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Researchers track New Hampshire moose in hopes of pinpointing cause of population decline

April 7, 2014 at 6:36 PM EDT
In some regions of northern New England, the moose population is down as much 40 percent in the last three years. The cause of this iconic animal’s dramatic die-off is not yet known, but researchers’ main theory is centered on the parasitic winter tick, and warmer winters may be partly to blame. Hari Sreenivasan reports from New Hampshire.


JUDY WOODRUFF: In northern New England researchers are increasingly worried about what’s happening to one of the region’s iconic animals, the moose. Their numbers are significantly declining, and investigators are trying to find out whether warmer winters in recent years may be a big part of the problem.

Hari Sreenivasan reports from New Hampshire.

And a warning: The story contains some graphic images.

MAN: Well, we get to the tower, we got to check on those two calves we’re getting funny signals on.

HARI SREENIVASAN: Scientists are bundling up and prowling the forest in pursuit of the wildest large animal in New Hampshire, the moose. Their into-the-woods exploration by both foot and air is part of a massive research effort to understand why America’s iconic wild moose are dying at alarming rates.

The first weeks after a long winner are a critical time for moose. And here in New Hampshire, wildlife biologists from the state fish and game department want to find out why, in the last three years, moose populations are down as much as 40 percent in some regions.

Kristine Rines of the moose project with New Hampshire Game and Fish Department.

KRISTINE RINES, New Hampshire Fish and Game Department: April is the month of death, when most of these animals seem to just — they are completely depleted and they just start dying.

HARI SREENIVASAN: According to Eric Orff, New Hampshire field biologist for the National Wildlife Federation, the deaths have been dramatic all along North America’s southern moose range.

ERIC ORFF, National Wildlife Federation: When you look at a precipitous decline in the last decade, you know, the needle is headed in the wrong direction, you know, all across the southern edge of the range, from Nova Scotia, New Brunswick, Minnesota, Michigan, all across the southern fringe of their range, moose numbers are in a significant decline.

HARI SREENIVASAN: To better understand what’s behind the decline, New Hampshire and Maine have hired capture teams, whose job it is to track down the moose and collar them with a radio transmitter.

MAN: Well, we need the radio frequency.

MAN: Yes, it’s 153.73.

HARI SREENIVASAN: Pete Pekins, professor of wildlife ecology at the University of New Hampshire, is overseeing the project.

PETER PEKINS, University of New Hampshire: The helicopter basically finds these animals, zooms down on that animal. A net is shot over the gun. We call that net gunning. And the animal trips up in the net. And what are called muggers jump out of the helicopter at low height. And they wrestle the moose to the ground. And the people actually, many of them have been professional rodeo cowboys.

HARI SREENIVASAN: The goal is to collar and release 200 moose between this winter and next.

PETER PEKINS: These people know how to handle big animals. Most importantly, though, is how to humanely handle an animal.

HARI SREENIVASAN: Professor Pekins’ team tracks the collared animals from a fire tower in northern New Hampshire. Each day, devices are checked for signs of life.

PETER PEKINS: Of the 40 moose out there, how many have we successfully monitored here today?

MAN: So, we picked up 37 of the 40. From this morning, there is one, 314, if you want to check that one, Nick.

HARI SREENIVASAN: When monitors signal a moose death, researchers are quick to get to the animal before vital information is diluted by weather and time.

KRISTINE RINES: What we’re going try and do is get to them much sooner, so that we have better information on exactly why they’re dying.

HARI SREENIVASAN: The main theory New Hampshire researchers are pursuing is that the massive moose die-off is caused primarily by a devastating parasite, the winter tick.

On the day we visited, biologists retrieved a dead calf that was completely covered with winter ticks.

PETER PEKINS: Literally, this is the walking dead. The animal is totally emaciated. And there is no way it can survive.

These are the engorged adult ticks.

HARI SREENIVASAN: It is suspected the ticks latch on in fall and live off the animal’s blood for months.

PETER PEKINS: They are literally being sucked dry of blood. So, they can’t consume protein to replace the blood loss. Their only choice is to catabolize their own tissues. And that is going to be their muscles. The hind legs on a moose are some the most powerful legs in North America. And that animal doesn’t have any. And it’s because it has chewed up its own body to survive as long as it can.

And you can see that that is quite a bit of blood.

HARI SREENIVASAN: The winter tick parasite is not new, but its explosive population growth is. Reaching an animal like this calf soon after death allows scientists to document just how many ticks there were before they drop off in pursuit of a live host.

Scientists suspect that warmer winter temperatures are leading to the increased number of parasites.

PETER PEKINS: Shorter winters, both on the spring and fall end, play to the advantage of the tick.

HARI SREENIVASAN: The National Wildlife Federation’s Eric Orff is not affiliated with the state’s research team. While this winter was cold, he worries the longer-term warming trend and the rise in tick populations are part of a larger problem: climate change.

ERIC ORFF: In New Hampshire, our winters have warmed some four degrees since 1970. So, the warming of the winter means less snow, means more ticks, means fewer moose.

HARI SREENIVASAN: When you don’t have snow in April, you don’t have snow in November, that means they breed.

ERIC ORFF: The population explodes.

HARI SREENIVASAN: It’s easy to see why the moose is so important in New England. Viewing moose has become an $11 million tourist industry here.

PETER PEKINS: If you came to New Hampshire this summer, the most common question would be, where I can see a moose? And literally every tourist wants to see a moose. And New Hampshire has a great reputation for that. The aesthetic value of this animal to the state is — it just can’t be measured.

ERIC ORFF: As we know, our moose numbers are down some 40 percent.

HARI SREENIVASAN: Eric Orff is take the question of New Hampshire’s warming winters to the political arena, asking businesses and New Hampshire’s outdoor industry to sign a letter in support of the Environmental Protection Agency’s proposal to reduce carbon emissions, emissions he believes play a role in climate change.

ERIC ORFF: In my lifetime, as a wildlife biologist, I witnessed the disappearance of winter here in New Hampshire. So we really need to curb carbon, get off the carbs world, and we need to put this earth on a diet of carbs, carbon, and bring back winter.

HARI SREENIVASAN: For their part, state researchers are not yet pointing the finger solely at climate change. Instead, they say the die-off is complex. Their plan is to keep their focus squarely on the biology of the moose and the best ways to sustain a healthy population.