The Influence of Precipitation on Reproduction by Myotis Bats in British Columbia

We compared the timing of reproduction by insectivorous bats in 1990, a wet year, with previously published data to test the prediction that reproduction is delayed by excess precipitation. The latest date of first capture of lactating, postlactating and juvenile bats occurred in 1990, whereas the earliest records for lactating females occurred in the driest year (1979). More important, the proportion of reproductive female Myotis lucifugus and M. yumanensis was significantly lower in 1990 than 1982. We conclude that high levels of precipitation delays reproduction and may induce some individuals to forego breeding altogether. Given the potential lifespan of temperate bats, this may be the best way of maximizing lifetime reproductive success.