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Project Work Plan

Department of Interior USGS GE PES
Fiscal Year 2014 Study Work Plan

Study Title: Ecology, Modeling, and Monitoring of Crocodilians in the Greater Everglades
Study Start Date: 2003 Study End Date: 2015
Location (Subregions, Counties, Park or Refuge): DOI lands in south Florida, the Greater Everglades
Funding Source: GE PES
Other Complementary Funding Source(s): to University of Florida from National Park Service
Funding History: FY03; FY04; FY05; FY06; FY07; FY08; FY09; FY10; FY11; FY12; FY13. In the past, this study was co-funded as a companion study to MAP crocodilian study. Unfortunately, MAP funding was eliminated prior to FY12. This project is therefore undergoing redesign to complete critical portions of the crocodilian study.
FY14 USGS Funding:
Principal Investigator(s): Kristen Hart, Michael Cherkiss
USGS Project Officer: Michael Cherkiss
USGS Technical Officer: Scott Padgett
Supporting Organizations: National Park Service
Associated / Linked Projects:

Overview & Objective(s): Many important questions concerning the effects of Greater Everglades restoration on crocodilian populations remain unanswered, such as the impacts of Decompartmentalization, the role of alligator holes as aquatic refugia, and the effects of hydrology on crocodilian population growth, survival and condition. Further, the methods for monitoring and evaluating restoration success are not clear or have not been adapted for use during Comprehensive Everglades Restoration Plan (CERP). Also, we need to continue to update and validate restoration tools such as population models for use in alternative selection, performance measure development, and prediction. This project will directly address the questions outlined above, develop monitoring methods, and validate restoration tools for use in CERP.

Specific Relevance to Major Unanswered Questions and Information Needs Identified:

This study was previously part of a larger study funded and guided by science questions identified by the NPS (Critical Ecosystem Studies Initiative) and USACOE (CERP Monitoring and Assessment Plan or MAP). This study previously addressed questions identified in DOI's Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida (DOI's Everglades Science Plan) including:

This study now addresses several science objectives in the USGS Science Plan in Support of Greater Everglades Restoration. Primarily, this work is concentrated under Goal 2B "Restore, Preserve, and Protect Natural Habitats and Species - Ecological Indicators." The tasks address all 5 science objectives:

Status: We are continuing to provide parameter information to contribute to population and simulation modeling efforts. We have established monitoring of crocodilian population growth, abundance, condition, and size distribution throughout the Greater Everglades. We have also implemented annual monitoring of juvenile growth, hatchling survival and nesting effort and success of American crocodiles. We are investigating quantitative and field methods to improve the precision and accuracy of our monitoring through the use of double-observer surveys, artificial surrogates, and most recently radio- and satellite-telemetry on both alligators and crocodilies, and mark recapture. We have completed mapping alligator holes and aquatic refugia within Everglades National Park and published a manuscript on this (see Fujisaki et al. 2012). We also have several crocodile modeling papers in preparation. All previously-developed models are fully functional and available for use in comparison of restoration alternatives.

Recent Products:


Rosenblatt AE, Heithaus MR, Mazzotti FJ, Cherkiss MS, Jeffery BM (2013) Intra-population variation in activity ranges, diel patterns, movement rates, and habitat use of American alligator in a subtropical estuary. Estuarine, Coastal and Shelf Science: 1-9.

Green TW, Slone DH, Swain ED, Cherkiss MS, Lohmann M, Mazzotti FJ, Rice KG (2012) Evaluating effects of Everglades restoration on American crocodile populations in South Florida using a spatially-explicit, stage-based population model. Wetlands DOI http://dx.doi.org/10.1007/s13157-012-0370-0.

Mauger, LA, Velez E, Cherkiss MS, Brien ML, Boston M, Mazzotti FJ, Spotila JR. (2012) Population assessment of the American crocodile, Crocodylus acutus (Crocodilia: Crocodylidae) on the Pacific coast of Costa Rica. International Journal of Tropical Biology and Conservation. 60 (4).

Mazzotti FJ, Cherkiss MS, Brandt LA, Fujisaki I, Hart K, Jeffery B, McMurry ST, Platt SG, Rainwater TR, Vinci J. (2012) Body condition of Morelet's Crocodiles (Crocodylus moreletii) from Northern Belize. Journal of Herpetology. 46(3):356-362.

Fujisaki I, Mazzotti FJ, Hart KM, Rice KG, Ogurcak D, Rochford M, Jeffery BM, Brandt LA, Cherkiss MS (2012) Use of alligator hole abundance and occupancy rate as indicators for restoration of human-altered wetland. Ecological Indicators 23:627-633.

