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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (GE PES) Initiative

Fiscal Year 2007 Project Summary Report

Study Title: Computer Simulation Modeling of Intermediate Trophic Levels for Across Trophic Level Systems Simulation of the Everglades/Big Cypress Region
Study Start Date: 1997 Study End Date: 12/31/08
Web Sites: ATLSS.ORG
Location: The Greater Everglades ecosystem
Funding Source: ENP Critical Ecosystem Studies Initiative (ENP CESI)
Principal Investigator: Michael S. Gaines, Department of Biology, University of Miami, Coral Gables, FL 33124 Phone: 305-284-3974 e-mail:
Study Personnel: Donald L. DeAngelis, Phone: 305-284-1690 e-mail:
Other Supporting Organizations: USGS/BRD, NPS, ACE, EPA
Associated Projects: Component of ATLSS Program

Overview & Objectives: This project has had the goal of developing models for key components of the Everglades landscape as part of the overall Across Trophic Level System Simulation. Past research has developed the basic model for freshwater fish biomass and a model of energy flow in the reptile and amphibian community. Current work has involved modeling and empirical studies on the snail kite, small mammals, and the oak toad. The objectives have been to understand the effects of hydrologic conditions on each of these taxa.

Status: No new PES money has been added to this project and existing funding has been extended through a no-cost extension to the December 31, 2007, and will be extended further into 2008. However, the University of Miami has received funding from the U. S. Fish and Wildlife Service to continue funding of the EVERKITE model. Small mammal research by Dr. Gaines will continue under other funding.

Recent Products:

Snail kite modeling:
The current version of EVERKITE is perceived as a useful tool by Department of Interior agencies, but the fact that the spatial resolution of the model is only at the wetland level is seen as a drawback. Also, the model is still difficult to operate by the agencies themselves. Finally, our scientific understanding of the functioning of the kite population in southern and central Florida has progressed since the wetland-based version of EVERKITE was developed. For these reasons, we propose a major revision of the EVERKITE model to improve its accuracy and make it easier for agencies working on Everglades restoration to use the model.

A postdoctoral student, Irene van der Stap, is being supported by USFWS to improve EVERKITE in several ways. DeAngelis is working with her under his support from FISC and GEPES funds. The following tasks are about 1/2 accomplished

  • improvement of the resolution of EVERKITE a grid-based version of this model will be developed, probably using the SFWMM 2*2 mile grid with an extension to the north to cover the northern range of the kites.
  • improvement of the ability of agencies to use EVERKITE, a simple but effective user-interface to the grid-based version will be developed with the specific aim to allow the agencies to independently produce grid-based output on critical parameters of the kite population for each hydrological scenario that produces grid-based water levels for the SFWMM grid and the northern wetlands/lakes.
  • improvement of the accuracy of EVERKITE, new empirical information will be included in the model on the vital rates and movement rules of the kites in response to hydrological and successional changes in their habitat. A strategy will be developed for inclusion of new empirical knowledge in future versions of the model.

Recent papers and presentations:

Mooij, W. M., J. Martin, W. M. Kitchens, and D. L. DeAngelis. 2007. Exploring the temporal effects of seasonal water availability on the snail kite of Florida. Pages 155-173, in Pulsed Resources and Wildlife Population Response: The Importance of Time. Editors: John Bissonette and Ilse Storch. Springer-Verlag Publisher.

Small mammal studies:
We have completed the initial analysis of an eleven-year mark-recapture study of two common small mammal species (Sigmodon hispidus, and Oryzomys palustris) of the Everglades National Park, Florida, USA. Data were collected monthly on 17 tree-islands by Dr. Michael S. Gaines and his graduate students for nearly 109 consecutive months. The results of this analysis revealed two interesting insights into the natural history of these species: 1) Large islands appear to be the source of cotton rat recruits. Sixty-five percent of reproductively active adults and 82 % of juveniles were captured on large islands. 2) Contrary to our expectations, water-levels did not significantly influence the average movement distance of hispid cotton rats or marsh rice rats, and movement distances did not differ between the species. This was surprising because unlike the marsh rice rat, the cotton rat is not a semi-aquatic species. The results of this analysis suggest that the decrease in tree island size, and overall area will likely negatively influence the small mammal community by affecting population recruitment rates.

