The sac-winged bat (Balantiopteryx plicata) is found in dry-tropical areas from Mexico to Costa Rica; and occupies a great variety of day roosts.  It feeds basically from insects. It is found in groups which size varies from 50 to 200, with a maximum colony size of 2000. Because B. plicata is a very abundant species in the Pacific coast of Mexico, which inhabits in almost any man made structure, it could be an important controller of insect’s populations. The aims of this work are: 1) to analyze the numerical variation of B. plicata in the roost, 2) to determine the sex ratio, age structure and reproductive condition of females, and 3) to determine its time of residence.  This study was conducted in Chamela, Jalisco; in an abandoned irrigation channel.  We carried out ten sample periods, in 2003 (April and July), 2004 (February, April and July), 2005 (March and September), 2006 (April and November); and in 2007 (April).  

Results/Conclusions

There were variations in the number of marked individuals, ranging from 0 to 108.  The maximums were found in the dry season during April 2003 (89), April 2004 (108), March 2005 (81) and April 2006 (99); whereas during part of the wet season most of the bats left the day roost.  Males and females were captured during the whole study, being always significantly more females than males (1:2.07; P < 0.05).  The adults were present during the whole study and the babies only in July.  The receptive females were captured from February to April, and in July nursing females.  July corresponds with the beginning of the rain period in the region that increases of insects abundance.  The maximum residence registered by females and males was three years.