洞庭湖区夏季温光条件及被迫迁移对东方田鼠繁殖的影响

IMPACT OF HIGH TEMPERATURE IN SUMMER AND THE MIGRATION FORCED BY FLOOD ON THE BREEDING OF MICROTUS FORTIS IN DONGTING LAKE AREA

在野外 ,从先年的秋初至当年春末被迫迁移前 ,东方田鼠在湖滩上能保持较高的繁殖能力 ;在夏季 ,不论栖息在农田还是岗地 ,都是东方田鼠的繁殖低谷。夏季 (6～ 8月 )在实验室自然温光条件下与人工控制较低温度条件下同时进行观察 ,结果表明 ,前种条件下东方田鼠的繁殖能力明显低于人工降低温度缩短光照条件下的繁殖力 ,此变动趋势与野外观察到的繁殖力季节动态一致 ,可以说明夏季温光条件不利于东方田鼠的繁殖。另一方面 ,东方田鼠的繁殖能力最低的 6月并非全年最热的月份 ,这是因为东方田鼠的被动迁移对体力的消耗加剧了夏季温光对繁殖的影响程度。因此 ,认为洪水引起的东方田鼠被迫迁移和夏季的温光条件共同影响了东方田鼠的繁殖。洞庭湖区东方田鼠主要在冬春季繁殖 ,而分布在高纬度地区的田鼠类动物和分布在高纬度地区的东方田鼠在夏季繁殖 ,在月份上虽不同 ,但其繁殖盛期的气温则相近 ,其实是田鼠类动物喜寒惧热特性的反映 ,乃是对当地的生态环境的适应。

The Yangtse voles ( M. fortis ) colonize the beach of Dongting lake area (28°13′～29°55′N, 111°11′～113°43′E) from early autumn to spring when the water level is low and migrate to farmlands during the flood season (from May to June). The Yangtze voles have a high breeding potential during autumn to spring when they inhabit on the lake beach, but the breeding rate largely declines after they move to farmland. It was found that following the migration the testes of males became smaller, and also the pregnant rate of females declined. This makes the breeding rate of the animals declines to lowest level in June and July. Our studies by field observations and laboratory experiments show that the temperature and light cycle in summer in Dongting Lake region depress the breeding of Yangtse voles. This is opposite to the most of Microtus species that live at high latitudes (above 35°N). The physical stress of the animals from migration during the flood reinforces the influence.