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Brumation of Introduced Black and White Tegus, Tupinambis merianae (Squamata: Teiidae), in Southern Florida
Michelle A. McEachern, Amy A. Yackel Adams, Page E. Klug, Lee A. Fitzgerald, and Robert N. Reed

Southeastern Naturalist, Volume 14, Issue 2 (2015): 319–328

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Southeastern Naturalist 319 M.A. McEachern, A.A. Yackel Adams, P.E. Klug, L.A. Fitzgerald, and R.N. Reed 22001155 SOUTHEASTERN NATURALIST 1V4o(2l.) :1341,9 N–3o2. 82 Brumation of Introduced Black and White Tegus, Tupinambis merianae (Squamata: Teiidae), in Southern Florida Michelle A. McEachern1,*, Amy A. Yackel Adams1, Page E. Klug1, Lee A. Fitzgerald2, and Robert N. Reed1 Abstract - An established population of Tupinambis merianae (Black and White Tegu) in southeastern Florida threatens the Everglades ecosystem. Understanding the behavioral ecology of Black and White Tegus could aid in management and control plans. Black and White Tegus are seasonally active and brumate during the winter in their native range, but brumation behavior is largely unstudied in either the native or the invasive range. We describe the first observations of Black and White Tegu brumation in southeastern Florida after monitoring 5 free-ranging, adult male Black and White Tegus through an inactive season using radiotelemetry and automated cameras. Duration of brumation averaged 137 days, beginning in September and ending by February. One of the 5 Black and White Tegus emerged to bask regularly during brumation, which to our knowledge represents the first documented instance of a free-ranging Black and White Tegu basking during brumation. These preliminary findings provide a basis for future research o f brumation behavior. Introduction Tupinambis merianae (Duméril and Bibron) (Black and White Tegu), sometimes referred to as Salvator merianae (Duméril and Bibron), is a large, diurnal, actively foraging, terrestrial lizard in the family Teiidae. One of 6 species in its genus, Black and White Tegus are sexually dimorphic with males growing larger than females; maximum reported total length and mass for Black and White Tegus are approximately 1.6 m and 4.7 kg, respectively (Andrade et al. 2004, Fitzgerald et al. 1991). The native range lies east of the Andes and extends from northern Patagonia in Argentina to Paraguay, Uruguay, and south of Amazonia in Brazil (Avila-Pires 1999, Fitzgerald et al. 1999a, Presch 1973). Black and White Tegus are generalists that exhibit a large habitat and microhabitat niche breadth (Vitt 1995). They occur through a range of habitats and climates including tropical, subtropical, and temperate zones and are found in the Gran Chaco, Caatinga, Cerrado, Pampas, and Atlantic Forest (Avila-Pires 1999, Chiarello et al. 2010, Fitzgerald et al. 1999a). Populations in their native range can achieve densities of >100 individuals/km2 (Bovendorp et al. 2008). Black and White Tegus are active seasonally over much, if not all, of their native range. During winter, however, they cease eating and brumate (a term describing 1US Geological Survey, Fort Collins Science Center, 2150 Centre Avenue, Building C, Fort Collins, CO 80526. 2Department of Wildlife and Fisheries Sciences, Texas A&M University, 210 Nagle Hall, College Station, TX 77843. *Corresponding author - mmceachern@usgs.gov. Manuscript Editor: John Placyk Southeastern Naturalist M.A. McEachern, A.A. Yackel Adams, P.E. Klug, L.A. Fitzgerald, and R.N. Reed 2015 Vol. 14, No. 2 320 winter dormancy in reptiles similar to mammalian hibernation) in underground thermal refuges (Abe 1983, 1995; Lopes and Abe 1999; Toledo et al. 2008). Some combination of temperature, rainfall, and day length is presumed to play a role in onset and cessation of brumation in Black and White Tegus (Abe 1983, Andrade et al. 2004), but cues for the beginning or end of brumation have not been identified. Reports on the inactive season of Black and White Tegus indicate considerable variation in brumation behavior. Lopes and Abe (1999) did not observe winter activity in captive Black and White Tegus even when ambient temperatures were equivalent to those experienced during the active season (Andrade et al. 2004); however, Abe (1983) and Sanders (2008) recorded captive Black and White Tegus in southeastern Brazil emerging from their artificial burrows regularly during the inactive season. The reported duration of brumation is also variable (see Abe 1983, Andrade