Biology subjects

Goerlitz, H. R.

Publications and source records attributed to Goerlitz, H. R..

7 recordsLinked to original sources

bioRxiv2023

Variation in echolocation call emission of Neotropical insect-eating bats in response to shifting ambient temperatures

The sensory systems of animals are essential for them to respond to environmental cues and signals. However, their functionality might be altered by climate change. Most bats, for example, rely on acoustic signal emission for acquiring food, but their high-frequency echolocation calls are strongly attenuated in the air. Attenuation in air changes with changing weather conditions, which can lead to shifts in echo-based prey detection distance. However, bats adjust call parameters to the task and environment, and this behavioural plasticity may also help them to counteract potential increases in sound attenuation to keep echo detectability constant. We explored this ability in a community of insectivorous bats in a montane forest of Costa Rica. We recorded bat echolocation calls in response to experimentally increased temperatures, simulating intermediate and arguably realistic projected climate change scenarios. We calculated atmospheric attenuation and detection distance for each temperature and echolocation call. We found some changes in source level and call duration, yet not in peak frequency, and responses were not consistent across species with increasing atmospheric attenuation. This might be explained by several non-mutually exclusive reasons, including that the experimental increase in temperature and change of atmospheric attenuation were not sufficient to affect close-range prey detection. Ultimately, this study contributes to our understanding of sensory system adaptation under the pressure imposed by climate change. SUMMARY STATEMENTStudying adjustments in bats call parameters can reveal responses to the pressure imposed by climate change.

ecology↗

bioRxiv2022

Echolocating bats prefer a high risk-high gain foraging strategy to increase prey profitability

Most bats catch nocturnal prey during active flight guided by echolocation but some species depart from this ancestral behaviour to capture ground prey using passive listening. Here, we explore the costs and benefits of these hunting transitions by combining high-resolution biologging data and DNA metabarcoding to quantify the relative contributions of aerial and ground prey to the total food intake of wild greater mouse-eared bats. We show that these bats use both foraging strategies with similar average nightly captures of 25 small, aerial insects and 30 large, ground-dwelling insects per bat, but with higher capture success in air (78 % in air vs 30 % on ground). However, owing to the 3 to 20 times heavier ground prey, 85 % of the estimated nightly food acquisition comes from ground prey despite the 2.5 times higher failure rates. Further, we find that most bats use the same foraging strategy on a given night suggesting that bats adapt their hunting behaviour to weather and ground conditions. We conclude that prey switching matched to environmental dynamics plays a key role in covering the energy intake even in specialised predators.

animal behavior and cognition↗

bioRxiv2020

Individual differences show that only some bats can cope with noise-induced masking and distraction.

Anthropogenic noise is a widespread pollutant that has received considerable recent attention. While alarming effects on wildlife have been documented, we have limited understanding of the perceptual mechanisms of noise disturbance, which are required to understand potential mitigation measures. Likewise, individual differences in response to noise (especially via perceptual mechanisms) are likely widespread, but lacking in empirical data. Here we use echolocating bats, a trained discrimination task, and experimental noise playback to explicitly test perceptual mechanisms of noise disturbance. We demonstrate high individual variability in response to noise treatments and evidence for multiple perceptual mechanisms. Additionally, we highlight that only some individuals are able to cope with noise, while others are not. We tested for changes in echolocation call duration, amplitude, and peak frequency as possible ways of coping with noise. Although all bats strongly increased call amplitude and showed additional minor changes in call duration and frequency, these changes cannot explain the differences in coping and non-coping individuals. Our understanding of noise disturbance needs to become more mechanistic and individualistic as research knowledge is transformed into policy changes and conservation action.

animal behavior and cognition↗

bioRxiv2019

Neural representation of bat predation risk and evasive flight in moths: a modelling approach

Most animals are at risk from multiple predators and can vary anti-predator behaviour based on the level of threat posed by each predator. Animals use sensory systems to detect predator cues, but the relationship between the tuning of sensory systems and the sensory cues related to predator threat are not well-studied at the community level. Noctuid moths have ultrasound-sensitive ears to detect the echolocation calls of predatory bats. Here, combining empirical data and mathematical modelling, we show that moth hearing is adapted to provide information about the threat posed by different sympatric bat species. First, we found that multiple characteristics related to the threat posed by bats to moths correlate with bat echolocation call frequency. Second, the frequency tuning of the most sensitive auditory receptor in noctuid moth ears provides information allowing moths to escape detection by all sympatric bats with similar safety margin distances. Third, the least sensitive auditory receptor usually responds to bat echolocation calls at a similar distance across all moth species for a given bat species. If this neuron triggers last-ditch evasive flight, it suggests that there is an ideal reaction distance for each bat species, regardless of moth size. This study shows that even a very simple sensory system can adapt to deliver information suitable for triggering appropriate defensive reactions to each predator in a multiple predator community.

neuroscience↗

bioRxiv2019

Active sensing in groups: (what) do bats hear in the sonar cocktail party nightmare?

