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Thermoregulation by a Brooding Burmese Python (Python molurus bivittatus) in Florida
Ray W. Snow, Alexander J. Wolf, Brian W. Greeves, Michael S. Cherkiss, Robert Hill, and Frank J. Mazzotti

Southeastern Naturalist, Volume 9, Issue 2 (2010): 403–405

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2006 NORTHEASTERN NATURALIST 13(1):39–42 Thermoregulation by a Brooding Burmese Python (Python molurus bivittatus) in Florida Ray W. Snow1, Alexander J. Wolf 2, Brian W. Greeves2, Michael S. Cherkiss2, Robert Hill3, and Frank J. Mazzotti2,* Abstract - We report an observation of shivering thermogenesis and insulation by a brooding Python molurus bivittatus (Burmese Python) just outside the northern boundary of Everglades National Park, fl. Temperature data loggers were placed in and around the brooding female’s nest, and video was taken of the female performing shivering thermogenesis. Nest temperatures were maintained both warmer and cooler than ambient temperatures. This observation of thermoregulation through shivering thermogenesis and clutch insulation is the first documented instance of a Burmese Python exhibiting this behavior in the wild. Python molurus bivittatus Kuhl (Burmese Python) is the larger of two subspecies of Python molurus (L.) (Indian Python) and is native to Southeast Asia. As a result of its popularity in the exotic pet trade and subsequent release and escape of captive specimens, the Burmese Python has established a viable breeding population in and around Everglades National Park, fl(Snow et al. 2007a, b). Shivering thermogenesis (creation of body heat through muscle contractions) has been reported in captive Indian Pythons (Hutchison et al. 1966, Van Mierop and Barnard 1976). We found no reports of wild pythons insulating eggs from higher temperatures. Here we document the first record of a brooding Burmese Python thermoregulating in the wild. Description of Observation. A female Burmese Python (snout–vent length= 2.86 m; total length = 3.22 m; mass = 11.11 kg) was discovered by R. Hill and R.W. Snow to be nesting in a relatively level area of a canal bank just outside of the northern boundary of Everglades National Park (25.7621°N, 80.7309°W, datum: WGS84) on 3 July 2008. The nest cavity was approximately 60 cm from the burrow opening, in an area of loosely packed soil, dense roots, and some trash, partially shaded by Schinus terebinthifolius Raddi (Brazilian Pepper), Myrica cerifera (L.) Small (Wax Myrtle), Rapanea punctata (Lam.) Lundell (Myrsine Floridana), and Chrysobalanus icaco L. (Coco Plum) (Supplementary Photos 1–3, available online at http:// www.eaglehill.us/SENAonline/suppl-files/s9-2-784-Cherkiss-s1, and, for BioOne subscribers, at http://dx.doi.org/10.1656/S781.s1). On 23 July 2008, the Burmese Python and 27 eggs were removed by R. Hill, R.W. Snow, M. Brien, and J. Carrigan as part of Everglades National Park exotic python control efforts. Methods. Two digital temperature data loggers set to continuously record temperature every 30 minutes were placed in and above the nest. One data logger was suspended approximately 10 cm above the nest to record ambient air temperature, and a second logger was placed within the nest next to the female, as close to the eggs as possible. The logger recording ambient air temperature above the nest was placed to receive the same amount of sun and shade as the nest. Both loggers recorded data from 7 July to 23 July 2008 (n = 768 and n = 767, respectively). Notes of the Southeastern Nat u ral ist, Issue 9/2, 2010 403 1South Florida Natural Resources Center, Everglades National Park, 40001 State Road 9336, Homestead, fl33034. 2Department Wildlife Ecology and Conservation, Fort Lauderdale Research and Education Center, University of Florida, 3205 College Avenue, Davie, fl33314.3South Florida Water Management District, Miami Field Station, 9001 NW 58th Street, Miami, Florida 33178. *Corresponding author - rhill@sfwmd.gov. 404 Southeastern Naturalist Notes Vol. 9, No. 2 A 2.5-cm diameter black-and-white infrared digital video camera, mounted on a 3-m long probe, was guided through the burrow to the female and recorded the female performing shivering thermogenesis. A total of 46 minutes 10 seconds of footage was recorded between 11:11 and 12:06 on 18 Jul 2008. (Supplementary Video 1, available online at https://www.eaglehill.us/SENAonline/suppl-files/s9- 2-784-Cherkiss-s2, and, for BioOne subscribers, at http://dx.doi.org/10.1656/ S781.s2). Results and Discussion. Mean, standard deviation, minimum, and maximum temperature readings for both data loggers are reported in Fig 1. Prior literature reported captive Indian Python nest temperatures ranging from 32–34 °C, which was up to 7.3 °C warmer than ambient air temperature (Hutchison et al. 1966). While this female was able to maintain nest temperature up to approximately 7 °C warmer than ambient air temperature (Fig. 1), mean nest temperature (29.2 °C) was cooler than those reported by Hutchison et al. (1966). Notably, nest temperature was also up to 13 °C cooler than ambient air temperature at times when ambient air temperature was above the desired nest temperature range. Of the total footage recorded, there were 11 minutes of video footage (consisting of several 1–3 minute segments) in which observers were not believed to be affecting the female’s behavior. When the camera was initially placed or moved in the burrow, the snake used spasms in an attempt to push the camera away. Only after the snake settled back into rhythmic breathing and shivering did we begin counting contractions. After reviewing the 11 minutes, we determined a mean rate of 16 contractions/minute (range = 10.5–20 contractions/minute), as compared to the 5–16 contractions/minute observed by Van Mierop and Barnard (1976). This observation is significant in several capacities. It confirms for the first time from field observations what has been observed in the laboratory for Burmese Pythons (Hutchison et al. 1966, Van Mierop and Barnard 1976) and surmised from the wild for other species of pythons (Shine et al. 1997, Slip and Shine 1988); The ability Figure 1. Ambient air temperature (n = 768) and nest temperature (in nest adjacent to female, n = 767) recorded 7 July– 23 July 2008. Mean ambient air temperature was 28.02 °C (standard deviation = 3.93; minimum = 21.16; maximum = 43.36) and mean nest temperature was 29.21 °C (standard deviation = 0.68; minimum = 26.94; maximum = 33.57). 2010 Southeastern Naturalist Notes 405 of Burmese Pythons to generate body heat through shivering thermogenesis. Those studies of Burmese Python, Liasis fuscus Peters (Water Python), Python spilotes spilotes Lacépède (Australian Diamond Python), and other python species (Harlow and Grigg 1984, Vinegar et al. 1970) all showed elevated and stable brooding temperatures. In contrast, we found stable temperatures that were both warmer and cooler than ambient temperatures. We hypothesize that as ambient temperatures went below the desired range, the female python performed bouts of shivering thermogenesis to elevate nest temperatures. Conversely, as ambient temperatures went above the desired range the female python could be loosening the coils to dissipate heat build up from the eggs, in addition to, or as an alternative to insulating the eggs from ambient air temperatures. This observation is also significant from a management point of view. Burmese Pythons are capable of reproducing in southern Florida (Snow et al. 2007b). The temperature data acquired from this observation demonstrate that these snakes are able to survive and reproduce in environmental temperatures that may fluctuate to several degrees hotter or colder than what captive breeders consider ideal (Clark 2006). A better understanding of Burmese Pythons’ thermoregulatory behavior can assist managers in predicting opportune times for implementing control methods, and in predicting possible range expansion of this invasive species. Acknowledgments. We thank the South Florida Water Management District, the US National Park Service (Critical Ecosystems Studies Initiative), and the US Geological Survey (Priority Ecosystems Sciences) for their continued support of and funding for the Burmese Python projects in southern Florida. We thank R. Reed and G. Rodda of the USGS, M. Dorcas of Davidson College, C. Carmichael of Malone University, and W. Meshaka of the Pennsylvania Historical and Museum Commission for reviewing the manuscript. We thank J. Carrigan and M. Brien for assistance in the field. Literature Cited Clark, B. 2006. Python egg incubation. Reptile Magazine. Available online at http://www. bobclark.com/a03_06.asp. Accessed 3 February 2009. Harlow P., and G. Grigg. 1984 Shivering thermogenesis in a brooding python, Python spilotes spilotes. Copeia 1984:959–965. Hutchison, V.H., H.G. Dowling, and A. Vinegar. 1966. Thermoregulation in a brooding female Indian Python, Python molurus bivittatus. Science, New Series 151:694–696. Shine, R., T.R.L. Madsen, M.E. Elphick, and P.S. Harlow. 1997. The influence of nest temperatures and maternal brooding on hatchling phenotypes in Water Pythons. Ecology 78:1713–1721. Slip, D.J., and R. Shine. 1988. Reptilian endothermy: A field study of thermoregulation by brooding Diamond Pythons. Journal of Zoology, London 216:367–378. Snow, R.W., K.L. Krysko, K.M. Enge, L. Oberhofer, A. Warren-Bradley, and L. Wilkins. 2007a. Introduced populations of Boa constrictor (Boidae) and Python molurus bivittatus (Pythonidae) in southern Florida. Pp. 416–438, In R.W. Henderson, and R. Powell (Eds.). The Biology of Boas and Pythons. Eagle Mountain Publishing, Eagle Mountain, UT. 448 pp. Snow, R.W., V.M. Johnson, M.L. Brien, M.S. Cherkiss, and F.J. Mazzotti. 2007b. Python molurus bivittatus: Nesting. Herpetological Review 38:93. Van Mierop, L.H.S., and S.M. Barnard. 1976. Thermoregulation in a brooding female Python molurus bivittatus (Serpentes: Boidae). Copeia 1976:398–401. Vinegar, A., V.H. Hutchison, and H.G. Dowling. 1970 Metabolism, energetics, and thermoregulation during brooding of snakes of the genus Python (Reptilia, Biodie). Zoologica 55:19–49.