Mother-young interactions in a maternity colony of Myotis formosus

The maternity colony of Myotis formosus in Yun-lin County, southwestern Tai wan, began to form in late March, and the numbers peaked (about 200) in May . Most bats left the roost site between mid-August and early October for un known hibernation sites. Females gave birth during May and June. Before par turition, females (n = 19) spent 563.9 min +/- 47.28 SD outside the roost p er night. Time away from the roost decreased significantly after they gave birth. Lactating females increased the total time that: they spent outside the roost per night by 37.8% from early to late lactation. Females spent mo re time grooming young than self-grooming during the first 2 weeks of lacta tion. From the 3rd week on, more time was spent on self-grooming. Forearm l ength and body mass of newborns were 21.46 +/- 1.90 mm (n = 13) and 3.71 +/ - 0.41 g (n = 12), about 42.8% and 24.1% of adult size, respectively. Young rarely moved during the 1st week after birth. They started to crawl at the 2nd week and to attempt short straight-line flight at the 3rd week. Female s always rested next to their young while roosting in the first 2 weeks of lactation but separated from them from the 3rd week on. Behavioral changes in females coincided with the growth and development of their young.