and Abe 1999, Chamut et al. 2012, Winck and Cechin 2008), which could be related to latitudes of the various study sites, observations of free-ranging versus captive individuals, or other factors. Between 2000 and 2002, over 7700 live Black and White Tegus were exported from Paraguay for the pet trade (Enge 2007, UNEP-WCMC 2014). Two populations of Black and White Tegus are now known to be established in the United States as a result of intentional or unintentional releases (Krysko et al. 2011, Pernas et al. 2012). The first known free-ranging Black and White Tegu in Florida was found in 2002; by 2011, there were 54 vouchered records from 11 different counties (Krysko et al. 2011). Two populations of Black and White Tegu are known to be established in Florida: 1 in Hillsborough and Polk counties and the other in southern Miami-Dade County (Enge 2007, Krysko et al. 2011, Pernas et al. 2012). As of June 2014, over 500 Black and White Tegus have reportedly been removed from the Miami-Dade population alone (University of Georgia 2014). Tegus may pose a significant threat to native wildlife in Florida because they are habitat and dietary generalists that can attain locally high densities and are known to prey upon nests of reptiles and ground-nesting birds (Bovendorp et al. 2008, Escalona and Fa 1998, Galetti et al. 2009). Burgeoning impacts on native reptiles in southern Florida have already been documented (Mazzotti et al. 2015). To reduce the potential for new or cascading impacts on the southern Florida ecosystem, Black and White Tegu management plans should be informed by an understanding of the behavior of the species in that environment. The purpose of this study was to provide the first detailed observations of brumation in free-ranging radiotelemetered Black and White Tegus in Florida. These detailed observations will serve as a basis for future research into brumation of this invasive species in the region. Field Site Description We conducted our study from September 2012 to March 2013 in the Southern Glades Wildlife and Environmental Area (WEA) in southeastern Florida at approximately 25°18'00"N, 80°28'12"W (Fig. 1). The hydrology of this area is managed actively via canals, levees, berms, and other structures. Regional and local waterregulation schedules developed in conjunction with restoration initiatives such as Southeastern Naturalist 321 M.A. McEachern, A.A. Yackel Adams, P.E. Klug, L.A. Fitzgerald, and R.N. Reed 2015 Vol. 14, No. 2 the Comprehensive Everglades Restoration Plan (CERP) dictate the hydrological management of the area. The Southern Glades WEA encompasses over 120 km2 of primarily seasonally inundated Sawgrass marsh but also marl prairie and tree islands. Roads, berms, and levee banks are dominated by native Metopium toxiferum (L.) Krug and Urb (Poisonwood) and Chrysobalanus icaco (L.) (Cocoplum), which offered ample shade and dense leaf litter. Our study region was in the sub-tropics but exhibited a tropical savannah climate with distinct wet and dry seasons and little variation between winter and summer temperatures (Deuver et al. 1994, Hela 1953). Winter high and low temperatures are usually above 25 °C and 10 °C, respectively, with occasional freezes (Deuver Figure 1. Map of study area within the Southern Glades Wildlife Environmental Area in southern Florida showing individual Tupinambis merianae (Black and White Tegu) thermal refuges. Activity ranges reported in Klug et al. (2015) are included and indicated by hashed polygons. Burrow sites—shown in black stars—are generally located in the center of the activity range. Southeastern Naturalist M.A. McEachern, A.A. Yackel Adams, P.E. Klug, L.A. Fitzgerald, and R.N. Reed 2015 Vol. 14, No. 2 322 et al. 1994). About 60% of rainfall in the Everglades falls from June to September (the wet season), and 25% falls from November to April (the dry season) (Deuver et al. 1994). Average annual rainfall in our study region from 2002 to 2012 was 1163 mm per year (US Geological Survey–SOFIA 2013). Methods Tegu tracking and brumation monitoring This study followed another investigation that utilized radio-telemetry to elucidate Black and White Tegu activity ranges for an invasive population (Klug et al. 2015). We trapped Black and White Tegus in the Southern Glades WEA (Fig. 1), equipped them with radiotransmitters using external harnesses over the pelvis, released them at the point of capture, and tracked them 3 times per week throughout the active season. We tracked 5 male