DULUTH The U.S. Fish and Wildlife Service on Tuesday, Sept. 15, issued a formal ruling that it will not move to put moose in the Midwest under Endangered Species Act protections.

The agency, part of the U.S. Interior Department, said there is not sufficient evidence to consider the Midwest population of moose, almost entirely in Minnesota, as different from moose in other regions and across the border in Canada.

The decision to deny federal protection means the animals will remain under state management, including in Minnesota where their numbers have dwindled to less than half their level of just 15 years ago.

The petition requesting endangered protections for moose was filed by the Center for Biological Diversity and Honor the Earth in July 2015. The federal government began its review in 2016, leading to Tuesday’s decision filed in the Federal Register.

“I’m incredibly disappointed that the Fish and Wildlife Service has denied Minnesota’s moose the lifesaving protections of the Endangered Species Act,” said Collette Adkins, a biologist and attorney who works in the Center’s Minneapolis office. “Growing up in Minnesota, I loved seeing moose during family vacations up north. But climate change, habitat destruction by mining companies and disease are driving moose to the brink. We’ll keep fighting to protect this iconic symbol of the northwoods.”

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The groups could challenge the decision in federal court, or file a new petition based on new information.

State wildlife managers have taken steps to protect moose, including ending the general hunting season. Only a limited number of Ojibwe hunters can harvest moose now. The state also has invested heavily in studying moose problems and more recently in improving moose habitat.

This winter saw the ninth year of a diminished but fairly stable population that comes after the state's moose numbers crashed rapidly, from a modern high of 8,840 moose estimated in 2006 to just 2,700 in 2013. This year’s official estimate by the Minnesota Department of Natural Resources, using aerial surveys in mid-winter, was roughly 3,150 — still less than the moose counted in 2006.

With Minnesota moose already at the southern edge of their habitat, scientists aren't encouraged about the animal's future here in a warming world. The decline in the state's Northeastern herd came after the once-thriving Northwestern Minnesota herd all but disappeared in the late 1990s.

Most of the state's remaining moose are in Cook, Lake and northern St. Louis counties.

Moose in Minnesota have been hit hard by a number of factors, including a long-term increase in deer across moose range. Deer carry a parasitic brain worm that, while harmless to whitetails, is fatal to moose. Moose also have been plagued by an increase in parasites, such as ticks, that thrive in a warmer climate.

Moose also have seen dwindling habitat, often due to fire suppression, aging forests and past forest management. Scientists have noted that some of the few areas with increasing moose numbers in recent years are where big fires have occurred, clearing the way for a younger forest that has the type of food moose thrive on.

The shrunken moose herd, especially newborn calves, also is more vulnerable to predators, especially wolves, but also black bears — predation that had little impact on the overall moose population when it was twice as big.

Research shows that wolf predation has consistently accounted for about two-thirds of the calf mortality and one-third of the adult mortality. In some cases, injuries suffered during predation attempts, not the predation itself, ultimately killed the adult moose. In others, sickness or disease likely made the adult moose more vulnerable to being caught and eaten by wolves.

In 2005, when the moose population was healthy, more than half of all cow moose surveyed had a calf with them in winter, 52%. Now, that number has dropped to less than one-third of cows with calves surviving until January, 32% — a number so low that the overall population can't trend up.