Skip to main content

Table 1 Summary of the device generations and select findings

From: Development and utilization of implantable cardiac monitors in free-ranging American black and Eurasian brown bears: system evolution and lessons learned






80 cc

104 h recording capacity

Programmable to allow duty cycling of recording intervals

Ursus americanus (Colorado and Wyoming, USA)

n = 6 devices in 6 bears

Longest asystole = 13.3 s

Extreme RSA identified

Avg HR increased when electromyograms (EMGs) were present

Longest duration of data collection = 68 days (HR Avg = 13.5 ± 3.8 bpm)

No significant changes in the QRS or QT intervals during hibernation

Rate dependence of QT interval lost during hibernation

Extreme foreign body response


9 cc

3-year battery life

Records daytime HR, nighttime HR, activity, and episodes with ECGs

Ursus americanus (Minnesota, USA)

n = 65 devices in 39 bears

Longest asystole = 14.4 s

Maximum HR = 261 bpm (bear shot by hunter)

Respiratory rate increased as investigators approached the den, serving to increase the average HR

Anesthesia eradicated the RSA


Ursus arctos (Sweden)

n = 35 devices in 33 bears

Maximum HR = 240 bpm (07 Oct 13 and 19 Oct 13; 2-year-old female)

Longest asystole = 15.8 s (26-Feb-2013; 2-year-old female)

GEN 2 with BearWare

GEN 2 features with

Avg HR every 2 min

Activity at 15-min intervals

ECGs for the 10 extremes for tachycardias and asystoles

Ursus americanus (Minnesota, USA)

n = 69 devices in 42 bears

Longest asystole = 33.8 s (03-Mar-2015; 4-year-old female)

Maximum HR = 261 bpm (02-Sep-2010; adult female)


Ursus arctos (Sweden)

n = 71 devices in 56 bears

Longest asystole = 39.4 s (03-Nov-2016; 3 1/2-year-old female)

Maximum HR = 222 bpm (07-May-2014; 2-year-old female)

GEN 3 with Telemetry Stations

GEN 2 features with

1.2 cc

3-year battery life



Wireless capability

Ursus americanus (Minnesota, USA)

n = 29 devices in 21 bears with 28 telemetry stations deployed

Demonstrated feasibility of remote web-based monitoring of bears in the wild

Cessation of long sinus pauses during parturition

Subcutaneous impedance decreased during hibernation

GEN 3 with B-Ware

GEN 3 and BearWare features with


Rejects asystoles > 60 s and tachycardias > 275 bpm

Ursus americanus (Minnesota, USA)

n = 10 devices in 10 bears

Results pending

  1. Avg average, HR heart rate, RSA respiratory sinus arrhythmia, bpm beats per minute, ± standard deviation