Active sensing animals perceive their surroundings by emitting probes of energy and analyzing how the environment modulates these probes. However, the probes of conspecifics can jam active sensing, which should cause problems for groups of active sensing animals. This problem was termed the cocktail party nightmare for echolocating bats: as bats listen for the faint returning echoes of their loud calls, these echoes will be masked by the loud calls of other close-by bats. Despite this problem, many bats echolocate in groups and roost socially. Here, we present a biologically parametrized framework to quantify echo detection in groups. Incorporating known properties of echolocation, psychoacoustics, spatial acoustics and group flight, we quantify how well bats flying in groups can detect each other despite jamming. A focal bat in the center of a group can detect neighbors for group sizes of up to 100 bats. With increasing group size, fewer and only the closest and frontal neighbors are detected. Neighbor detection is improved for longer call intervals, shorter call durations, denser groups and more variable flight and sonar beam directions. Our results provide the first quantification of the sensory input of echolocating bats in collective group flight, such as mating swarms or emergences. Our results further generate predictions on the sensory strategies bats may use to reduce jamming in the cocktail party nightmare. Lastly, we suggest that the spatially limited sensory field of echolocators leads to limited interactions within a group, so that collective behavior is achieved by following only nearest neighbors. SIGNIFICANCE STATEMENTClose-by active sensing animals may interfere with each other. We investigated if and what many echolocators fly in a group hear - can they detect each other after all? We modelled acoustic and physical properties in group echolocation to quantify neighbor detection probability as group size increases. Echolocating bats can detect at least one of their closest neighbors per call up to group sizes of even 100 bats. Call parameters such as call rate and call duration play a strong role in how much echolocators in a group interfere with each other. Even when many bats fly together, they are indeed able to detect at least their nearest frontal neighbors - and this prevents them from colliding into one another.

animal behavior and cognition↗

bioRxiv2019

Light suppresses the acoustically prompted predator-avoidance behaviour in moths

Urbanization exposes wild animals to increased levels of light, affecting particularly nocturnal animals. Artificial light at night might shift the balance of predator-prey interactions, for example of nocturnal echolocating bats and eared moths. Moths exposed to light show less last-ditch manoeuvres in response to attacking close-by bats. In contrast, the extent to which negative phonotaxis, moths first line of defence against distant bats, is affected by light is unclear. Here, we aimed to quantify the overall effect of light on both types of sound-evoked anti-predator flight, last-ditch manoeuvres and negative phonotaxis. We caught moths at two light traps, which were alternately equipped with loudspeakers that presented ultrasonic playbacks to simulate hunting bats. The light field was omnidirectional to attract moths equally from all directions. In contrast, the sound field was directional and thus, depending on the moths approach direction, elicited either only negative phonotaxis, or negative phonotaxis and last-ditch manoeuvres. We did not observe an effect of sound playback on the number of caught moths, suggesting that light might suppress both types of anti-predator flight, as either type would have caused a decline in the number of caught moths. As control, we confirmed that our playback was able to elicit evasive flight in moths in a dark flight room. Showing no effect of a treatment, however, is difficult. We discuss potential alternative explanations for our results, and call for further studies to investigate how light interferes with animal behaviour.

animal behavior and cognition↗

bioRxiv2018

Species-specific strategies increase unpredictability of escape flight in eared moths

Many prey animals form mixed-species groups. Mixed-species groups provide various benefits ranging increased food intake to increased chance of predator detection. The escape-tactic diversity hypothesis predicts another benefit. It postulates that the overall unpredictability of evasive movement is increased if multiple species with different evasive tactics mix, resulting in enhanced predator protection for the whole group. Echolocating bats and eared moths are a textbook example of predator-prey interactions. Moths exhibit evasive flight with diverse tactics; however, the variability of their evasive flight within and between species has never been systematically quantified. We therefore recorded flight strength of eight moth species in response to the same level of simulated bat predation. We show species-specific and size-independent differences in both overall flight strength and in change of flight strength over time, confirming the escape-tactic diversity hypothesis for eared moths. Additionally, we show strong inter-individual differences in evasive flight within some species. This diversity in escape tactic between eared moths increases the overall unpredictability of their evasive flight in mixed-species groups, likely providing better protection against predatory bats for the single individual.

animal behavior and cognition↗