Individually Ventilated Cages Severely Attenuate Inter-Cage Ultrasonic Vocalizations in Rats

Individually ventilated cages (IVCs) benefit rodent and researcher health but may limit animals' ability to communicate with cage-neighbours via ultrasonic vocalizations (USVs). Despite USVs' importance in rodent social behaviour, no previous research has investigated IVCs' impact on between-cage USV transmission. We recorded USV transmission between cages housing Sprague-Dawley rats in three conditions: in an open cage rack setting with microphone in an empty cage; from an open cage with a microphone outside an enclosed IVC; and between adjacent IVCs (with microphone in empty IVC). We compared the number and amplitude of USVs detected during 10-minute sessions across conditions. To verify results weren't due to differences in USV generation between cage types, we simultaneously recorded with two microphones, one inside an IVC and one in an adjacent enclosed IVC. Results showed USVs generated in open cages were clearly detectable in adjacent open cages but attenuated outside IVCs and virtually undetectable in adjacent IVCs. Since this loss of inter-cage USVs may affect animal behaviour, we recommend adjustments to cage design and handling procedures to mitigate these effects.