title: Bats aggregate to improve prey search but might be impaired when their density becomes too high.
abstract: Social foraging is a very common yet extremely complex behavior. Numerous studies attempted to model it with little supporting evidence. Studying it in the wild is difficult because it requires monitoring the animal's movement, its foraging success, and its interactions with conspecifics. We present a novel system that enables full night ultrasonic recording of freely foraging bats, in addition to GPS tracking. As they rely on echolocation, audio recordings of bats allow tapping into their sensory acquisition of the world. Rapid changes in echolocation allowed us to reveal the bats' dynamic reactions in response to prey or conspecifics—two key behaviors that are extremely difficult to assess in most animals. We found that bats actively aggregate and forage as a group. However, we also found that when the group became too dense, bats were forced to devote sensory attention to conspecifics that frequently entered their biosonar "field of view," impairing the bats' prey detection performance. Why then did bats fly in such high densities? By emitting echolocation calls, bats constantly provide public information about their detection of prey. Bats could therefore benefit from intentionally flying at a distance that enables eavesdropping on conspecifics. Group foraging, therefore, probably allowed bats to effectively operate as an array of sensors, increasing their searching efficiency. We suggest that two opposing forces are at play in determining the efficient foraging density: on the one hand, higher densities improve prey detection, but on the other hand, they increase conspecific interference.
authors.affiliation: Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel.
authors.forename: Noam
authors.initials: N
authors.lastname: Cvikel
authors.affiliation: Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 6997801, Israel.
authors.forename: Katya
authors.initials: K
authors.lastname: Egert Berg
authors.affiliation: Department of Entomology, University of Arizona, Tuscon, AZ 85721, USA.
authors.forename: Eran
authors.initials: E
authors.lastname: Levin
authors.affiliation: Department of Biology, University of Maryland, College Park, MD 20742, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: Hurme
authors.affiliation: Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel.
authors.forename: Ivailo
authors.initials: I
authors.lastname: Borissov
authors.affiliation: Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel.
authors.forename: Arjan
authors.initials: A
authors.lastname: Boonman
authors.affiliation: Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel.
authors.forename: Eran
authors.initials: E
authors.lastname: Amichai
authors.affiliation: Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 6997801, Israel. Electronic address: yossiyovel@hotmail.com.
authors.forename: Yossi
authors.initials: Y
authors.lastname: Yovel
mesh_terms: D000818:Animals; D002685:Chiroptera / Q000502:physiology*; D004455:Echolocation; D005426:Flight, Animal; D011156:Population Density; D011235:Predatory Behavior