Implant- versus collar-transmitter use on black bears

Bears are difficult to radiomark for long-term studies because of juvenile growth rates, dramatic seasonal weight changes, and similar head andneck girths for adults. Because collars may be discarded if mounted too loosely or cause neck ulcerations if mounted too tightly, we compared use of collar and implant radiotransmitters for black bears (Ursus americanus) at 3 locations in Washington during 1994â€"1999. We marked 22 females and 38 males with collar transmitters and 30 females and 40 males with implant transmitters. Marking bears with collars or implants and collecting morphological data and specimens required 20â€"55 minutes. Amount of Telazolâ„¢ used to anesthetize bears marked with collars and to conduct implant surgery and amount of drug used between fall and spring captures differed significantly. Amount of drug did not differ between genders or for bears captured by helicopter or snares. Bears lost collars with cotton breakaway spacers after approximately 21 (±3.4, SE) months in the study area where mean annual precipitation was 52 cm, and 10 (±2.5) months where mean annual precipitation was 200 cm. For bears marked with collars, detection rates (number of radiotelemetry relocations/aerial monitoring session) were similar for males and females and among study areas. In contrast, we detected implant-marked males at lesser rates than females and detected bears at different rates among study areas. Decreased signal strength for implant transmitters resulted in fewer locations and greater search effort for males because they used larger spatial areas and were more difficult to relocate than females. Differences in numbers of relocations obtained for male and female black bears marked with implant transmitters may affect precision of spatial and habitat use estimates and gender comparisons of resource use and mortality rates. For these reasons, implant transmitters may be adequate to monitor animals with small home ranges but may not be appropriate to monitor wide-ranging animals.