How long do wild rats live in the wild?
Wild rats have an average lifespan of about 1 year (Jackson 1982). Specifically, a wild rat population experiences about 95% mortality, which means that only 5% of rats remain alive after 12 months (Davis 1948, see also Brooks 1973). The longest-lived rat in the Davis (1948) study, which examined 1036 wild rats, lived to be 70 weeks old, e.g. 1 year and 4 months. In urban areas, the chances of surviving one year appear to be even less than 5% (Jackson 1982). Note that this “average lifespan” does not represent extremes. Whitaker (1980) reports that some wild rats can reach age 3, but such individuals are very rare. The vast majority of wild rats don’t make it to their first birthday. How long do wild rats live in a protected, semi-natural environment? Calhoun (1963) conducted a two-year study in which he kept wild rats in a 1/4 acre enclosure that was almost entirely predator-proof. He provisioned the rats with regular food and water. He started with ten wild rats and allowed the indiv
