A Review of European Owls as Predators of Bats

Abstract

Fossil evidence indicates that owls have been preying on bats from as far back as the Pleistocene. Overall, bats form quite small portions (i.e. trace to 0.2%) of the diets (by prey frequency) of European owls. An assessment of dietary studies and anecdotal accounts reveals that five species of European owls, the Eurasian scops owl Otus scops, Pygmy owl Glaucidium passerinum, Tengmalm's owl Aegolius funereus, little owl Athene noctua and Ural owl Strix uralensis, rarely feed on bats (with less than 0.1−0.4%) and a further two species, short-eared owl Asio flammeus and eagle owl Bubo bubo, may only take bats occasionally, while three species, long-eared owl Asio otus, barn owl Tyto alba and tawny owl Strix aluco, feed on bats more frequently. In this study, a total of 19,864 recorded bats have been preyed upon by these owls, with as many as 48 bat species being identified. Barn and tawny owls have captured most of this total (47.1 and 41.9%), followed by the long-eared owl (7.6%), while short-eared and eagle owls take similar amounts of bats (1.1 and 1.7%, respectively). Owl predation on bats deserves future research because it may help contribute to our knowledge on bat biodiversity and distribution and possibly identify an additional risk for small populations of endangered bats.

Continuous low-intensity predation by owls (Strix aluco) on bats (Nyctalus lasiopterus) in Spain and the potential effect on bat colony stability

“…Based on these approximate calculations, the three successful attacks on N. lasiopterus, with an average body mass of 48 g [28], may have contributed less than 0.3% of the owls' overall food intake during the study period. Even if the video recordings did not capture all owl predation, the proportion of bats in the diet of S. aluco in Doñana is probably similar to estimates from other studies in Europe [63], and far below the maximum 30% recorded contribution of bats to the diet of S. aluco that temporarily specialized on bats [9]. Considering that we recorded also only nine capture attempts on pipistrelles, none of which was successful, we conclude that the local breeding pair of S. aluco only opportunistically preyed on bats [64].…”

“…Exceptionally, the proportion of bats in the diet of owls can be much higher, when owl individuals specialize on bats. Individuals of three owl species in Europe have been found, at least temporarily or perhaps in exceptional situations, to include higher proportions of bats into their diet (up to 27% in barn owls Tyto alba [10]; up to 29% in long-eared owls Asio otus [11]; over 30% in tawny owls Strix aluco [9]). Despite the generally low proportion of bats in the owls' diets in the temperate zone, the impact of owl predation on bats may be ecologically significant, because of the bats' life-history traits, including their low fecundity [12].…”

Long-term population trends of the lesser horseshoe bat Rhinolophus hipposideros and the greater mouse-eared bat Myotis myotis in Poland

“…In particular, there are no predators specialized on bats in Europe 69 . Owls are the only nocturnal predators that can prey on bats in flight, but this is a rare and opportunistic phenomenon, and only two species of European owls, the barn owl Tyto alba and the tawny owl Strix aluco, feed on bats more frequently 70 . Occasionally, bats in roosts may be killed by domestic cats 71 and martens 72 .…”

Designed for Darkness: The Unique Physiology and Anatomy of Owls

“…Although some species of owls are specialist feeders, such as Fish Owls and Fishing Owls, and some have a definite preference for certain prey, such as the Barn Owl and the Short-eared Owl with voles, most owls are fairly generalist feeders, with prey as varied as rodents, birds, amphibians, insects and other invertebrates and, in a few opportunistic cases, even bats [50]. Not too long ago, because of their acknowledged diet of live prey, consisting of small vertebrates and invertebrates, it was widely accepted that owls did not scavenge, and any reported observation of this uncharacteristic behaviour was taken as an anomaly.…”