Review and Evaluation of Breakaway Devices for Bear Radiocollars

• Published in: Ursus (International Association for Bear Research and Management) Vol. 10; pp. 459 - 465
• Main Authors: Garshelis, David L., McLaughlin, Craig R.
• Format: Journal Article
• Language: English
• Published: International Association for Bear Research and Management 01-01-1998
• Subjects: Bears; Black bears; Boundary layer separation; Grizzly bears; Latex; Leathers; Neck injuries; Polar bears; Radio transmitters; Research Methods and Techniques; Survey design
• ISSN: 1537-6176; 1938-5439

Researchers often handle radiocollared bears on an annual basis, so collars can be readjusted. However, if a collar cannot be refitted (as when a bear becomes lost to the investigator because of radio transmitter failure), the animal may be subjected to lifelong neck irritation or more serious injury. To prevent this, devices have been developed that enable collars to eventually break away. During 1983-95, we used a piece of vegetable-tanned leather to link the 2 ends of radiocollars on black bears (Ursus americanus). The link was intended to break apart in 1-3 years if the bear was not handled and the link changed. We used unoiled links in Maine (n = 756) and oiled links in Minnesota (n = 549), and we set strict standards on the thickness of links used in Minnesota; we found that the Minnesota links were less prone (1%) to breaking off prematurely (<1 year). We also surveyed other bear researchers, 93% of which employed some sort of breakaway device; 13 different breakaway designs were described, of which 4 were commonly used. Of these, a linkage constructed of latex tubing tended to be most prone to premature breakage, whereas leather was least apt to break prematurely; links made of cotton belting or firehose were intermediate in their tendency to break too early. If the link did persist and was not changed in <1 year, an across-study average of about 75% of links made of latex, cotton, and firehose broke as intended, compared to 60% of leather links. However, breakage seemed to be prompted as much by pressure on the link as by weathering; thus, collars that did not break in the prescribed time might not have been tight. Despite the potential for premature breakage of some links and the chance that some last longer than desired, we strongly recommend their use over collars without breakaway devices.