Development of wing morphology in the Indian pygmy bat Pipistrellus mimus

The growth and development of the wing parameters of the Indian pygmy bat Pipistrellus mimus was studied under natural conditions. Newborn young were marked with nontoxic coloured paint and were later marked with split rings. The wingspan and wing area showed linear growth until the age of five weeks, after which the rate of growth decreased. The observations on flight showed that at the age of 19 days the young were able to flutter their wings, at the age of 22 days they flew for a short distance and at the age of 29 days they exhibited sustained flight. The development of wing loading and aspect ratio are also presented. The decrease in wing loading as the bat grows is discussed as an advantage to sustain flight. The aspect ratio showed a high degree of scatter at early stages of life which decreased at the later period of growth. In general the development of wing morphology of P. mimus is similar to that of other vespertilionid bats

Early outflying and late homeflying in the Indian pygmy bat under natural conditions

The outflying and homeflying activity pattern of a colony of the Indian pygmy bat Pipistrellus mimus occupying a tunnel was studied under natural conditions. Before leaving the tunnel for foraging, the bats made circling flights outside to sample the environmental light conditions. The onset and end of activity was related to the times of sunset and sunrise respectively. The onset of flight during evening commenced after sunset from mid-September to mid-April, before sunset during the rest of the year. Onset of activity occurred at higher light intensities compared to light intensities prevailing during the return flight to the roost in the morning. The duration of activity time showed a curvilinear relationship with the duration of the night. The phase relationship between onset and end of activity, and sunset and sunrise, showed marked seasonal variations in the values of ψonset, ψend, and ψmidpoint. However, such changes in the phase angle properties did not obey Aschoff's seasonal rule. Based upon the data obtained on the onset and end of activity patterns for five species of bats, including the data from this study, we report that P. mimus is the earliest to set out for foraging in the evening and among the last to return home in the morning. This might be due to dusk and dawn peaks in activity of the prey insects

Postnatal growth and age estimation in the Indian pygmy bat Pipistrellus mimus

The Indian pygmy bat Pipistrellus mimus produced two young per litter, which were altricial at birth. Empirical growth curves were derived by measuring length of forearm, body mass, and length of the total gap of the fourth metacarpal-phalangeal joint. Length of forearm and body mass followed a linear pattern of growth until day 20 and subsequently reached stability. The length of the total gap of the metacarpal-phalangeal joint showed a linear increase up to 20 days, followed by a linear decrease until ca. 80 days when it closed. A quantitative method of estimation of age was derived from values of length of forearm and length of the total gap of the fourth metacarpal-phalangeal joint during the preflight (first 20 days) and postflight stages, respectively. Width of the 95% confidence level was ±0.6 days at a mean length of forearm of 15.1 mm, and it was ±0.9 days at a mean length of the total gap of the fourth metacarpal-phalangeal joint of 2.0 mm. Initiation of flight occurred 21 days after birth. At 33 days of age, young were able to forage on their own. Females experienced their first parturition at the mean age of 112 days. Females of P. mimus apparently attains sexual maturity within 2 months after birth, which may be the youngest age for sexual maturity in a bat