu/tmot1/images/dmap258.jpg).
DeMers, M. M. 1997. Fundamentals of
geographic information systems. John Wiley & Sons:New York.
ESRI, 1997. Getting to know ArcView GIS.
Environmental Research Institute:Redlands, CA,:xx.
Hall, E. R. 1981. The mammals of North
America, Vol. II. Ronald Press Co., New York.
Harwell, G and P. D. Siminski 1990.
Listed cats of Texas and Arizona: recovery plan (with emphasis on the Ocelot).
For U. S. Fish and Wildlife Service, Region 2, Albuquerque, New Mexico. Ed. A.
M. Shull, S. Van Riper, S. P. Thompson & S. E. Jahrsdoerfer.
Haveson, P. M., M. E. Tewes, and G. L.
Anderson 1997. Using GIS to analyze habitat selection by Ocelots and Bobcats. Proceedings of the Caesar Kleberg Wildlife
Research Institute: Current Research 1996-97, Kingsville, TX,:33.
Jahrsdoerfer, S. E. 1988. Tamaulipan
brushland of the lower Rio Grande valley region of south Texas: description,
human impacts and management options. Biological
Report, 88(36). For U. S. Fish and Wildlife Service, Region 2, Albuquerque,
New Mexico.
Laack, L. L. 1991. Ecology of the Ocelot (Felis
pardalis) in south Texas. MS Thesis, Texas A & I University,
Kingsville.
Murray, J. L. and G. L. Gardner, 1997.
Leopardus pardalis. Mammalian Species,
548:1-10.
Navarro-Lopez, D. 1985. Status and
distribution of the Ocelot in south Texas. MS Thesis, Texas A & I
University, Kingsville.
Parvin, B. 1988a. Valley under siege. Defenders, 63:18-29.
.
1988b. The disappearing wild lands of the Rio Grande Valley. Texas Parks & Wildlife, 46:2-15.
Tewes, M. E., and D. D. Everett 1982. Study
of endangered ocelot occurring in Texas. Year-end report. U.S. Fish and
Wildlife Service, Region 2, Albuquerque,
NM.
Shindle, D. B. and M. E. Tewes 1998.
Woody species composition of habitats used by ocelots (Leopardus pardalis)
in the Tamaulipan Biotic Province. Southwestern
Naturalist, 43(2):273-279.
U.S. Fish and Wildlife Service, 1980.
Department of the Interior Habitat Preservation Plan- preservation of areas of
important fish and wildlife habitat: Cameron, Hidalgo, Starr and Willacy
counties. U. S. Fish and Wildlife Service, Region 2, Albuquerque, New Mexico.
Woodward, D. W. 1980. The Ocelot.
Selected vertebrate endangered species of the seacoast of the United States.
FWS/OBS-80/01.9.
World Wildlife Fund-US 1997. A framework for
identifying high priority areas and actions for the conservation of Tigers in
the wild. World Wildlife Fund, Washington, DC.