Black and White Tegus into the inactive season, when the present study commenced. We defined onset of brumation as the first date a Black and White Tegu was tracked to an underground refuge in which it stayed for the next 5 consecutive tracking days. For example, if a Black and White Tegu was tracked to a burrow on 19 September and then located at the same location on 21, 23, 26, 28, and 30 September ,we defined the onset of brumation as 19 September. We tracked each Black and White Tegu to its thermal refuge, recorded location (UTM), and assessed the site. We estimated elevation above the adjacent levee road and canopy cover directly over the thermal refuge to the nearest 25% increment. We located the burrow entrance and used a sighting compass to measure cardinal degrees of sun exposure to the entrance. We determined the relationship of thermalrefuge locations to previously established activity ranges as described in Klug et al. (2015) using ArcGIS 10.1. We deployed automated trail cameras (Bushnell Trophy Cam models 119467C and 119476) at the entrance of each burrow on 13 November 2012 to record aboveground brumation behavior. We placed cameras between 1.5 and 3.0 m from the burrow entrance and programmed them to take 3 consecutive pictures when triggered, followed by a 5-second delay prior to taking additional photographs. We changed batteries and secure digital (SD) cards when needed to avoid data loss. We confirmed presence of all 5 Black and White Tegus in their thermal refuges once per week via radio-telemetry. We defined cessation of brumation as the first date we located a Black and White Tegu away from its thermal refuge. We retrieved the trail cameras between 24 February and 03 March 2013 after all Black and White Tegus had left their brumation sites. We removed the Black and White Tegus from the field and transferred them to cooperators at the Florida Fish and Wildlife Conservation Commission (FWC) for humane euthanasia and disposal upon completion of the study as required by our research permit. Photo processing and data analysis We viewed each image from an automated trail camera to determine target (telemetered tegus) and non-target (including non-telemetered tegus) image captures, Southeastern Naturalist 323 M.A. McEachern, A.A. Yackel Adams, P.E. Klug, L.A. Fitzgerald, and R.N. Reed 2015 Vol. 14, No. 2 using unique markings and best judgment to confirm a Black and White Tegu was the target individual when the radiotransmitter was not visible in an image. We converted the processed image data into daily detection data indicating if an individual Black and White Tegu was detected outside the burrow on a particular day. Results Description of thermal refuges All thermal refuges were near the center of individual activity ranges established the previous active season by the respective tegus (Fig. 1) and were located in pre-existing cavities in limestone rock spoil deposited during excavation of adjacent canals (Fig. 2). There were no outward signs of occupancy around the burrows used by the radio-telemetered Black and White Tegus (e.g., tracks, trampled leaf litter, etc.). All burrows had southern orientations and were open to direct sunlight from 133° to 180°, though individual exposure ranges differed (Table 1). Minimum burrow exposure was from 117° to 220°, and maximum was fully exposed at 0° to 360°. Thermal refuges were sparsely vegetated, and canopy cover ranged from 0% to 75%. We could not measure burrow depth, length, or width because the internal structure was comprised of irregularly shaped, non-uniform limestone rocks of varying sizes. Figure 2. Image of a radio-tagged Black and White Tegu (TM12M04) at the thermal refuge. The entrance to the burrow is indicated by a white circle. Southeastern Naturalist M.A. McEachern, A.A. Yackel Adams, P.E. Klug, L.A. Fitzgerald, and R.N. Reed 2015 Vol. 14, No. 2 324 Behavioral observations All 5 Black and White Tegus commenced and ceased brumation within 21 and 25 days, respectively, of each other (Table 1). Duration of brumation averaged 137 days (range = 116–160, standard deviation = 15.9; Table 1). We captured 1116 images of Black and White Tegus over the 111 days we left cameras deployed. We image-captured one or more Black and White Tegus outside the burrow on 46 days. One Black and White Tegu emerged and basked regularly during brumation; it was detected aboveground on 41 days and alone accounted for 37 of the 46 days with positive aboveground detection (TM12M03, Table 