YELLOWSTONE NORTHERN RANGE — The excitement all unfolded shortly after daybreak, John Marzluff recounted.
All eyes were on the lookout for ravens, the species that was the target of the University of Washington ornithologists’ scientific inquiry — and a trap he had set out amid the sagebrush above Slough Creek. But instead of drawing in a wary raven pair that claims the territory, hunks of bait on this brisk Thursday morning were going down the hatch of another corvid: magpies.
“We had pizza there and Spam with a little bit of elk hide over there,” Marzluff said later that morning. “Yesterday there was not a single magpie here. And as soon as the Spam’s out, like 15 to 20 magpies go in and eat all of our Spam, and then they eat all of our pizza.”
To make matters worse, some cut grass concealing a gunpowder-propelled net gun proved appetizing for another of Yellowstone’s trademark species.
“The bison came in,” Marzluff said. “Unfortunately, they walked right over this, and exposed some of this line.”
The eaten-up bait and somewhat unconcealed trap were certainly a setback. Ravens are exceptionally wary birds when it comes to approaching new food sources. That’s even true for habituated birds, like those in Yellowstone that grow accustomed to receiving human handouts.
When Slough Creek’s unmarked resident raven pair were out of sight, Marzluff dashed out that morning to again conceal the trap. Then, along with assistant and wildlife technician Cameron Ho, he settled in for the second consecutive day of fruitless raven trapping.
“Nine hours of sitting and watching hot dogs and pizza,” Marzluff said of the work.
He’s used to it. Marzluff, his wife, Colleen, and German scientist Matthias-Claudio Loretto are now in their third year of an intensive research effort that’s assessing how ravens relate to wolves and mountain lions — three species that all are being tracked with GPS technology in Yellowstone’s Northern Range.
Gardiner, Montana, naturalist, photographer and raven enthusiast George Bumann has documented ravens’ legendary wariness around foreign food opportunities before. When ravens watch wolves take down an elk, they waste no time and will start picking away as soon as the opportunity arises. But the same species is extraordinarily leery of eating on the carcasses of animals that they didn’t watch get killed. So Bumann was very curious when he watched the old Druid Pack make a kill in the darkness long ago, and then head up to a nearby butte to bed before the birds awoke.
“I literally timed it,” Bumann said. “It was like 35 minutes before they would touch it. The ravens showed up, but it was like half an hour-plus before they would even touch it.”
Why would ravens better trust food they know was wolf-killed?