Presence of ultrasonic noise in the housing colony affects behavior and physiology of adult Sprague Dawley rats (2026)

Bigelow, L. J., Pope, E. K., Sohasky, V. K. et al.

Abstract

Perception is dictated by our sensory capabilities which vary widely across species. Hearing in humans is confined to a relatively narrow range, thus the presence of ultrasonic noise, sound with a frequency >20 kHz, is often overlooked. Concerningly, it has been determined that the laboratory is rife with ultrasounds which may be a stressor for rats not only due to their extended hearing range but also their use of ultrasonic vocalizations to communicate. To understand the significance of ultrasonic noise in the laboratory, rats were exposed to no noise, broadband noise (2–20 kHz, 70 dB SPL), or ultrasound (40 kHz, 70 dB SPL) for a 2-week period, based upon previous screening of facility background noise. Both behavioral and physiological parameters were subsequently investigated to assess the effects of noise exposure on animal welfare. Results indicated various differences: rats exposed to ultrasound spent significantly more time in the center of the open field and less time in the open arms of the elevated plus maze compared to animals exposed to no noise and broadband noise; rats exposed to ultrasound and no noise had significantly lower daily anal infrared temperatures and increased adrenal gland weights as compared to animals exposed to broadband noise. These findings bring attention to the presence of ultrasonic noise and its ability to significantly alter rat behavior and physiology in unexpected ways. Acknowledgment of ultrasonic noise as a confounding variable will not only lead to improved validity of rodent research but also improve animal welfare.