Wraith trackers, also known as a subspace tracking device, are implants used by the Wraith.
Overview[]
These small devices were implanted surgically into the body where they emitted a subspace signal which was capable of being detected by the Wraith. This allowed them to detect the target through the resulting frequency being emitted from the target. They were typically placed close to the spinal column in order to prevent the individual from cutting them out themselves. A group of Runners led by Nekai learnt that multiple trackers in close proximity to each other essentially cancelled each other out, allowing two or more Runners to "hide" from the Wraith so long as they remained within a few meters of each other at all times. (SGA: "Hunt and Run")
History[]
The Wraith often implanted these trackers in Runners in order for their hunters to track their targets across the Pegasus galaxy. (SGA: "Sateda")
Ronon Dex had one such device implanted in his body which meant he was hunted throughout the planets. When he met with the Atlantis expedition, Doctor Carson Beckett was able to remove the tracker, and Ronon subsequently joined the expedition. (SGA: "Runner")
The V'rdai Nehar'lem were a group of Runners assembled by Nekai, who each had trackers in them; close proximity to at least one more tracker disrupted their signal and prevented the Wraith detecting them. Nekai claimed that the trackers also had explosives that would go off if anyone attempted to remove their tracker, but he later admitted that was a lie to encourage the V'rdai to stay together. Nekai admitted to Ronon that while he had seen another Runner die attempting to remove his tracker, the death was only because the man practically mutilated his own back trying to cut it out rather than because of any explosive.
Another tracker was placed in Ronon when he was recaptured by the Wraith and turned back into a Runner and set loose on his homeworld on Sateda. McKay was able to use the device and Atlants' sensors to determine where he was and Sheppard, McKay, Teyla and Dr. Beckett came to his rescue. After Ronon, Sheppard, Teyla and Beckett killed all of the enemy Wraith and escaped in a Puddle Jumper, Beckett removed it from Ronon once again. (SGA: "Sateda")
Todd has shown an affinity for the device. He had a tracker implanted in his body and used it to summon his Hive ship when he was taken captive by the Atlantis expedition at Atlantis. (SGA: "The Seer")
This same implant was triggered again to alert Lt. Colonel John Sheppard's team of his capture by a rival Hive. His enemies, however, cut the implant from his body. (SGA: "Spoils of War")
He had the device replaced at some point as he used it to summon the team to a Wraith lab when he wanted to talk to them about the Hoffan drug outbreak. (SGA: "The Kindred, Part 1")
Some time later he used it as a means for Sheppard's team and his hive to track him while he was on the Primary's hive. (SGA: "The Queen")
Dr. Keller was kidnapped by another Runner named Kiryk, who wanted her to treat a seriously ill little girl, and offered to remove his tracker from him. However, she was unable to remove it as it was attached to both his spinal column and brain stem. Keller instead shorted it out with a defibrillator, rendering it useless. (SGA: "Tracker")
When the team was placed on trial by the Coalition of Planets, Sheppard asked Richard Woolsey if he had a tracker on him so Atlantis could find them. Woolsey tells them he doesn't as that's Wraith technology before admitting he called Todd for one but didn't get an answer. (SGA: "Inquisition")
When Todd was placed into stasis on Atlantis, Doctors Carson Beckett and Rodney McKay checked him over for trackers. They removed one and the components to make two more. Unknown to them, Todd had more inside of him in a dormant or seedling stage and grew a new tracker while in stasis. This one was described as being crude and more like an emergency beacon. When Todd passed through the Stargate to Manaria, the tracker was activated and signaled Todd's hive ship to come pick him up. Richard Woolsey was displeased at how Todd was able to signal his ship and that when they did come, Sheppard let him go. (SGA: "Legacy: Homecoming")