The adherence-monitoring IVR was evaluated in a Rambouillet X Columbia sheep at the Colorado State University Preclinical Surgical Research Laboratory (Fort Collins, CO, USA). A schedule of ring insertion and removal was is shown in Table 1. The IVR was immersed in warm water bath (50°C) to initiate data logging, and remained in the warm bath until insertion in the sheep vaginal cavity. The IN/OUT status of the IVR was measured and stored in non-volatile memory on a 1.00 min interval, using a reference temperature of 34.4°C. The insertion/removal pattern was followed for 29 hours, whereupon the ring was removed and logging stopped by cutting through the ring to sever the battery connection to the PCB. The insertion and removal periods were based on the workflow in the animal facility during the two days of the study, and were designed to provide both short and long insertion and removal periods with minimal disturbance to the animal. The stored IN/OUT data stream was downloaded from the device to a PC using the Microchip PICkit3 programmer USB interface, and the data in hexadecimal format was converted to a series of binary (0 or 1) values indicating IVR OUT or IN.