Isle Royale wolves doing well

March 06, 2000

HOUGHTON, MI­The wolves of Isle Royale National Park are doing well and should continue to hold their own in the foreseeable future, according to a just completed survey of the island's wolf and moose populations.

Park Superintendent Douglas Barnard said the island's wolf packs added five pups to the total population during the past year, but one adult wolf was killed this winter, leaving the park with 29 wolves at present. Just two years ago, the population had plummeted to 14 and biologists and park officials were concerned about the species' continued survival. But those concerns seem to have been allayed by the wolves' remarkable ability to withstand nature's challenges.

"In general, the island's wolves appear to be in good health and the packs are experiencing normal reproductive success," said Barnard. "We see no reason why this trend shouldn't continue over the next few years."

Michigan Tech University wildlife biologist Dr. Rolf Peterson, who has conducted the annual wolf/moose survey for the National Park Service for the better part of three decades, reports that this year there has been a realignment of pack territories on the island.

"Whereas we used to have three packs dividing the island, now there are essentially only two," said Peterson. "The Middle Pack, which had three surviving pups from last year and now numbers 12 animals, has virtually taken over the former West Pack territory. The West Pack's numbers have steadily declined and they are simply no longer able to defend their territory. There may be a couple of them still alive, but we haven't been able to determine that for certain ." He said there are also two other adult pairs roaming the island, as well as a single adult wolf. The East Pack successfully raised two pups from last year and now has 10 members, which continue to control the east end of the island.

Biologists picked up the carcass of one wolf which succumbed to interpack warfare and witnessed the near demise of another.

"An independent adult pair of wolves had been roaming the border area between the East and Middle Pack territories for some time," said Peterson. "One day we were flying over that part of the island tracking the signal from a radio collar of a male wolf that indicated the animal had died. When we located the site from which the signal was coming, we saw the Middle Pack standing there. Later we returned to the area and found the carcass of a wolf where the pack had been earlier. It turned out to be the male of the pair that had been using the border area. It had been killed by the Middle Pack.

"Two days later we were flying along the shoreline of the island and we saw a female standing on a rock out in Lake Superior facing 10 wolves from the Middle Pack, who were pacing the shore opposite her. Some of them crossed on rocks to where she was and attacked her several times. We watched this go on for about 45 minutes before she jumped into the water and swam away. She swam about 100 yards up the lake, then came ashore. As soon as she was on land, the wolves from the Middle Pack attacked her in force and appeared to have killed her. After a while they left her body and moved off into the woods and we returned to camp to refuel our plane and get a pack to haul out her carcass.

"When we returned to the site nearly three hours after the attack, we noticed a lone male from the Middle Pack casually walking along the shoreline trail. He had not been with the pack earlier and apparently was trying to catch up with them. When he came to the site of the battle, he became very uneasy and then noticed the body of the female. To our surprise, when he approached her, she raised her head and looked at him. After a while, she was able to pull her forelegs up under her, but she was still unable to stand. The male wolf then went over to a nearby rock, where he lay down and watched the female, who was in heat.

"We had planned on landing at a nearby inland lake and then hiking to the shore to pick up the female's body. When we saw she was alive, we left the area and went to check on other wolves. When we returned two hours later to check on the situation, both animals were gone.

"We saw them again five days later about a half-mile from the battle scene. They were standing atop a little knob and we were able to see clearly that the male was licking some wounds on the female's neck. We never saw them again, so we don't know for sure whether or not she made it."

Peterson said the Middle Pack now controls about three-fourths of the park's area, and by taking over the west end of the island, they have increased the number of moose available to them for food. The East Pack, however, while having a smaller territory, still maintains control over that part of the island with the greatest number of moose.

Isle Royale's moose population has increased slightly, from 750 last year to 850 this year, according to Peterson. He said the population seems stable, but calves are scarce, so overall growth potential of the herd appears minimal.

"I was surprised to see so few calves," he said. "It's one of the lowest levels we've ever recorded and we don't know why, but it could be weather- related. He said hot, dry summers such as Isle Royale experienced in 1998 create stress for moose. "Moose don't perspire," he explained, "so hot weather causes them to overheat and they don't eat as well as they should and as a result, aren't as healthy. Studies in Norway have shown that moose killed by hunters after a hot summer have greatly reduced body weights compared to those killed following a cool, moist summer which moose prefer.

He said early spring and hot summers also result in higher tick production and greater infestation on moose.

"This was almost a non-winter on Isle Royale," said Peterson. "So for the moose's sake, we should hope for a cool, moist summer. The short-term success of the island's herd probably depends as much on the weather as anything else."
-end-
For more information, contact Rolf Peterson at 906-487-2343 or email ropeters@mtu.edu .

Michigan Technological University

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