Extrusion of Intracoelomic Radiotransmitters by Hawaiian Ducks

Abstract

ABSTRACTSurgical implantation of transmitters into the coelomic cavity is a common attachment technique for ducks and geese. Although retention rates are assumed to be high, most studies utilizing this attachment method involve tracking in a system where low rates of recapture, resight, or recovery limit the ability of researchers to assess tag loss. We describe the extrusion and loss of coelomic radiotransmitters with percutaneous antennas from adult Hawaiian ducks (Anas wyvilliana; n = 117) monitored throughout the entire annual cycle on Kaua‘i, Hawai‘i, USA during December 2012–December 2014. Transmitter retention through 6 months following implantation was high (98 ± 2%). However, the probability of transmitter loss increased substantially afterward, and birds had a 30 ± 5% cumulative probability of losing implants within 1 year. Probability of transmitter loss did not vary between sexes or with body mass. The recapture rate of birds known to have lost tags (0.13 ± 0.08 [SE]) did not differ from birds with known fates (i.e., survived or died) that retained transmitters (0.12 ± 0.06; P = 0.72), suggesting transmitter extrusion did not influence short‐term survival (i.e., <1 yr). Examinations of recaptured and resighted birds indicated transmitters were extruded through the exit site of the percutaneous antenna and through the body wall in the ventromedial coelomic region. For studies spanning >6 months, researchers should be aware of the possibility for transmitter loss and integrate, where possible, methods to assess retention. © 2020 The Wildlife Society.