We propose to develop a prototype GPS radio collar to record thermal stress on medium-large size ungulates. It will be based on previously developed GPS units in collaboration with Donana Biological Station which have proven to be very reliable, small-size and economical. The new model will record air temperature, solar radiation and wind speed. These are the main factors which determine thermal exposure and because they operate at small spatial scale they need to be measured at the animal’s location. The information will be stored on the collar with the possibility of being downloaded remotely via mobile telephone technology. The dataset will be converted into a relative unit of thermal stress using an equation based on heated thermal models (e.g. mechanical heated models that simulate thermal stress of animals exposed to real environmental conditions).