Wolf pup survival a fragile thing

For Minnesota's wolves, their constant focus is finding food.

But in recent weeks, they've had something else on their minds: Romance.

The state's wolves breed from February to early March. And it's serious business. At stake is their very survival.

Though they are near the top of the food chain, reproduction isn't guaranteed. Wolves face the same life-or-death struggle that all wildlife confront every moment of their lives.

"Roughly 30 percent of wolves survive from birth to 1 year of age," said Dave Mech, senior research scientist with the U.S. Geological Survey in St. Paul and pre-eminent wolf expert who has been studying the animals for more than 50 years.

The late-winter timing of the breeding season is no accident. Though dogs come into heat generally twice a year, and at virtually any month, wolves have evolved to come into heat once in late winter, so that pups are born in the spring.

"It's the best time of year for the pups to survive, and the best time to get prey," Mech said. "Prey is at its weakest right now and for the next couple of months."

Weeks after they are born and finish nursing, wolf pups can have abundant offerings. Deer fawns and moose calves are born, offering a plethora of easy prey for wolves to feed their pups. And when spring arrives, ice melts, making beaver and other critters more available.

The spring births also means those wolf pups will be nearly adult-size when the first snow blows next fall, giving them a better chance to survive winter.

Still, 70 percent won't live a year. Two months after conception, generally late April to early May, the pups are born in a den, usually a hole or depression in the ground or a rock crevice. They're blind and deaf. Their eyes open when they're about 2 weeks old and they can hear at about 3 weeks, Mech said.

In Minnesota, the average litter is six pups.

"That means when these pups are born, the wolf population about doubles, which is something many people don't realize," Mech said.

The pups nurse for six to nine weeks, but also start eating solid food regurgitated by their parents at about 3 weeks old, when they start getting their teeth.

What causes wolf pups to die?

"All kinds of things," Mech said. "They are small and very vulnerable." They die from disease, accidents and are sometimes killed by other wolves or even other predators if they are discovered without their protective parents. Some may starve by fall after the easy prey becomes more elusive.

"Humans cause a lot of wolf mortality, whether there is a [wolf] hunting season or not," Mech said. Some are hit by cars, some are caught in coyote or fox traps. One study showed 80 percent of wolf mortality was caused by humans.

After seven or eight weeks, the wolf pups begin to explore outside their den and are moved to various "rendezvous sites" — places where they hang out, waiting for adult wolves to return with food.

"As adults leave to go hunt, the pups sometimes try to follow them," Mech said. "They're hard to see in Minnesota's woods, but I've watched them in the northern Canada tundra. Sometimes those pups will follow an adult for a mile. Adults don't like it; sometimes they will actually carry them back."

But eventually the pups get bigger and stronger, and by early fall, they move with the adults as a pack.

"By late November they weigh 50 or 60 pounds," Mech said. "We call them pups, because they are less than a year old. But they are nearly the weight of an adult, and if people see them, they wouldn't necessarily know they are pups."

That also is the time the young wolves lose their puppy teeth and get their adult canines, the fangs for which they are known.

"When adults bring down a deer or moose, the pups just join in. It's kind of an imitation game," Mech said.

By roughly 9 months old, the pups can kill prey on their own.

They stay with their pack for about a year, then between 1 and 2 years old they disperse and look for a mate, which starts the reproduction cycle all over.

"Their whole mission once they leave their pack is to find a mate and a space where there is adequate food and settle down and start their own families," Mech said. "The analogy to a human family is extremely good."

There is more potential peril, of course. Single wolves caught by other packs are often killed. And when they disperse, there is a better chance they'll get hit on highways or train tracks.

Meanwhile, this year's scarcity of snow was good news for deer (wolves' primary prey) and bad news for Canis lupus and the pups that will be born this spring. The lack of deep snow gives deer the advantage, allowing them to outrun their canine predators.

"I would say this isn't a good winter for wolves," said Mech.

Wolves weakened from lack of food may not produce as many pups this spring, and fewer of them might survive.

Just last year, deep snow tipped the scales to the wolves.

It's a never ending life-or-death battle between prey and predator that plays out — usually unseen by humans — in Minnesota's woods.

Doug Smith • 612-673-7667