ISLE ROYALE NATIONAL PARK, Mich. — Rolf Peterson, the Michigan Tech researcher who has spent the last half-century studying moose and wolves on Isle Royale, has documented one of the oldest wild moose on record.
Moose No. 5462 was 22 years old when she finally died, definitely a new age record for Isle Royale moose and maybe anywhere where moose roam.
Peterson, who spent parts of the last five years aging more than 400 moose skeletons, said the old cow was "a museum of pathology, with arthritis in 16 of her vertebrae, infections in both upper and lower molars and moderate osteoporosis."
She died of starvation in 2018 near Lane Cove on the island.
"We actually had two out of this last round that hit 22. ... And there were four moose over 20 years old," Peterson told the News Tribune.
That's an astounding first, Peterson noted, considering he has aged more than 3,000 adult moose over the years, many of them wolf kills.
"When you have four in one group over 20 years old after having maybe two over 20 in the previous 50 years, that's unusual," he said.
Peterson takes a molar from the dead moose's jaw, cuts it in half and polishes it to reveal annual lines in the tooth, much like the rings on a tree trunk. Peterson's effort has amassed a collection of thousands of moose jawbones.
The recent long-lived moose likely lucked out by living during a period when wolves on the island were declining, blinking out due to inbreeding and genetic deformities. Moose that lived during a time of wolf abundance likely would never have made it that long, especially with the ailments the old cow had.
The average life expectancy of a moose on Isle Royale is about 10 years. But that's brought down due to higher death rates for calves. Once they reach adulthood, the average age that a moose dies on the island is 12.
While some literature mentions moose living to 22 years, actual documentation has been hard to find.
"They had some cows in Alaska that hit 20 years, which a lot of people thought was impossible, but I've never heard of any others as old as 22 years," Peterson noted.
After 62 years of annual surveys, Michigan Technological University researchers couldn't go to the island in winter 2021 because of COVID-19 concerns. But they expect to head back to the island next week for the 63rd winter survey conducted from the air. It's the longest continually running predator-prey survey in the world.
The moose herd was estimated at about 1,800 in early 2020, after the last full survey, but that number has almost certainly dropped dramatically since then with moose starving, unable to find quality food to eat.
Researchers who went to the island in the spring said the state of the forest was the worst they had ever seen, with moose eating the forest faster than it could grow.
It's also unclear how many wolves now roam the island, but it's likely well over a dozen adults and many pups, all of them wolves relocated from Minnesota and Ontario and air-lifted to the island in recent years, or offspring of those wolves. None of the island's original wolves remain.
Moose came to the island around 1900, peaking at 2,445 in 1995 and hitting bottom at just 385 in 2007. Wolves are relatively new to the island, having crossed the ice from the North Shore in 1949. Their numbers reached a high of 50 in 1980, and 24 wolves roamed the island as recently as 2009 before they crashed to just two when the wolf transplant began in 2017.
At 45 miles long, Isle Royale is the largest island on Lake Superior, sitting about 14 miles off Minnesota's North Shore from Grand Portage. The island is a national park and mostly designated wilderness with few human visitors. There are no other major predators on the island; no human hunting is allowed; and moose are the only large prey species, making it a unique wild laboratory for the ongoing study.
This will be Peterson's 51st annual winter survey.
