It is still not fully understood how megaherbivores regulate their body temperature (T(b)), particularly with respect to their unfavourable surface to volume ratio. The paucity of information is probably owing to the difficulty obtaining physiological parameters from such animals. We developed a precise and reliable non-invasive method for determining the T(b) of large-bodied mammals. We used this method on African and Asian elephants. Small capsules (30 g) containing a temperature-sensitive transmitter and a memory for onboard data storage were hand-fed 71 times to elephants (N=21) and T(b) was measured during gut passage. In 64 cases, sensors were successfully retrieved. The operation and reliability of our data loggers was sufficient and compared favourably with any other published method. (C) 2010 Elsevier Ltd. All rights reserved.