The pocketed free-tailed bat (Nyctinomops femorosaccus) is a species of bat in the family Molossidae found in Mexico and in Arizona, California, New Mexico, and Texas in the United States. They resemble the Brazilian free-tailed bat (Tadarida brasiliensis) but differ morphologically. They are recognized as "least concern" by the IUCN and as "apparently secure" by Natureserve.[1]
The pocketed free-tailed bat shares similar features with the Brazilian free-tailed bat ("Tadarida brasiliensis") but is larger in size. The name is derived from a skin fold stretching from the medial side of the femur to the middle of the tibia. This fold produces a shallow pocket on the underside of the interfemoral membrane in the vicinity of the knee. Some defining characteristics include: Ears joined at the midline; second phalanx of the 4th digit is less than 5mm; anterior part of hard palate narrowly excised; upper incisors placed close together with longitudinal axes nearly parallel.[2]
The pocketed free-tailed bat also has a large broad head with grooved lips. The face has many stiff hairs with spoonlike tips. The ears are thick and leathery with the presence of a dominant tragus. Body dimensions: body length~112mm; feet~10mm; tail~46mm; ears~23mm; forearms~46mm. Body mass range is 10-.[3]
Like many other bats, this species is insectivorous; they eat a variety of insects including Lepidoptera, Hymenoptera, Homoptera, Coleoptera, Hemiptera, Orthoptera, Diptera, and Neuroptera. One research article showed that because of the limited flight maneuverability of the pocketed free-tailed bat compared with the Brazilian free-tailed bat the latter is better able to prey upon beetles. It also showed that the insect species diet for the pocketed free-tailed bats varies with season. In June and July, Lepidoptera accounted for the greatest volume of prey while diets in September and March consisting mostly of Hemiptera[4] Table 1. In the dry season, they seek drinking water from various open access water sources. The roosts are located in caves, crevices, mines, tunnels, and man-made structures [5] with colony sizes less than 100 individuals.
Like some other bats, pocketed free-tailed bats exhibit delayed fertilization. They mate just prior to ovulation in the spring.[6] Their young are born in early July. The gestation period is about 70 to 90 days and when the young are finally born, they weigh 3-4 grams, or about 22% of the adult weight.[7] This new generation is able to fly within 1-1.5 months[8]