Fujisaki I, Mazzotti FJ, Dorazoi RM, Rice KG, Cherkiss M, Jeffery BM (2011) Estimating trends in alligator populations from nightlight surveys. Wetlands. 31:147-155. DOI http://dx.doi.org/10.1007/s13157-010-0120-0.

Cherkiss MS, Romanach SR, Mazzotti FJ (2009) The American Crocodile in Biscyane Bay, Florida. Estuaries and Coasts. DOI http://dx.doi.org/10.1007/s12237-011-9378-6.

Beauchamp JS, Cherkiss MS, Rochford MR, Mazzotti FJ (2009) A recent capture of a large American crocodile (Crocodylus acutus) in Florida. Florida Field Naturalist 37(4):149-150.

Mazzotti FJ, Best GR, Brandt LA, Cherkiss MS, Jeffery BM, Rice KG (2009) Alligators and crocodiles as indicators for restoration of Everglades ecosystems. Ecological Indicators 9S(2009):S137-S149.

We will present results of our studies at the Crocodile Specialist Group meeting in FY14. Satellite-tracking results for crocodilians in the Greater Everglades are available on http://www.seaturtle.org/tracking/?project_id=580 and http://www.seaturtle.org/tracking/?project_id=677.


Task Leaders: Mike Cherkiss, Kristen Hart
Phone: 786-258-1409
FAX: 954-475-4125

Task Summary and Objectives:

The purpose of this task is to continue to evaluate the relative distribution, abundance, and demographic structure of crocodilians in various habitats in relation to water levels and salinities; however, our focus is now on collecting pertinent data on DOI lands, especially ones where restoration projects are planned or initiated. The relative distribution and abundance of crocodilians 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 on crocodilians from operation of CERP projects.

Prior to our PES and MAP funded work, the only surveys for alligators in Everglades National Park were systematic reconnaissance flight (SRF) surveys for nests and Florida Fish and Wildlife Conservation Commission night surveys for alligators in and adjacent to Water Conservation Areas 2 and 3 (a component of their public hunt program). We argued that these two field efforts, while valuable, were not sufficient to provide critical nesting information on crocodilians. For example, as restoration projects occur in ecosystems such as the rocky glades and the mangrove transition zone, it will take more than 10 years for dispersing juveniles to become nesting animals, and therefore to be detected in SRF or FWC surveys. Evaluating the relative distribution, abundance, and demography of crocodilians allows for a more rapid assessment of the impacts of CERP projects on target systems.

As important as crocodilians are in the Greater Everglades ecosystem (see Mazzotti et al. 2009 Ecological Indicators, Fujisaki et al. 2012 Ecological Indicators), surprisingly little was known about them outside of Everglades National Park until our group initiated sampling. In this project crocodilian monitoring will be continued on DOI lands in the Greater Everglades (i.e., in A.R.M. Loxahatchee National Wildlife Refuge, Everglades National Park, Biscayne National Park). Although with previous MAP funding we were able to conduct system-wide monitoring of both species of crocodilians, we now focus on DOI lands where specific restoration projects are either already underway or beginning soon.

Work to be undertaken during the proposal year and a description of the methods and procedures:

During FY14, we will concentrate our work on:

Surveys will be conducted during the peak wet and dry seasons. Replicates using spotlight surveys along with capture surveys of alligators will be used to assess the relative distribution, abundance, and demographic structure of the American alligator. Established survey routes of estuarine rivers and freshwater marshes extending from the mangrove fringe of Everglades National Park north to US 41 and within Arthur R. Marshall National Wildlife Refuge will continue to be performed at night by skiff, airboat, and truck. Environmental data including habitat type, air and water temperature, salinity, wind, and spot water levels will be recorded. Regional hydrologic data will be obtained from the SFWMD and the USGS through EDEN. To determine demographic structure (size class and sex) structure, semi-annual capture surveys will be performed 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 (Leslie 1997).

Crocodile nesting effort and success will be determined by searching known and potential nesting habitat in the Cape Sable area of Everglades National Park during July and August activity (tail drags, digging or scraping) or the presence of eggs or hatchlings. Hatched eggshells or hatchling crocodiles are evidence of successful nests. The number and causes of egg failure will be noted whenever possible. Nesting surveys of active nest sites and areas of suitable nesting habitat will be performed by skiff and truck throughout the hatching period (July-August). Growth, survival, and body condition of crocodiles will be initiated by capturing and marking hatchlings during nest success surveys, and therefore available for recapture during future surveys. Crocodiles will be captured by hand or Pilstrom tongs. Total length, snout-vent length, and weight will be measured and all hatchlings will be scute clipped.

