March 9, 2007
Wolves, Moose in Decline in National Park
TRAVERSE CITY, Mich. -- Chased into the Lake Superior shallows, mauled and left for dead by fellow wolves, the young female struggled to shore and collapsed. A lone male came to the rescue, licking her wounds and staying on as she recovered.
Together they formed a successful and prolific pack, with the female bearing at least 19 pups. But their love story has ended tragically: A rival pack killed the female this winter, a year after fatally attacking her mate as he munched on a moose carcass.
"All we found were the skull and a radio collar," Rolf Peterson, a wildlife research professor at Michigan Technological University, said Wednesday.
Because of its isolation, the Isle Royale National Park is an ideal setting for wildlife study - and researchers are noting a troubling development: the island's wolf and moose populations are declining.
The population of moose - the wolves' primary food source - is at its lowest since wildlife biologists began studying the two species' predator-prey relationship in the park 49 years ago.
The annual census turned up 385 moose, down from the previous low of 450 last winter. Wolf numbers fell from 30 to 21 during the same period, largely because of hunger.
"We're definitely in uncharted territory," said John Vucetich, a Michigan Tech assistant professor who teams with Peterson on the project.
Isle Royale had more than 1,000 moose as recently as 2002. But nature has dealt a one-two punch: a run of unusually hot summers and an infestation of blood-sucking ticks.
Instead of fattening themselves for winter, moose are spending too much of the fleeting summers seeking shelter from the sun and trying to remove the nasty parasites by rubbing against trees and biting their hair out.
One moose can host tens of thousands of ticks. Weakened by weight and blood loss, many are unable to fight off ravenous wolf packs.
Despite their dramatic slide, it's highly unlikely all the moose will die, Peterson said.
"The wolves are the ones that would be at risk, through their own actions in a way," he said. "Ten years from now, it will be pretty dismal for the wolves" because they're gobbling up moose calves before they can breed and rebuild the herd.
Yet the wolves have overcome other dangers, including a virus outbreak that nearly wiped them out in the late 1980s.
"It looks terribly precarious," Vucetich said. "But amazingly, these things tend to fix themselves more often than not."
Peterson, who witnessed the earlier attack on the female and her rescue by her future mate from an airplane in 2000, said only one other wolf is known to have borne more pups during the study period.
She and her mate produced seven litters. "It's pretty unusual for a pair to survive and do well for that long," Peterson said.
They were alpha members of what the researchers dubbed the Chippewa Harbor Pack, one of three packs roaming the 45-mile-long archipelago in northwestern Lake Superior. The rival East Pack apparently caught her trespassing in its territory, Vucetich said.
Chippewa Harbor has two new alphas, whose strength and tenacity will determine whether the pack survives.
Although focusing on the wolves and moose, the scientists also monitor how their ups and downs affect other species. Foxes, for example, are hurting because wolves are eating every morsel of their kills, leaving less for other animals to scavenge.
"It's all so connected, and that's half of what makes it so fascinating," Vucetich said.
On the Net:
Isle Royale wolf study site: http://www.isleroyalewolf.org/