Never Cry Wolf

Young, naive Canadian biologist Tyler (Charles Martin Smith) is assigned by the government to travel to the isolated Canadian arctic wilderness and study why the area's caribou population is declining, believed to be due to wolf-pack attacks; amongst his orders to study them he is also given a gun and required to kill one wolf and examine its stomach contents. Tyler receives a baptism of fire into bush life with a trip by bush plane piloted by Rosie (Brian Dennehy). After landing at the destination, Rosie leaves Tyler in the middle of a sub-zero frozen Arctic lake. Tyler is at a loss of what to do about his situation until he is rescued by a traveling Inuit named Ootek (Zachary Ittimangnaq), who transports him and his gear off the ice and builds a shelter for him.
Alone, Tyler divides his days between research and survival, while nights are fraught with nightmares of wolf attacks upon him. He soon encounters two wolves â which he names George and Angeline, who have pups, and discovers they seem as curious of him as he is of them. He and the wolves begin social exchanges, even urine-marking their territories, producing trust and respect between them. Noticing that they haven't eaten any caribou and only mice, he begins a side experiment of eating only mice for protein sustenance.
Another Inuit named Mike (Samson Jorah) encounters Tyler, sent by Ootek for companionship. Mike knows English and Inuit, translating between Ootek and Tyler. Ootek, the elder, is content and curious about Tyler, while the younger Mike seems not only more reserved but unhappy with the Inuit way of life, confessing to Tyler his social apprehensions, this is mainly due to the fact that Mike is missing nearly all his teeth as well as telling Tyler about the time he met a girl and how she was comfortable with him until he smiled. Tyler discovers that Mike is a wolf hunter, killing for pelts to sell to make a living. Tyler demonstrates a trick he has learned: by playing certain notes on his bassoon, he can imitate a wolf howl, calling other wolves in.
Fall nears, and Tyler hears that the caribou are migrating south, which will provide an opportunity for him to study the concept his superiors want to confirm. Ootek takes Tyler on a two-day hike to where the caribou will be. The caribou show up as predicted and Tyler observes the wolves make several unsuccessful attacks. Tyler helps drive caribou towards the pack, which soon takes one down. Tyler takes a bone and samples the marrow, discovering the dead caribou to be diseased. It confirms that the wolves are not ruthless killers but rather their predation kills off only the weaker caribou.
One day, Tyler encounters Rosie with two hunter-guests, making plans to exploit the area's resources. Rosie insists on flying out Tyler, who refuses. Rosie then offers to extract Tyler from his research campsite in two days, the time it will take Tyler to hike back.
Tyler returns to the base to find things very still. He ventures into the wolves' territory and goes into their den, only to find the pups cowering in fear and the two wolves nowhere in sight. Rosie's aircraft approaches outside. Believing that Rosie killed George and Angeline, Tyler shouts at Rosie to leave, then shoots at Rosie's plane, which makes him fly away.
Tyler goes back to his camp to find Mike, whose nervous demeanor causes Tyler to suspect that it was Mike, not Rosie, who killed the two wolves. Mike confirms Tyler's suspicions by smiling with a full set of new dentures and leaves, hiking for home.
Some time later, as the first snow begins to fall, Tyler plays the wolf call on his bassoon, bringing in other wolves from George and Angeline's pack. He reflects on his time in the wilderness and how he may have helped bring the modern world to this place. The narration implies that Tyler will return to civilization and recover from his experiences here. Ootek has returned, and in the final scene he and Tyler break camp and trek across the fall tundra to the south, enjoying each others company, along with the words of an Inuit song that Tyler translates:
I think over again my small adventures, my fears.
Those small ones that seemed so big.
For all the vital things I had to get and to reach.
And yet there is only one great thing, the only thing:
To live to see the great day that dawns
and the light that fills the world.

Question: Why do they think the caribou population declining?
Answer: Wolf-pack attacks