We investigated the consequences of mineral supplementation of mealworms at a facility where mustached bats (Pteronotus parnellii rubiginosus) from Trinidad were kept for experimental purposes. For 11 months after capture from the wild, the animals were constantly housed indoors and fed a diet of mealworms without mineral supplementation. After several animals died with skulls soft at palpation, this diet was suspected to be mineral deficient. From then on, mealworms were placed on a mineral mix one day prior to feeding, thus increasing their calcium content. For an assessment of the efficacy of the mineral supplementation, bone mineral density (BMD) was measured in the left radius with peripheral quantitative computer tomography. The animals were divided into 3 groups: six animals that died on capture were representing the free-ranging controls (Group A), eight animals died on the preliminary feeding regime without supplementation (Group B), and six animals fed the final, mineral-supplemented mealworms (Group C). BMD was highest in group A. Group B had significantly lower bone mineral density than Group A. Interestingly, Group C, receiving supplementation, showed no significant difference compared to Group A. This supports the assumption that it is important to feed a mineral supplementation to captive bats to conserve their normal bone structure.