1). The other 4 Black and White Tegus remained underground until the end of the inactive season. At the end of the inactive season, 2 of the 4 Black and White Tegus that did not bask during brumation emerged and basked daily for 3 days before basking and then leaving the thermal refuge on the fourth day (TM12M04 and TM12M07; Table 1). One of the 4 Black and White Tegus that did not bask during brumation emerged and basked for 1 day, then basked and left the site the next day (TM12M06; Table 1). The final Black and White Tegu that did not bask during brumation was only image-captured 1 day at the thermal refuge; it probably left the site immediately after emergence (TM12M05; Table 1). Discussion The Black and White Tegus we observed overwintered for an average of 137 days in thermal refuges located within activity ranges they established the previous active season (Klug et al. 2015). Relationships between thermal refuges and activity ranges have yet to be explored but could provide relevant information on where to expect thermal refuges. In our study, the latest in the year a Black and White Tegu entered brumation was 6 October, and the earliest an individual ended brumation was 29 January. Minimum duration of brumation was 116 days. Understanding minimum brumation duration and onset and cessation dates is important for planning efforts to control tegus because some methods target active animals Table 1. Individual Tupinambis merianae (Black and White Tegu) brumation observations. Onset and cessation indicate the dates an individual began and ended brumation. Duration indicates the length of brumation in days. Burrow elevation (elev.) is approximate elevation of the burrow entrance above the adjacent levee road (m). Exposure is the range of cardinal degrees the burrows were exposed to solar radiation (due North is 0° or 360° and due South is 180°). Cover indicates the estimated canopy cover over the thermal refuge rounded to the nearest 25% increment. Days indicates the number of days an individual was detected outside of the burrow (i.e., on camera) during the 111 days the cameras were deployed. Basking indicates if the individual was detected basking during brumation. ID Onset Cessation Duration Elev. Exposure Cover Days Basking TM12M03 16 Sep 2012 22 Feb 2013 160 1.5 m 117°–220° 75% 41 Yes TM12M04 24 Sep 2012 11 Feb 2013 141 2.5 m 65°–180° 25% 4 No TM12M05 25 Sep 2012 04 Feb 2013 133 6.0 m 133°–271° 0% 1 No TM12M06 06 Oct 2012 29 Jan 2013 116 0.0 m 0°–360° 0% 2 No TM12M07 01 Oct 2012 11 Feb 2013 134 less than 1.0 m 104°–274° 25% 4 No Southeastern Naturalist 325 M.A. McEachern, A.A. Yackel Adams, P.E. Klug, L.A. Fitzgerald, and R.N. Reed 2015 Vol. 14, No. 2 (e.g., trapping). One of the 5 Black and White Tegus (TM12M03) emerged to bask periodically during the inactive season, and this report is the first published observation of above-ground activity that we are aware of in a free-ranging Black and White Tegu during brumation. Thermal refuge locations and substrate Black and White Tegus are known to use pre-existing burrows in the native range (Fitzgerald et al. 1991), so it is not surprising that the individuals in our study used pre-existing cavities in limestone rock spoil for thermal refuges. The only habitats with natural substrate near selected thermal refuges were inundated when brumation commenced, preventing selection or construction of thermal refuges in these areas. The requirement for Black and White Tegus to overwinter using thermal refuges above the water table could limit the extent of their distribution as their introduced range expands. Identifying areas with suitable conditions for thermal refuges could help guide planning for landscape-scale control of invasive Black and White Tegus. Aside from Black and White Tegus using elevated artificial structures as dispersal routes (Klug et al. 2015), availability of thermal refuges or suitable substrate on elevated artificial structures has implications for Everglades restoration plans. If such elevated artificial structures such as berms, levees, and roads dissecting seasonally inundated habitats were not available as refuges, perhaps Black and White Tegus would not successfully overwinter in and therefore might be excluded from these areas. Brumation behavior and burrow characteristics We observed variation among individuals in brumation behavior despite our small sample size. The differences between thermal refuges of TM12M03 as compared to those of the other 4 Black and White