Biosonar signals impinging on the target during interception by big brown bats, Eptesicus fuscus.

Big brown bats (Eptesicus fuscus) were videotaped in the dark with a night-vision lens and infrared illumination while flying repeatedly along the same straight course to seize a tethered mealworm or a small electret microphone used to record biosonar signals impinging on the target. Bats emitted frequency-modulated sounds with first to third harmonics covering frequencies from 23 to 105 kHz. As the bats neared the target, the first harmonic shifted lower in frequency while the third harmonic strengthened and the fourth harmonic, and sometimes the fifth harmonic, appeared.

Steering by echolocation: a paradigm of ecological acoustics.

1. Flights of three big brown bats (Eptesicus fuscus) landing on a hand and catching a suspended mealworm were video analysed. 2.

Jamming bat echolocation: the dogbane tiger moth Cycnia tenera times its clicks to the terminal attack calls of the big brown bat Eptesicus fuscus.

Certain tiger moths emit high-frequency clicks to an attacking bat, causing it to break off its pursuit. The sounds may either orient the bat by providing it with information that it uses to make an attack decision (aposematism) or they may disorient the bat by interrupting the normal flow of echo information required to complete a successful capture (startle, jamming). At what point during a bat's attack does an arctiid emit its clicks? If the sounds are aposematic, the moth should emit them early in the attack echolocation sequence in order to allow the bat time to understand their meaning.

A computational model of echo processing and acoustic imaging in frequency-modulated echolocating bats: the spectrogram correlation and transformation receiver.

The spectrogram correlation and transformation (SCAT) model of the sonar receiver in the big brown bat (Eptesicus fuscus) consists of a cochlear component for encoding the bat's frequency modulated (FM) sonar transmissions and multiple FM echoes in a spectrogram format, followed by two parallel pathways for processing temporal and spectral information in sonar echoes to reconstruct the absolute range and fine range structure of multiple targets from echo spectrograms. The outputs of computations taking place along these parallel pathways converge to be displayed along a computed image dimension of echo delay or target range. The resulting image depicts the location of various reflecting sources in different targets along the range axis.

[Summer school of the Canadian Association of Medical Students and Interns--Haiti].

Six Canadian medical students record their experience at a summer school of tropical medicine in Haiti, sponsored by the Canadian Association of Medical Students and Internes. The social, economic and medical background is described, including “Voodoo” practices, language and Haitian art. Attention is directed to the occurrence of umbilical tetanus, diarrhea and malnutrition.