He can perceive exactly the same as everyone else. He just has a limited int to know what to do with that info.
He might be trained to roar if he spots a hostile.
Look up the animal trick seek and detect.
Seek (DC 15) The animal moves into an area and looks around for anything that is obviously alive or animate.
Detect (DC 25): The animal is trained to seek out the smells of explosives and poisons, unusual noises or echoes, air currents, and other common elements signifying potential dangers or secret passages. When commanded, the animal uses its Perception skill to try to pinpoint the source of anything that strikes it as unusual about a room or location. Note that because the animal is not intelligent, any number of strange mechanisms, doors, scents, or unfamiliar objects may catch the animal‘s attention, and it cannot attempt the same Perception check more than once in this way.
Still have to train them still have to roll (PFS) but you get extra tricks.
Home game they are intelligent so it's gm discression.
The listed DCs are the Handle Animal DCs for Handle Animal checks to teach the animal the trick in question. In each case, the animal would use its own Perception modifier.