中文摘要：

集群给动物带来安全、接触配偶机会等利益的同时,也存在增加竞争的风险。不同的物种以及生活史不同的阶段,动物会采取不同的集群策略。本研究设计实验,检验在繁殖期个体大小不同的高体鰟鮍对由同性个体组成的个体数不同的群体的偏好。结果显示,大个体雄性显著偏好于大的群体（第一次选择：V=72,n=12,P=0.0054;第二次选择：V=65,n=12,P=0.022）,大个体雌性对不同大小的群体则无显著偏好（第一次选择：V=54,n=12,P=0.13;第二次选择：V=41.5,n=12,P=0.44）;小个体雄性（第一次选择：V=59,n=12,P=0.0012;第二次选择：V=78,n=12,P=0.0013）与小个体雌性（第一次选择：V=75,n=12,P=0.0026;第二次选择：V=70,n=12,P=0.0083）均显著偏好于大的群体。这说明在选择加入某一群体时,大型和小型的雄性个体均主要考虑安全因素;而小型的雌性个体主要考虑安全因素,大型的雌性个体则同时考虑安全因素和繁殖竞争。

英文摘要：

Group living may provide a safe mating opportunity. However, living in a group may also impose certain costs, such as higher competition. Grouping strategies vary with species and life stages. This study designed experiments to investigate the preference for small versus large groups of same-sex conspecifics in breeding rose bittedings （ Rhodeus ocellatus） of different body size. The results showed that large males presented strong preferences for larger groups （first choice experiment ： V = 72, n = 12,P = 0.0054 ; second choice experiment ： V = 65, n = 12, P = 0.022） , while large females showed no such preferences （first choice experiment ： V = 54, n = 12, P = 0.13 ; second choice experiment ： V = 41.5, n = 12, P = 0. 44） ; both small males （first choice experiment ： V = 59, n = 12, P = 0. 0012 ; second choice experiment ： V = 78, n = 12, P = 0. 0013 ） and females （ first choice experiment ： V = 75, n = 12 ,P = 0.0026 ; second choice experiment ： V = 70, n = 12, P = 0. 0083 ） showed clear preferences for larger groups. Our results suggest that when joining a group, both big and small males are primarily concerned for safety, whereas small females consider mainly safety, but big ones both safety and reproductive competition.