Frank Mazzotti
1. Design and develop a monitoring program for relative distribution, size (condition), nesting and hole occupancy rates of the American alligator in response to Comprehensive Everglades Restoration Plan (CERP) projects as specified in the Monitoring and Assessment Plan (MAP). The monitoring program and procedures developed will provide the baseline for future comparisons and an effective means for evaluating restoration success for the American alligator in the Greater Everglades ecosystem.
2. Monitor changes in alligator populations due to restoration over short (body condition), medium (distribution, hole occupancy) and long (nesting) temporal and spatial scales.
3. Design and develop a monitoring program for growth and survival of crocodiles in areas that will be affected by CERP projects.
4. Conduct surveys for crocodiles as expressed in the MAP. Monitoring surveys will be separated into subtasks based on geographic area. In all areas, crocodile surveys and monitoring will include nesting effort and success and will focus on growth and survival of juvenile crocodiles.
The American crocodile thrives in healthy estuarine environments and, in particular, is dependent on freshwater deliveries (Mazzotti 1999). In this regard, crocodiles can be used to evaluate restoration alternatives and to set success criteria for Florida and Biscayne bays. The working hypothesis is that crocodiles that grow faster are also in better condition (relatively fatter) than crocodiles that grow more slowly.
Mazzotti, Frank J.
Mazzotti, F. J.
1) Task 1 - Alligator Distribution and Size (Condition). Distribution and size will be determined using night-light and semi-annual capture surveys. Correlations between alligator submergence and several environmental variables such as air and water temperatures, time, moon phase, season, and habitat will be investigated using transmitters with an integrated Global Positioning System (GPS).
a) Distribution of Alligators will be determined by:
1) Nightlight counts 2) Supplemental aerial and ground surveys 3) Correction factors for alligator surveys: distance sampling, wariness, and proportion of time at surface
b) Alligator Size (Condition) - Sizes of alligators will be estimated in quarter meter increments whenever possible.
Approach and Methods - Night-light (or spot-light) and capture surveys will be used to determine distribution and condition of alligators. Night-light counts are an accepted means of monitoring alligator populations as an index to population size, but many assumptions need to be tested to make the surveys reliable. To develop reliable relative population estimates using night-lighting counts, estimates of detection probability will be determined (Anderson 2003). Currently, variation in detection probabilities of alligators due to habitat, wariness, and animal behavior is not estimated. These sources of variation will be investigated using different sampling methods. These estimates of variation can then be used as correction factors for our night-light counts. If estimates of detection probability can be obtained, one can better detect and evaluate trends in populations of alligators over time as required by CERP. Capture surveys will be used in conjunction with night-light surveys to provide data for a body condition factor analysis.
2) Task 2 - Alligator Nesting Ecology: Differences in primary nesting habitat of alligators at ENP (open marsh area) and Loxahatchee NWR (tree islands) will require different survey techniques. Both survey techniques below have been used successfully in previous studies (Brandt and Mazzotti 2000).
a) System Reconnaissance Flights (SRF's) will be used at ENP: Extend SRF's into mangrove zone and rocky glades
b) Surveys in Loxahatchee NWR will use airboats.
Approach and Methods - The nesting ecology task has been separated into subtasks based on location because differences in primary nesting habitat of alligators at ENP (open marsh area) and Loxahatchee NWR (tree islands) require different survey techniques. Standard Reconnaissance Flights have been used successfully at ENP and airboat surveys have proven successful at Loxahatchee NWR (Brandt and Mazzotti 2000); thus, they will be used at these two study sites, respectively. After initial flights are completed, a series of nests will be selected for ground visits to examine eggs. A minimum of 20% of the estimated total nests will be sampled every year. Nests will be visited at least once during the incubation period. During the initial visit, eggs will be counted and their viability determined. During follow up visits, the fate of eggs will be determined.
ENP study area, SRF's will fly east west transects at 2-km intervals from a helicopter at a height of 40 m and ground speed of 50 knots. Since the greatest change in nesting is expected in freshwater-mangrove and rocky glades areas an evaluation of extending or modifying transects in those areas will be necessary before beginning the SRF survey. Observers on each side of the helicopter will count all nests in a belt 250 m wide for a total width of 500 m. The helicopter will be flown over each nest and its position will be recorded using a GPS. Areas surveyed will include Shark River Slough, Northeast Shark River Slough, mangrove estuary, portions of Big Cypress National Preserve, Rocky Glades, East Slough, and the Taylor Slough/C-111 basin.
For the Loxahatchee NWR study area, ten plots of 1.6 x 1.6 km have been selected using the 3.2 x 3.2 km grid cells of the SFWMD Water Management Model and the indicator regions developed for the Central and Southern Florida Project Comprehensive Review Study (Corps and SFWMD 1999) and the MAP. Three plots have been selected as areas to sample within each of the indicator regions. Nests will be located from the ground using airboats and all plots will be searched for alligator nests via north to south meandering transects (approximately 200 m width). A GPS will be used to record the path of each survey route. Tree islands and alligator holes will be circled to locate trails and nests. Trails going into tree islands will be searched on foot. The amount of time spent searching by boat and by foot will be recorded. Location (GPS coordinate), physical description of the area, and nest, as well as presence of a female, will be noted when a nest is located. Nests will be flagged and revisited in August or September to determine their fate. The presence and location of old nests also will be recorded. In addition to initial nest searches, limited "double sampling" will be conducted to determine the proportion of nests found by each observer and to estimate the total number of nests constructed in the area.
