Study On The Distribution, Diet, Growth And Sexual Dimorphism Of Yunnan Frog (Pelophylax Pleuraden)

Amphibians are indicators of environmental changes.It is significant to study amphibians ecology and conservation biology in order to protect speciesYunnan frog(Pelophylax pleuraden Boulenger) is a species endemic to Yunnan Province,southwestward of Sichuan Province and west of Guizhou Province in China.In this study,I conducted a filed survey to investigate the distribution,diet, individual growth and sexual size dimorphism of the Yunnan frogs.The main innovative findings are as follows:1) I investigated 103 frogs living in water in 16 cities in Yunnan Province between June to August 2008 by visual encounter surveys,acoustic method and eggs searching method. Results showed that the Yunnan frogs were mainly found in permanent lentic waters in Baoshan,Kunming,Dali,Lijiang,and Ninglang.There is a shrinking trend in the distribution of this species in Yunnan Province,compared to their historical records.2) I studied on the diet of 104 Yunan frogs in Ninglang and Kunming by using stomach content flushing method.The results indicated that insects account of the largest part of diet volume.There were differences in diets between species in different sites.Differences in food types and food volume were also found between male and female Yunnan frogs.3) We distinguished the mature female Yunnan frogs by using non-invasive incision method.And we adopted skeleton -chronological method.To investigate the mature age, population age structure,longevity,growth rate and sexual size dimorphisms(SSD) of 64 pond frogs.Results showed that male maturated earlier than females.Males at one year old show an obvious secondary sexual characteristics,while females reached sexual maturity at two years old.Both the oldest females and males can reach the age of four.The growth rate of both sexes decreased with age.There is an obvious declin ing trend in the sexual size dimorphism at the age of 3 after maturation.But adult females are larger than adult males between the age of 2 to 4.