Frank J. Mazzotti, Daniel H. Sloane, USDA Forest Service
1. Develop monitoring methods necessary for evaluation of restoration success in alligator populations. 2. Understand the effects of decompartmentalization and other CERP (Comprehensive Everglades Restoration Plan) projects on restoration of alligator populations. 3. Identify and quantify the extent of aquatic refugia maintained by alligators throughout the system and develop relationships necessary to predict restoration of refugia. 4. Validate and update ecological models for use in prediction of the effects of restoration.
U.S. Department of Agriculture - Natural Resources Conservation Service (NRCS) Department of the Interior - U.S. Geological Survey Department of Commerce - National Oceanic and Atmospheric Administration (NOAA) Environmental Protection Agency (EPA) Smithsonian Institution - National Museum of Natural History (NMNH)
3205 College Ave.
Moore, C. T.
Mazzotti, Frank J.
Brandt, Laura A.
Steven M. Davie and John C. Ogden, editors
Gross, Louis, Rice, Kenneth G.
Mazzotti, F. J., Brandt, L. A.
W. E. Meshaka and K. J. Babbitt, editors
Rice, K. G. Allen, J. C.
Mazzotti, F. J., Brandt, L. A., Rice, K. G.
The purpose of this project is to evaluate the relative distribution, abundance, and demographic structure of alligators in various habitats in relation to water levels and salinities. The relative distribution and abundance of alligators is a key indicator component of the conceptual ecosystem models for Big Cypress, marl prairie/rocky glades, ridge and slough, and mangrove transition zone ecosystems and has been identified as a performance measure in the CERP monitoring and assessment plan. Demographic data are needed for development of models to assess the potential impacts from operation of CERP projects.
During FY03, we will concentrate our work on:
1. Continued development of monitoring methods and correction factors for environmental conditions and sighting proportions. 2. Continued monitoring of South Florida’s alligator populations through night-light surveys on routes developed during FY02. Also, we will begin development of new survey routes based on the 2x2 mile cells developed for monitoring and evaluation of restoration success by RECOVER. 3. Continued alligator capture for comparison of condition through South Florida and through time.
After examining past survey data in Everglades National Park and evaluating the ability to detect change in an alligator population we believe it most effective to concentrate surveys to peak wet season and peak dry season replicate spotlight surveys along with capture surveys of alligators to assess the relative distribution, abundance, and demographic structure of the American alligator. Established survey routes of estuarine rivers and freshwater canals and marshes extending from the mangrove fringe of Everglades National Park north to Arthur R. Marshall National Wildlife Refuge will continue to be performed at night by skiff, canoe, jon boat, airboat, and truck. Alligator locations will continue to be recorded using GPS and field maps, and sizes of alligators will be estimated whenever possible. Environmental data including habitat type, air and water temperature, salinity, wind and wave action, and spot water levels will be recorded. Regional hydrologic data will be obtained from the SFWMD and the USGS.
To determine demographic structure (size class and sex) structure semi-annual capture surveys will be preformed using the same vehicles and locations described above. Alligators will be captured by hand, noose, dart, or tongs. Total length, snout-vent length, tail girth, and weight will be measured, and sex determined. In addition the relative condition of alligators will be determined by doing a condition factor analysis.
3205 College Ave.
Dry season refugia for aquatic animals, are assumed to be a critical component of the Everglades landscape (Craighead 1968, Mazzotti and Brandt 1994). They are an important attribute in the conceptual models being used to develop the monitoring and assessment plan for the Comprehensive Everglades Restoration Plan. The relationships among dry season refugia, aquatic fauna, wading birds, and alligators have been identified as a key uncertainty in the CERP monitoring and assessment plan. In addition, the distribution and occupancy of alligator holes has been identified as a performance measure for the marl prairie/rocky glades conceptual model. As important as aquatic refugia are imagined to be, their ecology has remained an almost completely unstudied phenomena.
The project began in FY02 in Loxahatchee NWR. We anticipate finishing the work in Loxahatchee in early FY03 and moving our work to Everglades National Park for completion during FY03.
The following subtasks have been designed to achieve the project objectives.
Mapping: Aquatic refugia will be located and mapped using a combination of aerial photography (supplied by Everglades National Park and/or Loxahatchee National Wildlife Refuge) and global position system (GPS) technology. Photographic imagery will be analyzed using a geographic information system (GIS). All GPS data will be managed using GIS.
Ecological characterization: The geography of aquatic refugia will be described using the map and GIS database completed above. Location of refugia can be categorized by position in central slough or peripheral wetland and by proximity to landscape features such as canals. Structure and function of aquatic refugia will be determined from field studies of selected holes.
Analysis of spatial patterns: With the emergence of GIS the ability to analyze spatial patterns of ecological resources has advanced significantly. State-of-the-art spatial statistics will be used to analyze the data obtained from the mapping activity.
