The parents of a seven-year-old boy who broke into an Australian outback zoo and fed a string of small animals to its resident crocodile are likely to be sued after police said the boy was too young to be held responsible.

A turtle, four western blue tongue lizards, two bearded dragons, two thorny devil lizards and a 1.8 metre adult female Spencer's goanna were fed or led into the jaws of a three-metre, 200kg saltwater crocodile named "Terry".

Security camera footage at the Alice Springs Reptile Centre showed the smiling youngster also bludgeoning to death a small blue tongue lizard and two more thorny devils during a half-hour of breakfast-time havoc last Wednesday.