Monitoring rodents with linear trap-barrier system in corn fields

The trap-barrier system (TBS) method has been used extensively in agricultural systems for trapping rodents in China because it is highly effective in preventing and controlling rodents with high capture rate, long and consistent control period and poses no harm to people and livestock as well as predators. Many researchers also have recommended the use of TBS in monitoring rodents due to its ability to capture rodents. In order to test the effects of TBS rodent monitoring, we set line trap-barrier system (L-TBS) and night snap-trap (NST, national industry standard of NY/T 1481—2007 ) systems from May to October 2015 to trap rodents in the corn fields of Boertala Mongolia Autonomous County, Xinjiang Uygur Autonomous Region. The purpose of this study was to investigate the scientific evidence of the application of L-TBS in field rodent surveillance and to explore the corresponding relations between rodent community collected by L-TBS and by NST. Three replications were carried out at different sites in the same region using the same operation mode. The rodent community structure and population structure of dominant rodent species, including population dynamics and reproduction characteristics of captured rodent species were analyzed. The results certified the relevance of rodent species, and population structure and reproduction characters of rodent community between two methods. Firstly, Chi-Square test on rodent species composition captured by the L-TBS and NTS showed no statistically significant differences (χ2 = 3.31, P = 0.35). The percentage of dominant species of rodent composition was also not statistically significantly different (Mus musculus: χ2 = 1.50, P = 0.44; Cricetulus migratorius: χ2 = 0.54, P = 0.63). Secondly, there was a statistically significant positive correlation between the abundance of the dominant species house mouse (Mus musculus) captured by L-TBS and NST (y = 0.143 1 + 0.146 5x, r = 0.707 7, P = 0.000 0). Meanwhile, the reproduction parameters of dominant species (Mus musculus) trapped by the two methods also had statistically significant positive correlation (sex ratio, r = 0.71; pregnancy rate, r = 0.926 8; percent male with prominent testicle, r = 0.869 2; reproduction index, r = 0.94). What is more, analysis of the age structure of the capture rodent species showed that L-TBS trapped more juvenile rodents than NST. L-TBS captured five groups of rodents with different age classes (juvenile, sub-adult, adult I, adult II and old-age classes), which fully reflected the age structure of rodent population in the region. Thus L-TBS more accurately reflected the population dynamics of field rodents in the study area. L-TBS captured some species of Soricidae (e.g., Sorex minutus) which were demanded to be monitored by the Epidemic Prevention Department of the government, but were hardly captured by NST method. Therefore, it was concluded that L-TBS method was applicable in preventing, controlling and monitoring over-ground rodent communities. It was necessary to set up 60 m long L-TBS system in the farm field of 6.67 hm^-2. Compared with NST method, L-TBS method saved time and labor cost. It was also safer and easier to operate, particularly applicable in remote areas that lacked monitoring personnel and traffic. In addition, it was possible to arrange L-TBS alongside fields, which was suitable for mechanized farming operations. Therefore, L-TBS had a promising prospect for wilder applications in monitoring field rodents. However, L-TBS method captured less proportion of Rattus norvegicus than NST method (χ2 = 9.54 > χ20.01 = 9.21, P = 0.004 5). This was because Rattus norvegicus shied away from new objects and jumped over traps due to their larger size. There was therefore need for improvement of the traps of L-TBS.