State and National Park police can also be called
park rangers.
Not attesting to exact accuracy of anything on the above site. But it has a good over-all explanation.
Your Park Rangers are very different from ours! We have over 500 National Parks, but even though they are called National, the National Parks and Wildlife Officers are employed by respective State and Territory governments. Our Park Rangers are not involved in criminal law enforcement, though they can issue fines for various offences and do investigate infringements of Park Laws and have people charged. They do just about everything else though - they are part scientist, part guide, part wildlife expert, part firefighter, part parking inspector, part gardener - you name it they do it! They certainly have no need of the kevlar vests, tasers, shotguns and other defensive weapons that yours do! They leave all that stuff to the police.
Meet a Park Ranger National Parks 
