Movements, Habitat Use, Diet, Thermal Biology, and Trapping of Burmese Pythons in the Southern Everglades Kristen M. Hart1, Michael S. Cherkiss2, Michael R. Rochford2, Skip Snow3, Michael E. Dorcas4, Gordon H. Rodda5, Robert N. Reed5, Ron Rozar5, Frank J. Mazzotti2

Introduction Thermal biology The Burmese python (Python molurus bivittatus) (Figure 1), native to Southeast Asia, are an established invasive species in south Florida. This species has the potential to adversely affect their new environment. The presence of Burmese pythons is especially troublesome Activity Patterns because the vast expanses of suitable habitats (both disturbed and undisturbed) and subtropical climate of the Greater Everglades may enable the species to thrive. The purpose of this project is to provide scientific support to develop control measures for Burmese pythons and to Monitoring python body temperatures can help us understand activity patterns and habitat use to develop more effective control methods. To evaluate impacts of pythons on native biological diversity through radio telemetry and habitat utilization, thermal biology, gut content maintain body temperatures within preferred ranges, pythons thermoregulate by moving among various microhabitats. Continuous measurements of analysis, and reproduction. snake and environmental temperatures allow researchers to determine when snakes are active and what microhabitats they are using.

Radio telemetry and habitat utilization Figure 1. Female Burmese python in Pa-hay- okee Hammock, Everglades National Park Little ecological information exists for Burmese pythons in their native range. Therefore, it is Energetics important to learn more about the distances and timing of pythons’ movements, as well as which Temperature data can also provide insight into python feeding frequencies and energetic requirements to help estimate pythons’ predatory impacts on habitats they are utilizing. native species. Since reptiles’ metabolic rates are dependent on temperature, mathematical models can be developed to predict pythons’ energetic Methods requirements based on body temperature. The models use temperature, snake mass, and other factors affecting energetic requirements of pythons (i.e. food processing, growth, reproduction, and locomotion) to estimate metabolic rate and thus, the number and type of prey items needed by the snake. • Since December 2005, we surgically implanted 37 Burmese pythons each with 2 radio When python models are run, they will provide estimates of predation levels that can be combined with diet analyses (described above) to better transmitters. predict impacts of pythons on native fauna. Using these data, we hope to provide information on python thermal biology, behavior, and activity that will assist in a better understanding of their overall ecology and development of effective population controls. • The snakes were released in Everglades National Park (ENP) (e.g. Figure 2). • Pythons are tracked weekly via fixed-wing aircraft (Figure 3) and on the ground Methods Results (Figure 4) to check health and presence of additional pythons. Figure 2. Example map of python habitat use in Figure 4. Ground tracking python in Everglades National Park •Radio-telemetered pythons were surgically implanted with •During most winters and early spring, pythons maintain body temperatures Coot Bay mangroves Results Onset Computer Tidbit temperature data loggers set to between 20-33°C and rarely dropped below 15°C (Figure 9). record temperature every 30 minutes (Figure 7). • Translocated pythons made long distance movements (up to 78 km), especially during periods of high water, and have shown tremendous dispersal abilities. •During late spring and summer, variation in body temperatures decreased and maximal body temperatures increased, but pythons rarely exceeded 35°C. • Pythons actively avoided areas of dry land during movements. •Data loggers were installed in ENP and downloaded monthly to record environmental temperatures in standing • Tracking pythons on the ground led researchers to breeding aggregations of pythons, allowing removal of more than 20 additional pythons from the Florida population. water bodies, as well as in terrestrial habitats using •In January of 2010 we experienced record low temperatures resulting in the biophysical models of pythons (Figure 8). deaths of 9 of the 10 telemetered pythons in the field at the time of the cold spell • We gained valuable data on habitat use through aerial and ground tracking (Figures 2 - 4). but 59 of 99 (60%) of non-telemetered found in the field after the cold snap were alive. Gut content analysis Burmese pythons are large generalist predators that consume a wide variety of Table 1. Prey items eaten by pythons found in Table 1 continued. vertebrates in their native range. It is important to assess which Everglades species Greater Everglades are at risk of predation by these large constrictors; this can be accomplished by Prey examining the gut contents of captured pythons. # Prey Mammals 340 # Rattus (Old World rats) 58 Birds 107 Figure 9. Temperatures of 3 pythons, water, air, and thermal python