Home Archived October 29, 2018
(i)
USGS Home
SOFIA Home

Spatial and Age-Structured Population Model of the American Crocodile for Comparisons of CERP Restoration Alternatives

Metadata also available as - [Questions & Answers] - [Parseable text] - [XML]

Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator:
Daniel H. Slone

Kenneth G. Rice; Frank J. Mazzotti

Publication_Date: Unpublished Material
Title:
Spatial and Age-Structured Population Model of the American Crocodile for Comparisons of CERP Restoration Alternatives
Online_Linkage:
<https://sofia.usgs.gov/projects/index.php?project_url=pop_model_croc>
Description:
Abstract:
To adequately understand crocodile populations and model population growth, existing data must be assembled and model parameters estimated. A simulation model can then be constructed and validated both with existing data and through expert opinion. A crocodile population model to simulate the south Florida ecosystem under varying management strategies is vital to evaluating and assessing restoration success under CERP.

The objectives of this project are to:

1. Build an age and spatially structured crocodile population model suitable for comparison of CERP restoration alternatives. 2. Couple the local age-structured models into a spatial dispersal model incorporating crocodile movement behavior. 3. Use spatial parameter maps from the Florida Everglades as driving functions on the spatially structured model and to construct crocodile finite rate of increase maps under different management regimes. 4. Perform sensitivity analysis on the model parameters, and release model concept and code for peer-review.

Purpose:
The American crocodile (Crocodylus acutus) is a federally endangered top consumer in south Florida, imperiled primarily by habitat loss due to expansion of a rapidly growing human population along coastal areas of Palm Beach, Broward, Dade, and Monroe counties. This loss of habitat has principally affected the nesting range of crocodiles, restricting nesting to a small area of northeastern Florida Bay and northern Key Largo by the early 1970's. When crocodiles were listed as endangered in 1975, scant data were available for making informed management decisions. Field and laboratory data suggested that low nest success, combined with high hatchling mortality, provided a dim prognosis for survival. Because of their small size, hatchling crocodiles are vulnerable to biotic and abiotic stressors, such as high levels of salinity. To grow and survive, hatchling crocodiles need to find food and benign environmental conditions (or at least avoid harsh conditions) and avoid predators. Diminished growth rates and higher mortaity or dispersal rates have been associated with areas that pose greater risk to hatchling crocodiles.

Crocodiles now occur in most of the habitat that remains for them in southern Florida. Most of the remaining habitat is currently protected in public ownership or engaged in energy production. In these areas, further loss of habitat is not an issue. However, questions of potential habitat modification through continued alteration of freshwater flow due to upstream development and potential curtailment of the range of crocodiles need to be addressed. Patterns of nesting, relative abundance and distribution, growth, and survival of crocodiles can provide insight into restoration of coastal ecosystems in Southeast Florida. For both Florida Bay and Biscayne Bay, restoring a more natural pattern of freshwater flow would provide the most benefit. Characteristics of flow patterns into Florida and Biscayne Bays that are beneficial for crocodiles include sheet flow through the fringing mangrove swamp that extends well into the dry season. Mid-to late dry season discharges of freshwater that cause a reversal of water levels in the receiving body are hypothesized to cause a dispersal of prey items, making them less available to crocodiles. If so, such discharges should be avoided. Shifting water delivery from Biscayne Bay to Florida Bay would degrade the quality of habitat in Biscayne Bay for crocodiles.

Restoration efforts in the Comprehensive Everglades Restoration Plan (CERP) will likely cause changes to salinity levels throughout the habitat of the American crocodile. Changes in salinity were seen after previous hydrologic changes in the area, when reduced freshwater flow was associated with increased salinity levels in Florida Bay estuaries, including one of the core nesting areas of the American crocodile. Large crocodiles are not significantly affected by high salinity, but previous work has shown that high salinity levels may reduce survival of hatchlings and juveniles. The detrimental effects of high salinity on hatchling and juvenile crocodiles has led to the hypothesis that increased freshwater flow to the estuaries will increase the animals' distribution, abundance, and growth.

Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 2008
Ending_Date: 2009
Currentness_Reference: ground condition
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Description_of_Geographic_Extent: southern Everglades
Bounding_Coordinates:
West_Bounding_Coordinate: -81.42
East_Bounding_Coordinate: -80.28
North_Bounding_Coordinate: 26.68
South_Bounding_Coordinate: 25.21
Keywords:
Theme:
Theme_Keyword_Thesaurus: none
Theme_Keyword: crocodiles
Theme_Keyword: model
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: biota
Theme_Keyword: environment
Theme_Keyword: 002
Theme_Keyword: 007
Place:
Place_Keyword_Thesaurus:
Department of Commerce, 1995, Countries, Dependencies, Areas of Special Sovereignty, and Their Principal Administrative Divisions, Federal Information Processing Standard (FIPS) 10-4, Washington, DC, National Institute of Standards and Technology
Place_Keyword: United States
Place_Keyword: US
Place:
Place_Keyword_Thesaurus:
U.S. Department of Commerce, 1987, Codes for the identification of the States, the District of Columbia and the outlying areas of the United States, and associated areas (Federal Information Processing Standard 5-2): Washington, DC, NIST
Place_Keyword: Florida
Place_Keyword: FL
Place:
Place_Keyword_Thesaurus:
Department of Commerce, 1990, Counties and Equivalent Entities of the United States, Its Possessions, and Associated Areas, FIPS 6-3, Washington, DC, National Institute of Standards and Technology
Place_Keyword: Miami-Dade County
Place_Keyword: Collier County
Place_Keyword: Monroe County
Place:
Place_Keyword_Thesaurus: USGS Geographic Names Information System
Place_Keyword: Everglades National Park
Place:
Place_Keyword_Thesaurus: none
Place_Keyword: Central Everglades
Taxonomy:
Keywords/Taxon:
Taxonomic_Keyword_Thesaurus: ITIS
Taxonomic_Keywords: animals
Taxonomic_System:
Classification_System/Authority:
Classification_System_Citation:
Citation_Information:
Originator:
U.S. Department of Agriculture - Agricultural Research Service (ARS)

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)

Publication_Date: 2000
Title: Integrated Taxonomic Information System (ITIS)
Geospatial_Data_Presentation_Form: Database
Other_Citation_Details:
Retrieved from the Integrated Taxonomic Information System on-line database, <http://www.itis.gov>.
Online_Linkage: <http://www.itis.gov>
Taxonomic_Procedures: unknown
Taxonomic_Completeness: unknown
General_Taxonomic_Coverage: American crocodiles are identified to the species level
Taxonomic_Classification:
Taxon_Rank_Name: Kingdom
Taxon_Rank_Value: Animalia
Applicable_Common_Name: animals
Taxonomic_Classification:
Taxon_Rank_Name: Phylum
Taxon_Rank_Value: Chordata
Applicable_Common_Name: chordates
Taxonomic_Classification:
Taxon_Rank_Name: Subphylum
Taxon_Rank_Value: Vertebrata
Applicable_Common_Name: vertebrates
Taxonomic_Classification:
Taxon_Rank_Name: Class
Taxon_Rank_Value: Reptilia
Applicable_Common_Name: reptiles
Taxonomic_Classification:
Taxon_Rank_Name: Order
Taxon_Rank_Value: Crocodilia
Applicable_Common_Name: alligators
Applicable_Common_Name: crocodiles
Taxonomic_Classification:
Taxon_Rank_Name: Family
Taxon_Rank_Value: Crocodylidae
Applicable_Common_Name: crocodiles
Taxonomic_Classification:
Taxon_Rank_Name: Genus
Taxon_Rank_Value: Crocodylus
Applicable_Common_Name: crocodiles
Taxonomic_Classification:
Taxon_Rank_Name: Species
Taxon_Rank_Value: Crocodylus acutus
Applicable_Common_Name: American alligator
Access_Constraints: none
Use_Constraints: none
Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Tim Green
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical address
Address:
Crown Pointe

2201 NW 40th Terrace

City: Gainesville
State_or_Province: FL
Postal_Code: 32605
Country: USA
Contact_Voice_Telephone: 352 264-3556
Contact_Facsimile_Telephone: 352 374-8080
Contact_Electronic_Mail_Address: tgreen@usgs.gov
Data_Set_Credit: Project personnel includes Timothy W. Green
Cross_Reference:
Citation_Information:
Originator:
Slone, D. H.

Rice, K. G.; Allen, J. C.

Publication_Date: 2003
Title:
Model evaluates influence of Everglades restoration plan on alligator populations (Florida)
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: Ecological Restoration
Issue_Identification: V. 21, n. 2
Publication_Information:
Publication_Place: Madison, WI
Publisher: University of Wisconsin Press
Cross_Reference:
Citation_Information:
Originator:
Mazzotti, F. J.

Cherkiss, M. S.

