Sample ECG plots acquired from denning bears. The top two panels show the minimum (16-second pause) and maximum heart rates (222 beats/minute) recorded during the study period. Both were recorded from bear 4067. The maximum rate occurred the day following our visit to the den and is believed to be associated with a subsequent visit to the den by the landowners. A 5-second pause is shown for bear 4061 in the third recording and the bottom two recordings include myograms relating to skeletal muscle activity (during the period of birthing for 4011 and post-parturition for 4021).