models during winter of 2006 Methods Sigmodon (Cotton rat) 141 unidentified 49 Figure 7. Temperature data logger Figure 8. Biophysical python model Sylvilagus (Cottontail rabbit) 14 Rallidae (sp. undetermined) 9 • Gut contents were removed from pythons, cleaned, and examined. Neofiber (Round tailed musk rat) 60 Anatidae (sp. undetermined) 2 Unidentifiable remains 21 Podicidae (sp. undetermined) 1 • Bones, teeth, hair, feathers, flesh, and other parts of prey items were separated and Procyon (Raccoon) 5 Ardeidae (sp. undetermined) 1 Reproduction dried. Neotoma floridana smalli (Key Columbidae (sp. undetermined) 1 Methods Results Largo wood rat) 4 • Mammalian prey species were identified by keying out hair and comparing teeth and Peromyscus gossypinus (Cotton Aramus guarauna (Limpkin) 7 •Pythons removed from Everglades National Park (ENP) • Based on data from 8 pythons, average clutch size in Florida is 36, most 4 bones to skeletons of known origin. mouse) Podilymbus podiceps (Pied-billed Grebe) 5 and surrounding areas have been necropsied allowing us to recorded 85 and worldwide record is 107. Sciurus (Tree squirrel) 4 Eudocimus albus (White Ibis) 4 study their reproductive status. Felis (Cat) 3 • Bird remains were sent to the Smithsonian Institute for identification using Rallus elegans (King Rail) 5 • The first documented nest in Florida was found May 17, 2006 when we Felis rufus (Bobcat) 2 •Pythons used for radiotelemetry have been observed microfeatures on feathers (Figure 5). Fulica americana (American Coot) 2 discovered one of our telemetered females on a clutch of 46 eggs (Figure 10). Didelphis (Large American Rallus longirostris (Clapper Rail) 2 while engaged in reproductive and nesting behavior. opossums) 11 • Based on data from 8 pythons, average clutch size in Florida is 36 Agelaius phoeniceus (Red-winged Odocoileus virginianus (White-tailed Results Blackbird) 1 deer) 4 • Pythons can be found in breeding aggregations (Figure 11) and as many as 8 Anas discors (Blue-winged Teal) 1 Oryzomys (Rice rat) 8 pythons have been found at one time. Anhinga anhinga (Anhinga) 1 Lutra canadensis (River otter) 1 • Examination has yielded 455 prey items (Table 1) composed of 340 mammals (Figure Ardea alba (Great Egret) 1 Reptiles 8 6), 107 birds, 8 crocodilians, and 1 unidentified sample. Prey items were absent in 6 Ardea herodias (Great Blue Heron) 1 Alligator mississippiensis (American samples. Alligator) 8 Egretta caerulea (Little Blue Heron) 1 Egretta thula (Snowy Egret) 1 • Pythons have been successful in detecting round-tailed muskrat (Neofiber alleni) in Fregata magnificens (Magnificent Everglades National Park (ENP), a species researchers have not directly observed Frigatebird) 1 there in years, and may be responsible for their decline in ENP as 60 individual Gallinula chloropus (Common muskrats have been found in python gut samples. Moorehen) 1 Gallus domesticus (Domestic Chicken) 1 Figure 10. Discovery of first documented python nest in Florida • Two federally endangered species, including 4 Key Largo woodrats (Neotoma Mycteria americana (Wood Stork) 1 floridana smalli), and one juvenile wood stork (Mycteria americana), have been Numenius phaeopus (Whimbrel) 1 Summary Figure 11. A breeding aggregation of Burmese pythons in Everglades National Park found in python gut samples. The American alligator (Alligator mississippiensis, Figure 5. American coot (Fulica americana) remains Porphyrio martinica (Purple Gallinule) 1 A multi-faceted approach is required to effectively control the expansion of, and ecological damage caused by, Burmese pythons in South from python gastro-intestinal tract federally threatened), limpkin (Aramus guarauna) and white ibis (Endocimus albus), Porzana carolina (Sora) 1 Florida. Only through a combination of methods can we hope to achieve success in controlling this invasive species and understanding its which are species of special concern in Florida, have also been identified from gut Rallus limicola (Virginia Rail) 1 effects of the endemic biodiversity of the Greater Everglades Ecosystem. For each of these areas, revision and improvement of methods is contents as prey. Sturnella magna (Eastern Meadowlark) 1 expected as data collection and data analysis proceed. Troglodytes aedon (House Wren) 1 1) U.S. Geological Survey, Southeast Ecological Science Center, Davie, FL, USA; 2) University of Florida, Fort Lauderdale • Based upon what is known of the diet of Burmese pythons in their native range and in Anser sp. (Domestic Chinese goose) 1 Research and Education Center, Davie, FL, USA; 3) U.S. National Park Service, Everglades National park, Homestead, FL, USA; Gallus sp. (Domestic rooster) 1 Florida, it is believed that federally protected species such as the Cape Sable seaside 4) Department of Biology, Davidson College, Davidson, NC, USA; 5) U.S. Geological Survey, Fort Collins Science Center, Fort sparrow (Ammodramus maritimus mirabilis), Florida panther (Felis concolor coryi), Collins, CO, USA and American crocodile (Crocodylus acutus) are at risk of predation by Burmese pythons. Figure 6. Opossum (Didelphis virginiana) recovered from python stomach