How do grizzly bears and wolves in Yellowstone National Park carry on when they don't think anyone is watching? Well, as these pictures show, they're not going after each other tooth and claw.

Nancy Ward, the park's acting chief of maintenance, was heading to Lake for a meeting back on May 4, before the park's interior roads were open for the public, when she spied a wolf and another animal in a snow-covered drainage.

As she continued on, she thought the other animal might be a bison struggling in the snow. With some time to spare, she turned around and headed back to where she had seen the animals. This is what she discovered: