He gets up close and personal with some of the fiercest predators in Yellowstone. Or at least his cameras do.

For photographer Ronan Donovan camera trapping is an art, and designing the setups with animal behavior patterns in mind can require creativity, patience, and determination. On assignment for National Geographic‘s 2016 issue on Yellowstone, he rolled up his sleeves, refused to give up, and captured amazing images of bears and wolves in their natural habitat.

Bears are naturally curious omnivores that tend to “lick everything,” Donovan says, and one of the biggest challenges in setting camera traps for them is what he calls “camera carnage.” Wolves, on the other hand, are much more elusive—and much harder to pin down.

Note: The video above features photographs that were made using a variety of techniques, including camera traps.

View Images This bison drowned in the Yellowstone River over the winter when it tried to cross. Donovan says a grizzly bear had been feeding on this carcass for several days before he set up a camera trap. Photograph by Ronan Donovan, Nat Geo Image Collection

According to Donovan, wolves are by nature more wary of anything new in their environment—even the slightest reflection from a lens could scare off an approaching wolf. Donovan spent months trying to invent ways to “trick” the wolves, building all sorts of structures to hide the traps and make them less conspicuous. One of the traps he built was disguised by a pile of river rocks and placed in the shallows of the Yellowstone River.

Not only did Donovan have the wolves’ wariness to contend with, but he also had to deal with ever changing weather patterns, which can cause a camera lens to fog or ice over. Out of the hundred traps he set in Yellowstone, only five produced viable pictures of wolves.

View Images A group of wolves feed on the same bison carcass from the previous image. Condensation made this shot a near miss. Photograph by Ronan Donovan, Nat Geo Image Collection

In one particularly heartbreaking instance, three wolves came to feed on a bison carcass on the Yellowstone River. Wolves are social animals, so photographing them together would be a coup. The camera fired a couple of thousand times, but because the lens had iced over, the shapes were rudimentary and the images unusable.

Though the wolves never again came back to that spot as a group, it wasn’t a total loss. After months of reformatting and rejiggering, Donovan’s hard work and persistence paid off with the amazing images shown in the video above.