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1. The challenge of detecting prey: Private and social information use in predatory bats

   https://doi.org/10.1111/1365-2435.13439  

   Page, Rachel A. ; Bernal, Ximena E. ; Fox, ed., Charles ( September 2019 , Functional Ecology)

   In the evolutionary arms race between predators and their prey, prey often evolve to be as cryptic as they can, while predators in turn hone their sensory strategies to detect prey. Examinations of the sensory strategies implemented by predators to detect their prey, as well as the ecological consequences of these interactions, are at the crux of understanding and predicting predator–prey dynamics.

   We review the sensory strategies used by predators that rely on private information (attending directly to cues and signals generated by their prey) and those that gather social information (attending to the signals and behaviours of others). We focus our enquiry on bats, an ideal group to shed light on these questions given their ecological diversity, varied foraging strategies and wide range of social behaviours.

   We discuss the costs and benefits of using private and social information for foraging. We investigate diverse strategies of information use and examine the effects different predatory strategies have on predator sensory systems.

   We provide an overview of the sensory ecology of information use in hunting in bats and, by identifying current gaps in knowledge, highlight fruitful directions for future research.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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2. Echolocating bats accumulate information from acoustic snapshots to predict auditory object motion

   https://doi.org/10.1073/pnas.2011719117  

   Salles, Angeles ; Diebold, Clarice Anna ; Moss, Cynthia F. ( November 2020 , Proceedings of the National Academy of Sciences)

   Unlike other predators that use vision as their primary sensory system, bats compute the three-dimensional (3D) position of flying insects from discrete echo snapshots, which raises questions about the strategies they employ to track and intercept erratically moving prey from interrupted sensory information. Here, we devised an ethologically inspired behavioral paradigm to directly test the hypothesis that echolocating bats build internal prediction models from dynamic acoustic stimuli to anticipate the future location of moving auditory targets. We quantified the direction of the bat’s head/sonar beam aim and echolocation call rate as it tracked a target that moved across its sonar field and applied mathematical models to differentiate between nonpredictive and predictive tracking behaviors. We discovered that big brown bats accumulate information across echo sequences to anticipate an auditory target’s future position. Further, when a moving target is hidden from view by an occluder during a portion of its trajectory, the bat continues to track its position using an internal model of the target’s motion path. Our findings also reveal that the bat increases sonar call rate when its prediction of target trajectory is violated by a sudden change in target velocity. This shows that the bat rapidly adapts its sonar behavior to update internal models of auditory target trajectories, which would enable tracking of evasive prey. Collectively, these results demonstrate that the echolocating big brown bat integrates acoustic snapshots over time to build prediction models of a moving auditory target’s trajectory and enable prey capture under conditions of uncertainty.

    

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3. A phantom ultrasonic insect chorus repels low‐flying bats, but most are undeterred

   https://doi.org/10.1111/1365-2435.13933  

   Sedlock, Jodi L. ; Gomes, Dylan G. E. ; Rubin, Juliette J. ; Woody, Sarah ; Hadi, Buyung A. R. ; Barber, Jesse R. ( October 2021 , Functional Ecology)

   The acoustic environment can serve as a niche axis, structuring animal behaviour by providing or obscuring salient information. Meadow katydid choruses occupy the ultrasonic, less studied, realm of this acoustic milieu, form dense populations in some habitats and present a potential sensory challenge to co‐occurring ultrasonic‐hearing animals. Aerial‐hawking insectivorous bats foraging immediately over vegetation must listen for echoes of their prey and other cues amidst the chorus din.

   We experimentally created the cacophony of a katydid chorus in a katydid‐free rice paddy using an aggregation of 100 ultrasonic speakers in a 25 × 25 m grid to test the hypothesis that aerially hawking bats are averse to this noise source. We alternated between chorus‐on and chorus‐off hourly, and acoustically monitored bat activity and arthropod prey abundance.

   We found that our phantom katydid chorus reduced bat activity nearest the sound source by 39.3% (95% CI: 7.8%–60.0%) for species whose call spectrum fully overlapped with the chorus, and elicited marginal reductions in activity in species with only partial spectral overlap.

   Our study suggests that ultrasonic insect choruses degrade foraging habitat, potentially suppressing bats’ ecosystem services as consumers of pests; and, given the global distribution of meadow katydids, may provide an underappreciated force modifying animal behaviour in other grassland habitats.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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4. Head shape predicts isotopic diet in anoles and day geckos

   https://doi.org/10.1111/1365-2435.14331  

   Figueira, Tyler J. ; Kennedy‐Gold, Stevie ; Piantoni, Carla ; Screen, Robyn M. ; Wright, Amber N. ( April 2023 , Functional Ecology)

   Trophic morphology affects resource acquisition; therefore, species differences in such traits may be informative for inferring resource use overlap and potential species interactions.

   In lizards, head size and shape determine the size and hardness of prey that can be consumed. Lizards with large differences in head morphology are expected to overlap less in prey use than lizards with more similar traits.

   Stable isotopes are increasingly being used to describe diet, yet how traditional functional traits affect isotopic diet is often not clear a priori.

   We measured head size, head shape, 𝛿¹⁵N, and 𝛿¹³C under controlled resource availability in an enclosure experiment using introduced lizards in Hawaiʻi to test whether functional traits predict isotopic diet.

   Brown anolesAnolis sagreihad the tallest and narrowest heads, the highest values of 𝛿¹³C, and the lowest values of 𝛿¹⁵N. Gold dust day geckosPhelsuma laticaudahad the shortest and widest heads, the lowest values of 𝛿¹³C, and the highest values of 𝛿¹⁵N. Green anolesAnolis carolinensiswere intermediate in both diet and morphology.

   As a result of isotopic diet overlap, green anoles have reduced competitor‐free resource space in the presence of both of the other lizard species.

   Head shape was the best predictor of diet and the only trait that explained variation within as well as among species. Head size was sexually dimorphic, and therefore the weaker diet correlations with this trait may be explained by sexual selection.

   Breadth in morphospace did not correlate with isotopic diet breadth, nor did the amount of overlap in morphospace predict the amount of overlap in isotopic diet space.

   While lizards were able to locally depress prey in experimental enclosures, no shifts in diet were detected in response to the presence of heterospecifics.

   The generality of head shape in predicting isotopic diet, and whether it does so independent of habitat use, warrants additional study. Head shape provides a potentially fruitful avenue for trait‐based approaches to studying ecology and evolution in lizards.

   Read the freePlain Language Summaryfor this article on the Journal blog.

    

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5. Sensory adaptations reshaped intrinsic factors underlying morphological diversification in bats

   https://doi.org/10.1186/s12915-021-01022-3  

   Arbour, J. H. ; Curtis, A. A. ; Santana, S. E. ( April 2021 , BMC Biology)

   Morphological evolution may be impacted by both intrinsic (developmental, constructional, physiological) and extrinsic (ecological opportunity and release) factors, but can intrinsic factors be altered by adaptive evolution and, if so, do they constrain or facilitate the subsequent diversification of biological form? Bats underwent deep adaptive divergences in skull shape as they evolved different sensory modes; here we investigate the potential impact of this process on two intrinsic factors that underlie morphological variation across organisms, allometry, and modularity.

   We use comparative phylogenetic and morphometric approaches to examine patterns of evolutionary allometry and modularity across a 3D geometric morphometric dataset spanning all major bat clades. We show that allometric relationships diverge between echolocators and visually oriented non-echolocators and that the evolution of nasal echolocation reshaped the modularity of the bat cranium.

   Shifts in allometry and modularity may have significant consequences on the diversification of anatomical structures, as observed in the bat skull.

    

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