Star Ka'at Series by Andre Norton, Dorothy Madlee

Two intriguing stray cats communicate with Jim and Elly Mae, convincing them that the cats are aliens from another planet.

Space Explorers!Jim and Elly Mae travel to a distant planet as guests of Tiro and Mer--members of a super-intelligent race of Ka'ats. On this strange world, work is done by machines, which are controlled by thoughts from the Ka'ats. But Jime and Elly cannot learn this power and become dependent on their hosts for everything--even meals! Determined to find their own food, Jim and Elly explore a nearby city where human-like beings once lived. But fierce robots now march down the streets... moreSpace Explorers!Jim and Elly Mae travel to a distant planet as guests of Tiro and Mer--members of a super-intelligent race of Ka'ats. On this strange world, work is done by machines, which are controlled by thoughts from the Ka'ats. But Jime and Elly cannot learn this power and become dependent on their hosts for everything--even meals! Determined to find their own food, Jim and Elly explore a nearby city where human-like beings once lived. But fierce robots now march down the streets. Tiro and Mer rush in to protect their human friends and are kidnapped by the robots. Jim and Elly must use all their courage and wits to find a way to rescue the Ka'ats! less

Follows the adventures of two children and a super race of cats as they rescue a group of plant people.

The Star Ka'ats make an interplanetary journey to another ka'at colony where life forms have grown to monstrous proportions and nearly exterminated the ka'at colonists.