Thermocron iButton and iBBat temperature dataloggers emit ultrasound

• Published in: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Vol. 179; no. 7; pp. 867 - 874
• Main Authors: Willis, Craig K. R., Jameson, Joel W., Faure, Paul A., Boyles, Justin G., Brack, Virgil, Cervone, Tom H.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-10-2009; Springer Nature B.V
• Subjects: Acoustics; Animal Physiology; Animals; Animals, Wild; Bats; Behavior, Animal - radiation effects; Biochemistry; Biology; Biomedical and Life Sciences; Biomedicine; Body temperature; Fourier Analysis; Hearing - physiology; Human Physiology; Insulation; Life Sciences; Mammals; Microclimate; Microcomputers; Original Paper; Physiology; Radio Waves - adverse effects; Skin; Sound pressure; Sound Spectrography; Stainless steel; Stress, Physiological - radiation effects; Telemetry - instrumentation; Telemetry - veterinary; Temperature; Ultrasonic imaging; Ultrasonics - adverse effects; Zoology; Canada; United States > US; Bats; Thermocron iButton; Mammals; Ultrasound; Chiroptera; Disturbance
• ISSN: 0174-1578; 1432-136X
• DOI: 10.1007/s00360-009-0366-0

Thermocron iButton dataloggers are widely used to measure thermal microclimates experienced by wild animals. The iBBat is a smaller version of the datalogger, also commercially available, that is used to measure animal skin or core body temperatures when attached externally or surgically implanted. Field observations of bats roosting under a bridge suggested that bats avoided locations with iButtons. A heterodyne bat detector revealed that the dataloggers emitted ultrasound which was detectable from a distance of up to 30 cm. We therefore recorded and quantified the acoustic properties [carrier frequency (Hz) and root mean square sound pressure level (dB SPL)] of iButton and iBBat dataloggers. All units emitted a 32.9 kHz pure tone that was readily picked up with a time expansion bat detector at a distance of 1 cm, and most were detected at a distance of 15 cm. The maximum amplitude of iButton dataloggers was 46.5 dB SPL at 1.0 cm—a level within the range of auditory sensitivity for most small mammals. Wrapping iButtons in plastic insulation severely attenuated the amplitude of ultrasound. Although there was a statistically significant reduction in rates of warming and cooling with insulation, this effect was small and we suggest that insulation may be a viable solution to eliminate unwanted ultrasonic noise in instances when small delays in thermal response dynamics are not a concern. We recommend behavioural studies to assess if the electronic signals emitted by iButtons are disturbing to small mammals.