Specific Task Product(s): This study will develop an index of relative abundance and condition of crocodilians in different habitats in relation to water levels and salinities. The results will be reported in technical reports (such System Status Report and annual Spotlight Report), fact sheets, scientific and public presentations and peer-reviewed publications. The survey routes and data summaries are available via RECOVER website. The data from this study will be used to update and validate population models (e.g. ATLSS) and can be used for the development and validation of other assessment tools (i.e. HSI models).

Products & Delivery Date


Phenology of crocodile hatching in the Greater Everglades (including Turkey Point), to be submitted in September 2014

Mark-recapture analyses of crocodiles in the Greater Everglades, to be submitted by December 2015

Satellite-telemetry of alligators in the Shark River, Greater Everglades, accepted with revisions April 2014

Crocodile encounter rates in the Greater Everglades

Individual variation in movement rates and habitat use of American alligators in an oligotrophic subtropical estuary revealed by GPS telemetry

Finally, PI Mike Cherkiss is collaborating with other scientists on several related papers:

Cherkiss MS, Mazzotti FJ, Hord L, Aldecoa M (accepted with revisions April 2014) Remarkable Movements of an American Crocodile (Crocodylus acutus) in Florida. Southeastern Naturalist.

Mauger LA, Velez E, Cherkiss MS, Brien M, Bahder L, Bolonos-Montero JR, Mazzotti FJ, Spotila JR (submitted March 2014). Conservation Genetics and Gene Flow in the American Crocodile, Crocodylus Acutus, Populations on the Pacific Coast of Costa Rica. Nature Conservation.

Rosenblatt AE, Nifong JC, Heithaus MR, Mazzotti FJ, Cherkiss MS, Jeffery BM, Elsey R, Decker RA, Silliman BR, Guillette LJ, Lowers RH, Larson JC (submitted January 2014) Factors Affecting Individual Foraging Specialization and Temporal Diet Stability Across the Range of a Large "Generalist" Apex Predator. Oecologia.

Perez-Falcon, G.L., D.H. Sloan, T.W. Green, E.D. Swain, L.B. Stefanova, F.J. Mazzotti and M.S. Cherkiss. Modeling the Response of the American Crocodile (Crocodylus acutus) to Climate Change and Sea-level Rise (Florida, USA). Currently undergoing USGS peer review.

Perez-Falcon GL, Sloan DH, Green TW, Swain ED, Stefanova LB, Mazzotti FJ, Cherkiss MS Modeling the American Crocodile (Crocodylus acutus) population: linking climate, hydrology, and demography (Florida, USA). Currently undergoing USGS peer review.


Spatial ecology of the American Crocodile (Crocodylus acutus) in Everglades National Park. University of Florida Master's thesis (by Jeff Beauchamp) Spring 2014, completed.


Mazzotti FJ, Cherkiss MS, Hart KM, Crespo R, Farris S, Beauchamp J, Brandt LA and Jeffery BM (2014) The Role of the American Alligator (Alligator mississippiensis) and American Crocodile (Crocodylus acutus) as Indicators of Ecological Change in Everglades Ecosystems, Poster presentation, May 26-30, Crocodile Specialist Group meeting, Lake Charles, LA.

Beauchamp J, Hart KM, Mazzotti FJ, Cherkiss MS, Jeffery BM, Crespo R, and Fletcher R. (2014) Spatial ecology of the American Crocodile (Crocodylus acutus) in Everglades National Park, FL, Oral presentation, May 26-30, Crocodile Specialist Group meeting, Lake Charles, LA.

Cherkiss MS, Mazzotti FJ, Hart KM, Beauchamp J, Crespo R, Farris S, Briggs-Gonzalez V, and Brandt LA, Oral presentation, May 26-30, Crocodile Specialist Group meeting, Lake Charles, LA.

Task Leaders: Kristen Hart, Michael Cherkiss
Phone: 786-258-1409
FAX: 954-475-4125
Task priority: High

Literature Cited:

Fujisaki I, Mazzotti FJ, Hart KM, Rice KG, Ogurcak D, Rochford M, Jeffery BM, Brandt LA, Cherkiss MS (2012) Use of alligator hole abundance and occupancy rate as indicators for restoration of human-altered wetland. Ecological Indicators 23:627-633.

Leslie AJ (1997) The ecology and physiology of the Nile crocodile, Crocodylus niloticus, in Lake St. Lucia, Kwazulu/Natal, South Africa. PhD Dissertation: Drexel University, Philadelphia, PA.

Mazzotti FJ, Best GR, Brandt LA, Cherkiss MS, Jeffery BM, Rice KG (2009) Alligators and crocodiles as indicators for restoration of Everglades ecosystems. Ecological Indicators 9S(2009):S137-S149.

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