Nightly News | September 02, 2013
>>> now to a growing mystery that has scientists baffled and on the hunt in minnesota . that state's once large and thriving moose population has been experiencing a rapid decline, disappearing at such an alarming rate it has some there worried they'll soon be endangered. we get the story from our chief environmental affairs correspondent, anne thompson .
>> reporter: they are the iconic animals of minnesota 's north woods . moose sightings like this one and this one are increasingly rare.
>> just made my week, man that is so cool.
>> reporter: seth moore is one of several scientists trying to figure out what's causing the dramatic decline in minnesota 's moose population. they've all but disappeared in the northwest part of the state, and here in the northeast, this are just over 2,700 left. some of these animals which should weigh up to 1,000 pounds are skin and bones with severe hair loss.
>> we're spending time and energy and research to try to understand it. the population itself still continues to decline.
>> reporter: the falloff is stunning. down 35% in the past year and more than 50% since 2010 .
>> here in grand forge, we're seeing about 85% pregnancy rates which is pretty good. this year, we only came out about 69% pregnancy rates.
>> reporter: in the office, moore and his team track the adults they've collared on the computer. in the field , a portable antenna guides him to where the animals feed and sometimes die. this spring he worked with tiffany wolfe of the minnesota zoo to collar calves.
>> it may not be one disease itself. that's the smoking gun here. but multiple factors that are contributing to the overall poor health that we're seeing.
>> reporter: what's happening in the summer, researchers say may be connected to the winter. historically, minnesota 's harsh winter have kept the deer and tick populations in check. now the season is shorter and milder and presents danger. parasites fatal to moose, ticks spread disease.
>> we may be able it change the landscape to benefit moose.
>> reporter: first they must understand what is driving these majestic animals from the landscape. anne thompson , nbc news, grand portage , minnesota .