a deer
Montag mistakes a deer for the Hound in Ray Bradbury's "Fahrenheit 451." The deer startles Montag with its sudden appearance, causing him to compare its eyes and movement to those of the mechanical Hound.
The hound doesn't like Montag and this is because the hound is programmed to be able to sniff out chemical compistions of books
After the Mechanical Hound stabs Montag in the leg with a needle containing anesthetic he destroys the Hound with the flamethrower he used to burn down his house.
The Hound growls at Montag in "Fahrenheit 451" on page 28 of the 60th Anniversary Edition.
The mechanical hound in "Fahrenheit 451" is a robotic creature programmed to track down and punish those who go against the societal norms of the dystopian world. It interacts with Montag by sensing his growing disillusionment with society, which causes it to target him as a threat.
during the manhunt for Montag by the hound, the camera identifies an innocent man as Montag because the hound had lost Montag. (Montag's disguise worked) In order to please the people watching the manhunt on television they killed a man but didn't get close enough to him with the camera for anybody to realize that it wasn't Montag.
After leaving the hound, Montag's leg starts to get numb.
Montag initially thinks he sees a person on the railroad tracks, but it turns out to be a mechanical hound.
Early in the novel, the Mechanical Hound growls at Montag, hinting at a future conflict between them. Beatty warns Montag that the Hound is never wrong and is capable of sensing any deviation from the norm, setting up a battle of wills between Montag and the Hound. When Montag becomes increasingly disillusioned with society and its reliance on technology, it sets the stage for a showdown with the Hound, which represents that same oppressive technology.
The Mechanical Hound smells like perfume to Montag. This unexpected smell alerts Montag to the fact that the Hound has been tampered with by Captain Beatty to track and catch him.
Montag believes that the Hound, a robotic creature in Fahrenheit 451, has been programmed and tampered with to ensure it identifies Montag as a threat and hunts him down. He is suspicious that the Hound has been manipulated to target him specifically.
After the men leave, Montag hears the Mechanical Hound growling and lurking in the darkness outside his home. This indicates that the Hound is still a threat to him.
Montag thought the eyes of the Mechanical Hound were looking at him. He felt a sense of unease and felt like the Hound could see through him.