 Why is Alan so surprised to hear blaster fighting?
Frowning, worrying about the sounds, Alan momentarily forgot to watch his step until his foot suddenly plunged into an ant hill, throwing him to the jungle floor. Alan started, "Blaster fighting! Then, through the trees he saw the clearing of the camp site, the temporary home for the scout ship and the eleven men who, with Alan, were the only humans on the jungle planet, Waiamea. Beyond, nose high, stood the silver scout ship that had brought the advance exploratory party of scientists and technicians to Waiamea three days before. He stepped forward just as a roar of blue flame dissolved the branches of a tree, barely above his head. Without pausing to think, Alan leaped back, and fell sprawling over a bush just as one of the robots rolled silently up from the right, lowering its blaster barrel to aim directly at his head. With an awkward jerk the robot swung around and fired its blaster, completely dissolving the lower half of the cat creature which had clung across the barrel. The robot started to shake, then clicked sharply as an overload relay snapped and shorted the blaster cells. The metal killers, tuned to blast any living flesh, would murder them the instant they stepped from the ship! Blaster ready, Alan rolled over onto his back. In the movement, his elbow struck the top of a small earthy mound and he was instantly engulfed in a swarm of locust-like insects that beat disgustingly against his eyes and mouth. The planet's double moon had risen and he could see a robot rolling slowly across the clearing in his general direction, blasting indiscriminately at whatever mind impulses came within its pickup range, birds, insects, anything. Apparently the robot hadn't sensed him yet, but Alan didn't know what the effective range of its pickup devices was. Minutes later, looking back he saw that the machine, though several hundred yards away, had altered its course and was now headed directly for him. Powerful as a small tank, the killer robot was equipped to crush, slash, and burn its way through undergrowth. Behind, the robot crashed imperturbably after him, lighting the night with fitful blaster flashes as some winged or legged life came within its range. Sharp screams punctuated the electric blue discharge as a pack of small feline creatures leaped snarling and clawing back into the night. His foot tripped on a barely visible insect hill and a winged swarm exploded around him.
 Alan is surprised because the planet is only inhabited by animals, not intelligent life.
 Alan is surprised because he came with a team of scientists, not soldiers.  Alan is surprised because he was sure they had escaped the enemy soldiers when they ran into the jungle for cover.  Alan is surprised because the planet is only inhabited by animals, not intelligent life.  Alan is surprised because the Waiameans don't have advanced weapons capabilities.