The design and operating characteristics of a heart rate transmitter designed for a wild grizzly bear (Ursus arctos) [cold adaptation physiology] study is described. The rigid capsule is durable and is easily implanted in the field. The transmitter can be regularly monitored at 4-5 km and has a life expectancy of about 1 yr in bears which experience winter torpor, and thus reduced heart rate, for about 7 mo. in northern Alaska, [USA].