Previous attempts to cull pika numbers, including mass poisoning campaigns and the construction of hundreds of perches for owls and eagles, have failed or had limited success.

• 以前也用过很多方法限制鼠兔的数量，如：大量投放毒药，为鹰和猫头鹰建立上百个栖息处，但是，最后都失败了，或是收效甚微。