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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 2010 Study Work Plan

Study Title: Assessing the Impacts of Pythons in the Greater Everglades: Examination of Diet and Thermal Biology of Python molurus bivittatus
Study Start Date: 1 October, 2008
Study End Date: 30 September, 2010, with possibility of future funding tied to progress
Web Sites:
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, GE PES FY2009
Principal Investigators: Kristen M. Hart, Frank J. Mazzotti, Michael E. Dorcas, Skip Snow
Study Personnel: Mike Rochford, Mike Cherkiss (FL REC)
Supporting Organizations: University of Florida, Davidson College, USNPS
Associated / Linked Studies: Movements and habitat use of Burmese pythons in the Greater Everglades, Trap Trial in the Frog Pond to Capture Burmese pythons (Collaboration with USGS PIs Reed and Rodda, NPS PI Snow, and UF PIs Mazzotti and Cherkiss)

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 Burmese 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. In 2008, 343 pythons were removed, and so far in 2009, 347 individuals have been removed.

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.

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 exotic 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, for example, 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 (radiotelemetry) and trap development are currently underway in Everglades National Park and adjacent lands managed by the South Florida Water Management District. We are also synthesizing the thermal data from snakes implanted with thermal data loggers for a peer-reviewed publication with Mike Dorcas (Davidson College), and the python diet data for another peer-reviewed publication in Biological Conservation. We are synthesizing information obtained in this project with other studies to evaluate risks of pythons to native fauna, and to make recommendations for further trapping programs and trap deployment strategies.

Planned Products: We are in the process of analyzing and writing up several manuscripts, all which should be completed in FY2010. These manuscripts include major synthesis of python radiotelemetry data, diet data, and thermal data. We also anticipate attending one national meeting in 2010 to present the synthesis of study results. We will also present these results at the 2010 Greater Everglades Ecosystem Restoration conference in Naples in July.


Title of Task 1: Diet of Burmese pythons
Task Funding: GE PES
Task Leaders: Kristen M. Hart, Frank J. Mazzotti (UF FL REC)
Phone: 954-577-6335
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 1: 2010
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 still 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, likely to be submitted to Biological Conservation because of the high-impact factor and the high-profile nature of the Burmese python issue for the Everglades.

Title of Task 2: Thermal biology of Burmese pythons
Task Funding: GE PES
Task Leaders: Kristen M. Hart, Michael Dorcas, Frank J. Mazzotti
Phone: 954-577-6335
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 2: 2010
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 which serves as a proxy for activity levels.

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 surgically implant miniature, temperature sensitive data-loggers (micro-dataloggers). We also radiotag each snake to track their movements. Dataloggers are coated with plastic tool dip before implantation into the body cavity, and we program each logger 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: 954-577-6335
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 3: 2010
Task Personnel: Mike Cherkiss, Mike Rochford (UF FL REC), and Nick Whitney (Mote Marine Lab)
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. We will also use the thermal data in particular to determine when pythons may be more available for removal, i.e., when they may be basking more and out on levees and roads. Such time periods would be ideal targets for python census and removal programs. A new test of python accelerometers also looks promising for determining very fine scale python activity patterns.

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 are in the process of determining the energetic requirements of Burmese pythons using measurements of metabolic rates of pythons at a range of body temperatures. To this end, we are starting to 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. We are also excited about the first pilot test of accelerometers on pythons to account for very fine scale activity patterns. Future plans to implant the devices inside pythons that are then re-released into the wild are planned for early 2010.

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: 954-577-6335
Task Status (proposed or active): Active
Task priority: High
Budget and Time Frame for Task 4: 2010
Task Personnel: Mike Cherkiss, Mike Rochford (UF FL REC)
Task Summary and Objectives: We are synthesizing 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 use micro-dataloggers to automatically monitor the body temperatures of free-ranging pythons in Task 2, our resulting data allows us 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 along with very fine scale activity information (derived from a current pilot study with accelerometers) also may indicate when pythons are feeding helping to determine whether it is better to bait or not to bait python traps that may be deployed within the Greater Everglades to protect native resources.

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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