Cameron Walker / National Geographic News
A single wolf may have nudged the threatened Scandinavian wolf pack along the road to recovery.
Less than two decades ago, only a handful of wolves loped across southern Scandinavia. Now their numbers have soared to more than 100.
One lone wolf turned the tide for this isolated group, report Scandinavian researchers. Past studies have suggested that dwindling populations could be resuscitated by new blood. But this is the first time scientists have spotted this boost in the wild, said Carles Vilà, a co-author of the study.
"Natural immigration may be extremely important for the recovery of small populations that are isolated," said Vilà, a conservation geneticist at Uppsala University, Sweden.
The Wolf Mystery
Wolves started vanishing from Scandinavia during the last century, and were thought to be extinct by the 1960s.
In the 1980s, a small group of roaming wolves reappeared. Hans Ellegren of Uppsala University, also a co-author of the study, said controversy swirled around the new pack's origins. Some thought the wolves had re-emerged from hiding. Others spread rumors of illegally-released animals or dogs run wild.
Ellegren and his colleagues tracked the pack's beginnings by following unique DNA markers, called microsatellites. By tracing these markers back through history, they determined that a single pair of wolves had started the first pack.
To uncover the homeland of the original pair, the researchers compared the genetic make-up of the founder wolves against likely possibilities. They pulled DNA samples from wolf teeth from the early 20th century, found tucked away in museum collections. Samples from modern-day packs in Russia and Finland also served time in the lab.
The team determined that a pair of wolves made the unlikely 620-mile (1,000-kilometer) journey from Finland to start a new Scandinavian pack. With no outside visitors, however, the emerging pack was mired in its own genes. Genetic snapshots caught the same genes recycling through the isolated Scandinavian population.
But in 1991, a fresh batch of DNA markers appeared unexpectedly in a litter of wolf cubs. Researchers pinned the new genetic juice to a single male wolf that had joined up with the first pack.
The inbred wolf population started to grow at an exponential rate.
"Now we have 100-plus wolves and some 10 reproducing packs," Ellegren said.
According to Ellegren, a new member like this lone wolf may counteract the negative effects of inbreeding, an event called "genetic rescue."
While the Scandinavian wolves appear to be on the rebound, their continued success may be another matter.
Scandinavia has plenty of good wolf habitat by European standards.
"However, these wildlands are not wilderness," said John Linnell, a senior research ecologist at the Norwegian Institute for Nature Research (NINA). Wolves and other large carnivores often patrol large territories in search of prey. Hunting, grazing, and logging interests all compete for the same habitat.
Reindeer, central to the lives of the nomadic Saami people, graze year-round in the mountains and forests and are prime prey for wolves. Sheep flocks, easy pickings for a hungry pack, also range across Norway and Sweden.
Forest owners rely on the sales of hunting permits as well as timber sales.
"The fact that wolves kill hunting dogs used for small game hunting makes it hard to sell licenses in wolf areas," Linnell said.
Even those who don't make their living from the land may harbor a fear of wolves. Wolves play the villain in folktales and legends across the world.
Scandinavia's wolf woes mirror those in this country. The wolf reintroduction to Yellowstone National Park sparked a near-record number of responses from citizens commenting on the government plan.
"The most dramatic thing a person sees is that conservation in both countries is the same," said L. David Mech, senior research scientist for the U.S. Geological Survey and founder of the International Wolf Center. "The human constituencies are the same-scientists, farmers, environmentalists."
According to a recent report by Linnell and colleagues at NINA, people's attitudes toward conservation may have become more positive during the past few decades.
A program established in 1995, the Large Carnivore Initiative for Europe, is working to bolster support for wolves and other large predators throughout Europe. The initiative, started by WWF International, partners organizations and experts in 17 European countries, and links carnivore researchers, managers, and policymakers from 29 countries to increase public support for carnivore conservation.
Researchers hope that this study may bolster conservation support for creatures big and small.
"I would say this is hopeful," said Mech, who has studied wolves for more than 40 years. With the addition of a single wolf, the new genes appear to be maintaining a small population, he said. "That allows the population to have a good chance of survival."
Vilà cautions that a single immigrant may not always do the trick. Incoming members might not adapt well to new territory, or could bring new diseases along with new genes, he said.
However, when animals move into an area from nearby locations, it's not likely to be a problem, Vilà said.
To improve the odds for threatened animals, "it may be important to arrange having 'genetic corridors' allowing immigration," said Ellegren.
But while the Scandinavian wolves remain threatened, it seems possible that a single set of paw prints may have crossed this corridor in time.