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projects > assessing the impacts of pythons in the greater everglades: examination of diet and thermal biology of python molurus bivittatus > work plan

Project Work Plan

Department of Interior USGS GE PES

Fiscal Year 2009 Study Work Plan

Study Title: Assessing the Impacts of Pythons in the Everglades: Examination of Diet and Thermal Biology of Burmese pythons (Python molurus bivittatus)
Study Start Date: 1 October, 2008
Study End Date: 30 September, 2009, with possibility of future funding tied to progress
Web Sites: www.sofia.usgs.gov
Duration: 12 months
Location (Subregions, Counties, Park or Refuge): Southern Florida, Everglades National Park, Big Cypress National Preserve, Crocodile Lake National Wildlife Refuge, John Pennycamp State Park (Miami-Dade, Monroe, and Collier Counties).
Funding Source: GE PES
Other Complementary Funding Sources: None
Funding History: GE PES FY2008
Principal Investigators: Kristen M. Hart, Frank J. Mazzotti, Michael E. Dorcas, Skip Snow
Study Personnel: Mike Rochford, Mike Cherkiss, Alex Wolf
Supporting Organizations: University of Florida, Davidson College, USNPS
Associated / Linked Studies: Movements and habitat use of Burmese pythons in the southern Everglades, Trap development for Burmese pythons

Overview & Objective(s): The Burmese python (Python molurus bivittatus), a native to Southeast Asia, can reach a length greater than twenty feet (Wall 1921, Pope 1961). This python is a long lived (15 - 25 years) behavioral, habitat, and dietary generalist, capable of producing large clutches of eggs (8 - 107) (Lederer 1956, Branch and Erasmus 1984). Observations of Burmense pythons exist in the United States primarily from locations within Everglades National Park (ENP), including; along the Main Park Road in the saline and freshwater glades, and mangroves, between Pay-hay-okee and Flamingo, the greater Long Pine Key area (including Hole-in-the-Donut), and the greater Shark Valley area along the Tamiami Trail (including L-67 Ext.). The non-native species has also been observed repeatedly on the eastern boundary of ENP, along canal levees, in the remote mangrove backcountry, and in Big Cypress National Preserve. From 2002 (when the numbers first began to climb) to 2005, 201 pythons were captured and removed or found dead. In 2006-2007 alone, that number more than doubled to 418. Measured total length for snakes recovered ranged from 0.5 m to 4.5 m including five hatchling-sized animals recovered in the summer of 2004, and two hatchlings captured in 2005.

The non-native semi-aquatic pythons's diet in southern Florida includes raccoon, rabbit, muskrat, squirrel, opossum, cotton rat, black rat, bobcat, house wren, pied-billed grebe, white ibis, limpkin, alligator and endangered Key Largo wood rat. As Python molurus is known to eat birds, and also known to frequent wading bird colonies in their native range, the proximity of python sightings to the Paurotis Pond and Tamiami West wood stork rookeries is troubling. The potential for pythons to eat Mangrove Fox Squirrels and Cape Sable Seaside Sparrows and to compete with Indigos Snakes is also of concern.

As do other non-native aquatic species, Burmese Pythons present a potential threat to successful ecological restoration of the greater Everglades (NRC 2005). Pythons are now established and breeding in South Florida. Python molurus bivittatus has the potential to occupy the entire footprint of the Comprehensive Everglades Restoration Project (CERP), adversely impacting valued resources across the landscape. Proposed management and control actions must include research strategies and further evaluation of potential impacts of pythons.

The results of this project will be applied to develop a comprehensive, science-based control and containment program. The proposed project will also increase our understanding of the impacts of Burmese pythons on native fauna in DOI and surrounding lands. Dealing with established species requires that we understand their status and impacts, and how to remove them. A current priority item for determining status is finding out the extent of invasion by established species. Once we know where the threat is occurring, we need a better understanding of how the threat may manifest itself ecologically-that is, what are the impacts of invasion? We can hypothesize that Burmese pythons compete with native snakes or affect populations of prey species; however, knowing with certainty that pythons eat wood rats better focuses eradication efforts and spurs action. A study of diet of Burmese pythons directly addresses this issue. Further, knowing how much pythons eat through a bioenergetic model allows us to forecast with more certainty predation impacts on native fauna.

