The biggest impact is reducing elk, deer, pronghorn, and Bighorn populations in and near the park.
That was a funny looking deer.
Annony Mouse's Link
My son-in-law owns and operates one of the top tour businesses running out of Jackson (Jackson Hole Wildlife Safaris). He runs tours into both national parks...Teton and Jackson. Jason and his staff have studied not only fauna, but flora and geology of the parks to provide the best park experience someone not familiar with the area can get.
Far far more people view the parks and wildlife via the roads than camp and hike. We've been fortunate to tour both parks numerous times with Jason and Carrie and often see much more wildlife than many visitors. My two granddaughters are some of the best critter spotters ever!
Some observations from spending time with Jason and his guides may be a little surprising.
The presence of apex predators like the wolves and male grizzlies has modified behavior of much of the prey population...they recognize the security provided by human presence. Elk, moose, bison can easily and often be seen from the public roads for the simple fact that human presence (the cars!) keep wolves and male grizzlies away from newborn. Jason has said that it is not a rare occurrence to see births occurring where visible from the roadways. Sow bears are often seen with cubs from this viewpoint. Thus, one can give thanks to predators for making wildlife viewing a positive experience for those that tour by roads ;o)
These animals get pretty used to human presence, so viewing and photographing opportunities are plenty. Still, they are not tame nor to be approached. From a safe distance, it is both educational and entertaining to watch them. Too many tourists don't seem to understand the concept of "distance".
Carrie and Jason get winter passes and snowmobile into the parks during winter to seek out an photograph wolves. During tourist season, it is rare to see them other than from the less traveled roads in the parks. To really see them, one must get out and actually walk!
During peak season, traffic is heavy and when animals are especially close to the road (or crossing it), a "jam" occurs where those in viewing distance just stop and traffic will back up till cars begin to move on. (The guides keep each other--even between competing companies--aware of "bear jams", "bison jams", etc. LOL)
Have to hand it to the rangers. When a bear is spotted, they get to the location pronto to make sure that visitors keep a safe distance away...and will even close down a road if necessary.
While out there the past couple of years, I find it amazing how many foreigners come to see the Tetons and Yellowstone...especially the Chinese. We took a hike up the mountains to Phelps Lake and had lunch at a very scenic site. Sitting there, conversations in Chinese, Japanese, French and German were heard from other people enjoying the view.
When it comes to wildlife and visitor conflict, it seems that the Chinese are in the forefront. Too often we would see them try to approach a large bull bison or bull moose to get a picture (and theirs taken by family/friends) and get far too close.
We, as hunters, can also help create bad images. I heard numerous stories about hunters seeking easy kills during the fall elk cull. Far too many of us hunt the edges of the parks in hopes of killing a trophy that exits the protected park area during the fall mating season rather than actually hunting the truly non-park areas.
(Kind of galls me personally as I passed on an easy 5' shot on three nice bucks opening day as they were on the wrong side of the fence on my property. Could have taken one and dragged it onto my land...but I am far too ethically constricted.)
The Tetons and Yellowstone are simply awesome and we are privileged to have these parks to enjoy. Looking forward to next summer's trip and when my wife retires in a little over a year, we're going to relocate out there.