The role of the flight membranes in insect capture by bats

Abstract

1. 1. A large series of electronic flash photographs of bats catching insects on the wing has demonstrated several common techniques employed. 2. 2. A small and slow-flying insect such as a fruit fly may be sometimes seized directly with the mouth. In most cases, however, the interfemoral membrane is formed into a pouch by forward flexion of the hind legs and tail just before an insect is intercepted. Immediately after contact with the insect, the head is enclosed within the pouched tail membrane while the insect is seized in the jaws. Examples of this technique occur when a Myotis lucifugus catches mealworms tossed into the air, and when Lasiurus borealis catches flying moths. 3. 3. When the insect is not directly in front of the approaching bat one wing is often extended so as to intercept it. Sometimes the terminal joints of the 3rd and 4th fingers are flexed to form a scoop in which the insect is rapidly conveyed to the mouth, usually by way of the pouched tail membrane. This technique has been photographed in Myotis lucifugus catching fruit flies and also mealworms that had been tossed into the air. The wing was also employed in this manner during a single case where a greater horseshoe bat, Rhinolphus ferrum-equinum, was photographed catching a flying moth. 4. 4. In a few cases the photographs show that the wing is used either deliberately or accidentally to flick an insect into a position where it is seized in the mouth or pouched tail membrane a fraction of a second later. This technique has been clearly photographed only with Myotis lucifugus catching tossed mealworms. 5. 5. While the use of tail and wing membranes greatly increases the potential area of contact with insect prey over the area of the opened mouth alone, the photographs almost invariably show that the bat's head is pointed at the insect well before contact with it. Preparatory movements such as cupping the tail membrane, flexing the terminal joints of the fingers, and reaching the wing toward the moving insect, all show that the insect is located quite accurately before it touches any part of the bat. These photographs strongly indicate that each insect is individually located and intercepted. 6. 6. The wing of these bats thus retains some of the prehensile functions of the hand in non-flying mammals.