Here is a link to an interesting article about wildlife vs. vehicle collisions in National Parks.
I know I spent a considerable amount of time conducting investigations and doing the paperwork resulting from such incidents. All such collisions did not just affect park visitors. We had quite a bit of damage done to government vehicles when they met deer on the road. I had several years when my operating budget was depleted by body shop repair bills. On the Blue Ridge Parkway it was not uncommon for deer to run into moving vehicles. So it was not always the driver's fault.
Lower speeds do allow for more driver recognition and reaction time to brake and or avoid collisions with animals in the roadway. These concepts apply to any driving route obstruction.
In many instances visitors would loose control of their vehicle attempting to dodge an animal in the road. If their speed was high the ability to regain control of the vehicle is more challenging and may result in hitting another object such as a tree, retaining wall, or side of a mountain.
Many years ago I sat in on a meeting at Shenandoah National Park. Apparently there had been several vehicle collisions resulting from employees swerving to miss deer on the Skyline Drive. The Chief Ranger was addressing the gathering of park rangers about this and in frustation stated, "The next time a ranger has a wreck because of a deer, I want that damn deer's body brought in." I always wondered if they ever found that one deer that was causing all that mayhem.