Effects Of Livestock Grazing On Grasshopper Behaviors And Performance

Grazing livestock and insects are important biological components of grassland ecosystems.They are numerous and coexist with each other,and play a vital role in maintaining the structure and function of grassland ecosystems.Grazing is one of the most important utilization methods in grassland ecosystem.Different kinds of large herbivores,such as cattle and sheep,change the structure characteristics,nutrient content and microenvironment of plant community through feeding,trampling and excretion of urine and feces,thus indirectly affecting the population density and individual behavior and performance of herbivorous insects.However,due to different ecosystem types or grazing types and intensities of large herbivores,the mechanism of livestock grazing on herbivores has not been unified.Therefore,exploring the effects of large herbivores on the individual behavior and performance of grasshoppers and the ways of action will help us understand the theory of species coexistence in nature,and provide guidance for the prevention and control of locust plague and the protection of grassland ecosystems.In this study,the representative phytophagous animals in Songnen grassland were selected as the research objects : large herbivores-cattle(Bos taurus),sheep(Ovis aries),and the dominant insect species in grassland ecosystem-Euchorthippus unicolor.The effects of grazing activities of different kinds of large herbivores on community structure,plant nutrient content and individual and population characteristics of grasshoppers were analyzed by field controlled grazing experiment and field cage experiment.Combined with indoor control experiments,the effects of locust population density on its individual behavior and performance were clarified,and the relationship between grazing activities,locust population density and its behavior and performance was deeply analyzed.The potential mechanism and action pathway of livestock grazing on locust individual behavior and population performance were revealed from multiple perspectives.The main findings and conclusions of this research are as follows:(1)Large-scale controlled grazing experiments in the field showed that there were significant differences in the effects of cattle grazing and sheep grazing on different plant functional groups.Sheep grazing significantly reduced the density,height and cover of miscellaneous grasses and significantly increased the nitrogen content of Leymus chinensis leaves.Cattle grazing slightly reduced L.chinensis density,but significantly increased miscellaneous grass density,cover,biomass,and very significantly increased L.chinensis leaf nitrogen content compared to sheep grazing.In addition,the microenvironment of grazing sample plots was measured in this study and it was found that grazing did not significantly affect the ambient humidity and light intensity,but significantly increased the air temperature at 30 cm from the ground,and the magnitude of the effect of cattle grazing was greater than that of sheep grazing.These experimental results were mainly due to the foraging preferences of these animals,with sheep preferring miscellaneous grasses with high nutritional value and cattle preferring L.chinensis.Therefore,the type of grazing livestock is a key factor affecting the characteristics of grassland plant communities.(2)Small-scale in situ control experiments in the field showed that sheep grazing significantly increased the population density of E.unicolor,while cattle grazing slightly decreased the population density of E.unicolor.Small-scale behavioral observations in the field showed that the effect of large herbivores on the performance of the grasshopper was modulated by sex,and grazing significantly reduced the survival rate and body size of female grasshoppers and significantly reduced the weight gain of males.In addition,the effects of sheep grazing and cattle grazing on the feeding frequency,jumping frequency and resting time of female and male grasshoppers were not significant;however,both grazing methods significantly reduced the crawling frequency of female and male grasshoppers.(3)Small-scale grasshopper population density control experiments in the field showed that grasshopper density significantly affected individual behavior and population performance of grasshoppers.Higher grasshopper densities increased feeding,walking,jumping,dry leaf consumption,mass gain and femur length,and decreased quiescence and survival rate of grasshoppers.In summary,livestock grazing significantly affected grasshopper population size,but the effects on individual grasshopper foraging behavior and population performance were inconsistent,with grazing having an indirect effect on grasshoppers mainly through the regulation of plant community characteristics and microenvironment.Changes in grasshopper population density can also affect individual grasshopper behavior and performance.Therefore,considering the interspecific competition and promotion relationship between different grazing animals and grasshoppers,and studying their response patterns from individual behavior to population performance and their differences,not only help to develop the theory of species coexistence,but also help us to accurately predict the outbreak trends of grasshopper populations under the conditions of increased human activities in the future,thus providing scientific basis for grassland management and pest control.