野生扬子鳄种群动态变化及致危因素

1998—2003年，采用问卷调查、走访居民、夜间灯光照射计数等方法，对可能有野生扬子鳄(Alligator sinensis)分布的安徽省、浙江省和江苏省的45个地点进行了调查。结果发现：目前野生扬子鳄呈点状分布在至少23个地点，个体总数约120条，主要集中分布在安徽扬子鳄国家级自然保护区内。通过连续调查和对比分析表明：自20世纪50年代扬子鳄数量急剧下降(从5000—6000条下降为120条)，但1998年至今其数量保持相对稳定(120条)，种群的致危因素主要是栖息地破坏、人为捕杀、环境污染、自然灾害、繁殖力低等。在不同时期导致数量下降的因素不同：1950—1990年问，主要是由于栖息地丧失、人为捕杀等；目前的主要致危因素是缺乏适宜的自然栖息地，环境污染和遗传多样性丧失是潜在的致危因素。旱灾对野生扬子鳄生存的影响并不明显。

Factors influencing the population status of wild Chinese alligators (Alligator sinensis)

During April - August 1998, 200 questionnaires were distributed and collected in each of 200towns and villages in the National Chinese Alligator Nature Reserve in Anhui Province. Based on the re-sults of the questionnaires, quantitative nocturnal spotlight surveys were carried out from July to Octoberof 1999, 2000, 2001, 2002 and 2003 in areas most likely to have wild alligator populations. The surveyarea included 36 sites in five counties or municipalities (Xuancheng, Jingxian, Guangde, Langxi, Nan-ling) in Anhui Province, seven sites in Changxing County and Anji County of Zhejiang Province, and twosites (Fuxijian and Dahanjie) near Yixing City in Jiangsu Province. Based on these surveys we estimate that the current size of the wild Chinese alligator population inAnhui and Zhejiang Provinces is 120 individuals. The population is fragmented into 23 isolated small lo-cal populations with 1 - 10 individuals each. No alligators were found in Jiangsu Province. Analysis ofour data revealed that the wild Chinese alligator population and its distribution have declined sharplysince the 1950s. The current population size of wild Chinese alligators has declined an estimated 76.5%from its levels in the 1980s. However, the population appears to have been stable from 1998 to 2003 withan estimated 120 individuals. The factors most responsible for the population decline have varied over the last fifty years but overallhave been habitat fragmentation and degradation, hunting, natural disasters (floods and drought), lowproductivity and pollution. From the 1950s to 1990s, habitat loss and the killing of alligators were themost significant factors. Presently, killing of alligators is less of an issue but the loss of habitat has beenvirtually complete. Therefore, the highest priority for conservation of Chinese alligators must be habitatrestoration as the first step towards reintroducing alligators by releasing captive-bred individuals. In addi-tion, the potential consequences of environmental pollution and reduced genetic diversity of wild Chinesealligator population must also be addressed.