Specific Relevance to Major Unanswered Questions and Information Needs Identified:

  • The proposed project responds to needs stated in the DOI Science Plan for research to develop effective control methods for exotic aquatic vertebrates, for research into the life history of non-native species, and to determine impacts of exotic species on native species on federally managed lands.
  • Specific projects that could affect the ultimate distribution and abundance of pythons in southern Florida include the Combined Structural and Operational Plan (CSOP) for modified water deliveries to Everglades National Park and Decompartmentalization of Water Conservation Area 3 (Decomp).
  • In January of 2008 a workshop on setting priorities for python-related research was convened. A high priority item identified for python control by participants was "Integrating Science and Management - Improving Our Understanding of the Current Range and Status of Burmese Python Snakes." Within this topic identifying at-risk populations of protected species vulnerable to predation and determining extent of risk to vulnerable native fauna were designated as important tasks to be accomplished.

Status: We are drawing on the collective knowledge gained by our USGS colleagues Reed and Rodda from battling reptile invasions elsewhere, primarily brown tree snakes on Pacific Islands. Important lessons learned from these areas are that invasions have to be taken seriously, the response needs to be immediate, comprehensive and thorough, and that research is instrumental in developing effective control and containment measures (Colvin et al. 2005). For example, natural history information such as diet, thermal biology, movements and habitat use can be used to determine how to design, deploy, and bait traps, evaluate impacts on native species, and develop recommendations for habitat modification (e.g. clearing or mowing vegetation) and ecosystem restoration (e.g. removal of levees and re-establishment of hydrological patterns).

Studies on movement and habitat use (radio-telemetry) and trap development are currently underway in Everglades National Park and adjacent lands managed by the South Florida Water Management District. We will conduct research on diet and thermal biology, and synthesize information obtained in this project with other studies to evaluate risks of pythons to native fauna, and to make recommendations for trapping programs.

Planned Products: We will present an overview talk of the Burmese python project and the initial results of analysis of python diet samples at the October 2008 meeting of the Florida Integrated Science Center in Orlando. We plan to submit one manuscript on the results of the diet study and a separate manuscript on the results of the thermal biology to peer-reviewed journals. We also anticipate attending one international meeting in 2009 to present the synthesis of study results.

WORK PLAN

Title of Task 1: Diet of Burmese pythons
Task Funding: GE PES
Task Leaders: Kristen M. Hart, Frank J. Mazzotti
Phone: 954-650-0336
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 1: 2009
Task Personnel: Mike Rochford, University of Florida

Task Summary and Objectives:

One purpose of this project is to provide science support to evaluate impacts of pythons on native biological diversity. To this end, we will determine the diet of Burmese pythons removed from Everglades National Park in 2008 (banked) and 2009 (currently being collected).

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

We continue to examine the stomach and lower gastro-intestinal tracts of euthanized pythons. Methods involve extracting and washing the stomach and gastro-intestinal tract of each individual python with ethanol, followed by close stereoscopic examination for feathers, hair, teeth, bone fragments, claws and scales. An attempt is made to identify mammal, bird and reptile remains to lowest taxonomic level possible.

Specific Task Product(s):

Peer-reviewed manuscript.

Title of Task 2: Thermal biology of Burmese pythons
Task Funding: GE PES
Task Leaders: Michael Dorcas, Frank J. Mazzotti
Phone: 954-577-6304
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 2: 2009
Task Personnel: Michael Dorcas, Davidson University and Skip Snow, Everglades National Park

Task Summary and Objectives:

To evaluate the impacts of pythons on native biological diversity and development of control measures for Burmese pythons, we must monitor temperature of pythons.

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

To record body temperatures of free-ranging Burmese pythons, we will surgically implant miniature, temperature sensitive data-loggers (micro-dataloggers) while tracking their movements using radio-telemetry. Dataloggers will be coated with plastic tool dip before implantation into the body cavity, and we will program them to record temperature every 30 minutes. After a period of time (e.g., one year), we will surgically remove the data-loggers and download the data. We will take simultaneous measurement of environmental temperatures using biophysical snake models (constructed to have the same thermal properties as live snakes) in different thermal environments to allow detailed interpretation of data that can be used for bioenergetic modeling and determination of activity patterns (see below, Task 3).

Specific Task Product(s):

Peer-reviewed manuscript.

Title of Task 3: Preliminary conceptual bioenergetic model for Burmese pythons.
Task Funding: GE PES
Task Leaders: Frank J. Mazzotti, Kristen M. Hart, Skip Snow
Phone: 954-577-6304
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 3: 2009
Task Personnel: Mike Rochford

Task Summary and Objectives:

To fully evaluate the impacts of pythons on native biological diversity, we must synthesize what is known with the new information provided in Task 1 and Task 2 to develop a preliminary conceptual bioenergetic model for Burmese pythons. While we will know what they are eating from Task 1 (Diet of Burmese pythons) and we will have thermal profiles for tagged pythons (Task 2 (Thermal biology of Burmese pythons), we seek to quantify the number and type of each specimen that they may be eating. This type of "impact" has not yet been quantified for this exotic species.

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

To develop a preliminary conceptual bioenergetic model, we must account for the metabolic rate (i.e., energy use) which is dependent on body temperature for pythons. We will determine the energetic requirements of Burmese pythons using measurements of metabolic rates of pythons at a range of body temperatures and develop mathematical models that will predict metabolic rate using temperature and snake mass. Other factors affecting energetic requirements of pythons (i.e., food processing, growth, reproduction, locomotion) will be incorporated into the models for more comprehensive predictions of energetic requirements of pythons in southern Florida.

Specific Task Product(s):

Conceptual model.

Title of Task 4: Inform removal programs.
Task Funding GE PES
Task Leaders: Frank J. Mazzotti, Kristen M. Hart, Michael Dorcas
Phone: 954-577-6304
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 4: 2009
Task Personnel: Mike Rochford

Task Summary and Objectives:

We will synthesize results of Task 2 (Thermal biology of Burmese pythons) along with radio-tracking results to understand python activity and movement patterns. Temperature affects nearly every aspect of snake biology, and understanding thermal biology allows detailed inferences regarding activity and microhabitat use of pythons providing data. Such data can be used for the development of more effective python control mechanisms. Because we will use micro-dataloggers to automatically monitor the body temperatures of free-ranging pythons in Task 2, we will use resulting data to develop a better understanding of python activity, microhabitat use, and feeding. Such data will allow better predictions of when animals are exposed and visible, and thus available for capture and removal. Thermal data also may indicate when pythons are feeding helping to determine whether it is better to bait or not to bait python traps.

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

We will analyze the results of data obtained in Task 1 and Task 2 and synthesize the results for management. In sum, we will use resulting data to develop a better understanding of python activity and microhabitat use. Such data will allow better predictions of when animals are exposed and visible, and thus available for capture and removal.

Specific Task Product(s):

Peer-reviewed manuscript for Journal of Wildlife Management.

Literature Cited

Branch, W. R. and H. Erasmus. 1984. Captive breeding of pythons in South Africa, including details of an interspecific hybrid (Python sebae natalensis x Python molurus bivittatus). Journal of the Herpetological Association of Africa 1984(30):1-10.

Colvin, B. A., Fall, M. W., Fitzgerald, L. A., and L. L. Loope. 2005. Review of Brown Treesnake problems and control programs: Report of observations and recommendations. Report to Office of Insular Affairs, Honolulu, Hawaii.

Lederer, G. 1956. Fortpflanzungsbiologie und Entwicklung von Python molurus molurus (Linne) und Python molurus bivittatus (Kuhl). Die Aquarien- Und Terrarien-Zeitschrift 9:243-248.

National Research Council. 2005. Re-engineering storage in the Everglades: Risks and opportunities. National Academies Press. Washington. DC.

Pope, C. H. 1961. The giant snakes. Alfred A. Knopf, New York.

Wall, F. 1921. Ophidia Taprobanica or the Snakes of Ceylon. Govt. Printer, Colombo.



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