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'Flooding effect' keeps mortality rate in check

Posted: Thursday, May 24, 2001

KENAI -- On or about May 25 is the birthday of every moose on the Kenai Peninsula. Through an amazing evolutionary adaptation called the "flooding effect," all moose here are born within a few days of each other.

"It's synchronized so the calves are born at the same time, so predators can only operate on them at one time, instead of throughout the summer," said Alaska Department of Fish and Game biologist Ted Spraker. "Predators can only eat so many per day, but if they are born throughout the summer, they'll have a new meal every day."

Moose calves can stand and take a few halting steps just hours after being born but become faster and stronger -- and better able to avoid predators -- as summer progresses.

The synchronized births come from synchronized breeding. Spraker said that in late September bull moose start gathering cows and mate with them in the first five days of October.

The flooding effect is the same for peninsula caribou, which Spraker said probably have already calved.

Studies have shown the majority -- 75 percent -- of calf predation occurs in the first five weeks of life.

"If a calf can make it to the middle of July, it has a pretty good chance to make it to the winter," Spraker said.

The primary predator for moose calves on the peninsula are black bears, which kill 30 to 40 percent of those that don't make it through the summer. Brown bears and wolves account for another 10 to 15 percent each.

"The reason for that is there are about 3,000 black bears, 200 wolves and between 250 to 300 brown bears on the peninsula. So just through sheer numbers black bears are a much more important predator to moose calves," Spraker said. "But the wolves aren't going hungry, they're killing adult moose, which is more detrimental to the population."

Coyotes aren't known to prey on moose calves, but do kill caribou calves, especially when they work in pairs or packs.

Caribou thus far have been a no-show on the Kenai River flats near Bridge Access Road. Spraker said many have been congregating between the gas fields south of Kenai to Kasilof this year.

As calving time approaches, a cow moose with yearlings will run them off.

"People call and report that they see a crazed cow moose being rude to their own calf. They have to be pretty aggressive to the calf to run it off, so you may even see a cow chasing them," Spraker said. "They call saying they see a rabid moose chasing its own calf, but they're not reporting anything strange or unique. The cows just want to get the yearling off and on its way to make room for the new one."

It may be a good spring for moose and moose predators this year because road kill on the peninsula was way down over the winter. In the winter of 1998-99, 323 moose were killed by motorists, while in the winter of 1999-00, the number was in the low 200s. This past winter it was just 140.

"It's not because people were better drivers and not just because there were less moose on the roads, but I feel it's mostly because the population is down due to the severe winters we had between 1998 and 2000," Spraker said.

He estimates the moose population to be 6,500, down from 8,000 in 1997. He said a survey of near-yearlings this year show about 20 percent of those born last May have survived. He called that a fairly high count. He said in the winters of 1998-99 and 1999-00, about 5 percent survived the winter.

"In some parts of the peninsula no calves survived," he said.

While momma moose is chasing off the yearlings, she will become extremely protective of her newborns.

"They should be given a wide berth for safety," Spraker said. "And people need to really understand and learn the warning signs."

He said if a cow moose lays its ears back or raises the hackles on its neck, it is feeling threatened and may attack.

"Urbanized" moose, those that may be accustomed to homes and cars, are just as dangerous as moose in remote areas.

"I've been chased by more urban moose than wild," Spraker said.

"The bottom line is they are large, unpredictable wild animals that can clearly be dangerous, and there is no way to outrun them," he added. "Read the signs and be alert."

Another thing to remember this time of year is that there is zero tolerance for dogs harassing moose.

"There is absolute zero tolerance. Owners need to be aware that if their dog is caught chasing a moose, there is a good likelihood an officer will shoot their dog," he said.

He explained that it also is legal for private citizens to shoot harassing dogs as well. Since moose belong to the people of Alaska, they can be protected just as one would protect their own private property.

"So if you've got a dog you want to keep, you better take care of it," he said.

Each year he says he has to dispatch many moose calves that have been mauled by dogs.

Something else people should remember this time of year is that cow moose often leave their young calves alone for several hours or almost a day at a time to forage for food, and people should not assume the calves are abandoned.

"People find moose calves, pick them up and stuff them full of cow milk and try to feed them. They need not to do that," he said.

"About the time they scoop them up and call Fish and Game is about the time the cow returns."

He said the bleating of the calf may put a nearby, though unseen, cow on the warpath, causing danger for the would-be good Samaritan.

"It is extremely dangerous to pick up a calf. Monitor the situation, even for 24 hours, and then give us a call," Spraker said. "Don't pick it up. You could get a good stomping."

Except for bison, moose are the largest land mammals in Alaska, and there have been instances of moose stomping people to death. Two people were killed in Anchorage in the 90s by moose.

Another problem with picking up a calf is that sometimes a young cow moose may be too spooked and just abandon it, leaving it to be raised by the department.



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