Moose calves dying at higher rate than expected
Out of 49 newborn moose calves that the Minnesota Department of Natural Resources (DNR) collared earlier this spring, only 10 are left for researchers to track. Predators are playing a large part in their demise, but other factors have contributed to their deaths as well.
Early in this project 11 calf deaths could be attributed to the trauma of being collared. Of those, 10 were abandoned by their mothers and one died when a mother stepped on it when field workers were trying to collar it. In addition, four calves slipped their collars, leaving 34 to be tracked.
During the summer, researchers found 16 calves eaten by wolves (four of those were probably eaten by wolves, researchers are not sure what killed them) and bears ate four. One died from drowning, one was abandoned by its mother, one was killed by an unknown predator and one died for unknown reasons, leaving 10 to be tracked. Of those mortalities, five were in Cook County, three killed by bears and two by wolves.
Glenn DelGiudice, Ph.D, research scientist/ moose project leader, is in charge of running the calf research project for the Minnesota DNR. He said so far calves have suffered a 71 percent mortality rate after the summer, but to sustain the moose herd, about 50 percent of them need to make it through the first year.
When asked about calf survival after one year, DelGiudice answered, “Can’t say, we’re already at a 71 percent natural mortality rate (24 of 34 dead) that’s close to what we were expecting over the entire year. What happens by next May depends on winter severity, etc.…So the mortality hit by predators has been fairly significant, but this is just one spring-summer, so this data can only be interpreted within the context of this year and the environmental conditions and variability that occurred this year. Also, we don’t know for sure how representative of the population this study cohort is…that’s why multiple years of study are needed.
“Additionally, documenting calf/cow ratios during the annual moose survey in January may give us a better idea if this calf survival rate is representative of the population.”
The calf study dovetails with an adult study of 103 moose also fitted with collars with GPS tracking devices. When a moose stops moving for a period of six hours it is assumed to be dead, and researchers try to get to the animal within 24 hours to determine what has killed it. Any longer and the fallen moose will likely have been eaten.
The moose population in northeastern Minnesota has fallen from an estimated 8,840 in 2006 to an estimated 2,760 in 2013. Theories abound to what is causing the calamity— everything from global warming to disease, lack of browse, winter ticks, predators, etc.— and maybe a combination of those things—but scientists want to find out why to see if there is anything that can be done before moose disappear entirely from northeastern Minnesota.
Because of the steep decline, the DNR cancelled its bulls-only moose hunt for 2013. Earlier this year the DNR added the moose to its endangered species list as a species of special concern. This is the first time since 1996 the state has updated its list of endangered species and the first time moose have appeared on it.
In an effort to help restore the population, the Grand Portage Band of Lake Superior Chippewa is managing 47,000 acres of moose habitat and the U.S. Forest Service is managing 40,000 acres in the Greenwood Lake area.
Seth Moore, biologist for the Grand Portage Band of Lake Superior Chippewa said, “Our long-term goals are to develop forestry management plans to develop, protect, and maintain quality moose habitat.”
Adult moose can grow to seven feet at the shoulders and weigh more than 1,800 pounds. They live an average of 15-25 years and tend to travel in a range of 3-5 miles, although some will wander further. Bulls can grow antlers that measure up to 5 feet across and weigh as much as 40 pounds, and healthy moose can run 35 miles an hour, easily swim 10 miles and walk nimbly and quietly through the brush and are Minnesota’s largest animal.
At birth calves typically weigh 25-35 pounds and within one week can swim and walk. Calves stay with their mothers 12-18 months before heading out on their own. But unfortunately, as researchers are finding out, it’s tough for moose to make it to 18 months.