Publication_Date: 2003
Title:
Status and Conservation of the American Crocodile in Florida: Recovering an Endangered Species While Restoring an Endangered Ecosystem
Geospatial_Data_Presentation_Form: report
Series_Information:
Series_Name: Technical Report
Issue_Identification: Final report V. 1
Publication_Information:
Publication_Place: Ft. Lauderdale, FL
Publisher:
University of Florida, Ft. Lauderdale Research and Education Center
Other_Citation_Details:
Prepared for the National Park Service

accessed as of 6/29/2010

Online_Linkage:
<http://crocdoc.ifas.ufl.edu/research/reports/american_croc2003.pdf>

Data_Quality_Information:
Logical_Consistency_Report: unknown
Completeness_Report: unavailable
Lineage:
Methodology:
Methodology_Type: Lab
Methodology_Description:
We will estimate population parameters of the crocodile across hydrological and habitat gradients from available databases (Mazzotti and Cherkiss 2003). Through the development of population simulation models based on these empirical data, we will evaluate restoration alternatives and assess restoration performance measures. By applying crocodile models to restoration alternatives and predicting population responses, we can choose alternatives that result in biotic characteristics that best approach historical conditions and identify future research needs.
Process_Step:
Process_Description:
The methods we will use for the American crocodile population model will be similar to those used in the ATLSS model of American alligator growth and dispersal, authored by D.H. Slone, J.C. Allen, and K.G. Rice (Slone et al. 2003), though there will necessarily be several major changes made to accommodate the different use of habitat, different driving parameters (salinity), and different dispersal parameters for crocodiles. We prefer a stage-space based model rather than an individual-based model for this purpose because it allows us to simultaneously evaluate landscape effects on each stage of the crocodile, and predict spatial density patterns and population size with much greater computational efficiency.

The crocodile model will be based on the ATLSS Alligator Population Model, which has been completed and has undergone expert review, calibration, and some validation. An Ecologist was hired late in FY-2007 to work on this task. He has begun training in Matlab programming, and is reviewing the alligator model. Meetings with crocodilian biologists are planned for the near future to outline changes that need to be made from the alligator model, and to begin parameterization of the crocodile model.

In FY2008 we will:

1. Build an age and spatially structured crocodile population model suitable for comparison of CERP restoration alternatives. 2. Couple the local age-structured models into a spatial dispersal model incorporating crocodile movement behavior.

In objective 1, we will represent the age-structured crocodile population as a 3-dimensional array indexing the number in an age group at a spatial location with space assumed to be 2-dimensional, subject to the effects on crocodile parameters relative to the hydrology effects brought on by elevation changes. The net effect will be that we can still use a 2-d spatial representation of the population. We will use a size-class structured version with a Lefkovitch projection matrix having partial class development in each time step. We note that since we can construct the projection matrix at each location, then we can obtain its largest eigenvalue, which will indicate whether the population will increase (l > 1) or decrease (l < 1) at each location. This will enable us to make maps of crocodile population growth and decline over time.

In objective 2, we will include movement and dispersal of certain age groups in the spatial map. We will introduce spatial structure into ecological models by using a discrete spatial convolution model

Process_Date: 2008
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Tim Green
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical address
Address:
Crown Pointe

2201 NW 40th Terrace

City: Gainesville
State_or_Province: FL
Postal_Code: 32605
Country: USA
Contact_Voice_Telephone: 352 264-3556
Contact_Facsimile_Telephone: 352 374-8080
Contact_Electronic_Mail_Address: tgreen@usgs.gov

Metadata_Reference_Information:
Metadata_Date: 20100630
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Heather Henkel
Contact_Organization: U.S. Geological Survey
Contact_Address:
Address_Type: mailing and physical address
Address: 600 Fourth Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: 727 803-8747 ext 3028
Contact_Facsimile_Telephone: 727 803-2030
Contact_Electronic_Mail_Address: sofia-metadata@usgs.gov
Metadata_Standard_Name:
Content Standard for Digital Geospatial Metadata Part 1: Biological Data Profile
Metadata_Standard_Version: FGDC-STD-001.1-1999
Metadata_Access_Constraints: none
Metadata_Use_Constraints:
This metadata record may have been copied from the SOFIA website and may not be the most recent version. Please check <https://sofia.usgs.gov/metadata> to be sure you have the most recent version.

This page is <https://sofia.usgs.gov/metadata/sflwww/pop_model_am-croc.html>

U.S. Department of the Interior, U.S. Geological Survey
Comments and suggestions? Contact: Heather Henkel - Webmaster
Generated by mp version 2.8.18 on Wed Jun 30 09:52:07 2010