The whole shell is covered in these stripes and markings that aid in camouflaging an individual. The head, legs, and tail are green with fine, irregular, yellow lines. The plastron is highly variable in pattern. The plastron is always a light yellow with dark, paired, irregular markings in the centre of most scutes. In young or recently hatched turtles, it is leaf green and gets slightly darker as a turtle gets older, until it is a very dark green, and then turns a shade between brown and olive green. The carapace usually has a dark green background with light and dark, highly variable markings. The color of the carapace changes depending on the age of the turtle. The carapace is oval and flattened (especially in the male) and has a weak keel that is more pronounced in the young. The upper carapace consists of the vertebral scutes, which form the central, elevated portion pleural scutes that are located around the vertebral scutes and then the marginal scutes around the edge of the carapace. The shell is divided into two sections: the upper or dorsal carapace, and the lower, ventral carapace or plastron. For this reason, they need to sunbathe frequently to warm themselves and maintain their body temperatures. These turtles are poikilotherms, meaning they are unable to regulate their body temperatures independently they are completely dependent on the temperature of their environment. The quality of their living environment has a strong influence on their lifespans and well being. Their life expectancy is shorter when they are kept in captivity. They typically live between 20 and 30 years, although some individuals have lived for more than 40 years. The females of the species are usually larger than the males. These results suggest that it is difficult to control RES turtles established in rivers but that it is feasible to effectively control RES turtles in enclosed small water bodies, such as irrigation reservoirs, by intensively capturing and eliminating the turtles during the drainage period.The carapace of this species can reach more than 40 cm (16 in) in length, but the average length ranges from 15 to 20 cm (6 to 8 in). Thereafter, the annual catch of RES turtles clearly decreased. Nearly half of them were caught for the initial two years, during which the pond was drained. At Teradaike Pond, a total of 1,831 RES turtles were captured over nine years. Nevertheless, the annual catch did not tend to decrease and only an effect of preventing population growth was observed. At the Taisho River, a total of 1,366 RES turtles were captured and eliminated over more than ten years. These sex ratios were markedly biased toward females and consistent between the adult and the juvenile turtles, thus suggesting that more females had been produced than males. At both sites, these sex ratios were almost the same as those of RES turtles that could be sexed only by necropsy after euthanasia (presumably juvenile turtles). The sex ratio (male/both sexes) of RES turtles that could be sexed by external morphology (presumably adult turtles) was 0.27 at the Taisho River and 0.26 at Teradaike Pond. We also examined whether the population of RES turtles could be reduced by continuously removing the turtles captured at each study site. Using trapping and muddling methods, we captured RES turtles and checked for sex, carapace length, and body weight. We conducted a long-term field study on RES turtles at two study sites: the Taisho River (a shallow river) and Teradaike Pond (an irrigation reservoir that was irregularly drained to maintain the embankment and water quality) in western Japan. Information on reproductive parameters, such as sex ratios, of RES turtles is needed to effectively control the invasive species. High abundance of invasive red-eared slider (RES) turtles ( Trachemys scripta elegans) in Japan has been a serious issue in freshwater ecosystems.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |