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Regulatory Focus™ > News Articles > Science & Technology: Rats!

Science & Technology: Rats!

Posted 01 June 2008

In an editorial published in the Journal of the American Medical Association more than 100 years ago, the writer described the prolific breeding habits, crop destruction, and disease and deaths caused by rats.1 The editorial called for their extermination by strict obedience to laws of sanitation. It was noted that rats breed three or four times a year, with females first breeding at the age of about four or five months. (The gestation period for a pregnant female rat is 21 days.) Male and female rats may have sex 20 times a day, and a dominant male rat may mate with up to 20 female rats in just six hours. The average litter size for rats is 10 or more; thus, a single pair, breeding three litters a year, would in three years have a progeny numbering up to 20 million.


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