Comparison of the Effects and Performance of Four Types of Radiotransmitters for Use With Scoters

Radiotransmitters are widely used in wildlife ecology, often providing data that cannot be collected using other methods. However, negative effects have been associated with the use of transmitters for some species. We evaluated the effects and performance of 4 radiotransmitter types for use with surf and white-winged scoters (Melanitta perspicillata and M. fusca): COEXT—coelomically implanted transmitters with external antennas, COINT—coelomically implanted transmitters with internal antennas, SUBCU—subcutaneous implants with external antennas, and PRONG—external mounts, attached by a subcutaneous anchor and glue, with external antennas. Survival was not related to radiotransmitter type during the immediate (14-d) post-release period when most deaths (8 of 12) occurred. Rates of signal disappearance (transmitters ceased to be detected in the study area) and transmitter shedding (transmitters recovered without sign of predation) were similar among types over 30and 60-day intervals; however, higher proportions of dorsally mounted radiotransmitters (SUBCU, PRONG) disappeared or were shed over course of the full 100-day monitoring period used in this study. All 4 radiotransmitter types allowed for relatively accurate location estimates, with linear error estimates (distance between actual and estimated location) averaging ,50 m when receivers were within 1 km of transmitters. However, signal strength was lower for COINT transmitters. Based on our results, we recommend COEXT transmitters for radiotelemetry studies .2 months in duration and for satellite telemetry studies of scoters. However, SUBCU and PRONG are recommended as cost-effective alternatives in shorter-duration radiotelemetry studies. (WILDLIFE SOCIETY BULLETIN 34(3):656–663; 2006)