After food and water, the highest biological imperative is to reproduce.
Birds do it, bees do it, and yes, people and gray wolves do it.
It is that biological imperative that has driven 66 wolves imported from Canada a decade ago, to grow to 835 individuals and 110 packs in the Northern Rocky Mountains today.
"Get a date or die trying," said Ed Bangs, wolf recovery coordinator for the U. S. Fish and Wildlife Service.
In addition to the three-state region surrounding Yellowstone National Park (Wyoming, Idaho and Montana), lone wolves have been spotted in Oregon, Washington, Utah and Colorado, Bangs said, though no breeding pairs or packs have moved into adjoining states. Midwestern wolves, from the Great Lakes area, have even been spotted in Kansas and Missouri.
Last June, a young female wolf was struck and killed by an unknown vehicle on Interstate 70, west of Idaho Springs, Colo. The two-year-old female wolf was last seen in January 2004 in Yellowstone. She had traveled 520 miles as the crow flies.
"It is not unusual for a lone wolf to travel 200 miles, but this female has the record," Bangs said.
He emphasized that the presence of a single lone wolf does not mean that there will automatically be more wolves-a breeding pair or a pack-any time soon.
Although there have been exceptions, by and large, young wolves must leave their home pack if they want to breed. It is risky to try to move into the territory of a strange pack, because quite often, packs kill alien wolves. As a result, new packs are most often created when a lone male and a lone female, from different packs, meet up in an area where there aren't other packs. If they like each other, they can become a breeding pair, set up housekeeping, raise their own pups and create a new pack.
Particularly for lone wolves who travel hundreds of miles, Bangs explained that there is so much open territory that the odds of a lone female and a lone male hooking up at the same time and the same place is a very rare event.
"The farther away they travel, the bigger the odds against them," Bangs said.
One reason is that lone wolves don't last very long out on their own-not compared to the greater security of a pack.
"Lone wolves have a high mortality rate," Bangs said. Of the three lone wolves spotted in Oregon, one was shipped back to the northern Rockies, one was shot and the third was run over, he said.
"New packs are set up by teenagers looking for an empty area that has a good food supply," Bangs said. Several times, a lone wolf will move into and start marking a new territory, then wait for months for true love to show up. When true love doesn't show up, the lone wolf will move on to try, try again.
Most times, new packs are formed just beyond existing pack territories, Bangs said, which means that packs spread incrementally over short distances, rather than dramatically over great distances.