Scientists use GPS, cameras and radio transmitters to monitor Denali's wolves

Denali National Park and Preserve is bigger than the state of New Hampshire.  

Denali is located in inland Alaska.

You can reach Denali by road from Fairbanks to the north and Anchorage to the south. 

The 92-mile Denali Park Road is the main road into the area.

The park was established in 1917.

Over 600,000 people visit every year. 

Mount Denali is the highest point in North America. 

It has an elevation of 20,310 feet. 

Red signs on the side of the road in Denali read:

AREA CLOSED: Critical Wildlife Habitat. Wildlife are denning or nesting in this area. Human presence may cause animals to abandon their young or become habituated. To minimize disturbance this area is closed to all entry. 

The 2-pound collar has been designed to withstand extreme weather, submersion in lakes and rivers, and animal bites. Each collar is outfitted with GPS- and radio-tracking technology. 

Nine collared wolf packs live in Denali. 

Wildlife is everywhere in Denali. 

Here's a caribou track next to a wolf track. 

An empty robin's nest is tucked in a tree.

Moose are a regular sight in Denali. 

Signs of bears, both Grizzly and black bears, are also common. 

Older wolf tracks fade into the sand.

Biological assistant Kaija Klauder (left) and wildlife biologist Bridget Borg use a radio telemetry antenna to determine if any collared wolves are in the area. 

No response means there aren't any collared wolves nearby. The antenna typically picks up signals from about 3 to 4 miles away.

Borg and Klauder visit wolf dens every year to set up cameras and remove old SD cards from existing cameras to review the previous year's footage.

The Teklanika River bridge is about 30 miles into the park. Wolves have been known to den in this area.

I'm following Borg and Klauder up river to see if any wolves denned here over the last year.

Wolf dens can vary a lot. Denali wolves often dig holes in sandy areas near rivers or up on hillsides under trees. 

It may look nondescript, but this section of exposed tree roots is a wolf den, where a wolf gives birth and cares for her pups until they're old enough to leave. 

The cameras can withstand extremely cold temperatures.

Temperatures range from 75 degrees Fahrenheit in the summer to minus 40 degrees in the winter. 

An outer casing helps protect the camera from the elements. 

Wolf pups play near their den. 

Bite marks on one of the camera cords show evidence it was used as a chew toy by wolf pups -- or other animals. 

Each camera uses twelve batteries. 

The cameras have night vision capabilities. Here, the pups are hanging out near the den site.

The pups stay near the den until the pack is ready to move to a rendezvous site, usually when the pups are about eight weeks old. A rendezvous site acts as an intermediary home base where pups can learn to hunt without having to travel very far. 

Pups become fully independent members of the pack when they're about six months old. This pup is much younger and will stay close to the den. 

A wolf with a GPS collar goes into the den.

Klauder scrolls through the SD card footage to see what images the camera has captured over the past year. 

Some pups stay with their original pack after they're fully grown. Others venture out and join an existing pack or start their own.

Borg sets up a new camera that will run until September 2019.

She uses sticks to give the camera a better view of the wolf den. 

Caribou and beaver remains are near the den, likely carried up there by the rest of the pack to feed the denning mother and her pups. 

As of a spring 2018 count, 75 wolves live in Denali.  

A single pack defends hundreds of square miles of territory. 

Wolves are considered a keystone species in Alaska, meaning their presence affects the entire ecosystem. 

It's early September in Denali, but the fall colors are already out.

Clouds and fast-changing weather can obscure the view of Mount Denali.