Implanted satellite transmitters affect sea duck movement patterns at short and long timescales

Abstract

Studies of the effects of transmitters on wildlife often focus on survival. However, sublethal behavioral changes resulting from radio-marking have the potential to affect inferences from telemetry data and may vary based on individual and environmental characteristics. We used a long-term, multi-species tracking study of sea ducks to assess behavioral patterns at multiple temporal scales following implantation of intracoelomic satellite transmitters. We applied state-space models to assess short-term behavioral patterns in 476 individuals with implanted satellite transmitters, as well as comparing breeding site attendance and migratory phenology across multiple years after capture. In the short term, our results suggest an increase in dispersive behavior immediately following capture and transmitter implantation; however, behavior returned to seasonally average patterns within ∼5 days after release. Over multiple years, we found that breeding site attendance by both males and females was depressed during the first breeding season after radio-marking relative to subsequent years, with larger relative decreases in breeding site attendance among males than females. We also found that spring and breeding migrations occurred later in the first year after radio-marking than in subsequent years. Across all behavioral effects, the severity of behavioral change often varied by species, sex, age, and capture season. We conclude that, although individuals appear to adjust relatively quickly (i.e. within 1 week) to implanted satellite transmitters, changes in breeding phenology may occur over the longer term and should be considered when analyzing and reporting telemetry data. LAY SUMMARY Implanted satellite transmitters are often used to study movements of waterfowl, but capture and implantation may also change individual behavior. Understanding these behavioral effects, and how long they last, is necessary to correctly interpret movement data from transmitters We used a set of multi-year data from sea ducks with implanted satellite transmitters to examine changes in individual movement patterns over time. Most sea ducks appeared to resume normal day-to-day movements within a week after capture; however, they nested later and at lower rates during the year after capture compared with later years. While behavioral effects of transmitter implantation seem to be relatively short-term, energetics and breeding decisions may be affected over longer timescales.