Coley was equipped with a lightweight GPS transmitter in May 2012 by Dr. Kennedy. It weighs 30 grams (about 1 ounce) and is strapped on like a backpack.
The transmitter is solar-powered and communicates Coley’s location, altitude, speed and course by satellite every hour for 12 hours a day.
Dr. Kennedy explains more about the tracking here:
This video shows him outfitting Coley with the backpack: