Bats Keep Consistent Echolocation and Response While Hunting in Light

Jim Crocker
30th April, 2024

Bats Keep Consistent Echolocation and Response While Hunting in Light

This figure illustrates the experimental setup in an anechoic room and the method used to digitally remove masking noise from the recorded bat calls.

Image adapted from: Uebel et al. / CC BY (Source)

Key Findings

  • In a study at Aarhus University, bats faced noise that hindered their echolocation but didn't rely more on vision
  • Bats increased their echolocation call volume in noisy conditions, showing a consistent Lombard response
  • Despite noise and light, bats didn't change their echolocation strategy, suggesting a hard-wired behavior
In the shadowy world of nocturnal hunting, the insectivorous bat Myotis daubentonii is a master of navigation and prey detection, primarily relying on echolocation to thrive in the dark. However, these bats also possess a complex eye anatomy, suggesting that vision plays a role in their nightly activities. Researchers at Aarhus University sought to understand the balance between echolocation and vision in these bats when faced with acoustic challenges[1]. Echolocation is a sophisticated biological sonar used by bats to emit calls and listen for the echoes that bounce back from objects. This system allows them to detect and capture prey with remarkable precision, even in complete darkness[2]. Despite this, the presence of complex eyes in bats like Myotis daubentonii hints at the importance of vision, even in their predominantly echolocation-based lifestyle. The study at Aarhus University tested whether these bats would adjust their reliance on echolocation when visual cues were available, especially under conditions that made echolocation less effective. To simulate a challenging environment, the researchers exposed the bats to broadband noise, which interferes with their ability to process returning echoes[3]. The bats were trained to land on a spherical target with varying light conditions, ranging from complete darkness to well-lit environments. The findings were intriguing. When faced with noise that masked their echolocation, the bats made almost three times more attempts to land on the target compared to their attempts in silence. This indicated that noise significantly affected their echolocation ability. Additionally, the bats displayed a Lombard response, a phenomenon where vocal animals increase the amplitude of their calls in the presence of noise[3]. In this case, the bats increased their call volume by 0.18 dB for every dB of noise they encountered. However, despite these challenges, the bats did not alter their echolocation behavior based on the availability of light. This suggests that echolocation is a deeply ingrained sensory system in Myotis daubentonii, with built-in strategies to compensate for difficulties such as target range and masking noise, regardless of visual cues. Interestingly, while the bats maintained consistent echolocation behavior across different lighting conditions, individual bats showed varied adjustments in call intervals and movement strategies when exposed to noise. This variability indicates a level of behavioral flexibility and potentially points to higher-order cognitive processes or even vocal learning abilities among these animals. These findings build upon previous research that has explored the resilience of echolocating bats to interference. For instance, earlier studies have shown that bats can maintain successful echolocation despite the presence of conspecific and heterospecific jamming, as well as the risk of eavesdropping by prey or competitors[2]. The Aarhus University study further demonstrates that bats can adapt their echolocation in noisy environments, but visual information does not seem to influence these adaptations. In conclusion, the research from Aarhus University provides valuable insights into the sensory world of Myotis daubentonii. It shows that while these bats are capable of adjusting their echolocation in response to acoustic challenges, they do so without taking visual cues into account. This hard-wired reliance on echolocation, along with the observed individual flexibility, highlights the complexity of these nocturnal hunters' sensory integration and their remarkable adaptability in the face of sensory interference.

EcologyAnimal ScienceEvolution

References

Main Study

1) Daubenton’s bats maintain stereotypical echolocation behaviour and a lombard response during target interception in light

Published 29th April, 2024

https://doi.org/10.1186/s40850-024-00200-4

Related Studies

2) Communication with self, friends and foes in active-sensing animals.

https://doi.org/10.1242/jeb.242637

3) Echolocating Daubenton's bats are resilient to broadband, ultrasonic masking noise during active target approaches.

https://doi.org/10.1242/jeb.242957


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