Heart rate values for beaver, mink and muskrat.

1. Implanted ECG transmitters were used to determine heart rates for several activities of beaver (Castor canadensis), mink (Mustela vison), and muskrat (Ondatra zibethicus) under free-ranging laboratory conditions within an aquatic tank. 2. All three species exhibited bradycardia when diving but mink heart rates returned to pre-dive levels if the dive lasted greater than 30 sec. 3. Heart rates for all other behaviours were significantly (P less than 0.05) higher than for diving and averaged about 120/min (beaver), 265/min (mink) and 240/min (muskrat). 4. Mink heart rate values were higher than would be expected based on general energetic equations if we assume heart rate to be reflective of energy costs. This was considered to be a function of this species' fusiform body shape.