| The Red-eared turtle(Trachmys script a elegans) was one of the world’s most dangerous100invasive species. There was the relatively systematic and comprehensive research in the country of origin, including morphology, physiology and reproductive biology and so on. In china, the research started late and less of the species, including habitat, home rang, feeding habits in short-term studies, but had yet to see the wild breeding research. Understanding of reproductive biology characteristics of invasive species played a key role for invasive species successful colonization and diffusion. That size of the fertility for invasion success is of great significance. We carried out a field breeding ecological research of alien species, T. scripta elegans, from October2011to September2012, at Shazhou Island of Wanquan River, Hainan. Main research results were as follows:Follicular development:the samples were obtained by trapped, and the samples were detected the number and size of follicles by ultrasonic technique. The results showed that54ultrasonic images of follicular of the samples were detected, which was detected in31individuals only one time, seven individuals test two times, three individuals tested three times. The average of size of follicles was greater than9.0mm (6.0mm-33.7mm, n=426) in each month. And follicles growth began in September and reached a maximum size in June (16.6±3.9mm, n=39), with maximum number in March (45±4, n=4). In study area, we forecasted that T. scripta elegans reproduced2.48clutches per year during breeding season.Nest site selection and characteristics:The process of selecting a nesting site is important to females in an immediate sense because they are more vulnerable to terrestrial predators at this time and because terrestrial predators also are often the major causes of nest mortality. Box tracer method was used to track20female pregnancy individuals. Eight nests of T. scripta elegans were found from different six individuals, weight2024±177g,(1745～2222g), carapace length232.77±3.71mm,(228.64-237.62mm), plastron length218.46±5.37mm,(212.44～226.38mm). Nesting behavior happened in between10:00～15:00, and there was no evidence of nocturnal nesting behavior. Hainan Island the nesting season generally occurs in May, and has a concentration of nesting activity on the water side. Statistical analysis method was used to analyze the difference between the usage plots (n=8) and contrastive plots (n=8). Five factors of sixteen factors between the usage plots and contrastive plots were significant, including Distance from water, Soil hardness, Vegetation cover, Slope position and Canopy. This indicates that the use of ecological factors by T. scripta elegans was selective. That place slope up position, distance from water (6.86±3.22mm), moderate soil hardness (8.92±6.49kg/cm2), vegetation cover lager (76.86±8.42%) and crown density smaller (35.62±18.79%) was selected by T. scripta elegans to use nest. Principal components analysis was used to analyze the important factors which affect nest-site selection by T. scripta elegans. The result showed that three type’s factors were as follow in decreasing order of importance:Topographic factors (Distance from water, Slope gradient), physical and chemical factors (Soil hardness, PH, Soil salinity) and vegetation factors (Canopy, Vegetation type). Three type’s factors can be used as reference index by T. scripta elegans nest-site selection. Although this study determined some important factors in nest-site selection, there may be more significant characteristics that not measured in this study. Nest is completely covered by soil, nest at the top of the soil moisture is obvious different from the surrounding soil, lying eggs are excreted in urine during nest above. The nesting was flask shaped as much as173.11±6.76mm depth and the linear regression model for nesting depth vs. female plastron length was significant (P<0.05).Laying eggs and hatching:The spawning behavior was firstly described in non-local place, all nesting behavior was observed from morning, and there was no evidence of nocturnal nesting behavior. Eggs were composed of leathery, and had white transparent of full-bodied. Clutch size ranged from10-15(n=S,12.4±1.7) and showed a significant relationship with female plastron length (P<0.05). We collected a total of99eggs, including36unfertilized eggs,11hatchling only success. Eggs were major preyed on by Oligodon formosanus, Polyrhachis dives, Pheidole indica. Hatchling had bright color, on the soil adhesion to the body, the ear after two red lines was not obvious, and egg yolk had yet to be fully absorbed, activity ability was weak. The average hatching temperature was27.7℃(27.1℃-28.8℃), the average incubation time of fertilized eggs was70.3d±9.2d (57d-78d).In conclusion, breed population of red-eared turtle was established in natural conditions on Hainan. Red-eared turtle had many reproductive characteristic, including a number follicular development, nest site selection widely, high reproductive ability, and less natural enemy. Red-eared turtle of the reproductive characteristics would be a threat to local freshwater turtle’s existence, resulting in a decrease of local biodiversity. Government departments should formulate relevant laws as soon as possible, in order to control the further breeding of the species diffusion. |
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