3) Task 3 - Alligator Hole Mapping and Occupancy: Alligator holes will be located and mapped using a combination of aerial photography and GPS technology. Occupancy rates of alligator holes will be determined by a combination of helicopter and airboat surveys.
a) Approach and Methods - Alligator holes will be located and mapped using a combination of aerial photography and GPS technology. This is a proven, cost effective method for mapping alligator holes at high resolution over a large area and has been used to map alligator holes in WCA's 2 and 3 (Campbell and Mazzotti 2001). A geographic information system (GIS) will be used to analyze photographic imagery and to manage GPS data. Occupancy rates of alligator holes will be determined by a combination of helicopter and airboat surveys. A series of transects similar to those described in the SRF will be used. Initially, those areas expected to be influenced most by CERP such as the rocky glades will be surveyed for alligator hole occupancy.
Semi-annual capture surveys will be performed to determine the condition of alligator populations. A minimum of 15 alligators greater than 75 cm total length will be captured by hand, noose, or tongs in each area twice yearly. Total length (TL), snout-vent length (SVL), head length (HL), tail girth (TG), and weight will be measured, sex determined, and any abnormalities/deformities noted. At Loxahatchee NWR, clipping the tail scutes will mark alligators; elsewhere, GFC/FWC web tags will be used to identify recaptured individuals. Location, habitat characteristics, and environmental data including habitat type, air and water temperature, salinity, water depth, muck depth, wind and wave action, and spot water levels will be recorded at set locations along routes.
1) Estimate juvenile growth and survival rates of crocodiles in areas affect by CERP projects. To help in the execution of this task all work will be conducted in two distinct phases:
a) Phase 1 - This phase consists of two subtasks to determine the appropriate quantitative methods for performing the spatial and temporal analyses required by MAP and to apply that analysis to developing a detail work plan that combines existing methods of data collection with the appropriate experimental design and statistical analysis. Since all of the previous studies on the status and ecology of the American crocodile (Crocodylus acutus) in Florida have been summarized (Mazzotti and Cherkiss (2003)) that effort is unnecessary.
Subtask 1 - Analyze existing data to determine the appropriate analytical methods.
1) Approach and Methods - Analyze existing databases on crocodiles (Mazzotti and Cherkiss 2003) to determine appropriate statistical methods for making the spatial temporal comparisons required by the MAP. Models of crocodilian growth (Brandt 1991) and vertebrate survival (White and Burnham 1999) will be evaluated for their usefulness in evaluating data collected. Mazzotti and Cherkiss used empirical estimates of growth (absolute growth) and survival (direct enumeration) to compare growth and survival among the nesting colonies in South Florida. These measures may not be adequate to make the spatial and temporal comparisons required of MAP.
Subtask 2 - Use the results of Subtask 1 above to refine the sampling procedures in the succeeding subtasks.
1) Approach and Methods - Develop a detailed work plan that will utilize the results of subtask 1. Refine appropriate analytical methods for crocodile monitoring and meet the requirements of the MAP performance measure.
b) Phase 2 - This phase consists of a series of recurring subtasks to acquire the data needed to make the analyses and assessments. The subtasks are separated by location, with the same activities conducted within each area.
Subtask 1 - Juvenile Crocodile growth and survival monitoring in Biscayne Bay through Barnes Sound.
1) Approach and Methods - Population surveys and monitoring in Biscayne Bay through Barnes Sound will include nesting effort and success, and will focus on growth and survival of juvenile crocodiles. Population surveys and monitoring of crocodiles will be conducted following the methods described by Mazzotti and Cherkiss (2003). Growth and survival of juvenile crocodiles will be assessed by quarterly surveys and capture efforts (Mazzotti 1999, Mazzotti and Cherkiss 2003).
Subtask 2 - Juvenile crocodile growth and survival monitoring in northeastern and central Florida Bay, ENP
1) Approach and Methods - Population surveys and monitoring in northeastern and central Florida Bay, ENP will include nesting effort and success, and will focus on growth and survival rates of juvenile crocodiles. Population surveys and monitoring of crocodiles will be conducted following the methods described by Mazzotti and Cherkiss (2003). Growth and survival of juvenile crocodiles will be assessed by quarterly surveys and capture efforts (Mazzotti 1999, Mazzotti and Cherkiss 2003).
Subtask 3 - Juvenile crocodile growth and survival monitoring in the Cape Sable/Flamingo Area, ENP.
1) Approach and Methods - Population surveys and monitoring in the Cape Sable/Flamingo Area, ENP will include nesting effort and success, and will focus on growth and survival of juvenile crocodiles. Population surveys and monitoring of crocodiles will be conducted following the methods described by Mazzotti and Cherkiss (2003). Growth and survival of juvenile crocodiles will be assessed by quarterly surveys and capture efforts (Mazzotti 1999, Mazzotti and Cherkiss 2003).
Subtask 4 - Juvenile crocodile growth and survival monitoring in the west coast river system (Broad River to Chatham River), ENP.
1) Approach and Methods - Population surveys and monitoring in the west coast river system (Broad River to Chatham River), ENP will include nesting effort and success, and will focus on growth and survival of juvenile crocodiles. Population surveys and monitoring of crocodiles will be conducted following the methods described by Mazzotti and Cherkiss (2003). Growth and survival of juvenile crocodiles will be assessed by quarterly surveys and capture efforts (Mazzotti 1999, Mazzotti and Cherkiss 2003).
Determining crocodile nesting effort and success is necessary for maximizing the ability to mark hatchling crocodiles and will be determined by searching known and potential nesting habitat during April and May (effort) and July and August (success) for activity (tail drags, digging or scraping) or the presence of eggs or hatchlings. Hatchlings will be captured, measured, marked, and released.
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U.S. Department of the Interior, U.S. Geological Survey
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