The methods described below have proven cost effective for mapping aquatic refugia at high resolution over a large area and has been used to map alligator holes in Water Conservation Areas 2 and 3 (Campbell and Mazzotti 2001). It is important that these data be collected now, prior to major changes, so that the influences of CERP projects can be evaluated.
Alligator holes will be mapped using color infra-red (CIR) aerial photography. CIR photography will be obtained from Everglades National Park or Loxahatchee National Wildlife Refuge. Selected photographs will be professionally scanned at one meter resolution and the digital images stored on CD-ROM. Photographic prints (contact prints) of the original film also will be made.
Potential alligator holes will be located on the contact prints using a light table and magnifying lens. The alligator holes found on each image will be plotted on a 9x9 inch clear acetate overlay with a permanent marker. For each image the location of the two to four ground control points also will be plotted on the overlay. Ground control for the photos will be plotted on a clear overlay, and included with the original data set.
All image overlays will be assembled and potential alligator holes mapped. Then a second, continuous transparent overlay will be placed over the mosaiced overlays, and all alligator holes and control points retraced onto a final single sheet. The large overly will be photographically reduced and scanned into the computer using a standard flatbed scanner.
The digital image, with potential alligator holes and ground control, will be imported into an image processing software, and the coordinates (Universal Transverse Mercator ) for the ground control entered into the computer. The digital image will then be reprocessed by the software producing a complete spatially referenced image.
The spatially referenced image will then be imported into GIS software after conversion to raster image format. A point layer for the GIS then will be digitized on screen and a database for the individual points with their locations can be developed.
Other layers of information for the GIS will be created in the same manner from the photographic contact prints. These include the study area boundary, canals and levees, major airboat trails, minor airboat and buggy trails, and islands. The GIS system also will include information obtained from other sources. These data layers include the Florida Landcover vegetation layer, developed form landsat satellite imagery by the Florida Cooperative Fish and Wildlife research Unit, University of Florida, and vegetation information from other sources.
Field measurements to describe alligator holes will include structure (size, shape, substrate, and vegetation) and function (hydrology, wildlife use, and water quality).
Alligator holes will be located in the field using a GPS receiver and printed field maps of the hole from the digital imagery. At each alligator hole field measurements will proceed in the following order:
1. Photo of the alligator hole. 2. Dissolved oxygen, conductivity, pH and temperature (air and water) of the pond will be measured. 3. Wildlife sightings, including tracks, scats, alligator trails, footprints, and tail drags will be recorded throughout the survey. 4. Surrounding vegetation will be recorded onto the color infra-red field-maps. 5. Transects will be established across both the length and width the alligator hole. Transects will extend into the marsh matrix. Depth of water will be recorded with a round fiberglass measuring pole at half meter intervals. Muck depth will be measured by sinking a thin fiberglass baton down to the limestone bedrock and noting the difference on the measuring pole. Vegetation or open water will be recorded at each point.
Based on these field observation alligator holes will be separated into the following descriptive classes: origin, status, size, shape, depth, muck, and island. A description of each of these categories follows:
1. origin: natural = created by alligators artificial = created by humans 2. status: active = inhabited by alligators inactive = no alligators present, or signs of alligators 3. size: area of the alligator pond small = < 20 square meters medium = 20 - 40 square meters large = > 40 square meters 4. shape: shape of the alligator pond circular = width ? half the length oval = width < half the length irregular = any non-elliptical shape 5. depth: shallow = < 15 cm average water depth medium = 15 - 30 cm average water depth deep = >30 cm average water depth 6. muck: shallow = < 30 cm average muck depth medium = 30 - 60 cm average muck depth deep = >60 cm average muck depth 7. island: yes = an island is within 20 meters of the alligator pond no = an island is not within 20 meters of the alligator pond
The spatial patterns of aquatic refugia will be analyzed for all located refugia and for refugia of different type and characteristics as identified in the ecological characterization above. It will be determined if holes are distributed randomly, uniformly, or clumped. In addition, the scale of the pattern will be identified. A combination of indicies of spatial patterning such as: nearest neighbor distances, Pielou’s index of dispersion, Clark and Evens’ nearest neighbor, and Ripley’s K will be used for this task. Pielou’s index and the Clark and Evens’ index are used to determine if the holes are randomly distributed, uniformly distributed, or clumped. Ripley’s K is used to examine the scale of clumping. Density maps that illustrate the concentration of holes will be produced for each area. Distance from canals or other significant features will be calculated for each hole and these data along with available data on vegetation, hydrology, topology, etc. will be used to explore the relationships between hole location and type and physical and ecological landscape features.
3205 College Ave.
An alligator population model is currently in the calibration phase for use in evaluating CERP restoration alternatives and developing performance measures. The model will require periodic updates, further calibration, and validation as new data becomes available. This data is being collected during monitoring of the alligator throughout South Florida.
