When Mbytes are not enough: long term, multiple channel, physiological telemetry implantable datalogger

Telemetry monitoring is an established tool that allows measurements from unrestrained animals and most telemetry systems for large animals have a typical range of less than 6‐8m in air. When an experimental design requires that instrumented animals are released into a large outdoor environment or mesocosm settings or when the animals are water living or have an amphibious lifestyle, this precludes the use of an RF link to transfer the implanted data to the computer and requires local storage means such as a datalogger. We have developed an implantable, low power datalogger that interfaces directly to a bio‐telemetry system (EG1‐V2S3T, Transonic EndoGear Inc). The datalogger has the capacity to store up to 6 channels of data at 100 Hz which results in about 125MB/day of continuous data. The datalogger has a capacity of 8GB and is capable of continuous operation for over 8 weeks. Datalogging is controlled via the same computer interface controlling the implant and can be started either during implantation or at a later stage after post‐surgical recovery period before the animals are released from the lab environment. These dataloggers were field tested in six crocodiles (apprx. 22‐42kg, 1.4 ‐2.2m long) instrumented with the EG1‐V2S3T implants for blood flow, pressure, ECG and temperature and connected to a datalogger (Model EG1‐DTL). The animals were released in a mesocosm setting at Mongena Game Reserve in South Africa and were allowed to remain undisturbed for 4 weeks. Video cameras were used to correlate physiological data with behavioral data and external time depth recorders were used to monitor diving events.