Frontiers in Zoology, an international English-language journal sponsored by the Zoological Society of Germany, published a research paper from the Laboratory of Animal Behavior and Chemical Communication at the Institute of Zoology, Chinese Academy of Sciences, reporting on the behavioral characteristics and physiological mechanisms of rattus tanezumi's northward expansion and invasion, and competition with local brown rats (R. norvegicus).
Yellow-breasted rats and brown rats are two main domestic-inhabited rats, which are closely related species. Yellow-breasted rats are smaller than brown rats, which were mainly distributed in the yellow river and the south of the Yangtze River in China in the past, and have expanded significantly north in the past two decades, and have now reached the central part of Hebei Province, the northern part of Shanxi Province, and even Qinghai, and partially or completely replaced the local brown rats.
There are many factors that influence the success of species invasions, among which the interspecific competition between invasive species and local relatives is one of the concerns of ecologists and evolutionary biologists. Using indoor populations of wild rats, the researchers conducted several experiments to explore the characteristics and mechanisms of competition with indigenous brown rats (North China subspecies) (R. n. humiliatus) during the invasion of yellow-breasted rats. Invasive species tend to have stronger aggressive behavior and competitive ability than local relatives, but there is no direct confrontation between the two rats, but after long-term mutual stimulation of interspecific odors, etc., the sexual attraction of male yellow-breasted rats' own odors is enhanced and more liked by female rats of the same species; on the contrary, the sexual attraction of male brown rats' own odors is weakened, reducing the attraction to female rats of the same species. It shows that long-term interspecific interaction may promote the reproductive success of yellow-breasted rats and reduce the reproductive success of brown rats, thereby promoting the invasion of yellow-breasted rats and replacing brown rats.
Further analysis of the physiological endocrine system found that yellow-breasted rats had significantly higher blood cortisol than brown rats, and long-term stimulation of interspecific odors had no effect on blood cortisol levels in both mice. However, the expression of the GR (glucocorticoid receptor) gene in the hippocampal tissue of the brain is significantly upregulated in brown mice, which may increase the damage of blood glucocorticoids to the hippocampus; the expression of the BDNF (brain-derived neurotrophic factor) gene in the hippocampal tissue is significantly upregulated in yellow-breasted mice, which contributes to the development of the hippocampus. These physiological data also indicate that long-term stimulation of interspecific odors is conducive to the long-term competition between yellow-breasted rats and brown house mice.
The study was funded by the National Foundation of China and the Pilot Project B of the Chinese Academy of Sciences.
相关论文：Hong-Ling Guo, Hua-Jing Teng, Jin-Hua Zhang, Jian-Xu Zhang and Yao-Hua Zhang. Asian house rats may facilitate their invasive success through suppressing brown rats in chronic interaction. Frontiers in Zoology: 201714:20 DOI: 10.1186/s12983-017-0202-4
Yellow-breasted rat (left) and brown rat (right)
Small mice found in animals use odor to inhibit large mice and promote northward expansion and invasion of the distribution area