The zoo, which is based at a farm in Old Hurst near Huntingdon, has more than 100 animals, including lions, tigers and meerkats.
The crocodiles were not seized or put down by the authorities.
The arrested man, who is from Norfolk, is believed to have learning disabilities and was on a trip to the zoo with carers.
He is not believed to have known the child.
The man was released on bail until 18 September, and police said he was “assessed as not being fit for interview”.
People may be considered unfit for interview because of their physical or mental state.
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