As he watched the trio of wolves tugging at the elk carcass, Rick found his eye drawn back to the gray female. She had no collar, which meant she had not been given a number, but she did have a nickname: O-Six, for the year in which she had been born. At this range, his scope revealed every detail; she might as well have been sitting at his feet. She was a wonderful specimen, with a dense coat and a heavier physique than most females, who averaged around 90 pounds.

Not much usually distinguished one black wolf from another, but every gray was different. O-Six had unusually attractive markings—a faint black oval around each eye, off set by twin wedges of white along the bridge of her nose. Her cheeks were also white, and an unbroken streak of gray ran from the tip of her head to the end of her nose, tapering off into buff along the sides of her snout. The overall effect was of a vaguely owl-like mask, which gave her a look of quiet concentration.

She had been born a member of the Agate Creek Pack, in a den about five miles to the south, not far from where Agate Creek spilled into the chossy, sulfurous canyon that held the Yellowstone River. After leaving her pack as a yearling, she had been more or less on the run for the last two years, looking for a mate and a territory of her own.

So far she had been unsuccessful. Rick had observed her mating with five different males the previous winter without settling down with any of them, which was unusual behavior for a lone female. It was also hazardous. Young wolves had to leave their natal packs in order to find a mate, but outside their home territory, alone, they were in constant danger. Almost every part of Yellowstone’s landscape belonged to one pack or another, and the various tribes patrolled their holdings relentlessly. Lone wolves caught trespassing could count on being chased, and entire packs occasionally clashed with one another, especially along the borders of adjoining territories. Territorial conflict was the most common cause of death for the park’s wolves, most of whom didn’t live beyond four or five years. Life for wolves was an adventure, but it was usually not a long one.