The Jekkari lived in villages in the trees of Jekkar. They were vegetarians and pacifists by nature, though they could kill if provoked. They also distrusted machinery, though they could make use of it. Jekkari communicated by tapping each other's palms in certain patterns. (PROSE: Shakedown)
The Jekkari lived in the forests of Jekkar until the human colonists came to the planet. They attempted to take back their planet in stealthier methods, pretending to be stupid animals. Though they were originally shot by the humans, they were eventually accepted and taken in to be used for cheap labour. The Seventh Doctor went to help them, living in the forests and helping their efforts.
When the Sontarans invaded and took over the planet, the Jekkari simply switched their targets. They freed the Doctor after he had been captured by the Sontarans, then began a guerilla conflict against the Sontarans. They would waylay convoys, leave traps, steal weaponry and kill Sontarans who tried to fight back. Eventually, the Sontarans abandoned the planet when they couldn't hold it any longer. The human colonists left shortly afterwards, afraid that the Sontarans would return. The Jekkari were then allowed to have the planet to themselves. (PROSE: Shakedown)