February 16, 2022

This skull comes from what may be the oldest moose on record on Isle Royale, Mich. | CBC News

The remains of a moose that might be the oldest ever recorded on Isle Royale National Park in Michigan have been discovered — and the data suggests the moose lived to be a decade past the animal’s usual natural lifespan. 

Rolf Peterson, a wildlife researcher from Michigan Technological University, in Houghton, Mich., has been studying moose on Lake Superior’s largest island for five decades

He’s recently aged a skull of cow moose that was 22 when it died. 

“Some of the former volunteers were cross-country hiking on the island and ran across the skull and they gave us GPS coordinates,” said Peterson. “So in August, we sent a team there and found the skull and brought it back here.”

Peterson said an examination of the skull, mandible and the metatarsal bone determined the cow moose probably died of starvation in 2018. Peterson said beyond that, the moose didn’t seem out of the ordinary.

But when he sectioned the tooth and began counting cementum lines, that’s when he noticed something out of the ordinary.

“There were lots and lots of them!” he said. “So yeah, the estimate was 22 years old.”

Rolf Peterson has studied moose and wolves on Isle Royale for over 50 years. He is seen here examining a moose skull. (Supplied by Rolf Peterson)

Peterson said the average lifespan of a moose is nine to 10 years. If there is hunting in the area where it lives, often 10 years can be considered a long lifespan. 

Isle Royale is a unique situation as it is an island park and there’s no hunting there — except from the local wolves, he said. 

“Wolves kill quite a few calves, but then the moose are pretty safe from wolves until they’re eight, nine or 10 years old,” he said. “Then they start suffering from old age. So the most common age of death for an adult moose on Isle Royale is 12.”

To put the rare nature of a 22 year old moose in perspective, Peterson estimates it would be the equivalent of someone “well over 100 years old.”

Twenty-five moose were collared on Isle Royale in March 2020. A moose/wolf predator study has been underway on the island since 1959. (Sarah Hoy/Michigan Tech)

While the moose lived to a ripe age, it was not without ailments. The cow had arthritis in 16 out of the 26 vertebrae. Peterson said the the cow also had osteoporosis, which can be see in the thinning of the bones on the top of the skull. Peterson said the cow also had dental issues.

“Yeah, she had some pretty bad tooth infections, both upper and lower. And she had them a long time.”

Peterson has been an integral part of a decades long study of the relationship between predator and prey on Isle Royale that began in 1959.

The moose population on the island has been a roller coaster over the years, with estimates of between 500 and 2,500 animals since 1980.

A relocated wolf leaves its crate on Isle Royale National Park. The island received wolves from Ontario and Minnesota in 2018 and 2019. (U.S. National Park Service)

Wolves have traditionally kept the moose in check,but the population peaked around 50 animals in 1980, and gradually fell to just a pair. That lead to an explosion of moose, and the gradual starvation of some animals.

A cross border re-introduction program was undertaken in 2018 and 2019, using wolves from both Minnesota and from Michipicoten Island, in northern Ontario.

A sectioned moose tooth from the 22 year old moose. The annual lines are in cementum, which covers the roots of teeth in mammals. (Supplied by Rolf Peterson)

Peterson was kept away from his work on Isle Royale last winter due to COVID-19 but he said the re-introduced wolves have had two seasons of good reproduction, and he expects the predators should be up, and the moose population on its way back down.

“We want to thank Ontario again for contributing some wolves,” he said. “They’re nice, big moose killing wolves.”

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