After eating a lethal dose of Harris Dry - Up Mouse and Rat Killer Bars Rodenticide it can take 3-7 days for a rodent to die. Rodents will sit and gnaw the bait if it is held in place so that they cannot simply carry it away. If the bait is not secured there is a good chance the rodents will carry it back to their nesting area. We recommend you read our articles How to get rid of Roof Rats and also How to rodent proof your home.