A report on the 11-year study is in preparation. Also, a Habitat Suitability Index for small mammals will be produced, but currently the statistical results are not strong enough to produce an HSI. Better statistical methods are being sought.

Recent presentations:

Fernandes, Miguel V., Donald DeAngelis, and Michael S. Gaines. 2007. The effects of tree island size and water depth on population patterns of the cotton rat (Sigmodon hispidus) and marsh rice rat (Oryzomys palustris) in the Florida Everglades. Poster at Ecological Society of America Annual Meeting, San Jose, CA

Gaines, M. S., D. L. DeAngelis, M. Fernandes, J. Warren, and H. Beck. 2006. Effects of Patch Size and Hydrology on Population Dynamics of Small Mammals in the Everglades. GEER Meeting, Lake Buena Vista, FL

Gaines, M. S. 2006. Effects of Habitat Patchiness on Small Mammal Populations in Everglades National Park. June 2006, University of Tokyo.

Everglades Landscape Modeling
DeAngelis is working with Leo Sternberg (U. of Miami) and Tom Smith (USGS) on an Everglades vegetation pattern issue.

Recent papers:

Teh, S. Y., D. L. DeAngelis, L. S. L. Sternberg, F. R. Miralles-Wilhelm, and T. J. Smith. Disturbance events can cause regime shifts between vegetation types: A model study of mangroves and hardwood hammocks. (In press, Ecological Modelling.)

Sternberg, L. da S. L, S.-Y. Teh, S. Ewe, F. Miralles-Wilhelm, and D. L. DeAngelis. Competition of hardwood hammock and mangrove vegetation. (In Press, Ecosystems).

Related papers:

Liu, R., Z. Feng, H..Zhu, and D. L. DeAngelis. Bifurcation analysis of a plant herbivore model with toxin-determined functional response. (Submitted to Journal of Differential Equations)

Feng, Z., R. Liu, and D. L. DeAngelis. Plant-herbivore interactions mediated by plant toxicity. (Submitted to Theoretical Population Biology, revision requested.)

Ruan, S., A. Ardito, P. Ricciardi, and D. L. DeAngelis. Coexistence in competition models with density dependent mortality. (In press, CR Biologies)

Fish Modeling

This project is focused on improving on ATLSS's fish modeling capabilities and make these readily usable in South Florida. DeAngelis, under FISC and GEPES funding, is working with Joel Trexler (FIU) to accomplish this goal. The new model (GEFISH), supercedes ALFISH.

Related papers:

Beeck, P., D. L. DeAngelis, H. Doerner, and J. Borcherding. Piscivory in combination with bimodal size distribution in young-of-the-year Eurasian perch: an overlooked phenomenon? (Submitted to Oikos.)

Petersen, J. H., D. L. DeAngelis, and C. P. Paukert. Developing bioenergetics and life history models for rare and endangered species. (In press, Transactions of the American Fisheries Society.)

Planned Products: Work is continuing in the following directions:

Snail kite population modeling.

  • SFWMM 2*2 mile grid with an extension to the north to cover the northern range of the kites.
  • simple but effective user-interface to the grid-based version will be developed with the specific aim to allow the agencies to independently produce grid-based output
  • To improve the accuracy of EVERKITE, new empirical information will be included in the model

These will be produced by February, 2008

Small mammal studies

  • Final report on project and manuscripts for publication are in preparation
  • Habitat suitability index will be developed for the two species O. palustris than S. hispidus

These have been delayed because of but are being worked on

Everglades Landscape modeling

  • Testing of model using stable isotopes at U. of Miami

Fish modeling

Testing of GEFISH model and use in exploring hypotheses on what controls fish biomass as a function of hydroperiod and nutrients.

Key Findings:

  1. Extension of EVERKITE to examine the effects of intrannual variation in water depths
  2. GEER presentation of major results of 11-year study of small mammals in the Everglades.
  3. Paper showing that storm surge events can cause major shifts in mangrove - hardwood hammock boundaries.

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