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Animal and Plant Health Inspection Service
U.S. Department of Agriculture

Fertility Control for Rats

It’s estimated that about 7 billion rats roam the planet on any given day. One of the more common species — the Norway rat — can produce up to 2,000 descendants per female in a year. Given these high numbers, it’s no wonder rodents can cause a lot of damage to agricultural crops and property, as well as spread disease.


In many parts of the world, people try to prevent rodent damage by using rodenticides to reduce rat populations. These poisons, however, are non-specific and hazardous to non-target species, such as dogs, cats, hawks, and owls that may feed on rodents.


In an effort to find a nonlethal damage management method, NWRC scientists teamed up with SenesTech Inc. and The University of Arizona to test the effectiveness of a liquid bait to control fertility in Norway rats. Two chemicals (4-vinylcyclohexane diepoxide and triptolide) known to target ovarian function in female rats were fed to captive Norway rats via the liquid bait. Triptolide is also known to affect spermatogenesis in males.


No offspring were born to treated females that were mated with treated males, while control pairs produced normal litter sizes of 9-10 offspring. The number of primordial follicles in ovaries collected from treated females were less than control females; and the weights of testes and epididymis taken from treated males were lower than in control males.


Researchers are optimistic that these results show the liquid bait inhibits fertility in both male and female rats and may be a feasible alternative to rodenticides for reducing rat populations.


The U.S. Environmental Protection Agency recently granted a registration for the liquid bait formulation for use with Norway rats and black rats under the product name ContraPest.


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