To exploit a rich food resource that remains largely inaccessible to most predators, Europe's largest bat captures, kills, and consumes nocturnally migrating birds in flight high above the ground, according to a new study. The findings confirm this behavior of the greater noctule (Nyctalus lasiopterus) using direct biologger observations. Billions of birds seasonally migrate at night and over long distances at high altitude. These massive flocks represent an enormous – albeit challenging – food resource for predators. Yet only three fast-flying echolocating bat species, including the greater noctule, are known to exploit this opportunity, hunting passerine birds at night and in flight, despite the birds' relatively large size and evasive aerial abilities. However, direct evidence of these activities is scarce and based largely on bird remains in bat feces. It remains unknown where and how these bats hunt such formidable prey.
To address this gap, Laura Stidsholt and colleagues equipped 14 greater noctules with high-resolution biologging tags that recorded altitude, echolocation, and 3D movement, and tracked their hunting behavior. In contrast to the typical short, low-altitude insect hunts, Stidsholt et al. observed two notable attacks; the bats climbed above 400 meters before spotting prey and then executed prolonged, high-speed downward chases. Each chase included over 40 echolocation buzzes at rapid intervals, indicating sustained pursuit of a single target. Although one attack ended unsuccessfully, the other resulted in the capture of a European robin, which was confirmed by recorded audio of the bird's distress calls. After capture, the bat dispatched the bird, likely via a lethal bite. Subsequent chewing sounds, recorded between echolocation calls, indicate that the bat consumed the bird continuously during flight for 23 min without losing altitude. Analyses of bird wings collected beneath the bats' hunting grounds, using predator DNA barcoding and x-rays, revealed distinctive bite marks from greater noctule bats. According to the authors, this suggests that the bats, while in flight, remove the wings to immobilize their prey, reduce drag, and ease prey handling – a technique reminiscent of aerial-hawking strategies used for capturing large insects. This aerial handling contrasts sharply with birds of prey and other carnivorous bats, which typically consume large prey while perched.
