Under the influence of multiple factors such as Vietnam’s rising comprehensive strength,the complex security situation in Southeast Asia,and the intensification of competition between China and the United States,Viet...Under the influence of multiple factors such as Vietnam’s rising comprehensive strength,the complex security situation in Southeast Asia,and the intensification of competition between China and the United States,Vietnam has adjusted its national defense policy in recent years,promulgated relevant regulations,cultivated and raised national defense awareness,continued to strengthen traditional security defense in border and coastal areas,and gradually expanded prevention and cooperation in non-traditional security areas.It has also combined defense construction with socio-economic development,prioritized defense investment in border areas,islands,and military modernization,developed military science and technology,and improved maritime military forces.It will also continue to diversify its defense cooperation and expand defense exchanges and cooperation with ASEAN and overseas powers.It will attach importance to defense and friendly relations in the border areas of China and Vietnam,while at the same time seeking to reap maximum benefits from the competition between major powers and disputes in the South China Sea.These policies will help Vietnam strengthen its defense forces and realize its aspirations as a regional military power.展开更多
2016 witnessed more major terrorist attacks around the globe,some of which killed and injured100 or more people.Many countries,including China,face the threat of terrorism.When delivering his Report on the Work of the...2016 witnessed more major terrorist attacks around the globe,some of which killed and injured100 or more people.Many countries,including China,face the threat of terrorism.When delivering his Report on the Work of the Government in March2017,Premier Li Keqiang outlined the tasks and goals of national defense,and emphasized the importance of counterterrorism in safeguarding stability.展开更多
Many birds join cooperative mobbing aggregations and collectively harass predators. Individuals participating in these ephemeral associations benefit by deterring the predator, but also incur energetic costs and incre...Many birds join cooperative mobbing aggregations and collectively harass predators. Individuals participating in these ephemeral associations benefit by deterring the predator, but also incur energetic costs and increased risk of predation. Ex- plaining the evolution of mobbing is challenging because individuals could prevail by selfishly seeking safety while allowing others to mob. An important step in understanding the evolution of mobbing is to identify factors affecting its expression. The ecological constraints model suggests that animals are more likely to cooperate under adverse environmental conditions, such as when local predation pressure is high. We tested this prediction by comparing the mobbing responses of several species of birds to the local abundance of their primary predator, the ferruginous pygmy-owl Glaucidium brasilianum. We used acoustic playback to elicit mobbing responses in environments where owls were common, uncommon, or rare. Stimuli were either the song of a fer- ruginous pygmy-owl or the mobbing calls of three of the owl＇s common prey species. During each playback, we characterized mobbing responses by noting the number of species and individuals that approached the loudspeaker, as well as the closest ap- proach by any bird. Mobbing responses to both stimuli were strong in locations where Ferruginous Pygmy-owls were common, intermediate where owls were uncommon, and weak where they were rare. This pattern persisted even after controlling for dif- ferences in species richness and composition among the three environments. Results support the ecological constraints model and provide strong evidence that intense predation pressure increases the expression of cooperative mobbing in tropical birds [Cur- rent Zoology 58 （5）： 781-790, 2012].展开更多
基金This work was supported by the National Social Science Foundation of China(Grant no.18AGJ007).
文摘Under the influence of multiple factors such as Vietnam’s rising comprehensive strength,the complex security situation in Southeast Asia,and the intensification of competition between China and the United States,Vietnam has adjusted its national defense policy in recent years,promulgated relevant regulations,cultivated and raised national defense awareness,continued to strengthen traditional security defense in border and coastal areas,and gradually expanded prevention and cooperation in non-traditional security areas.It has also combined defense construction with socio-economic development,prioritized defense investment in border areas,islands,and military modernization,developed military science and technology,and improved maritime military forces.It will also continue to diversify its defense cooperation and expand defense exchanges and cooperation with ASEAN and overseas powers.It will attach importance to defense and friendly relations in the border areas of China and Vietnam,while at the same time seeking to reap maximum benefits from the competition between major powers and disputes in the South China Sea.These policies will help Vietnam strengthen its defense forces and realize its aspirations as a regional military power.
文摘2016 witnessed more major terrorist attacks around the globe,some of which killed and injured100 or more people.Many countries,including China,face the threat of terrorism.When delivering his Report on the Work of the Government in March2017,Premier Li Keqiang outlined the tasks and goals of national defense,and emphasized the importance of counterterrorism in safeguarding stability.
文摘Many birds join cooperative mobbing aggregations and collectively harass predators. Individuals participating in these ephemeral associations benefit by deterring the predator, but also incur energetic costs and increased risk of predation. Ex- plaining the evolution of mobbing is challenging because individuals could prevail by selfishly seeking safety while allowing others to mob. An important step in understanding the evolution of mobbing is to identify factors affecting its expression. The ecological constraints model suggests that animals are more likely to cooperate under adverse environmental conditions, such as when local predation pressure is high. We tested this prediction by comparing the mobbing responses of several species of birds to the local abundance of their primary predator, the ferruginous pygmy-owl Glaucidium brasilianum. We used acoustic playback to elicit mobbing responses in environments where owls were common, uncommon, or rare. Stimuli were either the song of a fer- ruginous pygmy-owl or the mobbing calls of three of the owl＇s common prey species. During each playback, we characterized mobbing responses by noting the number of species and individuals that approached the loudspeaker, as well as the closest ap- proach by any bird. Mobbing responses to both stimuli were strong in locations where Ferruginous Pygmy-owls were common, intermediate where owls were uncommon, and weak where they were rare. This pattern persisted even after controlling for dif- ferences in species richness and composition among the three environments. Results support the ecological constraints model and provide strong evidence that intense predation pressure increases the expression of cooperative mobbing in tropical birds [Cur- rent Zoology 58 （5）： 781-790, 2012].
