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The largest continent, Asia, which harbored some of the world's oldest civilizations, constitutes one-third of the earths land area. The physiography of central Asia is dominated by the mightiest ranges: the Himalayas, Hindukush, Kunlun, and Tien Shan. The distribution and abundance of rodents in Asia indicate a broad pattern which, in a way, corresponds to the terrain physiography and bioclimate of the region. Periodic as well as sporadic outbreaks in the rodent populations enhance their numbers menacingly. Such outbreaks can be caused either by failure of monsoon, by favorable reproductive conditions after a fairly long spell of climates, or can be associated with flowering of bamboo in forests. Quantified information on actual damage caused by rodents to agricultural crops in China is not available; however, 10% loss in field crops is reported. Rodent damage to grasslands and fodder crops is very severe, especially in the arid tracts.

The availability of anticoagulant rodenticides, particularly that of the second generation, has generated ample hope that, by their use, rodent populations can be reduced below the threshold level, thereby substantially reducing the losses incurred by these pests. The acute toxicant, zinc phosphide, still remains the most used and popular rodenticide in most parts of the world. In a control operation, zinc phosphide baits are recommended for distribution in the fields on three consecutive days. When poison baits are exposed to the rodent populations, some of them consume a lethal quantity and succumb, whereas those which ingest only a sublethal dose of poison survive the poisoning. The bait shyness and poison aversion phenomena, due to ingestion of various poisons, persist for varying durations in different species and with different rodenticides. Even after acquiring considerable knowledge about phenomena of bait shyness and poison aversion, we know very little about how to overcome them with a view to enhance success of control operations.