For reasons I don't know, there were two completely different games released by the same company and author that were both titled Attack of the Mutant Camels. The original Attack of the Mutant Camels is a Defender clone of sorts. However, Gridrunner 2 was also released as Attack of the Mutant Camels in the U.S.
The box art and screen shots in this post are for the Gridrunner 2 variant. The full alternative name is Matrix: Gridrunner 2 and it was released for both the Commodore 64 and VIC-20.
You play the role of a starship captain defending the world from attacking aliens. The primary enemies are chains of pods that meander down the screen towards you and break up into smaller chains and eventually individual pods (resembling mutant camels) as you shoot them, much like the centipede in Centipede. There are some unique twists such as guns shooting at you from the bottom of the screen and the enemy shooting back at you, along with traitors and defectors that help the enemy by improving their aim or deflecting your shots back at you.
Like most Jeff Minter games, this one is quite entertaining. It's not completely original but it has enough original twists along with excellent gameplay that make it a worthwhile game.
While you won't find the original game re-released on any modern platforms it isn't too hard to emulate. A more modern sequel was released in 2009 titled Gridrunner Revolution for Windows based computers.