Design of an underwater telemetry antenna for locating and retrieving submerged radiocollars

Abstract Radiocollars represent a significant investment of financial resources, particularly global positioning system (GPS) collars, and loss of data imposes analytical limitations from reduced sample sizes. Radiocollars on large, terrestrial mammals are seldom lost in the water. However, several instances in Oklahoma, USA necessitated a reliable and cost‐effective technique for retrieving GPS collars from underwater to salvage the financial investment and data. We designed an underwater telemetry antenna to find and retrieve collars in ≤3 m of water. We describe field simulations under varying environmental and water conditions, and provide a list of materials along with instructions and considerations for building and using an underwater telemetry antenna. We successfully used our underwater antenna to locate and retrieve our submerged collar that was disposed of in a pond after illegal harvest; we also located and retrieved all collars used for field simulation ( n  = 11). On average, search time for collars was 30 min. The design of our underwater antenna was inexpensive (US$30), easy to build, and effective at locating submerged collars in 0.6–3.0 m of water, with varying water turbidity and substrates. Although our underwater telemetry antenna was designed to meet our needs, it could be modified for more specific or alternative circumstances. © 2011 The Wildlife Society.