This massive American Bison was walking with its herd at the Rocky Mountain Arsenal National Wildlife Refuge when it stopped in its tracks. It raised its head and did what is called the flehmen response – a curling of the lips and closing of the nostrils.
Many mammals do this and then inhale deeply allowing them to get a better sampling of a particular smell that interests them – kind of like a human taking a big whiff to smell something. You most likely have seen horses do this and I have seen deer and elk do it as well. This was the first time I saw a bison do it though.
In the background you see Denver’s famous ‘cash register building’, formally known as Wells Fargo Center. It is the third tallest building in the city at 698 feet high.