A problem defining temporal pattern in animal behaviour: clustering in the emergence behaviour of bats from maternity roosts

Does a Live Barn Owl (Tyto alba) Affect Emergence Behavior of Serotine Bats (Eptesicus serotinus)?

“…Therefore, we suppose bats could perceive a silhouette of an avian predator as a potential threat. Nevertheless, experiments with plastic owls have proven unsuccessful (Speakman et al, 1992;Kalcounis and Brigham, 1994), and we can speculate that bats may discriminate Tyto alba and Eptesicus serotinus 181 between a plastic (not stuffed) and a real owl. It is also possible that more than one stimulus are used by bats (silhouette plus movements or silhouette plus calls).…”

“…Kalcounis and Brigham (1994) and Speakman et al (1992) disputed that bats were able to distinguish models and playback calls of predators, used during their experiments, from real ones. Both authors presented plastic models of owls to emerging bats, Kalcounis and Brigham (1994) together with recorded owl calls.…”

“…At all colonies, increasing numbers of bats decreased the risk of predator attack (Fenton et al, 1994). Kalcounis and Brigham (1994) and Speakman et al (1992) proposed that bats should increase their clustering in the presence of a predator to decrease their probability of attack. However, their experiments with models of owls did not reveal any significant effect of predation risk on the extent of clustering during emergence.…”

“…This behavior has been called outburst activity or clustering (Speakman et al, 1992). Two hypotheses concerning the functional significance of clustering are considered (Speakman et al, 1999).…”

“…Speakman et al (1992), Kalcounis and Brigham (1994) and Petrelková and Zukal (2001) used a predator model associated with or without recorded calls, to study the response to predation risk on emergence behavior. Effective antipredator defense mechanisms depend on efficient recognition of potential predators.…”