Work to be done during FY2003:
The core model component is a 3-D matrix that records the density of each stage of alligator in each 500x500m spatial location (500m pixel size based on the mean adult female home range size). This structure is manipulated in its entirety with 3-D matrix operations, and interacts with survival and condition 3-D matrices, each in turn calculated for each time step based on water level, crowding, etc. Alligators either survive and grow to the next stage of development (SD), survive but not grow (SND), or die. The proportion of each stage that falls into the three categories depends on water levels and alligator condition throughout the year, and the density of adult alligators at each spatial location:
Adult female alligators produce offspring at each spatial location, depending on water levels during the nesting period, habitat type, and the age and condition of the female over the previous season. The nesting potential of each cell is predicted by the ATLSS American Alligator Production Index which incorporates local habitat data and hydrological dynamics to predict the probability of producing nests and offspring successfully in each cell, if a healthy female is present.
To disperse alligators, we use a discrete spatial convolution method . This is similar to a 'blur filter' used by many image-processing computer programs, and is a process that takes the contents of a cell and redistributes it according to a dispersal kernel). The dispersal kernels are sized according to average dispersal distance of each alligator stage. The subadult stage is most mobile, while adults and hatchlings are more sedentary.
Output of the model is a 3-D alligator density matrix, with space (x and y) along two axes, and the stage classes along the third axis. Also included are a 'running average' of the historical health and survival rates of each stage in each cell. This construct is easily summed for total alligator population, or subsampled to check for corroboration with field data. Instantaneous densities, and local rates-of-change can be calculated from this model.
We will concentrate our work on: 1. Developing 'virtual' night-light and nesting survey routes that correspond with NPS SRF, USFWS alligator monitoring. This will allow calibration and validation of the current model and checks on future model modifications. 2. Further modification of the model to incorporate new monitoring data. 3. Providing model runs and interpretation for CERP projects.
1. Relative distribution, abundance, and demographic structure of the American alligator in relation to habitat, water levels, and salinities:
a. Continue monitoring of alligator populations throughout the Greater Everglades. b. Complete estimates of correction factors for environmental conditions and detection probabilities. c. Continue monitoring of alligator condition throughout the Greater Everglades. d. Provide data essential for validation of the ATLSS alligator population model.
To determine demographic structure (size class and sex) semi-annual capture surveys will continue to be performed using the skiffs, jon boats, airboats, and trucks at night along estuarine rivers and freshwater canals and marshes extending fromt he mangrove fringe of Everglades National Park north to Arthur R. Marshall National Wildlife Refuge. Alligators will be captured by hand, noose, dart, or tongs. Total length, snout-vent length, tail girth, and weight will be measured, and sex determined. In addition the relative condition of alligators will be determined by doing a condition factor analysis.
2. Mapping and Characterizing Aquatic Refugia in Everglades National Park and Arthur R. Marshall Loxahatchee National Wildlife Refuge
Mapping: Aquatic refugia in Everglades National Park will be located and mapped using a combination of aerial photography (supplied by Everglades National Park and/or Loxahatchee National Wildlife Refuge) and global position system (GPS) technology. Photographic imagery will be analyzed using a geographic information system (GIS). All GPS data will be managed using GIS.
Ecological characterization: Location of refugia can be categorized by position in central slough or peripheral wetland and by proximity to landscape features such as canals. Structure and function of aquatic refugia will be determined from field studies of selected holes.
Analysis of spatial patterns: State-of-the-art spatial statistics will be used to analyze the data.
3. Population-Based Simulation Modeling of American Alligator Populations in Support of CERP
a. Continue refining the alligator model, to continue with validation as new data are released, and to actively seek out and gather data from any new scenarios that are developed in 2003. b. Simulate these hydrologic scenarios and provide results to project planners. c. Develop an intuitive graphical user interface for the model and release it to CERP managers.
At this time, we have performed simulations using all of the available data sets (calibration 1979-95, 1995 and 2050 base 1965-95, and the restoration scenario D13-R 1965-95). We have also devised a validation regimen that will allow us to check the accuracy of the predicted output from the calibration data set by comparing nighttime spotlighting surveys along georeferenced trails with a virtual survey performed along the same paths through the simulation output. Preliminary tests indicate that the model has a close fit to actual survey counts. The calibration data have only been released through 1995, which is approximately the same time that comprehensive spotlight surveys were started, so we have a very limited overlap from which to draw validation data. In the near future, these data should be released through 2002, at which time we will be able to run a more comprehensive set of comparisons. In addition, new project scenarios have been proposed, and when the water management simulation data is released, there will be a need for alligator population responses to those projects.
3205 College Ave.
3205 College Ave.
U.S. Department of the Interior, U.S. Geological Survey, Center for
Coastal Geology
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