Activity Rhythm And Home Range Of Exotic Species Red-eared Turtle In Wanquan River, Hainan Island, China

The red-eared slider (Trachemys scripta elegans; TSE) is listed as one of the100worstinvasive species in the world. At present, it is widely distributed in the wild of China.However, there is no scientific evidence to formulate and implement managerial measureswhich would restrict the import and release of TSE, due to the lack of relevant research. Inorder to collect detailed ecological data of TSE in invasive regions, to clarify the invasivestatus, ecological impacts and adaptative mechanism, and to provide data for legislation andmanagement of TSE, we conducted a study of TSE. The study took place on Wanquan River,Hainan Island from July2010to October2012and assessed the activity rhythm, home range,basking habit and introduction pathway for TSE.The main methods and conclusions are as follows:1. The activity rhythm of TSE was studied with two indices (activity percentage andactivity intensity) by radio telemetry. Annual activity rhythm: The TSE was active duringevery mouth, and the phenomenons of hibernation and aestivation were not found in thisstudy. When the activity is counted with activity percentage, it has only one obvious peak,which occurs in March; Counting with the activity intensity, it has three obvious peaks, inMarch, May and July, and it has a small fluctuation of peak in October. The activitypercentage and activity intensity of female TSE was significantly higher than male TSE inJanuary, and the activity intensity of female was significantly higher than male in October. Asignificant deviation of activity level was not found within the sexes in other months. Asignificant positive correlation was found between monthly activity percentage and solarillumination, and a correlation was not found between monthly activity percentage andtemperature. The significant positive correlation was found between monthly activity intensityand solar illumination, temperature. Daily activity rhythm: The TSE is primarily diurnal andexhibits a unimodal pattern in daily activity. The peak time of activity percentage and activityintensity is12:00-14:00and6:00-8:00, respectively. A significant deviation of daily activitywas not found within sex and age groups; A significant positive correlation was foundbetween daily activity and solar illumination, and no correlation was found between dailyactivity and temperature when located a narrow range of daily temperature (27.29–29.11℃)in Wanquan River. The activity of TSE during the daytime was affected by weather (clear,cloudy, gloomy, light rain, moderate rain, heavy rain), and the activity of TSE at night was notaffected by rainfall. 2. The home range of the invasive TSE and the native Chinese stripe-necked turtle(Mauremys sinensis; MS) was studied by radio telemetry. The home range size of eachindividual was calculated by methods of minimum convex polygon and line home rangebased on2043locations from32individuals tracked, and home range overlap degree ofvarious individuals were analysed. The home range area of TSE and MS is, respectively,8.15±2.83hm2,5.82±3.95hm2; and the line home range is534.07±74.98m,504.00±222.96m.Interspecific difference in home range area and length were not found between the twospecies of turtle. Female home range area and length were significantly larger than those ofmale in adult TSE. The intraspecific home range overlap degree of TSE and MS is,respectively,0.27±0.02,0.08±0.06; and the intraspecific home range overlap degree of TSEwas significantly larger than that of MS. The interspecific home range overlap degree betweenTSE and MS is0.20±0.02. The results of this study suggest that TSE may have a potentialcompetitive threat to MS in the wild.3. The basking habit of exotic TSE in the wild was studied by comparing the turtles’selected body surface temperature to the environmental temperature using data loggers.Basking time showed a clear unimodal pattern, with the peak in11:00-13:00; Daily baskingduration was51.43±26.08min, and there was great disparity during different days, the rangewas0~330min; Daily basking frequency was0.69±0.29, and the single basking durationwas72.83±20.55min; The body surface temperature was significantly higher during periodsof basking in comparison to periods of non-basking, the mean temperature of carapace surfaceafter basking was36.01±0.68℃, and the heating rate in basking duration was0.18±0.01℃/min. Aquatic basking significantly increased when water temperature approached31.5℃.Daily basking was significantly affected by weather conditions (clear, cloudy, showers,gloomy, light rain, moderate rain, heavy rain).