This paper presents a methodological approach used to assess the wearability of biotelemetry devices in animals. A detailed protocol to gather quantitative and qualitative ethological observations was adapted and tested in an experimental study of 13 cat participants wearing two different GPS devices. The aim was twofold: firstly, to ascertain the potential interference generated by the devices on the animal body and behaviour by quantifying and characterising it; secondly, to individuate device features potentially responsible for the influence registered, and establish design requirements. This research contributes towards the development of a framework for evaluating the design of wearer-centred biotelemetry interventions for animals, consistent with values advocated by Animal-