Two methods of radio transmitter attachment and their effects on the behavior and energetics of captive long-tailed ducks (Clangula hyemalis) during winter

Abstract

Attachment of external devices can have negative consequences for the health and fitness of subjects, but these effects are often overlooked. In preparation for a field study with small sea ducks, we investigated the effects of two types of external radio transmitter attachments on activity budgets and energetics of captive long-tailed ducks (Clangula hyemalis) during winter. We conducted behavioral observations on 15 ducks over 3 months and measured oxygen consumption rates while resting on water and during preening. Ducks were either sham handled (‘Control’) or had transmitters attached with subcutaneous anchors (‘Prongs’) or Tesa tape/sutures (‘Tesa’). Following transmitter attachment, the activity budgets of Prong and Tesa birds changed significantly, while Controls remained largely unchanged. Prong and Tesa birds reduced locomotor activity (−58 and −54 %, respectively) and the proportion of time spent in water (−48 and −35 %, respectively), while they concomitantly increased time allocated to maintenance behavior (+98 and +151 %, respectively). Tesa birds recovered from these changes over time, at least partially, but Prong birds did not. Also, two of the five Prong birds developed a bacterial infection that spread from the attachment site. Retention time of transmitters was significantly greater for the Prong attachments (4 of 5 tags were retained for the entire 59-day study) than the Tesa technique (26.0 ± 3.2 days). Energy metabolism of ducks resting on water did not change significantly after transmitter attachment. Preening, the primary maintenance behavior, increased oxygen consumption rates by ~70 % over resting. The greater allocation of time to maintenance behavior after transmitter attachment most likely increased daily energy expenditure in these ducks, although the concurrent reduction in locomotor activity might have mitigated this effect. Ducks in our study had food ad libitum and were able to reduce locomotion after transmitter attachment without compromising food intake and, hence, energy balance. In the wild, this strategy might not be viable. Given the short retention time, the tape-based attachment technique we applied is not suitable if monitoring periods greater than ~2 to 3 weeks are desired. Both methods resulted in significant behavioral changes with energetic consequences that should be considered when planning to attach external transmitters to small sea ducks in the wild.