Twenty-two species of bats worldwide are known to use modified leaves as their roost, known as ‘tents’. It has been suggested that the mating system of these species is resource-defense polygyny, with the presumably male-constructed tent serving as an attractant of females, but in Ectophylla alba a female was observed building a tent. The objectives of this work were to determine: 1) if both sexes build the tent; 2) if there is a relationship between number of tents and mating seasons and 3) the time availability of the Heliconia leaves that this species uses to makes its roost as well as the effect of the bats on the plant. The study site was the Tirimbina Biological Reserve, Sarapiqui, Costa Rica. During 53 weeks, we censused the tents of E. alba in nine hectares. Construction of tents was filmed with a video camera and infrared lights. To measure the average life of the tents and the leaves that had not been modified, we marked leaves that were visited weekly to monitor for deterioration. Our results show that both females and males construct tents. Roost construction is costly in terms of time and effort, so the bats maximize the time spent occupying the tent. The modifications that the bats make to the leaves considerably reduce the lifetime of the leaves. This has implications for both the plant used and for the bats that build the tents.