Bats coordinate sonar and flight behavior as they forage in open and cluttered environments

Self Cite

Echolocating bats face the challenge of coordinating flight kinematics with the production of echolocation signals used to guide navigation. Previous studies of bat flight have focused on kinematics of fruit and nectar-feeding bats, often in wind tunnels with limited maneuvering, and without analysis of echolocation behavior. In this study, we engaged insectivorous big brown bats in a task requiring simultaneous turning and climbing flight, and used synchronized high-speed motion-tracking cameras and audio recordings to quantify the animals' coordination of wing kinematics and echolocation. Bats varied flight speed, turn rate, climb rate and wingbeat rate as they navigated around obstacles, and they adapted their sonar signals in patterning, duration and frequency in relation to the timing of flight maneuvers. We found that bats timed the emission of sonar calls with the upstroke phase of the wingbeat cycle in straight flight, and that this relationship changed when bats turned to navigate obstacles. We also characterized the unsteadiness of climbing and turning flight, as well as the relationship between speed and kinematic parameters. Adaptations in the bats' echolocation call frequency suggest changes in beam width and sonar field of view in relation to obstacles and flight behavior. By characterizing flight and sonar behaviors in an insectivorous bat species, we find evidence of exquisitely tight coordination of sensory and motor systems for obstacle navigation and insect capture.

Section: Duration Adjustments and Inner Window With Respect To Net Posupporting

confidence: 68%

Section: Strouhal Numbermentioning

confidence: 99%

Tight coordination of aerial flight maneuvers and sonar call production in insectivorous bats

Falk

Kasnadi

Moss

2015

Self Cite

“…We discovered substantial interspecific differences in aEMG modulation across wind tunnel flight speeds comparable with reported flight speed ranges for the two species [C. perspicillata, 2.8-6.6 m s −1 (Heithaus and Fleming, 1978); E. fuscus, 2.0-9.2 m s −1 (Hayward and Davis, 1964;Kurta and Baker, 1990;Falk et al, 2014)]. We observed considerable aEMG modulation in C. perspicillata, contrasted by a lack of modulation in E. fuscus.…”

Section: Interspecific Differences In Speed Modulation Of Aemgsupporting

confidence: 77%

“…perspicillata range of over-ground flight speeds for the species, 2.0-9.2 m s −1 (Hayward and Davis, 1964;Kurta and Baker, 1990;Falk et al, 2014). In bats, pectoralis power consumption is likely a smaller component of flight energetics than in birds because a greater number of muscles contribute to aerodynamic force production.…”

mentioning

confidence: 99%

Speed-dependent modulation of wing muscle recruitment intensity and kinematics in two bat species

Konow

Cheney

Roberts

et al. 2017

Animals respond to changes in power requirements during locomotion by modulating the intensity of recruitment of their propulsive musculature, but many questions concerning how muscle recruitment varies with speed across modes of locomotion remain unanswered. We measured normalized average burst EMG (aEMG) for pectoralis major and biceps brachii at different flight speeds in two relatively distantly related bat species: the aerial insectivore Eptesicus fuscus, and the primarily fruit-eating Carollia perspicillata. These ecologically distinct species employ different flight behaviors but possess similar wing aspect ratio, wing loading and body mass. Because propulsive requirements usually correlate with body size, and aEMG likely reflects force, we hypothesized that these species would deploy similar speed-dependent aEMG modulation. Instead, we found that aEMG was speed independent in E. fuscus and modulated in a U-shaped or linearly increasing relationship with speed in C. perspicillata. This interspecific difference may be related to differences in muscle fiber type composition and/or overall patterns of recruitment of the large ensemble of muscles that participate in actuating the highly articulated bat wing. We also found interspecific differences in the speed dependence of 3D wing kinematics: E. fuscus modulates wing flexion during upstroke significantly more than C. perspicillata. Overall, we observed two different strategies to increase flight speed: C. perspicillata tends to modulate aEMG, and E. fuscus tends to modulate wing kinematics. These strategies may reflect different requirements for avoiding negative lift and overcoming drag during slow and fast flight, respectively, a subject we suggest merits further study.

“…These bats dynamically change the duration, spectrum, directional aim, number and temporal patterning of their emitted pulses, and thus the acoustic sampling of the spatial scene, to reflect the complexity of their surroundings (Surlykke and Moss, 2000;Moss et al, 2006;Moss and Surlykke, 2010;Petrites et al, 2009). In particular, the time intervals [inter-pulse intervals (IPIs)] between the individual pulses in a train are known to vary with the perceived difficulty of the experimental task and according to the bat's individual strategy for navigating the scene (Surlykke and Moss, 2000;Petrites et al, 2009;Barchi et al, 2013;Falk et al, 2014;Kothari et al, 2014;Sändig et al, 2014;Knowles et al, 2015;Wheeler et al, 2016). Changes in IPIs thus provide one index of the bat's vocal adaptations to its surroundings, particularly when steering through and foraging within cluttered acoustic environments.…”

Section: Introductionmentioning

confidence: 99%

Echolocation behavior in big brown bats is not impaired after intense broadband noise exposures

Hom

Linnenschmidt

Simmons

2016

Echolocating bats emit trains of intense ultrasonic biosonar pulses and listen to weaker echoes returning from objects in their environment. Identification and categorization of echoes are crucial for orientation and prey capture. Bats are social animals and often fly in groups in which they are exposed to their own emissions and to those from other bats, as well as to echoes from multiple surrounding objects. Sound pressure levels in these noisy conditions can exceed 110 dB, with no obvious deleterious effects on echolocation performance. Psychophysical experiments show that big brown bats (Eptesicus fuscus) do not experience temporary threshold shifts after exposure to intense broadband ultrasonic noise, but it is not known if they make fine-scale adjustments in their pulse emissions to compensate for any effects of the noise. We investigated whether big brown bats adapt the number, temporal patterning or relative amplitude of their emitted pulses while flying through an acoustically cluttered corridor after exposure to intense broadband noise (frequency range 10-100 kHz; sound exposure level 152 dB). Under these conditions, four bats made no significant changes in navigation errors or in pulse number, timing and amplitude 20 min, 24 h or 48 h after noise exposure. These data suggest that big brown bats remain able to perform difficult echolocation tasks after exposure to ecologically realistic levels of broadband noise.