东方田鼠家群个体体重、攻击性及胆量对其扩散的影响

扩散作为动物适应生存环境的重要特征之一,受到自身生物学特征及环境等方面的制约。以家群形式生活和子代雄鼠扩散为主的东方田鼠,其成员个体是否因领地食物和空间资源竞争导致体重小、攻击性弱及胆小个体先行扩散。以新鲜马唐叶片构建三块密集均质的食物斑块,在食物斑块周边以透明玻璃设置观测箱,采用透明塑胶管连接三块食物斑块作为动物扩散的通道,构建东方田鼠扩散行为观测装置。将东方田鼠家群子代成员投放至带有自身家群气味的食物斑块,测定成员个体在食物斑块上的觅食行为序列过程和参数,以及向其他食物斑块扩散的行为过程和参数以及家群中先行扩散个体体重、攻击性及胆量占所有家群数的比率,检验成员个体的体重、攻击性及胆量对扩散的影响。结果发现,体重小、攻击性弱和胆小个体的觅食启动时间极显著地大于体重大、攻击性强和胆大个体的,但其先行扩散的比率却显著地大于体重大、攻击性强和胆大个体的;然而体重小、攻击性弱及胆小个体的扩散开始时间显著或极显著地大于体重大、攻击性强及胆大个体的。结果揭示,东方田鼠家群成员随着年龄的增长和对食物及空间资源竞争的加剧,体重大、攻击性强及胆大个体会迫使体重小、攻击性弱及胆小个体先行扩散。

Effects of body weight, aggressiveness, and boldness on dispersal in a family group of reed voles (Microtus fortis)

Dispersal is a crucial characteristic for animal adaptation to their environment, but it can be influenced by various biological and environmental factors. In the case of the reed voles (Microtus fortis), which lives in family groups with male offspring predominantly responsible for dispersal, the question arises as to whether individual members with smaller body size, lower aggression, and timidity disperse earlier due to competition for territorial food and spatial resources. To test this hypothesis, an observation device was constructed to record the dispersal behavior of reed voles. This device consisted of three densely packed and homogeneous food patches made of fresh crabgrass (Digitaria sanguinalis) leaves. Surrounding each food patch, we placed transparent glass observation boxes, and transparent plastic tubes connected the three food patches, serving as channels for animal dispersal. We released offspring members of reed vole families into the food patches, which were scented with their own family odor. The experimental approach involved the implementation of clipped fur markings and video recording techniques, as well as post-experimental slow-motion video replay. We measured the foraging behavior sequence and parameters of individual members on the food patches, as well as the behavioral processes and parameters related to dispersal to other food patches. Additionally, we calculated the ratio of body weight, aggressiveness, and boldness of the first individuals to disperse compared to the total number of families in the group. This allowed us to assess the impact of individual body weight, aggression, and boldness on dispersal. The results showed that individuals with smaller body size, lower aggressive, and timidity exhibited a significantly longer delay in foraging initiation compared to individuals with larger body size, higher aggressive, and boldness. Surprisingly, the rate of initial dispersal among the smaller, less aggressive, and timid individuals was significantly higher than that of the larger, more aggressive, and bold individuals. However, the smaller individuals also had a significantly or extremely significantly longer dispersal start time compared to their larger counterparts. The results suggest that as reed vole family members age and face increased competition for food and spatial resources, individuals with larger body size, higher aggression, and boldness force the smaller, less aggressive, and timid individuals to disperse earlier. This finding highlights the influence of individual characteristics and resource competition on the dispersal behavior within the family group. In conclusion, our study reveals the dynamics of dispersal behavior in reed vole family groups. As individuals grow older and competition for food and spatial resources intensifies, larger, higher aggression and boldness individuals tend to exert pressure on smaller, less aggressive, and timid individuals to disperse earlier. These findings enhance our understanding of the factors shaping dispersal behavior in animal populations and contribute to the study of animal adaptation and population dynamics.