What does Spitz do to Buck during the attack?

Spitz deeply resents Buck, seeing him as a threat to his dominant position in the pack. Buck is a strong, hardworking dog, so it's not hard to see why Spitz should come to regard him as such a dangerous rival. One night, when Buck goes to try and get some food, he finds his space occupied by Spitz. Tensions have been building between the two alpha dogs for some time, and as they circle each other threateningly, it seems that a full-blown fight is imminent.
But just when it looks like the fur's about ready to fly, the camp is suddenly invaded by a pack of half-starved huskies, crazed with hunger. Three of them attack Buck, wounding him badly, but not before he sinks his own fangs into one of their jugulars. As if this isn't bad enough, Buck's also being attacked by the treacherous Spitz, shamelessly stealing an opportunity amidst all the confusion to grab him by the throat. This shows just how much Spitz really hates Buck. Instead of standing alongside his fellow trail dog to see off the pack of wild, crazy huskies, he uses their vicious attack as a cover for attacking his rival.