ST. PAUL, Minn. (AP) — Recent snowfall in northeastern Minnesota is letting researchers finally get going on their annual aerial survey of the region’s struggling moose population.

The survey, conducted yearly since 1960, provides critical data for determining the moose population and setting the number of moose hunting permits.

The Department of Natural Resources says the count was supposed to begin three weeks ago, but researchers had to wait until now because they need at least eight inches of snow on the ground to make it easier to spot moose in heavy cover. The survey is expected to last two to three weeks, depending on the weather.

Researchers are trying to determine why northeastern Minnesota’s moose population has fallen from about 8,000 during the middle of the last decade to less than 5,000 now.

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