Tegus may have contributed to his behavior during brumation. The burrow of TM12M03 had the highest canopy cover and the least solar exposure of the 5 thermal refuges in this study, and these characteristics may have reduced the thermal stability of this burrow, with greater fluctuations in temperature leading to the increase in basking b ehavior. Aboveground activity during the inactive season The specimen identified as TM12M03 is the first reported free-ranging Black and White Tegu we are aware of in either native or introduced ranges observed emerging from a thermal refuge and basking during the inactive season. Winck and Cechin (2008) conducted the only study we are aware of describing seasonal behaviors of wild, free-ranging Black and White Tegus, but they did not observe them over an inactive season and did not report whether they emerged during brumation. The only studies that report Black and White Tegus emerging from thermal refuges during brumation were those conducted in captivity (Abe 1983, Sanders 2008). Abe (1983) suggested that light could affect brumation activity because Black and White Tegus kept in outdoor pens under natural light regimens had vastly different behaviors, including occasional basking, during the cold season as compared Southeastern Naturalist M.A. McEachern, A.A. Yackel Adams, P.E. Klug, L.A. Fitzgerald, and R.N. Reed 2015 Vol. 14, No. 2 326 to those kept indoors on a 12-hour photoperiod and exposed to cold temperatures. Sanders (2008) found that captive Black and White Tegus that roused in his study did so during the last 2 months of their 3-month brumation, always in the afternoon, and suggested artificial thermal refuges in his study might not have been sufficiently deep or constricted to induce deep brumation. Although we were unable to investigate the internal structure of the thermal refuges used by Black and White Tegus in our study because of their complexity and non-uniform structure, it is possible that the thermal refuge of TM12M03 was not sufficiently deep, constricted, or dark to induce deep brumation. We found that 1 in 5 adult male, free-ranging Black and White Tegus emerged to bask during brumation, which suggests that the behavior is uncommon. However, further study with larger sample sizes is needed to determine the prevalence and predictability of emergence during the inactive season in Florida. Understanding interactions among thermoregulatory constraints, energetics, and body size with seasonal weather patterns will enhance our understanding of why and when Black and White Tegus are most likely to enter and cease brumation (Fitzgerald et al. 1999b). Brumation and management Although limited in scope, this study provides preliminary information on brumation behavior of Black and White Tegus in southeastern Florida, which can be used as a basis for future research into brumation behavior. To better inform plans for the management and control of invasive tegus, brumation behavior of both sexes and juveniles should be better characterized. Patterns of emergence are closely linked with the timing of spring dispersal and mating (Chamut et al. 2012, Fitzgerald et al. 1994, Noriega et al. 2002, Winck and Cechin 2008, Winck et al. 2011). Therefore, information on these patterns could facilitate control and eradication of Black and White Tegus. For example, if we determine when adult, female Black and White Tegus emerge, land managers could devise strategies to remove adult females before they construct nests and lay eggs. Acknowledgments Research and collecting permits were issued by the Florida Fish and Wildlife Conservation Commission and the South Florida Water Management District, and research methods were approved by the Institutional Animal Care and Use Committee of the USGS Fort Collins Science Center. Funding was provided by the US Fish and Wildlife Service and the Greater Everglades Priority Ecosystem Science and Invasive Species programs of the US Geological Survey. We thank E. Metzger III, J. Duquesnel, R. Rozar, S. Goetz, L. Bonewell, and R. Irwin for assistance with project planning, logistics, fieldwork, and/or data management. We thank Erin Muths and 2 anonymous reviewers for providing valuable comments on an earlier version of the manuscript. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the US Government. Literature Cited Abe, A.S. 1983. Observations on dormancy in tegu lizards: Tupinambis teguixin (Reptilia, Teiidae). 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