Modern methods for tracking polar bear populations have been employed only since the mid-1980s, and are expensive to perform consistently over a large area.
跟踪北极能种群的现代方法仅在20世纪80年代中期才被采用，而且，要在大范围内连续采用这种方法，其代价非常高昂。
Modern methods for tracking polar bear populations have been employed only since the mid-1980s, and are expensive to perform consistently over a large area.
跟踪北极能种群的现代方法仅在20世纪80年代中期才被采用，而且，要在大范围内连续采用这种方法，其代价非常高昂。
应用推荐